National Conference Emerging trends of Energy Conservation in

National Conference on Emerging Trends of Energy Conservation in Buildings
Nov 1-3, 2012
CSIR-Central Building Research Institute, Roorkee-247667 (India)
Abstract.
Energy Efficient Green Building Insulation
K. K. Mitra
Llyod Insulation (India) Limited, New Delhi
Corresponding author, Email: kk.mitra@lloydinsulation.com
We spend 90% of our lives in buildings that protect us from the extremes of nature like cold,
heat, wind, rain, hailstorms and snow. However, our buildings use enormous amounts of
energy, water and materials throughout their entire lifecycle. They also create a large amount
of waste and have a profound effect on the ecosystem that surrounds them as well as on the
people who occupy them. The economic, health and environmental impact of our buildings is
apparent in our society. To meet the challenges of our built environment, a new way of
designing and constructing building has evolved. It’s called Green Building and its purpose
is to help make buildings and the communities they make up become more livable,
sustainable, resource efficient and healthier.
1. Introduction
“Thermal Insulation System” is a term used to cover the entire combination of materials and
endeavored provisions which together perform thermal barrier duty. Often, it is
misunderstood that only the material (insulant) is of consequence for design. However, the
way it is applied, the ancillary provisions that are needed to keep it in place, protective
coverings that are necessary and compatibility with other provisions such as water proofing
etc. Determine its final effectiveness in the applied state. Even the best insulating material
can fail in service if not properly applied.
2. Application of Thermal insulation
In warm locations throughout India, the predominant
insulation duty pertains to summer ambient conditions and
the concurrent requirement for cooling of the air in the
building interior. The major obstacle in achieving

comfort conditions within the enclosure on a summer day is the enormous amount of solar
heating to which the roof is subject, apart from heat inflow from the high ambient air itself.
In case of extreme cold ambient temperatures during night, cold
passes through the walls to inside of buildings. The principal
offender is always the roof apart from the walls which, if not
properly insulated can allow large quantities of heat / cold to
enter the building envelope. Thermal Insulation have been
applied to building’s roof for long time with the idea of only
stopping the heat ingress but with Green Building architecture
designing the concept is further improved and termed as
Upgraded Insulation System, which defines Thermal Insulation
not only to stop heat ingress but also act as Energy
Conservation to the inside of building cooling or heating device.
The paper will cover this concept of Upgraded Insulation
system of roof & wall. The various methods of roof insulation
in terms of Under the Roof or over the roof insulation along
with related ancillaries and finishes will be covered in the paper.
Similarly various applications of wall both internal & external
along with finish will be covered in the paper including various
sketches and pictorials. The technical paper would cover briefly
various categories of insulation materials and then application
of roof & wall and highlight about the thermal properties and
thermal resistance value.
3. Importance of Thermal Insulation
The importance of Non-combustible insulation
for internal application and Water Repellant
properties for external application will be
discussed. The latest technique of ‘ETICS’ –
Insulation application from outer side of brick
walls finished with cement plaster will be
covered. The concept of energy conservation
accrued in building operation in case of uninsulated
building and insulated building will be
highlighted. The energy savings will be defined
in terms of energy units as well as monitory value.
Energy Conservation Building Code (ECBC) with
respect to thermal insulation requirement will be
covered and how different category of insulation
materials are covered by this standard, will be
shown i.e. in general what thickness will be
required of different materials to meet ECBC
standard, will be covered. The concept of
embodied energy, material disposal and
manufacturing with respect to green properties
will also be covered.

4. Latest Concept of Insulation
The latest concept of building construction involving steel technology and prefab insulated
panels will be covered briefly. The suitability of this technology as a green concept and
allowing energy conservation and also the most suitable mode of tall building construction
will be covered. Prefab panel is
ideal for construction of Insulated
Steel Buildings.
The concept of NET-ZERO
Buildings involving Insulation,
Pre-fab panels, Solar panels – all
in a building will be presented
briefly. IGBC & GRIHA
ADARSH Compliance insulation
for Buildings will also be covered.

Comparative Studies on Two Different Methods of Thermal
Conductivity Measurements
Abstract.
S. P. Agrawal, B. M. Suman and Rajni Lakhani
CSIR-Central Building Research Institute, Roorkee
Corresponding Author, Email: subodhagrawal@cbri.res.in
Number of materials is available for thermal insulation purposes (heat conduction) in
buildings. Before using them in buildings its prior judgment of performance is required. Also
during development of new insulating materials using different methods for frequent
measurement of thermal conductivity is needed. The standard method consumes lot of time,
power, and cost. In order to reduce time, power, and cost, other faster methods are available.
In this paper the suitability of these new faster methods of measurement is judged for use by
the researcher and workers.
Key-words: k-Thermal Conductivity, Thermal Engineering, Heat Transfer, Heat Flow,
Conduction, Insulation.
1. Introduction
Heating or cooling processes, equipment or enclosed environments are within the purview of
thermal engineering. Thermodynamics, fluid mechanics, heat transfer and mass transfer are
the major disciplines which are involved in solving a particular thermal engineering problem.
The applications include engineering, cooling of computer chips, boiler, solar heating etc. In
heat transfer, the thermal conductivity of a substance, k, is an intensive property that indicates
its ability to conduct heat. In physics k is the property of a material’s ability to conduct heat.
It appears primarily in Fourier’s Law heat conduction. Heat transfer across materials of high
thermal conductivity occurs at a higher rate than across materials of low thermal
conductivity. Correspondingly materials of high thermal conductivity are widely used in heat
sink applications and materials of low thermal conductivity are used as thermal insulation.
Thermal conductivity of materials is temperature dependant. The reciprocal of thermal
conductivity is thermal resistivity. Thermal conductivity is important in material science,
research, electronics, building insulation and related fields especially where high operating
temperatures are achieved. However, materials used in such trades are rarely subjected to
chemical purity standards. Cooling solutions for electronics or turbines usually use high
thermal conductivity materials such as copper, aluminum, silver to cool down specific
components. On the other hand, applications in construction or furnaces use low thermal
conductivity materials such as polystyrene, alumina for insulation purposes. Measurement of
thermal conductivity of materials is most important parameter in thermal engineering. A
minor error in its measurement may lead a major error in design which may fail the solution

completely. There are number of possible ways to measure thermal conductivity, each of
them suitable for a limited range of materials, depending on the thermal properties and the
medium temperature. The paper describes the different methods for the measurement of
thermal conductivity with state-of-art methods and the results of standard steady state method
and the latest TCi method of a few materials are compared as reference to the workers.
2. Thermal conductivity measurements
There are two major classes of methods exist to measure the thermal conductivity of
materials i.e. steady state and non-steady state (or transient) methods. The methods where
temperature of the material measured does not change with time comes under steady state
methods while under non steady state (or transient) techniques perform a measurement during
the process of heating up. The advantage is that measurements can be made relatively
quickly. Besides these two major classes of thermal conductivity measurement techniques,
there is one more technique which is known as thermo-reflectance. The techniques are
described in brief here under.
3. Steady state methods
This technique makes the signal analysis straightforward (steady state implies constant
signals). The principle of guarded hot plate apparatus is that the heat flows from guarded hot
plate normal to the specimens to isothermal cold plate maintained at lower temperature. The
temperature balance between the center and guard sections of the main heaters which are the
separated by the small gape is maintained by using the output of the thermocouples to control
the power supplied to the guarded heater. The balance conditions can be checked by using the
output of thermocouples pairs mounted in the surface plates on either side of the plates; In
case of measurements at high temperature
from 50-250 o C two auxiliary plates are
used on either side of the specimens to
increase the mean temperature. When the
temperatures of the guard, central and
cold plates becomes constant and remain
steady about two hours; the desired steady
state is reached. The power and the
temperature difference between the hot
and cold plate is measured and the
thermal conductivity is computed. The
Guarded hot plate Apparatus is working
as per Indian Code, IS: 3346-1980.
Figure1. Equipment for Thermal Conductivity
Measurement based on Steady State Method
The shortcoming of this method is that a
well engineered experimental setup is
needed. The equipment available in
CSIR-Central Building Research Institute,
Roorkee based on this method is shown in
Figure 1.

3.1 Transient methods [1]
In this method, the measurements are carried out during heating process itself. This is also
known as non-steady state or un-steady state method. In this non-steady state or transient
method to measure the thermal conductivity do not require the signal to obtain a constant
value. Instead, the signal is studied as a function of time. The advantage of these methods is
that the test can be performed more quickly, since there is no need to wait for a steady state
situation. The disadvantage is that the mathematical analysis of the data is in general more
difficult. The methods normally available include;
1) Transient plane source method – this method is suitable for various kinds of materials,
such as solids, liquid, paste and thin films etc. this require two samples in sandwiching
the sensor between two pieces of a homogenous material. The probe is a flat sensor with a
continuous double spiral of electrically conducting nickel (Ni) metal etched out of thin
foil and clad between two layers of polyimide film Kapton. The thin Kapton provides
electrical insulation and mechanical stability to the sensor. The sensor is placed between
the surfaces of two sample pieces of the sample to be measured. During the measurement
a current is allowed to pass through the nickel and creates an increase in temperature. The
heat generated dissipates through the sample on either side of the sensor at a rate
depending on the thermal transport characteristics of the material. The temperature vs
time response in the sensor is recorded and thermal conductivity of the material can be
calculated.
2) Modified transient plane source (MTPS) method[3] – this method is developed by
Nancy Mathis of the University of New Brunswick and commercialized through her
company Mathis Instruments Ltd. (now C-Therm Technologies Ltd.) the device uses a
one sided, interfacial, heat reflectance sensor that applies a momentary, constant heat
source to the sample. The difference between this method and traditional transient plane
source technique is that the heating element is supported on a backing, which provides
mechanical support, electrical insulation and thermal insulation. This modification
provides a one sided interfacial measurement in offering maximum flexibility in testing
liquids, powders, pastes and solids. Equipment procured in CSIR-Central Building
Research Institute, Roorkee based on this technology is shown in Figure 2 where a
sample is put on the sensor (center) to measure the thermal conductivity at room
temperature.
Figure 2. Equipment for Thermal Analysis based on MTPS Method

3) Transient line source method – in this method an infinite line heat source is used with
constant power per unit length of the heat source. The temperature is measured at a fixed
distance from the line heat source. The physical model behind this method is the infinite
line source with constant power per unit length. The temperature profile T(t,r) at a
distance r at time t is as under;
Where,
Q is the power per unit length in W.m -1
k is the thermal conductivity of the sample in Wm -1 .K -1
Ei (x) is the experimental integral, a transcendent mathematical function
r is the radial distance to the line source
a is the thermal diffusivity in m 2 .s -1
t is the amount of time that has passed since heating has started in seconds
4) Laser flash method – the laser flash method is used to measure thermal diffusivity of a
thin disc in the thickness direction. This method is based upon the measurement of the
temperature rise at the rear face of the thin disc specimen produced by a short energy
pulse on the front face. With a reference sample specific heat can be achieved and with
known density the thermal conductivity of materials can be calculated.
Where,
k(T) = a(T).Cp(T).ρ(T)
k is the thermal conductivity of the sample in Wm -1 .K -1
a is the thermal diffusivity of the sample in m 2 .s -1
Cp is the specific heat of the sample in Jkg -1 .K -1
ρ is the density of the sample in kgm -3
It is suitable for a multiplicity of different materials over a broad temperature range from
-120°C to 2800°C.
5) 3 ω method - 3 ω method is one popular technique for thermoelectric materials. Thin
metal strip is evaporated on the sample acts heat source and a thermometer. The heater is
driven with AC current at frequency ω, which causes heat source to oscillate at frequency
2 ω by monitoring AC voltage as a function of the frequency of the applied AC current
thermal conductivity can be determined.
3.2 Other methods
Other methods for measuring thermal conductivity of good conductors may include Searl’s
Bar Method and for poor conductors Lee’s disc method can be used. Thermo-reflectance is of
more important method amongst other methods. Thermo-reflectance is a method by which
the thermal properties of a material can be measured, most importantly thermal conductivity.
This method can be applied most notably to thin film materials (up to hundreds of neonmeters
thick), which have properties that vary greatly when compared to the same material in

ulk. The idea behind this technique is that once a material is heated up, the change in
reflectance of the surface can be matched to the model containing coefficients that
correspond to thermal properties.
4. Experimental
A few of the materials are characterized by standard steady state method as per IS standard
and with the Modified transient plane source (MTPS) method both at same mean temperature
and the results are given in Table-1. The materials chosen for this comparison include
expanded polystyrene, glass wool slab, rigid expanded polyethylene, foamed cement slab,
and low density Coir CNSL Board. In all these materials the Coir-CNSL Board is an
alternative material developed in CBRI.
Table 1. Thermal Conductivity of Materials Determined at Laboratory
No. Sample (Density in kg/m 3 ) Mean
Temp
Thermal Conductivity in Wm -1 .K -1
Steady
State
Method*
MTPS
Method
%
Deviation
1. Expanded Polystyrene (24.00) 25°C 0.035 0.037 +5.71
2. Glass Wool Slab (24.00) 25°C 0.036 0.040 +11.11
3. Expanded Polyethylene (35.00) 25°C 0.037 0.039 +5.40
4. Foamed Cement Slab (400.00) 25°C 0.084 - -
5. Low Density Coir CNSL Board 25°C
(500.00)
0.078 0.062 -20.51
6. Ceramic wool (115.00) 25°C 0.055 0.059 +7.27
7. Low Density Board of Paper
Industry Waste (286.00)
* Considered as the standard value.
25°C - 0.061 -
The equipments used for measuring the thermal conductivity in the laboratory are shown in
Figure 1 and Figure 2. Both are available at CSIR-Central Building Research Institute,
Roorkee. There are certain limitation with MTPS based equipment. This equipment is
suitable only for the materials which are continuous and homogenous in composition. This
equipment is not suitable for the materials having larger size particles or composites having
larger size fibers or particles or air bubbles etc. Here the thermal contact conductance plays a
very important role during measuring the thermal conductivity of materials by MTPS
method. A temperature drop is observed at the interface between the two surfaces in contact.
Here the two surfaces are the surface of the sample and the surface of the sensor. Sensor and
the surface of the sample must be in intimate contact. For making intimate contact between
these two surfaces some specific liquids of known characteristics may also be used. A
correction factor is included to nullify the effect of used liquid on thermal conductivity.

5. Conclusion
The results of thermal conductivity of different materials measured by using steady state
method and by modified transient plane source method are shown in Table-1. Results for
Expanded Polystyrene, Expanded Polyethylene, and Ceramic wool are close to each other
and the deviation is varying from +5.40 to +7.27%. The deviation in case of Glass Wool Slab
and Low Density Coir CNSL Board is quite high due to presence of entrapped air in between
the reinforcing material in the matrix. The censor in case of MTPS method is very small and
entrapped air gaps contribute major error. Therefore, it may be concluded that for
approximate determination of k value for these products is not justified. However this
approximation can easily be done for Expanded Polystyrene, Expanded Polyethylene, and
Ceramic wool. The time involved in determining the thermal conductivity by steady state
method is very large. Around 7-10 hours are needed for performing one single test. The other
methods require only 1-2 minutes time for one observation. However, the transient method
cannot be considered as standard method since environmental conditions which do not have
any control may affect the results. Therefore, for the development of a new material or for
designing some heat sink or heat insulation with sophistication, the steady state method
should be used. For other general or less sophisticated instances, the MTPS method can be
used without any difficulty.
6. Acknowledgement
Authors are thankful to the Director Prof. S. K. Bhattacharya, Central Building Research
Institute, Roorkee for permitting to publish this work.
References
1. www.tainstruments.com
2. Thermal Properties of Materials, Homsey, R. I., ENG 2000 series Chapter 9.
3. Principal Methods of Thermal Conductivity Measurement, a publication of TA
Instruments, Argentina.
4. Conference/ Conductivity/Home%20Heating%20Energy.htm
5. IS: 3346, “Methods for determination of thermal conductivity of thermal insulation
materials by two slab guarded hot plate”.

Abstract
Development of Energy Efficient Material from Vermiculite
Rajni Lakhani, S. P. Agarwal and Sapna Ghai
CSIR-Central Building Research Institute, Roorkee, India
Corresponding Author; Email: rlakhanhi_cbri@rediffmail.com
In the present study, thermal insulated tiles has been prepared by using exfoliated vermiculite
as a filler material because of its low bulk density, high refractoriness, low thermal
conductivity and adequate chemical inertness. The ordinary Portland cement of 43 grade was
used as a binding material for vermiculite. Various mixes were prepared using different
percentage of vermiculite and water cement ratio. In order to obtain desired consistency,
polymer admixtures such as SBR latex and super plasticizer (1 wt% of cement) was added in
the mixes at 0.15 polymer cement ratio. Based on the test results, an optimum formulation
was worked out for the vermiculite cement tiles on the basis of wettability of vermiculite
surface & its proportion, vermiculite cement ratio and polymer-cement ratio. The developed
vermiculite cement tiles exhibited low water absorption, better strength properties and low
thermal conductivity compared with the conventional clay tiles used for thermal insulation
purpose.
Keywords: Vermiculite, Thermal insulation, clay tiles, Exfoliation.
1. Introduction
Cost of energy and its crisis are alarming and adversely affecting the individual and the
society in one form or the other. Thermal insulation (Barrier) has been considered as the best
solution to reduce the energy load on individuals. Maximum heat transmission (more than
60%) takes place through roof surface of the buildings. Thermal Insulation provides a barrier
for incoming heat into the building envelop and prevent inside heating. Use of thermally
insulating materials impart comfort inside the room on one end and reduce the energy
requirement for cooling in summer. These materials are the key tool in constructing energy
thrifty buildings [1-5].
A range of materials can be employed in the manufacture and construction of insulation
products.
(a) Synthetic polymers eg. Polystyrene, Polyisocynene, Polyurethane, Polyisocyanurate
(b) Aerogel
(c) Mineral wools(insulation)-eg.fibre-glass, rockwool, slagwool
(d) Minerals- Vermiculite, Perlite
(e) Natural plant materials- cellulose insulation, cork, hemp, cotton
(f) Animal fibres-wool

In this study, exfoliated vermiculite has been used with Portland cement as binder to develop
thermal insulated tiles. Vermiculite is an excellent material characterized by high thermal
insulation parameters which make it useful for many purposes, including those for
manufacturing different kinds of fireproofing materials as well as production of boards. From
the geochemical point of view, vermiculite belongs to a group of hydrated aluminum-ironmagnesium
silicates. Vermiculite occurs as golden-brown to greenish flakes. As a mineral it
is distinguished by an outstanding ability to gain in volume (10-30 times) when exposed to
high temperatures. This phenomenon is accompanied by water loss. Its bulk density in the
natural form is between 600 and 1050 kg/m 3 and after swelling 65-130 kg/m 3 . Because of low
density, it is mainly used in expanding form.
Exfoliated vermiculite is also characterized by the
following properties:
Good sound insulation,
Good thermal insulation,
Good adhesion to different kinds of surfaces.
Figure 2. Different fractions of exfoliated vermiculite
Figure 1. Vermiculite
Vermiculite occurs in different fractions Non-combustible vermiculite products emit neither
smoke nor toxic fumes and make no hazard to the environment. Vermiculite is formed by
hydration of certain basaltic minerals. Its chemical formula-
(MgFe,Al)3(Al,Si)4O10(OH)2.4H2O. It is honey in color. It’s moulded shapes, bonded with
sodium silicate for use in – high temperature insulation, refractory insulation, packing
material, fireproofing of structural steel and pipes, as loose fill insulation, light weight
aggregate for plaster and cementitious spray fireproofing. Vermiculite is 2:1 clay, meaning it
has 2 tetrahedral sheets for every one octahedral sheet. Vermiculite clays are weathered micas
in which the K + ions between the molecular sheets are replaced by Mg 2+ and Fe 2+ cations.
There are several advantages attributable to the use of vermiculite and perlite such as:
i) Weight advantage
Vermiculite or perlite as the aggregate will have a weight density of approx. ranging
approximately from 30-35 PCF as compared to premixed sanded mortars which typically
have weight densities 120-150 PCF. This provides significant advantage in handling and
shipping.

ii) Moisture retention
Since dry roof tile absorbs much water from the mortar, the higher holding capacity of the
vermiculite and perlite based mortars can withstand this absorbency and still contain enough
water to keep the mortar plastic enough to assure bonding to roof tile as well as the roof
underlayment. It also allows the cement to complete the hydration process and achieve its
highest strength.
iii) Insulation
Vermiculite and perlite mortars provide superior insulation values than heavier sanded
mortars. A benefit of its ultra light weight is that the mortar could be used to completely bed
the roof tile with an average of one inch of mortar across the entire roof area. One inch of
vermiculite mortar would provide an R factor of 1.49, and the perlite mortar an R factor of 1.72.
iv) Uplift resistance
The improved water retention capability of these mortars result in consistent bond strengths
on both the bonds to the tiles and the bonds to the roof underlayment. Compressive strengths
are related to density. While the mortar necessarily has lower compressive strengths than
normal weight mortars, it has more than enough compressive strength for roof tiles
application. Further, its high uplift resistance and low load on the roof make this mortar very
advantageous as compared to prior art mortars.
2. Review of Literature
Studies conducted by researchers shows that vermiculite improves thermal insulating
properties as well as is chemically stable compared to diatom earth, allophane and zeolite
which were added into various building materials to improve living environment. According
to Philip M. Carkner [6] a light weight insulating concrete composition includes a
cementitious forming material and a light weight aggregate combination of expanded
vermiculite and expanded perlite, the weight ratio of one to the other not exceeding about 2:1.
Charles S. Breslaure [7] developed a premixed ultra-light sandless mortar for use with clay
and concrete tiles. The mortar uses ASTM .C-332 aggregate, vermiculite aggregate in place
of heavy aggregates such as sand. The mortar cement is made from Portland cement, lime, air
entraining agents & water repelling agents. The resulting compound retains large amount of
moisture which increases hydration time resulting in improved bonding strength and increase
tile uplift strength. The light weight of mortar also allows a full bed of mortar to be laid on
the roof with the resulting benefit of an addition insulating layer for building. The mortar is
suitable for roofing or floor tile application. M.Akao etal [2-8] developed Vermiculite Board
by using slurry of vermiculite, Ca (OH)2, silica sand and pulp. The resultant slurry was
formed into a green sheet by suction filtration. The sheet was heated at 187 degree C for 24h.
The product had a density of 910 Kgm -3 and also describes fungus resistance of the board and
compares it with calcium silicate board and gypsum wall board. Fungus resistance of the
board test acc. to JIS Z2911 and results shows that vermiculite board showed higher fungus
resistance in comparison to the other building products. A novel approach to the preparation
of polymer nanocomposites utilizing a low-molecular-weight reactive modifying reagent has
been developed by S.C.Tjong, Y.Z.Meng and A.S.Hay [9-10]. In this study maleic anhydride
used as a reactive reagent that acts both as a modifying additive for the polymeric matrix and

as a swelling agent for the Silicate Polypropylene[PP]-Vermiculite nanocomposites with an
intercalated or exfoliated structure can be achieved by simple melt mixing of maleic
anhydride-modified vermiculite with PP. The nanocomposite structure is evidenced by the
absence of vermiculite reflections in the X-ray powder diffraction patterns. Tensile tests show
that the tensile modulus & strength of the nanocomposites tend to increase dramatically with
vermiculite addition. Such enhancement in mechanical properties results from the formation
of intercalated & exfoliated vermiculite reinforcement in the composites. Lignocellosic
boards, including particleboards, fiber boards, flake boards & the like are among the most
popular materials used in the building industry, for outfitting (furniture) and for interior
decoration (wall & ceiling paneling). However, due to their unfavorable behavior under fire
condition, their use has often been limited. Yian Zheng etal [11] studied the swelling
behaviors of vermiculite super absorbent composite. A series of super absorbent composites
were synthesized by copolymerization reaction of partially neutralized acrylic acid on
unexpanded vermiculite(UVMT) micro powder using N,N’-methylene bisacrylamide (MBA)
as a crosslinker & ammonium persulfate(APS) as an initiator in aq. solution and the samples
further characterized by means of FTIR, SEM, transmission electron microscope(TEM),
XRD & TGA. TGA implies that introduction of UVMT into the polymer network leads to an
increase in thermal stability of composites. Vermiculite concrete roof deck system is a
lightweight concrete consisting of Portland cement, water and vermiculite concrete aggregate.
Vermiculite roof deck systems are applied by an applicator familiar with using and applying
light weight vermiculite concrete. Its advantages are lightweight, fireproof. Vermiculite
concrete has excellent insulating properties as 3 inches of vermiculite concrete is equivalent
to 1 and half inch of rigid board insulation laid over steel decks. Therefore keeping this in
view, the work has been carried out to develop cement based vermiculite tiles
3. Experimental
In the present study, exfoliated vermiculite was used as a filler material because of its low
bulk density, high refractoriness, low thermal conductivity and adequate chemical inertness.
Its average particle size was 1.1 mm as measured by the sieve analysis. The ordinary Portland
cement of 43 grade was used as a binding material for vermiculite. Various mixes were
prepared using different percentage of vermiculite ranging between 5% and 50% at 0.5 water
cement ratio. In order to obtain desired consistency, polymer admixtures such as SBR latex
and super plasticizer (1 wt% of cement) was added in the mixes at 0.15 polymer:cement ratio.
Based on the test results, an optimum formulation was worked out on the basis of wettability
of vermiculite surface & its proportion, vermiculite cement ratio and polymer-cement ratio.
Various cubes of size 50 x 50 x 50 mm were cast under vibration. The sheets of size 300 x
300 x 25 mm were prepared on a hydraulic press at a pressure of 8-10 kg/cm 2 for 10 min
retention. The prepared samples were cured for 7 days and 28 days in moist condition. The
water absorption, compressive strength and flexural strength of cured samples were tested as
per ASTM C196. The thermal conductivity of cast plates was determined as per IS 3346
using hot guarded plate at 40 0 C. The developed tiles are shown in Fig. 1. The results obtained
have been compared with the commercially available tiles and are reported in Table 1.

Figure 1. Vermiculite cement tiles
Table 1. Properties of Vermiculite cement tiles
Properties CBRI tiles Conventional tiles
Water Absorption (%) 24 hrs soaking 8-10 12-16
Flexural Strength (MPa) After 7 days curing 2.9-3.4 1.8
After 28 days curing 3.2-3.5
Compressive Strength After 7 days curing 4.2-5.0 3.9-4.2
(MPa) After 28 days curing 4.6-4.8
Thermal Conductivity, (Kcal/m/hr/ o C) 0.10-0.18 0.18-0.20
4. Results and discussion
It is found that increase of vermiculite content decreases compressive strength and increases
water absorption of the resulting mixes. At higher loading, w/c ratio of the mix is
comparatively more than the mix containing low vermiculite content because of porous
nature of vermiculite flakes. The thermal conductivity of sheet is found in the range of 0.12-
0.18 Kcal/m/hr/ o C. When compared with conventionally used tiles, it is observed that water
absorption is 33% less after 2 hrs soaking and 28% after 24 hrs respectively. About 61%
increase in the flexural strength is noted probably due to reinforcing effect of vermiculite.
The value of compressive strength of vermiculite cement tiles is comparable to the
conventional tiles. The strength properties of vermiculite cement tiles determined after 7 days
curing are almost same as that of 28 days water curing. This is attributed to the formation of
polymer layer on the cement particles surface as a result water is trapped inside and
contributing towards hydration of cement. Based on the results, it is concluded that
vermiculite cement tiles exhibited low water absorption, better strength properties and low
thermal conductivity compared with the conventional clay tiles used for thermal insulation
purpose.
5. Application
The tiles obtained are light in weight and provide thermal insulation to computer rooms; cold
storages etc. as the product arrest the heat dissipation.

6. Acknowledgement
Authors are thankful to the Director, Prof. S. K. Bhattacharya, CSIR-Central Building
Research Institute, Roorkee for granting permission to publish this work. Thanks are due to
BMTPC, New Delhi for sponsoring grant-in-aid project for carrying out these studies.
References
1. Papadopoulos, A.M. (2005), “State of art in thermal insulation materials and aims for
future developments”, Energy and Buildings, Pages 3777-86.
2. Akao, M., Yamazaki, A., Fukuda. Y. (2003), “Vermiculite board for novel building
material”, Journal of Material Science Letters, Volume 22, Pages1483-1485.
3. Norman M.P. Low. (1984), “The Thermal insulating properties of Vermiculite”, Journal
of Building Physics, Volume 8, Issue 2, Pages 107-115 “Vermiculite- A promising
material for high-temperature”, Refractories & Industrial Ceramics, Volume 44 (2003)
No.3.
4. Norman M.P. Low. (2003), “Vermiculite- A promising material for high-temperature”,
Refractories & Industrial Ceramics, Volume 44, No.3.
5. Suvorov, S.A., Skurikhin, V.V. (2002), “High-Temperature heat insulating materialsbased
on Vermiculite”, Refractories & Industrial Ceramics, Pages 43383-389.
6. Carkner, P.M. “lightweight insulating concrete and method for using same”, U.S.Patent
no.6290769.
7. Charles S.B., “Ultra-Light High Moisture Retention Tile Mortar”, U.S. Patent-5,718,758
8. Akao, M. (2004), “Fungus resistance of vermiculite board & comparison to calcium
silicate board & gypsum board “, Journal of material science, 39 No.-18.
9. Tjong, S.C., Meng, Y.Z., Hays, A.S. (2002), “Novel preparation and properties of
Polypropylene-Vermiculite Nanocomposites”, Chemistry of Material, Volume 14, Issue
1, Pages 44-51.
10. Al- Homoud, M.S. (2005), “Performance Characteristics & Practical Application of
Common Building Thermal Insulation Materials”, Building and Environment, Volume
40, Issue 3, Pages 353-366.
11. Zheng, Y., Li, P., Zhang, J., Wang, A. (2007), “Study on superabsorbent composite XVI.
Synthesis, characterization & swelling behaviours of poly (sodium acrylate) / vermiculite
superabsorbent composites”, European Polymer Journal, Volume 43, Pages1691-1698

Roof and Wall Insulation
A Key to Energy Conservation and Sustainable Development
Abstract
Himanshu Agrawal
BASF India Limited, Mumbai
Corresponding Author, Email: himanshu.agarwal@basf.com
Buildings across the globe consume 60-70% of the total electricity generated and are a major
contributor to the greenhouse gases. The maximum share of this energy usage is in
conditioning (heating or cooling) the building interiors. In India, which has a tropical climate,
insulation of building envelope would result in major energy saving and minimizing the
greenhouse gas emissions which would contribute to a green and sustainable development.
This paper dwells on the various aspects of “Total Insulation” of building envelope that
includes moisture insulation (waterproofing) and thermal insulation.
1. Introduction
Today’s modern buildings – marvels in terms of architecture and technology – have led to an
adverse impact on the environment. Buildings are responsible for more than half of harmful
greenhouse gas emissions in most major cities of the world. It is estimated that across the
total life-cycle of a building, the design and construction of a commercial building constitutes
just 20-30% of the overall cost; the rest comprises of operations and maintenance costs.
Hence, it is important to actually consider how the high cost of operating can be reduced
substantially. The maximum energy demand 50-70% in a building is for conditioning
(heating or cooling) the interiors. This major energy demand in a building is due to “Building
Envelope” which contributes to 60-75% of the heat gain/loss. Recognizing the need to save
energy and minimize green house gases, efforts are being made to increase the awareness and
importance of reducing energy loads in a building. Insulation of building envelope has
become one of the key practices across the globe to effectively manage heat incidence in the
buildings and save on the high energy cost.
For roofs, both LEED-India and GRIHA advocate over-deck insulation as against the
conventional way of under-deck insulation; green credit points for building envelope
insulation are credited for over-deck roof insulation.

In over-deck insulation, a thermal insulation with waterproofing is provided over the RCC as
a barrier against direct solar heat on RCC roof slab. This prevents the RCC slab from heating
up. The conventional method is under-deck thermal insulation by using methods like false
ceiling or extruded polystyrene. However its effectiveness is always a question since the
thermal barrier is provided under the RCC roof slab. Some heat passes through the underdeck
insulation and decreases the comfort level of the room. If the building is air-conditioned,
this heat leakage increases the AC load. Hence it can safely be concluded that over deck
insulation has its own advantages against under deck.
2. Building envelope insulation – a holistic approach
2.1 Roof insulation (over-deck)
This type of insulation has to take a composite approach to provide –
Thermal insulation
Waterproofing and
Slope built-up.
The traditional and conventional systems of waterproofing and thermal insulation in India
worked well for ages to suit the Indian construction and economics. However, these systems
do not have a long life and require frequent maintenance. These systems also do not suit the
complicated site dynamics of today’s construction and do not offer insulation values to
comply to ECBC norms.
2.1.1 Mud Phuska
In this conventional system of providing thermal insulation, a 10 cm layer of puddled clay
mixed with grass straw is applied in slope on a sand-bitumen waterproofing layer. This layer
is consolidated and plastered with 13 mm of cow-dung mortar. Tile bricks are laid flat on
plastered surface and the joints are grouted with cement mortar.
The Thermal and surface properties of mud phuska are as below;
Density = 1622 kg/m 3
Thermal conductivity = 0.750 W/mK
Specific heat capacity = 0.88 kJ/kg-K
[Reference: SP 41, Handbook on functional requirements of building (Other than industrial
buildings), Part 1-4, Bureau of Indian Standard (1988)]
2.1.2 Brick bat coba
The love of the Indian construction industry is the use of brick
bat coba for roofs. This system consists of putting brickbat on
flat roofs to give a slope and then grouting the same with
cement mortar admixed with some water proofing compounds.
This is mostly finished with IPS topping with a tile pattern cut
into the top to form crack inducer joints to prevent cracks from
appearing; alternatively China mosaic is done as the top
wearing course. There is a myth that brick bat coba offers

waterproofing and also insulation against heat. Nobody can rightly call it a waterproofing
material because it is porous and allows the entry of water into it very easily, serving as a
reservoir. Neither is it, by any stretch of the imagination, a thermal insulation product. In fact
the heat absorbed by brick bat coba it is the same as that absorbed by concrete.
Advantages
Provides Slope: This system provides an excellent slope for the water to drain away. As
water does not accumulate and as it has a certain capacity to absorb water, there is no
leakage.
Disadvantages
Impose Dead Load: This system puts unnecessary dead load on the structure.
Cracks Up: Brick bat coba cracks up due to temperature variation and movements due to
thermal stresses. Once cracks appear, water travels below the coba and leakage starts. It is
very difficult to trace the inlet point and repair it.
Difficult to Dismantle: Some parts of the coba stick so well to the concrete that an attempt
to dismantle the system may damage the slab.
2.1.3 Tar felt / APP membrane
This system uses layers of tar interspersed with various
forms of reinforcements to hold the layer together and
prevent cracking to provide impermeable layer between
the water and the surface to be protected.
Advantages
Cheap
Suitable for AC sheet roofing
Disadvantages
Not UV Resistant: Tar/Bitumen - the binder in the system disintegrates on contact with
'UV' radiation leading to biodegradation of reinforcement leading to collapse of the
system.
De-bonding: Vapour trapped inside exerts vapour pressure resulting in de-bonding of the
membrane.
2.1.4 Total insulation concept – the modern approach
To provide over-deck roof insulation that complies to ECBC requirements, a composite builtup
is required which consists of a thermal insulation material with high “R-value”, coupled
with a suitable waterproofing and complete with a light weight material for the slope built-up
for water run-off. A typical schematics of total insulation built-up would be as shown in the
diagram below;

2.2 Roof insulation components
Thermal insulation
MASTERSEAL
300H
Protective
coating
Coving using,
Polymer
Modified Mortar
Peripor Board: The water-resistant insulation
When building components are subject to pressure and
moisture, the insulating materials used should absorb as
little water as possible since water absorption has a
significant detrimental effect on thermal insulation.
Peripor Board has been developed specifically for such
applications. It is a high-quality thermal insulation
product with a water-resistant bead surface. This
combination of properties greatly reduces water
absorption and is thus suitable for use in the tropics.
Elastopor Board: thermal insulation PUR board
Polyurethane Resin (PUR) based thermal insulation boards offer best in class insulation
performance. Higher densities make the boards tough and can be used in trafficked system
built-ups. Elastopor Boards are specially designed with skin layer on both faces, making it
resistant to water ingress and long lasting.
Masterseal 755 SPF: Spray
applied PU foam
For thermal insulation is a two
component system, spray applied at
site. This allows spray application
on complex substrate shapes and
confined spaces, besides it lowers
materials transportation cost. A
comparative graph of “R-value”
with the above insulation materials
as compared to brickbat coba is
shown here:
MASTERSEAL
Waterproof coating
Tile Grout Stone Tile/
China
Peripor / Elastopr
Board/
PU Spray Foam
Insulation
Bedding
mortar
THERMOCRETE
EPS Bead Mortar
Overlay

2.2.1 Waterproofing
MASTERSEAL ® 550 EL: Two-component, flexible, cementations, polymer modified,
brush-applied, water-proof coating can be applied directly on the concrete substrates and
provides watertight sealing of pores and dormant cracks in the substrate.
SONOSHIELD ® HLM 5000R: Single component, moisture curing, liquid applied,
modified polyurethane, Elastomeric water-proof membrane has >600% elongation.
MASTERPREN ® TPO: Single-ply, preformed, TPO waterproof
membrane is a single-ply, water-proof membranes
available in glass/polyester reinforced versions.
MASTERPREN ® TPO can be selected and designed on the
basis of the roof overlay like green roof, podium, ballasted
roof, metal deck. It is also capable of re-roofing the existing
leaking roof without dismantling the existing system.
CONIROOF ® : Spray-applied, PU water-proof membranes consists of low-modulus PU
membrane which is best in class for high elasticity and high adhesion capability which
makes it perform on variety of substrates like natural stones, bricks, metal sheets, marine
ply and even old/leaking bitumen membranes and PVC membranes.
2.2.2 Slope built-up
THERMOCRETE TM – A revolutionary concept
A need is felt in the construction industry for a suitable material to
replace brickbat coba for the purpose of making slope/fall on the flat
roof slab for the purpose of water run-off and also for the protection of
waterproofing and insulation layers. This material should have ease of
application, be light weight, not crack up as brick-bat coba and also
impart insulation properties to the roof built-up.
Thermocrete - developed by BASF India - is an excellent replacement for brickbat coba on
a roof built-up due to its light weight, high thermal insulation, better
compressive strength, low water absorption and ease of installation.
Thermocrete is site-batched light weight trowelable concrete using
selective grades of expanded polystyrene beads (EPS) as thermal
insulating aggregates.
It combines the construction ease of concrete with the thermal
insulation properties of EPS and can be used for a very wide range of application where
lighter loads or thermal insulation or both are desired.
Following are comparative charts for Dead Load & Thermal Resistance “R” for 150mm thick
overlay of Thermocrete TM as against brick-bat coba and concrete;

3. Wall insulation
In India which has a tropical climate and a high level of sunshine, a major contribution to
heat gain in buildings is from walls! Still, wall insulation has
never been of much concern or simply, wall insulation has just
been neglected. Some traditional ways of providing thermal
insulation to the walls have been in the form of using light
colored stone tiles on exteriors to minimize sunlight, doublewall
with air cavity, cavity wall with mineral/glass wool
insulation as infill, insulating panels on interiors, etc. However,
each of these methods have their own disadvantages as apart
from not offering a high thermal insulation, they have the
problem of rain water seepage, water filling the cavity, poor
indoor air quality, decrease of valuable internal space, etc.
All these drawbacks are avoided by using “External Insulation & Finishing System” (EIFS)
on the walls.
SENERGY EIFS system offered by BASF consists of Neopor insulation board, adhesive
for fixing insulation board to the substrate, anchoring system for fixing the reinforcing
mesh in place over the insulation board and base coat which provide the mineral substrate
for the application of the top coat. The top coat provides the long lasting aesthetics and
finish to the system. Based on the insulation performance warranted, the type and
thickness of insulation board is designed.
EIFS offers the following benefits which are not offered/matched by other wall insulation
methods;
EIFS has superior energy efficiency by reducing heat transmission and helps in reducing
HVAC load.
The adhesive coat, base coat & top finish coat are polymer based and provide high degree
of water resistance to the wall.
It can be applied to new & existing structures.
External Location; Virtually Seamless – Reduced Air Infiltration
Offers design flexibility, shapes, colors and textures
Flexible and Lightweight Material
Little Routine Maintenance
It is the only solution for insulating existing buildings.
Sections of EIFS on a framed sheathing and on a concrete/plastered brick surface are as
shown below

Neopor Insulation Board: This high
performance thermal insulation board is
used in SENERGY EIFS.
Contains Infrared absorbers/ deflectors
20% higher energy efficiency then EPS
Flame retardant grade (B2)
K value of 0.032 W/m.K
Free of CFC, HCFC or HFC
4. Conclusion
With the fast depleting fossil fuel reserves and ever increasing electricity prices, it is
imperative to adopt energy saving measures. Buildings consume a major portion of electricity
generation and put a lot of stress on the society at large in terms of electricity shortage and
emission of greenhouse gases. It is necessary for the construction industry to adopt green
measures which would benefit their own pocket and the society. We should adopt workplace
strategies to meet sustainability goals while reducing overall occupancy costs.
Today, global companies like BASF are offering to the Indian construction industry, new
products, technology, systems and application expertise as a one-stop 360 O solution from
design to installation for the building envelope insulation. Adopting Green Building practices
will substantially reduce or eliminate adverse environmental impacts and improve upon
existing unsustainable design, construction and operational practices.

Abstract
Glass Wool Insulation
ECBC Compliance and Green Building Aspect
Biswajit Roy
U.P. Twiga Fiberglass Limited, New Delhi
Corresponding Author, Email: marketing@twigafiber.com
The scope of the paper is to understand the compliance of the prescriptive requirement of
ECBC-2007. It also reveal information of product and application that comfortably exceed
the thermal requirement while maintaining high standard of Fire-safety and acoustic values.
The environmental objective is also met by the product/application and that helps to satisfy
requirement of project’s Green certification.
Keyword: K-value, R-value, U-value, ECBC, Glass wool, LEED, GRIHA, FM, IMO,
BS476.
1. Introduction
The efficiency of resource consumption and an impact of the built environment on human
health & natural environment during the building lifecycle can be significantly influenced by
opting for the right insulation.
Thermal insulation material offers significant resistance to the path of heat flow and helps to
Reduce energy requirement
Reduce green house gas emission.
Save scarce environmental resources like fossil fuel
Hence, thermal insulation materials are used in buildings to provide a comfortable working &
living environment efficiently.
2. Insulation performance of Glass wool in the context of ECBC
Glass wool is one of the best thermal insulation materials known to mankind. As a green
building material, it is a preferred option by specifiers and users from among all the
insulation materials available, owing to its superior performance as mentioned below –
2.1 Thermal performance
Glass wool helps in reducing energy loss through roof and wall by up to 30% owing to [1]:

Low and yet wide range of thermal conductivity values (K values; in range of 0.03 to 0.04
W/m.K) pertaining to its wide range of densities (10 - 130 Kg/cu.m), Uniform fibre
distribution, Resilient and Hydrophobic nature. [2]
High and stable thermal resistance (R-value) over long time period.
Glass wool when used in optimum thickness and mass in building envelope conforms to Uvalue
as recommended in various standards like ECBC 2007, Ashrae 90.1,2007.
Table 1. Building Envelope application to comply the Thermal requirement of
ECBC-2007 [3]
Application Requirement
ECBC Criteria
Under-deck R-2.1 sq.mK/W
U-0.409 W/sq.mK
Cavity Wall insulation R-2.1 sq.mK/W
U-0.44 W/sq.mK
Wall insulation-installed
internally
Façade insulationspandrel
insulation
Advantage
R-2.1 sq.mK/W
U-0.44 W/sq.mK
R-2.1 sq.mK/W
U-0.44 W/sq.mK
Product
Glass Wool insulation
Density-24 Kg/cu.m to 48 Kg/cu.m
Thickness- 65 mm to 75 mm
Lamination- Alu. Foil
And Polypropylene based vapour
barrier
Density-24 Kg/cu.m
Thickness-50 mm
Density-24 Kg/cu.m
Thickness-50 mm
Density-32 to 48 Kg/cu.m
Thickness-50 mm
Lamination- Black Glass Tissue
An insulated building envelope contributes around 3-5 % energy saving by reducing heat
conduction.
There is a significant amount of saving on heat load because of insulation.
For non air conditioned building insulation is very important because it retards heat
ingression and tends to maintain thermal comfort
2.2 Fire performance
Glass wool will not support combustion even in direct prolonged contact with flames as it is
made from pure silica sand. It emits no toxic fumes or smoke, the two biggest hazards to
health and life. It is in compliance with stringent fire norms as per the following standards –
FM [5]
International Maritime Organisation (IMO) [6]
BS 476 part 4 – Non combustible [7]
BS 476 part 6 & 7 - Class ‘O’ /Class 1 rated. Probably the only insulation that conforms
to ZERO spread of Flame.
BS 476 part 5. - Class P rated (highest class for ignitability test)

Table 2. HVAC application to comply thermal requirement ECBC-2007 [4] / ASHRAE-90.1
Application Requirement Product Advantage
Supply Duct R-1.4 Twiga Glass Wool
insulation –
Density-24
Kg/cu.m
Thickness-50 mm
Lamination- Alu.
Foil or
Polypropylene
based Toughguard
Return Duct R-0.6 Twiga Glass Wool
insulation –
Density-24
Kg/cu.m
Thickness-50 mm
Lamination- Alu.
Foil or
Polypropylene
based Toughguard
Chilled water
pipe insulation
Branch flexible
duct
2.3 Environmental performance
R-0.35 Twiga Glass Wool
preformed
pipesections and
Lamella
R-0.6 Twiga Flexible
duct with Glass
wool insulation
sandwiched
between inner and
outer core
Temperature control of
conditioned air.
Most cost effective solution to
satisfy the Energy efficiency
compliance.
Available with various
laminations like Aluminum foil,
black alu. Foil. Toughguard
Completely safe from fire.
Maintain chilled water
temperature with sufficient
thickness.
Easy to apply.
Completely safe from fire.
Glass wool is classified as a “Green Building Material” for following reasons
Cover wide range of chilled water
pipes
Flexibility to adapt practical site
condition.
Raw material is silica sand, the earth’s most abundantly occurring natural material which
replenishes itself in nature. Unlike in other insulation material, primary raw materials are
not based on fossil fuel

Recycled content like glass cullet from industrial waste is used which otherwise would be
destined for landfills .In-house waste of glass wool scraps is recycled, too.
Site waste of glass wool can be sold off to various local equipment manufacturers. Even
when it is disposed off to landfill, it does not create any kind of environmental pollution.
Normally no adhesive is used for installation of glass wool in buildings. It is easy to apply
and easy to reclaim.
Glass wool is packaged through a vacuum packaging system that reduces its volume
significantly (e.g reduction ration 1:7). It saves transportation cost and energy.
No VOC as the material is oven-cured and no CFC present as there is no blowing agent
present.
2.4 Acoustic performance
Glass wool has interconnected open cell structure which makes it a good sound absorbing
material. It is used to cut down internal noise level caused by airborne or impact sound. Noise
Reduction coefficients (NRC) of the material can be in a range of 80% to 100% where as
Sound transmission class (STC) of various glass wool insulated system can be 35 to 45.
Table 3: Acoustic application for HVAC and building
Application Requirement Product Advantage
Duct Acoustic NRC-0.6 Twiga Glass
Wool 48
Kg/cu.m-25 mm
AHU/mechanical
room acoustic
Partition Wall-
Drywall
construction
2.5 Durability
with FGT
NRC- 1.0 Twiga Glass
Wool -48
Kg/cu.m-50 mm
with BGT
STC-32-50 Twiga Glass
Wool-24 to 48
Kg/cu.m-50 mm
Glass wool helps to increase the life span of the system as it is
Noise reduction
inside the duct.
Noise Isolation
Acoustic
privacy
Chemically almost neutral & hence minimum or zero reactivity with any material.( pH
value is close to 7)
Non corrosive ( it does not contain impurities like sulphur, chloride)
Hydrophobic (water repellent chemicals are added in the product). There is no capillary
(wick-type) action and hence does not retain significant quantum of moisture. In ‘wet to
dry’ cycle, it breathes out moisture and regains its original performance.
3. Ease of application
Glass wool Insulation is very easy to apply as it is available in rolls (with long/tailored made
roll lengths), rigid boards, in resilient and lightweight form (say 10-48Kg/cu.m), with/without
inbuilt vapour barrier, mechanical barrier of various kind.

4. Glass wool compliance with LEED India NC, green building rating system
LEED Credit Category
Table 4. Contribution of Fiberglass wool in LEED credit category
Energy and Atmosphere-
Optimize energy
performance
Material and resource-
recycled content
Material and resource-
regional/local
manufacturing
Innovation and Design
process
LEED Requirement
1-10 points depending on
percent reduction on
energy used.
”Project should comply
with final version of
ECBC-LEED-INDIA NC”
1-2 points depending on
post consumer, post
industrial recycled content
1-2 points depending on
20% total building
material is locally
manufactured (within 800
KM radius)
1-4 points depending on
the innovation applied
Fiberglass Insulation
Contribution
It helps to reduce building
energy consumption by
providing adequate insulation
(achieving required R, Uvalue)
in building envelop and
HVAC system.
15% post industrial waste (e.g
Glass cullet) is recycled.
Fiberglass wool can be reused.
In India 2 existing
manufacturing units in North
(U.P) and West (M.H) can
help to provide these points
Acoustic benefit in buildings,
water proofing with fiberglass
tissue, fiberglass wool as
concrete reinforcement.
Note: No individual building material enables a credit point taken within LEED

Table 5. Contribution of Fiberglass wool in GRIHA credit category
GRIHA Credit Category
Credit 12 &13: Optimize
building design to reduce
conventional energy
demand; Optimize Energy
(embodied+ construction)
performance…
Criteria 26, Minimize ODP
Criteria 28, Acceptable
outdoor and indoor noise
level
Criteria 32. Bonus
5. References
GRIHA Credit points
available
6+12 points
3 points.
2 points
4 points
Fiberglass Insulation’s
Contribution
It helps to reduce building
energy consumption by
achieving required Uvalue,
R-value.
Low embodied energy as :
-Renewable content - 42%
-Recycled content - 15%
ZERO ODP. No
CFC/HCFC content.
Complete inorganic
material.
Good acoustic
performance:
-High Noise Reduction
Coeff.(NRC)
-High Sound Transmission
Class (STC)
Reusable material.
Compressed/ Vaccum
packaging lead to saving in
Transportation energy/cost.
Thermal and acoustic
benefit with same
application.
1. A year-long study in 2005 was made by Winroc International on the energy
saving at Sikandrabad Factory, Bulandshar.
2. CBRI project on Thermal Conductivity for all range of Fibergalss insulation product
(Twiga make).
3. ECBC 2007 Table 4.3.1, Table 4.3.2
4. ECBC 2007 Table 5.2.4.2
5. FM Approval certificate for Twiga Insulation, U.P. Twiga Fiberglass
6. IMO certification through LRS.
7. PSB certification of Glass wool insulation as per BS 476 standard

Use of Autoclaved Aerated Concrete (AAC) Blocks for
Augmenting the Thermal Radiation Flux Resistance Capacity of
Administrative Building and its Related Benefits
Abstract
Amarjit Sahu and Moni Sankar Hazra
Haldia Refinery, IOCL (West Bengal)
Corresponding Author, Email: sahua@indianoil.in
EIL had carried out consequence modeling for catastrophic rupture of debutanizer reflux
drum of FCC unit in Haldia refinery and analyzed the mitigation measures required. The
catastrophic rupture may produce thermal radiation distances due to fireball of 12.5kW/m 2 ,
which will be extending up to administrative building. It was recommended that any openings
facing towards process unit should be blocked and protective measures to be taken to
withstand thermal radiation of 12.5kW/m 2 . Therein, extensive study was carried out on the
properties of the AAC blocks and it was found that they are light weight, can withstand
temperature below 3000 0 C without crumbling and have excellent fire resistance properties.
Plate glass in a window can absorb some 40 to 60% of the radiation from a building fire and
cannot be relied on to afford protection as large areas are liable to crack and fall out. Hence,
glazed openings of the Administrative Building towards the Process Units were closed with
AAC blocks of 125mm thickness. Apart from ensuring desired safety requirements and
reducing spread of incident heat flux to internal parts of the building during a fire, this has
also brought down the heat load on the air-conditioning system due to lower interior
temperature.
Keywords: Thermal Radiation, Fire Resistance, AAC Blocks.
1. Introduction
Engineers India Limited (EIL) had carried out ‘Limited Rapid Risk Analysis Report for Fire
Water Pump House, Fire Station, Raw Water storage, specified Operator cabins and
Administrative Building of IOCL-Haldia Refinery’. They have reviewed the findings of
consequence modeling for the case of catastrophic rupture of debutanizer reflux drum of FCC
unit of IOCL Haldia refinery, and also analyzed the impacts of consequences and requirement
of mitigation measures upon administrative building for the same. The case considered deals
with the catastrophic failure of the drum, a scenario with a low likelihood of occurrence but
with serious consequences.
In case of catastrophic rupture of debutanizer reflux drum, lower flammability limit (LFL)
contour shall be limited within FCC unit. In the analysis of catastrophic failure, it is assumed
that the gases are immediately ignited in presence of flame source to form a fireball whereas,

in reality this would not always be the case if no flame source is available at the time of
failure and release of hydrocarbon vapours shall disperse safely. If the sources of ignition are
eliminated from nearby debutanizer reflux drum area within LFL limit, then probability for
occurrence of fireball event will become almost unlikely. Based on the above, the occurrence
of such events is very rare but severity is very high due to presence of people inside
Administrative building.
Figure1. Flash Fire hazard distance in case of catastrophic rupture of debutanizer reflux drum
of FCC unit. (Courtesy: EIL)
The catastrophic rupture of Debutanizer Reflux Drum (Event Frequency is 1x10 -6 per year) of
FCC unit may produce thermal radiation distances due to fireball of 12.5 kW/m 2 , which will
be extending upto administrative building [1]. The flash fire and fireball hazard distances are
tabulated below.
Wind Speed
(m/s) and
Pasquill
Stability
Table 1. Flash Fire and Fireball hazard distances (Courtesy: EIL)
Flash Fire
Distances (m)
Thermal Radiation distances (m) due to Fireball
4 kW/m 2 12.5 kW/m 2 37.5 kW/m 2
1.5 / F 46.10 398.37 209.86 65.68
1.5 / D 41.85 397.00 209.08 64.92
1.1 / C 38.04 410.138 216.55 71.98

Figure 2. Fireball hazard distances in case of catastrophic rupture of debutanizer reflux drum
of FCC unit. (Courtesy: EIL)
1.1 Recommendations by EIL
Based on the consequence analysis results and subsequent impacts on administrative
building, a number of recommendations were given which shall reduce the probability of
occurring of such events and mitigate the hazardous effects due to such events. A few of
those recommendations pertaining to the scope of the present study is mentioned below:
1. Any window/door facing towards process unit should be blocked. Ensure that there is no
entrance/exit point from administrative building which is facing towards process unit.
However, doors/windows may be given to North West/ South Side of Administrative
building, if required.
2. Ensure alternate escape routes are provided and marking of same should be displayed in
the administrative building for evacuation of people during realization of such event.
However based on debutanizer reflux drum catastrophic rupture case, emergency
response plan to be developed, so that fast evacuation may take place if required.
3. Ensure that administrative building is designed to withstand thermal radiation of 12.5
kW/m 2 or suitable protective measures to be considered which can protect the
administrative building.

2. Methodology
Fire protection techniques have to be based on the fire behavior characteristics of various
materials and structural elements of buildings. The activities pursued by the occupants of
buildings must also be taken into consideration for assessing the extent of hazards, and
method should then be devised by which the hazards could be minimized. Fire resistance is a
property of an element of building construction and is the measure of its ability to satisfy for
a stated period some or all of the following criteria [3]:
a) Resistance to collapse.
b) Resistance to penetration of flame and hot gases, and
c) Resistance to temperature rise on the unexposed surface up to a maximum of 180 0 C and /
or average temperature of 150 0 C.
To ensure that Administrative Building is designed to withstand a thermal flux of
12.5kW/m 2 , a study on the thermal resistivity of the Administrative Building was carried out
at Engineering Services Department (Civil Section) of Haldia Refinery. The Administrative
building is a framed structure building with infill brick masonry wall of 250 mm thick with a
layer of 20mm thick plaster in cement mortar (1:6) over it. Masonry consisting of either
brick-work or of concrete block-work is inherently stable in fire and are bad conductor of
heat. Bricks can withstand temperatures of around a 1000 0 C and they melt at about 1400 0 C
[2]. They have no serious effect of heat until the temperature during fire rises above 1200
degrees to 1300 degrees. Similarly, concrete is a bad conductor of heat and an effective
material for fire resistant construction. There is no loss of strength in concrete when it is
heated up to around 250 0 C. The reduction of strength starts when the temperature of fire
increases beyond 250 0 C. Normally reinforced concrete structure can resist fire for about one
hour at the temperature of 1000 degrees centigrade without any serious damage. Minimum
thickness (mm) required for Solid Masonry walls to resist fire from one side at a time is
tabulated below [3]:
Table 2. Thickness of solid Non-load bearing masonry walls required to resist fire from one
side at a time
Sl. No. Nature of Construction & Materials
1
2
Bricks of Clay: with 13mm lightweight
aggregate gypsum plaster
Bricks of Aerated Concrete: without
finish
Non-Load Bearing Walls
[for a Fire resistance (hours) of]
1 1.5 2 3 4
75 90 90 90 100
50 63 63 75 100
The northern side of the Administrative building had a large number of glazed windows with
aluminium framing facing towards the process unit side. The aluminium glazed windows
covered a major portion in the elevation of the building, primarily to give an aesthetic look to
the building elevation. However, in this role, glass has little resistance to fire and generally
cracks very quickly because of the temperature difference across the exposed surfaces. For an
interior fire, a layer of hot, buoyant gases forms beneath the ceiling and descends, subjecting
the inside of the window to a two layer convective and radioactive environment. For an
exterior fire, the window is subjected to a fairly uniform heat flux. The heat flux absorbed by

the glass causes the exposed glass to heat up, while the shielded glass border remains cool.
With sufficient heating, the thermally induced stresses exceed the yield stress of the glass and
the glass cracks. Double glazing does not improve this behaviour significantly. Wire
reinforcement does provide relatively greater integrity; however in general glazing should not
be relied upon to remain intact in a fire. Although plate glass in a window can absorb some
40 to 60% of the radiation from a building fire, it cannot be relied on to afford protection to
the contents of the room as large areas are liable to crack and fall out [4]. Hence, it was
decided that all the openings towards the process units i.e. the openings towards the northern
side of the buildings for the entire elevation shall be blocked using Autoclaved Aerated
Concrete (AAC) Blocks of 125mm thickness.
Figure 3. North side (Front) elevation of Administrative building.
(The shaded portion depicts the aluminium glazed windows)
2.1 Reasons for using autoclaved aerated concrete (AAC) blocks
Autoclaved Aerated Concrete (AAC) blocks makes an excellent building material because of
its outstanding thermal properties, superior fire resistance and excellent acoustical absorbing
abilities. AAC blocks consist of Quartz (Silica & Pulverized Fuel Ash) which is the largest of
the dry material involved. The Silica along with the cement and lime mixture reacts with the
aluminium to form the millions of tiny air cells that give AAC block its unique properties.
2.1.1 Fire resistance
Most residential fires do not exceed 1200°C, not begin to break down until well over 3000°C.
This allows it to maintain its structural integrity even after a fire. AAC blocks are totally
inorganic, incombustible and are especially suited for fire-rated applications.
Figure 4. Fire test results for a 100mm thick wall made of AAC blocks.(Courtesy: JVS
Comatsco Industries Pvt. Ltd.)

2.1.2 Energy efficiency
AAC blocks provide superior thermal insulation by offering an array of benefits such as
thermal mass, thermal inertia, whole wall coverage and low air infiltration. These combine
and translate into energy savings which continue to appreciate over time. It has better thermal
and sound insulation due to fewer joints. This results in saving energy costs of airconditioning.
Building material with high thermal mass hold their temperature for a long
period of time. Thermal inertia is a resistance to change in temperature. AAC blocks have
both thermal mass and thermal inertia causing it to maintain constant temperatures. Test
results for a 250 mm thick AAC wall, painted black with one side facing the furnace heat and
the temperature was monitored on the outside and inside of the wall for 24 hours is shown
below [5]:
Figure 5. Test results for a 250 mm thick AAC wall to examine effects of thermal
mass and thermal inertia. (Courtesy: JVS Comatsco Industries Pvt. Ltd.)
2.1.3 Environment friendly
AAC blocks are manufactured with abundant recycled raw materials and produce no waste
products or pollution. Its manufacturing requires little energy as compared to other materials.
The use of AAC blocks avoids usage of topsoil. Traditional bricks are made of precious
topsoil. Once bricks are moulded & dried they go in for the elaborate firing process. The
firing process creates pollution. It then leads to a high loss of energy, incomplete & unequal
firing further result in poor quality bricks and a high percentage of SPM (Solid Particulate
Matter) which is released into the atmosphere and attributes to environmental issues like
global warming and ozone depletion. Since AAC blocks consist of approximately 80% air,
the finished product is up to 5 times the volume of the raw materials used, making it even
more resource efficient.

2.1.4 Light weight
AAC blocks are light weight and possess high structural integrity. Its light weight and easy
workability means that it is very quick to install on site, thereby saving in steel, cement,
mortar and related costs. Since AAC blocks are uniform in size and shape and are factory
made, wastage during transportation, loading and unloading are reduced by a great extent.
2.2 Significance of a radiant thermal flux of 12.5kW/m 2
The effect of thermal radiation on equipment and structures depends on whether they are
combustible and the nature and duration of the exposure. Thus, wooden materials will fail
due to combustion, whereas steel will fail due to thermal lowering of the yield stress. Many
steel structures under normal load will fail rapidly when raised to a temperature of 500 to
600°C, whereas concrete will survive for much longer. Flame impingement is generally more
severe than thermal radiation. The minimum flux for piloted ignition of wood was deduced as
approximately 12.5kW/m 2 (for African mahogany) [4]. An incident heat flux of 12.5 to
15kW/m 2 , based on an average 10 minutes exposure time is the minimum energy required to
ignite wood with a flame [6]. The external facia of the administrative building is not clad in
timber. Hence, the lowest critical heat flux for a material at the exterior of the building is that
for refuse (waste, rubbish), implying a critical heat flux of 15kW/m 2 . At radioactive fluxes of
less than 14.7kW/m 2 , no ignition will occur for dwellings, thereby, secondary fires will not be
produced within the building and no fatalities will result [4]. While no single number can be
used for all equipment, a value of 300°C (572°F) is considered as a safe operating maximum
for steel structures and process equipment. Computer modeling equates 300°C to an exposure
of approximately 12.5kW/m 2 (4000 BTU/hr-ft 2 ) for exposure without fireproofing or water
spray [7].
Incident Heat Flux
(kW/m 2 )
3. Conclusion
Table 3. Some Thermal Radiation damage levels [4].
35.0 to 37.5 Process Equipments.
25.0
18.0 to 20.0
12.5 to 15.0
Causes damage to Remarks
Minimum energy to ignite
wood at indefinitely long
exposure without a flame.
Plastic cable insulation
degrades.
Minimum energy to ignite
wood with a flame i.e.
piloted ignition.
Melts Plastic tubing.
Generally includes Steel
tanks, Chemical process
equipments and Industrial
machinery.
The Administrative building is a framed structure building with infill brick masonry wall of
250 mm thick with a layer of 20mm thick plaster in cement mortar (1:6) over it. From the

various studies carried out, it is inferred that, the brick masonry wall of 250 mm thick will
have a fire resistance of around 4 hours during an incident of fire. Bricks have much higher
thermal resistivity than that of wood. So, a radiant thermal flux of 12.5kW/m 2 (which is the
minimum flux for piloted ignition of wood) will cause minimal damage to brick walls on
prolonged exposure and is likely to pose almost no threat to the population within. The glazed
openings of the Administrative Building on the North side towards the Process Units have
been covered with AAC blocks of 125mm thickness. This will reduce the spread of incident
heat flux during a fire to the internal parts of the building to a very minimum level. These
walls are inherently stable, unlikely to collapse and provide good resistance to penetration of
flame and hot gases in the event of a fire. The administrative building is an old structure and
use of heavier weight traditional bricks for blocking the window openings would have
generated structural stresses on the existing building and might have impaired the structural
integrity with time. AAC blocks being light weight, having comparable weight with
aluminium glazed windows, will not add additional load on the building than what it was
already subjected to. The Administrative building can thus sustain a radiant thermal flux of
12.5kW/m 2 in case of fireball event due to catastrophic rupture of debutanizer reflux drum.
The use of AAC blocks has ensured the desired safety requirements and has also brought
down the heat load on the centralized air-conditioning system of the building due to higher
energy efficiency and better thermal insulation.
References
1. Singh, L. K., Kumar, D. (2011), “Limited Rapid Risk Analysis Report for Fire Water
Pump House, Fire Station, Raw Water storage, specified Operator cabins and
Administrative Building of IOCL-Haldia Refinery”, Doc. No A046-04-41-RA-1102,
Engineers India Limited.
2. Gillie, M., “Fire Resistance of Structures 5”, School of Engineering and Electronics, The
University of Edinburgh.
3. SP: 7, (2005), “National Building Code of India 2005”, Bureau of Indian Standards, New
Delhi, India.
4. Ashe, B. S. W., Rew, P. J. (2003), “Effect of flash fires on building occupants”, Research
Report 084, WS Atkins Consultants Ltd., Surrey.
5. Brochure of Ecolite Autoclaved Aerated Concrete Blocks, M/s. JVS Comatsco
Industries Pvt. Ltd., Maharashtra, India.
6. Thomas F. Barry, P. E. (2003), “Risk-informed, Performance-based Industrial fire
protection, an alternative to prescriptive codes”, TFBarry Publications.
7. API Publication: 2218, (1999), “Fireproofing practices in Petroleum and Petrochemical
Processing plants, 2nd Edition, American Petroleum Institute, Washington D.C., United
States of America.

Additives Filled Rigid Polyurethane Foam - A Fire Retardant and
Energy Efficient Building Material
Abstract.
Harpal Singh
CSIR-Central Building Research Institute, Roorkee
Corresponding Author, Email: harpalcbri@yahoo.com
Rigid polyurethane foam (RPUF) has many advantages over other insulating materials as
lowest thermal conductivity, high mechanical and chemical properties at both high and low
temperatures and the ability to form sandwich structures with various facer materials.
Buildings around the globe consume more than 40% of the total energy generated and are a
major contributor to the increased level of greenhouse gases. Effective insulation is therefore
a significant contributor towards sustainable construction. Studies showed that buildings
insulated with RPUF typically use 30% less energy for heating and cooling compared to other
insulation materials. However, RPUF is highly flammable and generates smoke containing
CO and HCN. Chemically modified RPUF is a perfect fire retardant and energy efficient
material for building applications. A fire retardant composition was prepared from
phosphorus-nitrogen (P-N) based additives. The fire retardancy of rigid polyurethane foam
(RPUF) was studied by impregnating it with various concentrations of P-N based additives
composition. Optimum impregnation time, retention and density of RPUF samples with P-N
composition were also studied. The morphology and fire performance of RPUF and RPUF-P-
N samples were investigated using scanning electron microscopy (SEM) and BS: 4735
respectively. The results showed that phosphorus-nitrogen additives composition enhances
the fire retardancy of RPUF samples.
Keywords: Rigid polyurethane foam, fire retardant, energy efficient, thermal insulation,
impregnation, morphology, mass loss, burning rate.
1. Introduction
Rigid polyurethane foam (RPUF) is high molecular weight polymer based on the
polyaddition of polyfunctional hydroxyl-group containing compound and polyisocyanate in
the presence of catalyst, surfactant, chain extender and blowing agents. Compared with other
insulating materials such as fiberglass, wood wool, mineral wool, rock wool, polyethylene
foam, polystyrene foam and phenolic foam, RPUF is highly competitive as shown in Table 1.
There are many product-related advantages as lowest thermal conductivity, high mechanical
and chemical properties at both high and low temperatures, the ability to form sandwich
structures with various facer materials, and the new generation of RPUF is CFC-free and
recyclable [1]. Buildings around the globe consume more than 40% of the total energy
generated and are a major contributor to the increased level of greenhouse gases. The greatest
energy demand in a building is for conditioning the interior by heating or cooling. Buildings

gain or lose heat through conduction, radiation and convection. Most of the energy in a
building is lost through the building envelope which contributes to over 60% of the total heat
gain/loss. Effective insulation is therefore a significant contributor towards sustainable
construction. The utilization of thermal insulation in the building envelope can substantially
reduce the building thermal load and consequently its energy consumption. The performance
of the thermal insulation material is mainly determined by its thermal conductivity (shown in
Table 2), which is dependent on the density, porosity, moisture content and means
temperature difference of the material [2]. The right insulation material plays an important
role in achieving energy efficiency. Studies showed that buildings insulated with RPUF
typically use 30% less energy for heating and cooling compared to buildings insulated with
traditional fibrous insulation material. RPUF has high thermal insulation value due to its
highly cellular closed cell structure with low moisture permeability [3-4]. However, RPUF is
highly flammable due to its chemical nature, high air permeability and high inner surface area
of the foam structure to mass ratio. During RPUF burning diisocyanate converts into yellow
smoke containing HCN, and rest of the other groups convert to white smoke containing CO2
and CO. HCN and CO are the prominent toxicant gases which on inhalation lead to death [5-
8]. Various fire retardants such as phosphorus-halogen mixture, ammonium polyphosphate
(APP) and organophosphorus compounds either alone or in combination with nitrogen or
silicone have been used to impart fire retardancy to RPUF [9-11]. Modesti et al. were
recently reported the successful incorporation of various combinations of halogen free fire
retardants such as APP with melamine, expandable graphite with triethyl phosphate and red
phosphorus, and expanded graphite with melamine into the RPUF formulations [12-15]. As
phosphorus and other halogen free fire retardants containing RPUF give off non-toxic
combustion products, thus they are preferred over halogen containing fire retardants [16-17].
On exposure to heat, phosphorus compound decomposes at lower temperature than
polyurethane foams to produce phosphoric or polyphosphoric acids. These acids catalyse the
char formation in the condensed phase. This phosphorus rich char prevents heat transfer by
reducing the production of combustible gases [18-20]. The main objective of this study is the
preparation of phosphorus-nitrogen additives based composition and to investigate the effect
on the fire retardancy of RPUF impregnated with P-N composition. Earlier such fire retardant
compositions have been studied in cellulosic paper and wood [21] but never in RPUF to the
best of our knowledge. RPUF impregnated with P-N composition was prepared in our own
laboratory and the results are reported [22]. RPUF samples of similar density were
impregnated with different concentrations of P-N composition. The density of RPUF samples
impregnated with P-N was measured as per ASTM D1622. The morphology and fire
performance of RPUF and RPUF-P-N samples were investigated using scanning electron
microscopy (SEM) and BS: 4735 respectively.
Table 1. Material thickness at equal thermal insulation value
Insulation material Thickness (mm)
Rigid polyurethane foam
Expanded polystyrene
Mineral wool
Cork
Wood fiber
Softwood
Light weight concrete
Dense bricks
50
80
90
100
130
200
760
1720

2. Method
Table 2. Comparison of thermal conductivity of common insulation materials
Insulation material Thermal conductivity (W/mK)
Dense bricks 1.31-1.60
Light weight concrete 0.14-0.18
Soft wood 0.13-0.17
Wood fiber 0.11-0.15
Cork 0.055-0.070
Mineral wool 0.036-0.042
Expanded polystyrene 0.029-0.035
Rigid polyurethane foam 0.023-0.026
2.1. Preparation of P-N additives composition
An aldehyde solution mixed with distilled water was charged in a 1000 ml three-neck round
bottom flask equipped with thermometer, stirrer and reflux condenser. The medium of the
solution was adjusted to alkaline by adding a few drops of an alkali solution. The solution
was then heated over water bath until it attains the temperature of 80-90 0 C. A mixture of
nitrogen additives was then added incrementally with constant stirring over 20 min. Upon the
completion of the addition, the reaction mixture was allowed to reflux for 10 min. The
resulting solution was cooled to ambient temperature by putting the flask under cold-water
stream. Phosphorus additive was then added slowly with constant stirring. During the
addition of phosphorus additive, the whole assembly was continuously kept under cold-water
stream to avoid the heat up of flask due to the heat generated by the reaction of phosphorus
additive and mixture solution. The final product was a colorless viscous liquid mixture of
phosphorus-nitrogen additives. This viscous mixture was designated as P-N additives. The
basic formulation used for the P-N additives preparation is presented in Table 3.
2.2. Sample preparation
Table 3. Basic Chemical Formulation of P-N Additives Composition
Chemical Quantity per mole
Phosphorus additive 1.0
Nitrogen additive-1 0.25
Nitrogen additive-2 1.0
Aldehyde solution 3.0
Water 8.0
RPUF samples of 49.19-kg/m 3 densities were used for impregnation with P-N additives
composition. P-N additives composition concentration, impregnation time, retention and

density are considered to be the most important parameters during the preparation of RPUF
samples. A P-N additive is water based composition, thus its various concentrations ranging
from 10-100% were prepared by mixing it with water. Optimum impregnation is the time at
which RPUF samples retain the maximum quantity of P-N additives with optimum time
period. Optimum impregnation time was investigated by impregnating the RPUF samples
with 100% P-N additives solution concentration from 10–60 min. with an increment of 10
min. at the ambient conditions. Retention is the quantity of P-N additives solution
concentration absorbed by the RPUF samples and subsequently retained in it. Retention of
RPUF samples was investigated by impregnating the 30 samples for optimum time with 10-
100% P-N additives concentrations with an increment of 10%. The effects of P-N additives
concentration and impregnation time on retention were studied by impregnating the 180
RPUF samples into the P-N additives solution concentration ranging from 10–100% and
every three samples were removed from the solution at an interval of 10 min. The effect on
the density of RPUF samples was observed by impregnating the samples for optimum time
with 10-100% P-N additives concentrations with an increment of 10%. After complete
impregnation, RPUF samples were removed from their respective P-N additives solution
concentration and allowed to dry for 24 hours at room temperature. P-N additives solution
concentration and optimum impregnation time of RPUF samples (RPUF-P-N) are shown in
Table 4. In the sample code, P-N denotes the phosphorus-nitrogen additives composition
concentrations used for impregnation. RPUF samples impregnated with P-N additives are
shown in Figure 1(a). RPUF and RPUF-P-N samples with maximum retention were prepared
for SEM. The flammability characteristics of RPUF and RPUF-P-N samples of dimensions
1505013 mm were investigated by impregnating the three samples with each P-N additives
composition concentrations ranging from 0-100% with an increment of 10%. After
impregnation the RPUF samples were removed from the solution and dried for 24 hours at
room temperature. Dried RPUF samples were marked across their width by a line (gauge
mark) 25 mm from one end.
Sample codes
(RPUF-P-N)
Impregnated with P-N additives based composition
P-N Concentration
(%)
Water
(%)
RPUF-0.0 0.0 0.0 0.0
RPUF-P-N 10 90 20
RPUF-P-N 20 80 20
RPUF-P-N 30 70 20
RPUF-P-N 40 60 20
RPUF-P-N 50 50 20
RPUF-P-N 60 40 20
RPUF-P-N 70 30 20
RPUF-P-N 80 20 20
RPUF-P-N 90 10 20
RPUF-P-N 100 0.0 20
2.3. Measurements
Impregnation time
(min)
P-N additives impregnation extent to the RPUF samples mainly depends upon the
concentration, impregnation time and retention. These three parameters are linked to each
other in which impregnation time depends upon the maximum retention, and retention

depends on both concentration and impregnation time. Optimum impregnation time was
measured on the basis of maximum P-N additives retention attained by the RPUF samples
with respect to time. Further, optimum impregnation time on the basis of maximum retention
of every three RPUF-P-N samples was calculated and averaged. Retention on each P-N
additives concentrations were also calculated and averaged. The density of conventional
RPUF and RPUF-P-N samples was measured according to ASTM D1622. The size
(lengthwidththickness) of the specimen was 303030 mm respectively. RPUF and
RPUF-P-N specimens were conditioned at 25 0 C and 55% relative humidity for 48 hours prior
to their density measurement. The density of five specimens per sample were measured and
averaged. The morphology of RPUF and RPUF-P-N samples was observed with LEO (438
VP, UK) scanning electron microscopy (SEM). The samples were cryogenically fractured
and gold coated to render them conductive prior putting under scanning observation. During
scanning 15 KV accelerating voltage was used. The SEM was used to observe the P-N
additives deposition on the cell walls, surfaces and the difference in the shape and size of the
cells between RPUF and RPUF-P-N samples. To define the cell size, measured cell sizes
were averaged except the sizes for the largest and smallest cells. Flammability characteristics
of RPUF and RPUF-P-N samples were evaluated according to BS: 4735. The specimens were
weighed before placing horizontally on support gauge inside the non-combustible chamber.
The farthest end away from gauge mark of the specimen was exposed for 60s to 10 mm
diameter wing top fitted LPG burner of 38 mm non-luminous flame height. Exposed RPUF-
P-N samples are shown in Figure 1 (b). After complete fire exposure extent burnt, burning
rate, percent mass loss (PML) and extinction time of three specimens per sample were
measured and averaged for analysis.
(a) (b)
Figure 1. RPUF-P-N samples: (a) before flammability test and (b) after flammability test
3. Results and discussion
3.1 P-N additives composition
Chemical reactions involved in the preparation of P-N additives composition were already
studied. It was found that one mole of nitrogen additive in alkaline medium reacts with one
mole of aldehyde to form monomethylol product. Similarly to nitrogen additive-1, nitrogen
additive-2 in alkaline medium reacts with aldehyde to yield monomethylolated product.
When the amount of aldehyde is increased to two moles, the dimethylolated product is

PMUF Retention (%)
formed. The rate of dimethylolated product formation is very slow at room temperature.
When the temperature is raised in the range of 80-90 0 C, the end product was dimethylol and
no monomethylol product was formed. Thus the major intermediates in the P-N additives
composition are N, N’-dimethylolated nitrogen additive-1 and N, N’-dimethylolated nitrogen
additive-2. These dimethylolated products react with phosphorus additive to give 6membered
ring compound which acts as fire retardant by polymerization [21].
3.2 Concentration, Impregnation, Retention and Density
The add-on of phosphorus-nitrogen (P-N) additives composition to the RPUF samples was
mainly measured from P-N concentration, impregnation time and retention. Results presented
in Figure 2 show that the retention of RPUF samples was ranged from 1.98 to 64.29% when
they were impregnated with 10 to 100% P-N additives concentration for 10 to 60 min.
respectively. After 20 min. impregnation the retention of RPUF samples were ranged from
1.98 to 62.98% with 10 to 100% P-N additives concentration respectively and further up to
60 min. impregnation only 1.09% average increase in the retention was observed. This may
be possible due to the fact that the vacant cell space was fully occupied by P-N additive
composition after 20 min. of impregnation, and no enough space was left for further
impregnation at the same rate. Thus after 20 min. and up to 60 min., no appreciable increase
in the retention was observed. Therefore, 20 min. is considered as the optimum impregnation
time of RPUF samples. The retention and density of RPUF and RPUF-P-N samples
impregnated for optimum time are shown in Figure 3. As shown in Figure 3, the density
increases as the retention of RPUF-P-N samples increases. When retention of RPUF samples
increases from 2.49 to 62.98%, the density increases from 50.42 to 80.17 kg/m 3 respectively.
Thus the impregnation of RPUF samples with P-N additives composition increases their
densities up to 62.98%.
75
60
45
30
15
0
PMUF
Concentration
10 %
20 %
30 %
40 %
50 %
60 %
70 %
80 %
90 %
100 %
0 10 20 30 40 50 60
Impregnation Time (min)
Figure2. Effect of P-N
concentration and impregnation time
on retention of RPUF-P-N Samples
PMUF Retention (%)
75
60
45
30
15
0
RPUF - PMUF - Retention
RPUF - PMUF - Density
0
0 20 40 60 80 100
PMUF Concentration (%)
Figure 3. Effect of P-N concentration on
the retention and density of RPUF-P-N
samples
90
75
60
45
30
15
Density (kg/m 3 )

3.3. Morphology
The cross-sectional surfaces of RPUF and RPUF-P-N samples were observed at the similar
magnification under SEM. Micrographs of the RPUF and RPUF-P-N samples are shown in
Figure 4 (a, b). As shown in Figure 4 (a), RPUF sample has the polyhedral and spherical cell
structure of 357 m average cell size. Figure 4 (b) shows the deposition of P-N additives on
the cell surfaces in addition to the polyhedral and spherical cell structure of RPUF. The
average cell size of RPUF-P-N sample was reduced to 285 m. This suggests that the
decrease in the cell size may be due to the deposition of P-N additives on the cell walls also.
The P-N additives deposition on the RPUF skeleton is further confirmed by the fact that
polyurethane phase is optically transparent [23]. Thus P-N additives were deposited on the
cell surfaces and walls of impregnated RPUF sample.
(a) (b)
Figure 4. Micrographs of RPUF samples: (a) Control RPUF and (b) RPUF-P-N impregnated
4. Fire performance
Fire performance of RPUF and RPUF-P-N samples and their comparison is mainly measured
from extent burnt, burning rate, percent mass loss (PML) and extinction time obtained during
the fire test. All these parameters are expressed in terms of average values. The variations of
extent burnt and burning rate, PML and extinction time of RPUF and RPUF-P-N samples
with respect to P-N concentrations are shown in Figures 5 and 6 respectively. Figure 5
presents the results as expected with an increasing concentration of P-N from 0 to 100%, the
extent burnt and burning rate were decreased from 125 to 27 mm and 2.23 to 0.44 mm/s
respectively. However, exponential difference was observed between RPUF and RPUF
samples impregnated with minimum (10%) P-N concentration in their extent burnt and
burning rate which were 125 mm, 2.23 mm/s and 45 mm, 1.07 mm/s respectively. The rates
of decrease of extent burnt and burning rate are almost linear with the increase of P-N
concentration. However, when P-N concentration increases over 90% up to 100%, there is an
increase of 16.39% in the retention of RPUF-P-N, whereas, extent burnt and burning rate are
decreased only by 4 mm and 0.05 mm/s respectively. Thus there is no appreciable decrease in
the rate of extent burnt and burning rate, at the increasing rate of P-N concentration. As
shown in Figure 6, the increasing concentration of P-N from 0 to 100% reduces the PML

Extent Burnt (mm)
from 100 to 8.82%, but extinction time increases slightly from 56s to 60s respectively. RPUF
and RPUF samples impregnated with minimum (10%) P-N concentration show great
difference in their PML and extinction time which are 100%, 56s and 16.92%, 40s
respectively. The rate of PML reduction is almost linear to 90% P-N concentration and above
this PML reduces slightly as the concentration increases to 100%. RPUF samples in
flammability test are consumed up to gauge mark (125 mm) in 56s. For comparison, 56s is
considered as extinction time of RPUF. The extinction time of RPUF sample reduces to 42s
with minimum P-N concentration, however, increases to 61s with maximum concentration.
This slightly different flame extinction behavior of RPUF-P-N samples can be explained by
considering the fire retardant action of phosphorus-nitrogen additive.
250
200
150
100
50
0
0.0
0 20 40 60 80 100
PMUF Concentration (%)
During flammability test the presence of phosphorus-nitrogen additive accelerates the
decomposition of foam at lower temperature which leads to an increase in the amount of high
temperature stable char residue [7-9]. Flame extinction time is increased slightly with the
increase of P-N concentration and the combined effect of these two resulted into the
formation of large amount of stable char residue. The stabilized char residue acts as
protective thermal barrier which does not allow further flame spread. This may leads to
reduced burning rate which resulted into enhanced fire retardancy. Thus depending upon the
decrease 24.8% in extent burnt, 21.9% in burning rate and 89.7% in PML and, 46.59%
increase in the density of RPUF-P-N samples, P-N additives concentration of 90% can be
considered as optimum.
5. Conclusion
RPUF - PMUF - Extent burnt
RPUF - PMUF - Burning rate
Figure 5.Extent burnt and burning rate of
RPUF and RPUF-P-N samples
2.5
2.0
1.5
1.0
0.5
Burning Rate (mm/s)
PML (%)
0 20 40 60 80 100
PMUF Concentration (%)
In order to understand the effect of P-N composition on the structure and flammability
characteristics of RPUF, large number of RPUF samples impregnated with various
concentrations of P-N were investigated using SEM, and BS: 4735. Fire retardant chemical
composition was prepared from phosphorus-nitrogen additives. P-N additives composition
was a colorless viscous liquid miscible with water. P-N concentrations were decreased with
200
160
120
80
40
0
RPUF - PMUF - Mass loss
RPUF - PMUF - Extinction time
Figure 6. PML and extinction time
of RPUF and RPUF-P-N samples
75
60
45
30
15
0
Extinction Time (s)

the increasing water content. Retention and density of RPUF-P-N samples were increased
with the increased concentration of P-N for optimum impregnation time of 20 min. Retention
and density of RPUF samples with optimum impregnation time were increased up to 62.98%
and 80.17 kg/m 3 respectively. The results of morphology showed that the cell size of
impregnated RPUF samples was decreased from 357 to 285 m. The cell size was decreased
by the increased thickness of cell wall which may be due to the deposition of P-N on the cell
walls and surfaces. The results of extent burnt, burning rate and PML under flammability test
indicate that an optimum 90% P-N concentration is adequate to render RPUF fire retardant.
RPUF samples containing 46.59% P-N retention exhibit 46.6% increase in the density,
however, remarkable decrease in extent burnt (66.25%), burning rate (90.19%) and PML
(91.18%) were observed under flammability test. Thus phosphorus-nitrogen additives
impregnation enhances the fire retardancy of RPUF which can be used for buildings
insulation with added advantage of total safety from fire.
6. Acknowledgement
The author is grateful to the Director, CSIR-Central Building Research Institute, Roorkee for
his encouragement and kind support.
References
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today, PUAI, Volume 6, Issue 2, Pages 20-23.
2. Adel A. A, Ismail M. B. (2005), “Comparison of Thermal Conductivity Measurements of
Building Insulation Materials under Various Operating Temperatures”, Journal of
building physics, Volume 29, No. 2, pages 171-184.
3. Oertel, G. (1985), Polyurethane Handbook, Hanser Publisher, New York.
4. Szycher, M. (1999), Handbook of Polyurethanes, CRC Press, Washington DC.
5. Lefebvre, J., Bastin, B., Bras, M. L., Duquesne, S., Paleja, R., Delobel, R. (2005),
“Thermal stability and fire properties of conventional flexible polyurethane foam
formulations”, Polymer Degradation and Stability, Volume 88, Pages 28-34.
6. Tang, Z., Valer, M., Anderson, J. M., Miller, J. W., Listemann, M. L., McDaniel, P. L.,
Morita, D. K., Furlan, W. R. (2002), “Thermal degradation behavior of rigid polyurethane
foams prepared with different fire retardant concentrations and blowing agents”, Polymer,
Volume 43, Pages 6471-6479.
7. Levchik, S. V., Weil, E. D. (2004), “Thermal decomposition, combustion and fireretardancy
of polyurethanes-a review of the recent literature”, Polymer International,
Volume 53, Pages 1585-1610.
8. Pielichowski, K., Kulesza, K., Pearce, E. M. (2003), “Thermal Degradation Studies on
Rigid Polyurethane Foams Blown with Pentane”, Journal of Applied Polymer Science,
Volume 88, Pages 2319-2330.
9. Leu, T. S., Wang, C. S. (2004), “Synthesis and Characterization of a Novel Nitrogen-
Containing Flame Retardant”, Journal of Applied Polymer Science, Volume 92, Pages
410-417.
10. Yang, C. P., Hsiao, S. H. (1988), “Flameproofed polyesters prepared by direct
polycondensation of aromatic dicarboxylic acids and brominated biphenyls with tosyl
chloride and N, N-dimethylformamide in pyridine”, Journal of Applied Polymer Science,
Volume 36, Pages 1221-1232.

11. Duquesne, S., Bras, M. L., Bourbigot, S., Delobel, R., Camino, G., Eling, B., Lindsay, C.,
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Ammonium Polyphosphate”, Journal of Applied Polymer Science, Volume 82, Pages
3262-3274.
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flame retardants on fire behavior of modified PIR/PUR polymers”, Polymer Degradation
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Polymer Degradation and Stability, Volume 78, Pages 167-173.
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foams: use of different charring agents”, Polymer Degradation and Stability, Volume 78,
Pages 341-347.
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PUR foams: use of an halogen-free flame retardant”, European Polymer Journal, Volume
39, Pages 263-268.
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copolymers II. Thermal behavior and mechanism of degradation”, Polymer International,
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retardant properties of phosphorus-containing polymers based on poly(4hydroxystyrene)”,
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219-237.

Thermal Insulation Materials for Energy Efficient Buildings
Abstract
Omna Suman* and Dr. B. M. Suman**
* M.Tech student, MNIT Allahabad
** CSIR- Central Building Research Institute, Roorkee
Corresponding Author, Email: omnasuman@gmail.com
Insulation in buildings is assuming tremendous importance and has a potential to reduce
energy consumption to an extent of 15-18 %. A number of categories and range of insulation
materials can be installed in roof, floor and walls of the building. Optimum level of building
insulation not only helps lower monthly energy bills, but also adds to the overall comfort.
Heat balance of a building would reveal that at least 15 to 20 % of the heat ingress into a
building can be through walls and roof. Hence, insulating walls and roof is extremely critical
in the energy performance of a building. Insulation helps maintain comfort temperature by
reducing leakages. The paper deals with different categories and range of insulation
materials, merits, demerits and their application in buildings.
Keywords: Thermal insulation, building insulation materials, spray foams, fiberglass, merits
and demerits of insulation.
1. Introduction
The materials, that are used to reduce heat transfer by conduction, radiation or convection and
are employed in varying combinations to achieve the desired outcome are known as thermal
insulation. Building insulation materials are thermal insulation used in the construction or
retrofit of buildings. Builders, Architects and Service Consultants alike are constantly looking
for ways to enhance energy-efficiency in buildings. Buildings without insulation and air-tight
envelope can result in major energy wastage. Use of thermal insulation is an important
method for reducing heat flow from a hot system or into a cold system. Its primary functions
are,
i. Conservation of energy
ii. Better process of control
iii. Anti condensation, and
iv. Fire protection.
The most important property of a thermal insulating material is the thermal conductivity
value. Lower the thermal conductivity better will be the thermal insulation performance. In
general thermal conductivity is a function of density, mean temperature and moisture content.

Thermal Insulation may be categorized by its composition of material, by its form of
structural or non-structural, or by its functional mode of conductive, radioactive or
convective. Non-structural forms include blankets, loose-fill, spray foam, and panels.
Structural forms include insulating concrete forms, structured panels, and straw bales.
Sometimes a thermally reflective surface called a radiant barrier is added to a material to
reduce the transfer of heat through radiation as well as conduction. The advantages and
disadvantages of different types of thermal insulations such as, Spray foams insulation),
closed-cell over open-cell foams, Insulating concrete forms, Rigid panel, Structural insulated
panels, Fiberglass batts and blankets (Glass wool), Natural fiber, Cotton batts (Blue Jean),
Loose-fill (including cellulose), Aerogels, Straw bales, Reflective insulation and radiant
barriers, Types of reflective insulation, Hazardous and discontinued insulation, Spray
polyurethane foam (SPF), Fiberglass, Loose-fill cellulose are described in detail. Their
suitable applications are also suggested in brief.
2. Types of thermal insulation
Thermal insulation can be divided on number of parameters. Such as, Structural nonstructural
form, Composition, Functional mode, Radiant barrier, Close cell and Open cell,
Reflectivity, Hazardous and discontinued insulation, Spray foam, Fiberglass, Loose-fill
cellulose etc.
3. Factors affecting the insulation
The factors affecting to thermal insulation are, Climate, Ease of installation, Resistance to
degradation from compression, moisture, decomposition, Ease of replacement at end of life,
Cost effectiveness, Toxicity, Flammability, Environmental impact and sustainability. Often a
combination of materials is used to achieve an optimum solution and there are products
which combine different types of insulation into a single form.
Thermal Conductivity of single layered homogeneous material is determined by the
Automatic Guarded Hot Plate apparatus. Thermal resistance (R) can be computed by dividing
the length with thermal conductivity of the material. It is the property which resists heat flow
and can be determined by the following equation.
Where, lo and Ko are thickness and thermal conductivity of the first layer and so on.
Overall thermal transmittance of the material is determined by putting the value of thickness,
thermal conductivity and inside and outside surface heat transfer coefficients. It is determined
as,

4. Merit and demerit of insulation
4.1. Spray foams (insulation)
Spray foam is a type of insulation that is sprayed in place through a gun. Polyurethane and
Isocyanate foams are applied as a two-component mixture that comes together at the tip of a
gun, and forms an expanding foam. Spray foam insulation is sprayed onto concrete slabs, into
wall cavities of an unfinished wall, against the interior side of sheathing, or through holes
drilled in sheathing or drywall into the wall cavity of a finished wall.
Advantages
Blocks airflow by expanding and sealing off leaks, gaps and penetrations.
Can fill wall cavities in finished walls without tearing the walls apart (as required with
batts).
Works well in tight spaces (like loose-fill, but superior).
Provides acoustical insulation (like loose-fill, but superior).
Expands while curing, filling bypasses, and providing excellent resistance to air
infiltration (unlike batts and blankets, which can leave bypasses and air pockets, and
superior to some types of loose-fill. Wet-spray cellulose is comparable.).
Increases structural stability (unlike loose-fill, similar to wet-spray cellulose).
Can be used in places where loose-fill cannot, such as between joists and rafters.
When used between rafters, the spray foam can cover up the nails protruding from the
underside of the sheathing, protecting your head.
Can be applied in small quantities.
Disadvantages
The cost can be high compared to traditional insulation.
Most foams, with the exception of cementitious foams, release toxic fumes when they
burn.
Depending on usage and building codes and environment, most foams require
protection with a thermal barrier such as drywall on the interior of a house. For
example a 15-minute fire rating may be required.
Although CFCs are no longer used, many use HCFCs or HFCs as blowing agents.
Both are potent greenhouse gases, and HCFCs have some ozone depletion potential.
Most, such as Polyurethane and Isocyanate insulation, contain hazardous chemicals
such as benzene and toluene. These are a potential hazard and environmental concern
during raw material production, transport, manufacture, and installation.
R-value will diminish slightly with age, though the degradation of R-value stops once
equilibrium with the environment is reached. Even after this process, the stabilized R-
value is very high.
4.2. Structural insulated panels (SIPs)
These are also called stressed-skin walls, use the same concept as in foam-core external
doors, but extend the concept to the entire house. They can be used for ceilings, floors, walls,
and roofs. The panels usually consist of plywood, oriented strand board, or drywall glued and
sandwiched around a core consisting of expanded polystyrene, polyurethane, poly

isocyanurate, compressed wheat straw, or epoxy. SIPs come in various thicknesses. When
building a house, they are glued together and secured with lumber. They provide the
structural support, rather than the studs used in traditional framing.
Advantages
Strong. Able to bear loads, including external loads from precipitation and wind.
Faster construction than stick-built house. Less lumber required.
Insulate acoustically.
Impermeable to moisture.
Can truck prefabricated panels to construction site and assemble on site.
Create shell of solid insulation around house, while reducing bypasses common with
Stick-frame construction. The result is an inherently energy-efficient house.
Do not use formaldehyde, CFCs, or HCFCs in manufacturing.
True R-values and lower energy costs.
Disadvantages
More expensive than other types of insulation.
Thermal bridging at splines and lumber fastening points unless a thermally broken
spline is used (insulated lumber).
4.3. Cellulose insulation
Loose-fill materials can be blown into attics, finished wall cavities, and hard-to-reach areas.
They are ideal for these tasks because they conform to spaces and fill in the nooks and
crannies. They can also be sprayed in place, usually with water-based adhesives. Many types
are made of recycled materials and are relatively inexpensive.
Advantages
Cellulose insulation is environmentally preferable (80% recycled newspaper) and
safe. It has a high recycled content and less risk to the installer than fiberglass (loose
fill or batts).
R-Value 3.4 - 3.8 (RSI-0.60 - 0.67) per inch (imperial units)
Loose fill insulation fills the wall cavity better than batts. Wet-spray applications
typically seal even better than dry-spray.
Class I fire safety rating
No formaldehyde-based binders
Not made from petrochemicals nor chemicals with a high toxicity
Disadvantages
Weight may cause ceilings to sag if the material is very heavy. Professional installers
know how to avoid this, and typical sheet rock is fine when dense-packed.
Will settle over time, losing some of its effectiveness. Unscrupulous contractors may
"fluff" insulation using fewer bags than optimal for a desired R-value. Dry-spray (but
not wet-spray) cellulose can settle 20% of its original volume. However, the expected
settling is included in the stated R-Value. The dense-pack dry installation reduces
settling and increases R-value.

R-values stated on packaging are based on laboratory conditions; air infiltration can
significantly reduce effectiveness, particularly for fiberglass loose fill. Cellulose
inhibits convection more effectively. In general, loose fill is seen as being better at
reducing the presence of gaps in insulation than batts, as the cavity is sealed more
carefully. Air infiltration through the insulating material itself is not studied well, but
would be lower for wet-spray insulations such as wet-spray cellulose.
4.4. Reflective insulation
Reflective insulation is commonly made of either aluminum foil attached to some sort of
backing material or two layers of foil with foam or plastic bubbles in between creating an
airspace to reduce convective heat transfer also. The aluminum foil component in reflective
insulation will reduce radiant heat transfer by up to 97%. As reflective insulation incorporates
an airspace to reduce convective heat flow, it carries a measurable R-Value.
Advantages
Very effective in warmer climates
No change thermal performance over time due to compaction, disintegration or
moisture absorption
Thin sheets takes up less room than bulk insulation
Can act as a vapor barriers
Non-toxic/non-carcinogenic
Will not mold or mildew
Radon retarder, will limit radon penetration through the floor
Disadvantages
Must be combined with other types of insulation in very cold climates
May result in an electrical safety hazard where the foil comes into contact with faulty
electrical wiring
4.5. Fiberglass
Fiberglass is the most common residential insulating material, and is usually applied as batts
of insulation, pressed between studs. Health and safety issues include potential cancer risk
from exposure to glass fibers, formaldehyde off-gassing from the backing/resin, use of
petrochemicals in the resin, and the environmental health aspects of the production process.
Green building practices shun Fiberglass insulation. Rock and slag wool, also known as
mineral wool or mineral fiber, made from rock (basalt, diabase), iron ore blast furnace slag,
or recycled glass. Clumps and loses effectiveness when moist or wet, but does not absorb
much moisture, and regains effectiveness once dried. Older mineral wool can contain
asbestos, but normally this is in trace amounts. Fiberglass, usually pink, yellow, or white,
loses effectiveness when moist or wet, but does not absorb much water, nonflammable.
Advantages
Higher R-Value than typical fiberglass batts
Recycled content, no formaldehyde or other toxic substances, and very low toxicity
during manufacture (only from the polyolefin)

May help qualify for LEED or similar environmental building certification programs
Fibers do not cause itchiness, no cancer risk from airborne fibers
Disadvantages
Difficult to cut. Some installers may charge a slightly higher cost for installation as
compared to other batts. This does not affect the effectiveness of the insulation, but
may require choosing an installer more carefully, as any batt should be cut to fit the
cavity well.
Even with proper installation, batts do not completely seal the cavity against air
movement (as with cellulose or expanding foam).
Still requires a vapor retarder or barrier (unlike cellulose)
5. Hazardous and discontinued insulation
5.1. Spray polyurethane foam (SPF)
All polyurethane foams are composed of petrochemicals. Foam insulation often uses
hazardous chemicals with high human toxicity, such as isocyanates, benzene and toluene.
The foaming agents no longer use ozone-depleting substances. Personal Protective
Equipment is required for all people in the area being sprayed to eliminate exposure to
isocyanates which constitute about 50% of the foam raw material.
5.2. Asbestos
Asbestos once found common use as an insulation material in homes and buildings because it
is fireproof, a good thermal and electrical insulator, and resistant to chemical attack and wear.
It has been found that asbestos can cause cancer when in friable form (that is, when likely to
release fibers into the air - when broken, jagged, shredded, or scuffed). Some people exposed
to asbestos develop cancer. When found in the home, asbestos often resembles grayish-white
corrugated cardboard coated with cloth or canvas, usually held in place around pipes and
ducts with metal straps. Things that typically might contain asbestos:
Boiler and furnace insulation.
Heating duct wrapping.
Pipe insulation ("lagging").
Ducting and transit pipes within slabs.
Acoustic ceilings.
Textured materials.
Resilient flooring.
Blown-in insulation.
Roofing materials and felts.
6. Energy saving by application of different types of insulation
Study carried out earlier for evaluation and performance of roof and wall insulation applied in
building to assess its energy saving potential in air conditioned building during summer
season show that more than 29 % energy can be saved by treating a building with exterior

insulation finishing system. This study had been undertaken for a period of one year for a
single zone building in composite climate of India. The study has been undertaken in two
identical rooms one is being untreated and other by treating with good insulation. Similarly,
the provision of Heat Reflective Paint insulation with thermal resistance 0.0012m 2 h/W
treatment on roof and wall brings down the indoor surface temperature of wall and roof by
2.2 to 6 o C in comparison to the room with white wash application. The energy saving was
recorded of the order of 5.56% in treated room over reference room when walls of the room
were treated with heat reflective paint and white wash was applied on walls of the reference
room. As per this study, energy saving was recorded of the order of 12.73% when both roof
and walls of treated room was treated by heat reflective paint and white wash was applied on
walls and roof of the reference room. It means 7.16% electrical energy may have been saved
by treating roof only with heat reflective paint over conventional white wash
7. Conclusion
The paper discussed almost each category of thermal insulation and its merits and demerits.
Some of them are suitable for wall insulation, some for roof and some for floor insulation.
The advantage and disadvantages of Spray foams (insulation), Structural insulated panels
(SIPs), Cellulose insulation, Reflective insulation, Fiberglass are discussed in detail. The
Hazardous and discontinued insulation, Spray polyurethane foam (SPF), Asbestos are
hazardous materials and their limited use have been described. Energy saving by reflective
paint on external surfaces of building can be up to 7.16%. Similarly, a simulation study show
that 29% energy can be saved by treating and AC building with exterior insulation finishing
system.
References
1. Performance Evaluation of Resin Bonded Rockwool mattresses for
thermal conductivity. Project report no. E(S)-4527, (2009), pages 7-9.
2. IS: 3346 -1980, Method for determination of thermal conductivity of
thermal insulation materials, (Guarded Hot Plate method).
3. www.fao.org/docrep/006/y5013e/y5013e08.htm.

Energy and Environmental Concerns in Building Materials
Abstract
Manjit Singh
Former Scientist, CSIR-Central Building Research Institute, Roorkee
Corresponding Author, Email: manjit_csr@rediffmail.com
Production of traditional building materials such as cement, steel, brick, lime and pozzolana
consume enormous energy in the form of coal, oil, electricity, steam, etc. The energy
requirement varies extensively depending upon the level of automation involved in the
manufacturing of the building materials. The knowledge of energy requirement in the
production of building materials using various materials including hazardous industrial
wastes lays the foundation for fresh research and development in the production technology
so that further energy may be curtailed to economize the process. Saving of energy is
significant in the case of green house gases emission (GHG) into the atmosphere and
reducing cost of materials. Energy consumption in the production of basic building materials
(such as cement, steel, aluminum, gypsum, etc.) and different types of materials used for
construction has been discussed. The energy consumed in different types of masonry mortars
based on industrial wastes and gypsum plaster and gypsum products has been detailed. The
use of geopolymers from natural clay and other resources and making calcium bricks at
lower energy compared to burnt clay bricks are presented in the paper.
1. Introduction
In recent years, awareness of environmental aspects has grown in the building and
construction sector. Manufacturing processes of building materials contribute greenhouse
gases (GHG) like CO2 to the atmosphere. There is a great concern and necessity in reducing
the GHG emission into the environment in order to control adverse ecological effect. Energy
requirements for production and processing of different building materials and the CO2
emissions and the implications on environment have been studied by Buchanan and
Honey[1], Suzuki et al.[2], and Debnath, et al.[3], etc. These studies belong to New Zealand,
Japan and India. Indian construction industry is one of the largest in terms of employing
manpower and quantity of materials produced (cement, brick, steel, timber and other
materials). Construction sector in India is responsible for major input of energy resulting in
the largest share of CO2 emissions (22%) into the atmosphere. Demand and supply gap for
residential buildings is increasing every year (20 million units in 1980 to 40 million units in
2000. Cement (>290 million tones per annum), steel (>15 million tones per annum) and
bricks (> 90 billion per annum) are the largest and bulk consumption commodities in the
Indian construction industry. This paper deals with detailed embodied energy in alternative
building materials and techniques and compares the embodied energy in buildings built with
traditional and the new building techniques. Energy saving through use of some industrial
wastes are highlighted.
1

2. Background
Energy and CO2 implications of building construction in New Zealand has been examined by
Buchanan and Honey. The study indicates that significant decrease in GHG gases like CO2
emissions may result from a shift in construction from steel, concrete and aluminium to
greater use of timber in construction. Suzuki et. al threw light on energy consumption and
CO2 emission due to housing construction in Japan. Total energy required and CO2
emissions/m 2 of area of different types of constructions have been compared. Energy
consumption for the construction of steel and reinforced concrete (RC) multi-storeyed family
houses has been found to be 8-12 GJ/m 2 , whereas, for timber single family houses it is 3
GJ/m 2 . They conclude that wooden houses score over other types of constructions in terms of
energy requirements and GHG gases like CO2 emissions. Studied to estimate the energy
requirements for different types of residential buildings are reported in India[4]. Energy in
buildings can be grouped into two types: 1) energy for the maintenance / servicing of a
building during its useful life, and 2) energy capital that goes into production of a building
(embodied energy) using various building materials. Examples of buildings using alternative
building technologies can be found in India and elsewhere.
Embodied energy can be divided into: 1) energy consumed in the production of basic
building materials, 2) energy needed for transportation of the building materials, and 3)
energy required for assembling the various materials to form the building. This paper
presents these aspects of embodied energy.
It is hoped that the information provided in this paper could help in selecting energy efficient
building technologies and building systems based on embodied energy as well as various
types of useful industrial wastes thereby reducing cost of materials and also GHG gas like
CO2 emission into atmosphere.
3. Energy in building materials
3.1 Basic building materials
Portland cement represents one of the major materials consumed in bulk quantities for
building construction. Energy of cement arises from the use of coal in the rotary kilns and
energy needed for crushing and grinding of the clinker. In India, cement is manufactured by
employing both the wet (old cement plants) and dry (new plants) process. Wet process used
in old cement plants loads to an energy consumption of 7.5 MJ/kg of cement, whereas
modern plants employing pre calcination and dry process consume 4.2 MJ/kg of cement. The
value of 5.85 MJ/kg of cement given in Table 1 represents the average value of 7.5 and 4.2
MJ. The average value of 5.85 MJ/kg of cement has been used in the computation of energy
in various components and systems.
Hydrated lime consumes 3-6 MJ of thermal energy/kg, which is about the same as that for
cement. High-energy consumption for lime can be attributed to low thermal efficiency of
small scale kilns employed for lime burning in India. LP cements are effective alternative to
Portland cement, mainly for secondary applications such as masonry mortar, plastering,
base/sub-base for flooring, roads, etc. A typical LP cement will consist of 30% lime, 60%
pozzolana and 10% calcined gypsum, all three being inter-ground in a ball-mill. Such cement
possesses an energy content of 2.5 MJ/kg.
2

Aluminium and steel are the two high-energy metals commonly used in building
construction. Even though aluminium is much lighter than steel, consumes six to seven times
more than the energy of steel per unit weight. The use of aluminium doors and windows can
contribute significantly to the energy input into a buildings. The use of these metals should
be kept minimum in the buildings. Glass is another energy intensive material used in
buildings. Its energy consumption is next to steel, but its density is much lower than steel.
3.1.1 Masonry building materials
Masonry walls is the major energy consuming components of the building, particularly in
case of load bearing masonry structures. Varieties of materials are used for the construction
of masonry walls. The building blocks viz. stone burnt clay brick, soil-cement block, hollow
concrete block and steam cured mud block were examined in detail.
3.1.2 Stone block
Natural building stones have been extensively used for the building construction in India and
elsewhere. In India, stone blocks are generally produced by splitting the hard natural stone
into convenient sizes. Stone blocks of size approximately about 180 mm x 180 mm x 180
mm are generally used in the Indian construction practices.
3.1.3 Soil-cement blocks
These are produced by pressing a wetted soil-cement mixture into a solid block using a
machine (manually operated or mechanized) and then cured. Soil-cement blocks produced by
employing manually operated machines have become popular in India and elsewhere[5-6].
Detailed information on the production, properties and masonry using soil-cement blocks can
be obtained from the references[7-8]. Energy content of the blocks is mainly dependent upon
the cement content. Soil-cement blocks used for the load bearing masonry buildings
generally contain cement content of about 6-8% and posses energy content of 2.6-3.56 MJ
per block of size 230 mm x 190 mm x 100 mm.
3.1.4 Hollow concrete blocks
These are light weight low density blocks very commonly used for the construction of nonload
bearing filler walls in multi-storeyed buildings in India. They are also used for the
construction of load bearing masonry walls to a limited extent. The basic composition of the
blocks consists of cement, sand and coarse aggregates (~6 mm size). The energy content of
the block will mainly depend upon the cement percentage. Energy spent for crushing of
coarse aggregate will also contribute to the block energy. The cement percentage generally
varies between 7 and 10% by weight. Quality of the block, particularly compressive strength
is the deciding factor for cement percentage. Energy content of the hollow concrete block of
size 400 mm x 200 mm xx 200 mm may be in the range of 12.3-15.0 MJ.
3.2 Energy in transportation of building materials
Transportation of materials is a major factor in the cost and energy of a building. Bulk of the
building materials in urban and semi-urban centres are transported using trucks in India. The
transportation distance may vary depending upon the location of construction activity. In
urban areas, the materials travel anywhere between 10 and 100 km in the Indian sub-
3

continent. Materials such as sand aggregates are transported from a distance of 80-100 km in
the like cities. Similarly, cement and steel travel even longer distances, of the order of 500
km or more. Large quantities of cement and steel is handled through rail transport. Fancy
building materials such as marble, paints, etc. are sometimes transported from great distances
(over 1600 km) in India.Natural sand and crushed stone aggregate consume about 2.0 MJ/m 2
for every one km of transportation distance. Similarly bricks require about 2.5 MJm 2 per km
travel. Assuming steel and cement are also transported using trucks, diesel energy of 2
MJ/tonne/km is spent during transportation.
3.3 Energy in mortars
Mortar is a mixture of cementitious material and sand. It is used for the construction of
masonry as well as plastering. Cement mortar, cement-soil mortar, cement-pozzolana mortar
are used for masonry construction and plastering. Cement mortar is a common choice for
masonry and rendering works. Cement-soil mortar has been used for the construction of
SMB masonry. Cement-pozzolana and LP mortars can also be used for masonry construction
and other applications 9 . Total energy content of these four types of mortars is given in Table 1.
Table 1. Energy in Mortars
Type of mortar Proportion of materials
Cement Sand Soil
Energy m 3 (MJ)
Cement mortar 1 0 6
1270
1 0 8
1050
Cement pozzolana mortar 0.8:0.2 0 6
925
0.8:0.2 0 8
750
Cement-soil mortar 1 2 6
860
1 2 8
790
LP mortar 1(1:2) 0 3 740
Energy content: Cement -5-8 MJ/kg, Sand-175 MJ/m 3 , Pozzolana-1.75 MJ/m 3
The use of industrial wastes may save considerable energy when used as part replacement of
the blended cements i.e. PPC, PSC, masonry cement, burnt bricks, etc. Table 2 lists energy
saving through use of industrial wastes. Energy content of brick masonry is the highest with a
value of 2141 MJ 3 . Soil-cement block masonry consumes only about one-third of brick
masonry energy. Hollow concrete block masonry requires about 38-45% of the brick
masonry energy. Steam cured mud block masonry consumes about two-thirds of that needed
for brick masonry. Soil-cement block masonry is the most energy efficient among the
alternatives listed in the table.
4. Energy performance of gypsum based building materials
Gypsum has many uses, but the most important by far in the manufacture of gypsum building
plaster and plaster board and as a retarder in Portland and the blended cements which account
for the greater chunk of the gypsum produced. For use in plaster industry, the gypsum is
calcined to produce hemihydrate or anhydrite plaster forms. Ground gypsum is used as a soil
conditioner, particularly on green legumes to provide good calcium and sulphur
deficiencies in soil, to mitigate soil alkalinity and to flocculate soil particles thereby
4

improving drainage. Gypsum has important application in reclaiming barren land which has
been flooded by the sea waters, by displacing sodium ions from clay minerals and thus,
allowing these ions to be removed by percolation of ground water. Gypsum is also used as
the filler in many industries and several relevant standards (Indian) have been laid for their
proper applications.
Table 2. Energy Saving through Use of Industrial Wastes
Sl. Building material Composition Material compared Energy
No.
saving (%)
1. Portland pozzolana 75% OPC
cement
25% Flyash 100% OPC
20
2. Portland blast
furnace slag cement
3. Masonry cement
4. Lime-pozzolana
mixture
5. Calcium silicate
brick
60% OPC
40% BF Slag
50% OPC
50% Tailings/waste
Chalk
25% Lime
75% Flyash
90% FA Tailings
10% Lime(waste
source)
6. Burnt brick 75% clay 125%
Flyash
5
100% OPC
30
100% Masonry cement
(50%OPC + 50% 20
Limestone)
25% Acetylene gas 25
lime
75% Calcined brick
Burnt clay brick 30
Burnt clay brick
The importance of industrial application of gypsum is due to its conversion into variety of
calcined products i.e. hemihydrate plasters (alpha & beta) and different type of anhydrite
plasters ranging from soluble to insoluble anhydrite or dead burnt gypsum. All type of these
plasters when mixed with water, set and hardened to the dihydrate gypsum of variable
properties and form basis of the gypsum products. Off course different type of admixtures
like retarders, activators, polymers, plasticizers, super-plascitizers, flocculating agents, fibres,
etc. are added to the gypsum plaster to formulate insitu or preformed building products.
Extensive R &D efforts have been made across the world to synthesize variety of plasters,
binders, boards, tiles, blocks and many other useful building products. Based on these
researches, valuable cost effective gypsum building products covering vast technological
aspects have been launched in the market to fulfill needs of the people for ecstasy, aesthetic,
comforts and safety.
4.1 Manufacture and setting of plaster of Paris of different grades
Gypsum is used as the raw material for most of the gypsum based products used in building
construction such as plaster of Paris, building plaster, gypsum sheathing board, gypsum
backing board, gypsum partition blocks, gypsum wallboard, anhydrite or Keene’s cement etc.
Although gypsum has its greatest use in the building industry and civil construction works in
most of the developed countries like Germany, Canada, France, Australia, USA, China, etc.
its use is not yet popular in India in spite of extensive availability as mentioned above.
15

Except gypsum plaster, the production and use of other gypsum products in the country is
small. The process of Production of gypsum plaster involves calcination of raw gypsum at an
optimum temperature to drive off three quarters of water of crystallization at temperature
around 120-150 0 C. Commercially it can be manufactured by pan calcination, kettle
calcination, rotary calcinations, fluidized calcination and using vertical shaft kiln. The
manufacture of plaster of Paris therefore requires best energy of the order 0.83 x 10 6 BTU/T
or 0.21x10 6 kcal which is only one seventh of the energy needed for producing an equivalent
amount of Portland cement. CBRI has developed and installed an energy efficient gypsum
calcinator comprising of a two separate furnaces for two pans of 500 kg each. The plant has a
capacity of 8TPD. Its thermal efficiency is 70% as against 12 % for the open pan calcination.
The technology has been commercialized and also bagged NRDC award [10].
Enormous R & D work has been accomplished at Central Building Research Institute
(CBRI), Roorkee on the mineral and by-product gypsum (phospho, Fluoro, Dye industry
waste, boro gypsum) for scientific studies and industrial applications since more than three
decades. The results obtained on the investigations carried out, have been utilized for
developing technical know-how of certain industrial products and building materials [11-14].
The performance data of making various calcined phases are given Table 3.
Table 3. Performance Data for Calcined Gypsum (per metric tonne)
Phosphogypsum
Utilities Plaster of Paris Wall Plaster Anhydrite II
Fuel 1.4x10 6 BTU/
0.35x10 6 Kcal
1.6x10 6 BTU/
0.4x10 6 Kcal
Electricity 30 kWh 35 kWh 45 kWh
Fuel 0.83x10 6 BTU/
0.21x10 6 Kcal
Electricity
for
calcinations
Plaster
board
4.2 Properties of plasters
Natural Gypsum
1.2x10 6 BTU/
0.3x10 6 Kcal
15 kWh 17 kWh 30 kWh
8-11 (MJ) --- ---
6
2.0-2.2x10 6 BTU/
0.5-0.55x10 6 Kcal
1.6-1.8 x10 6 BTU/
0.4-0.45x10 6 Kcal
There are mainly two types of plaster namely α- and β hemihydrate generally used in
construction. The two varieties are identical in chemical composition but their physical
properties vary widely. The quality of a plaster is determined by its physical properties like
normal consistency i.e. water/plaster ratio, compressive strength, modulus of rupture, impact
strength, porosity etc. depending upon the actual use of the material. α-hemihydrate is denser,

has lower water/plaster ratio, higher fluctural strength, higher compressive strength and
lower porosity when compared to β-hemihydrate. The anhydrite plaster made at higher
temperatures (>700 0 C) attains quite high strength and durability. The raw gypsum and the
calcined gypsum/plaster are shown in Fig.1.
Figure1. (a) Gypsum Crystal (b) Calcined Gypsum/Plaster
4.3 Plaster boards and blocks
Plaster of Paris of uniform particle size usually of the cheaper variety namely β –hemihydrate
is mixed with water (70-80%) to form slurry and moulded in the form of boards, hollow
blocks etc. These component can be artistically finished, with design impressions or can be
coated with wall papers for a modern aesthetic look and can be utilized for non-load bearing
partitions ceilings, etc. They have better properties than the conventional partition boards
such as ply wood, asbestos sheet, gypboards, due to their thermal insulation, acoustic
properties and cheapness. CBRI has developed gypsum boards, blocks, water resisting
binders, tiles both from natural and waste phospho and other variety of gypsum. Several
assignments have been done for the industry based on phospho, fluoro, dye industry gypsum,
etc.
4.4 Gypsum anhydrite cement
Anhydrite cement is the anhydrous calcium sulphate produced by calcining gypsum at high
temperature (700-1000 0 C)[15]. It is also called Keene cement. Anhydrite plaster is ground to
a fineness of 350-400 m 2 /kg (Blaine’s) and blended with different chemical activators for
setting & strength development in the plaster. Anhydrite cement sets to a hard mass (20-360
Min.) and gives sufficient strength (30-35 MPa) which is comparable to that of Portland
cement.Plastering work (Finish and Undercoat, Mix.1:2, Anhydrite:Sand)) with this cement
gives a smooth finish and perfectly white appearance. Building bricks and flooring tiles have
been produced from the phospho and fluoro anhydrite and patent has been claimed by CBRI
[16]. Anhydrite cement can replace Portland cement in most of the indoor constructions as
well as outdoor purposes. The anhydrite binders based on water resistant formulations may
be fit for exposed situation[17].
5. Geopolymer cement
Geopolymer cement is the new state of art cement discovered by Davidovits, a French
scientist.The word ‘geopolymer’ was coined to describe the new material. ‘Geo’ meaning
earth combined with ‘polymer’ meaning many molecules. Geopolymer cement can be made
without limestone. The key ingreidients are mineral kaolinite, blast furnace slag, fly ash,
7

etc.It is the result of geosynthesis, a reaction that chemically integrates minerals, that
involves silicon-aluminium at a high pH in the presence of soluble alkali metal silicates. The
silica, aluminium and oxygen atoms react to form moleculesthat are chemically, structurally
comparable to those binding natural rock. Geopolymers cements are inorganic hydraulic
cements that are based on polymerization of minerals 18 . Geopolymers have many advantages
such as flexibility of raw materials, energy saving and environment protection, simple
separation techniques, good volume stability, quick gain of strength, excellent durability,
higher fire resistance , low thermal conductivity, etc.
6. Energy conservation in the manufacture of bricks
In a traditional building, the bricks occupy a major portion of the total building materials. It
has been realized that clay bricks alone can not meet the heavy demand for building bricks
and hence the potential for alternative material such as calcium silicate bricks (sand lime) has
been recognized. The CBRI, has done extensive work for development and production of
calcium silicate type of bricks and has developed a small capacity rotary press for
demonstration and experimental work 18 . It has been found that by experiments that sand lime
bricks are quite comparable with those of clay bricks in respect of energy consumption and
also total energy consumed in manufacturing process is less than that of clay bricks.
The sand lime bricks are produced by thoroughly mixing the sand and hydrated lime in the
ratio 90:10 by weight with small quantity of water to make semi dry mixture. The mixture is
filled in the moulds of the press where a pressure of 200-300 kg/cm 2 is applied to the mixture
followed by removal of bricks from the moulds and then autoclaving them in saturated steam
pressure at 14 kg/cm 2 for a period of 4-5 hours. While the clay bricks are manufactured by
four major operations : preparation of raw materials, mixing, shaping/extrusion and
firing/burning. By comparing the two case, it has been found that saving in total energy in the
manufacture of sand lime bricks is about 30%.
7. Concluding remarks
1. Soil-cement block is the most energy efficient among the alternative material for walling,
consuming only one-fourth of the energy of common burnt clay brick. Concrete blocks
and steam cured blocks also consume much less energy during manufacturing process
when compared to burnt clay brick. LP mortars have lowest energy content when
compared with other mortars like cement mortar, cement-pozzolana mortar, etc.
2. The hemihydrate plaster based building products like boards, blocks, binders consume
less energy than the anhydrite plaster based building materials. As compared to OPC,
gypsum (natural/waste) based building materials comparatively consume less energy and
will help in protecting the environment.
3. The production of geopolymer from slag or fly ash and its use in concrete may reduce
enormous energy compared to OPC.
4. About 30% energy can be saved in the manufacture of calcium silicate bricks vis-a vis
burnt clay bricks.
8

References
1. Buchanan, A.H., Honey, B.G.. Energy and carbon dioxide implications of
buildingconstruction. Energy and Buildings 20 (1994) pages 205-217.
2. Suzuki M., Oka T., Okada K., The estimation of energy consumption and CO2 emission
due to housing construction in Japan. Energy and Buildings 22(1995) pages 165-169.
3. Debnath, A., Singh, S.V, Singh, Y.P., Comparative assessment of energy requirements for
different types of residential buildings in India, Energy and Buildings 23(1995) pages
141-146.
4. Energy Directory of Building Materials, Development Alternatives, New Delhi, India
5. K.S, Jagdish. The Progress of Stabilized Soil Construction in India, in Proceedings of
National Seminar on Application of Stabilized Mud Blocks in Housing and Buildings,
Bangalore, India, Nov. 1988, pages 17-43.
6. Mukerji, Soil Block Presses, Report on Global Survey, German Appropriate Technology
Exchange, Dag-Hammerxjold-Weg 1, 6236.
7. B.V. Venkataraman Reddy, K.S. Jagdish, Properties of Soil Cement Block Masonry,
Masonry International 3 (2) (1989) 80-84/
8. B.V. Venkataraman Reddy, K.S. Jagdish, Influence of Soil composition on the strength
and durability of soil-cement blocks. The Indian Concrete Journal 69 (9)(1995) 517-524.
9. K.M Rao, B.C. Venkatarama Reddy, K.S. Jagdish, Influence of flexural bond strength on
the compressive strength of masonry, in : proceedings of the National Conference on
Civil Engineering Materials and Strucures. Osmania University, Hyderabad, India,
January 1995.
10 Singh, M.; Rai, M.: Autoclaved Gypsum Plaster from Selenite and By-product
Phosphogypsum, J Chem.Tech.Biotechnol, 43 (1988), pages 1-12.
11. Singh, M.; Garg M.: Investigation of Waste Gypsum Sludge for Building Materials,
Zement-Kal-Gips, 53 (2000) 6, pages 362-364.
12. Singh, M.: Utilization of By-product Phosphogypsum for Building Materials, Build.
Res.Note No.9, CBRI Publication, Roorkee, India, March, 1988.
13. Singh, M.; Garg, M.: Phosphogypsum-Fly ash Cementitious Binder-Its Hydration and
Strength Development, Cement concrete Research (USA), 25(1995) 4, pages 725-758.
14. Singh, Manjit; Trends in Global Gypsum Industry, Indian Concrete Journal, Vol.35,
No.10, 2011, pages 49-60.
15. Singh, Manjit; Durable Cost Effective Building Materials from Waste
Fluorogypsum, New Building Materials & Construction World, Vol. 17, March
2012, pages 202-217.
16. Singh, Manjit and Garg Mridul, Indian Patent No. 696/Del/2000 – A Novel High
Strength Plaster Composition and Flooring Tiles Made There from.
17. Singhvi, M.K., Mission Geopolymer and India Vision 2020: A perspective,
International Seminar & Exhibition- Cost Effectiveness in Cement Manufacture and
Construction Technological and Management Options, 11-12 January, 2005,
Mumbai, India, Vol. II, pages 58-62
18. Rai Mohan and Gupta, R.L., Energy Conservation in the Manufacture of Sand Lime
Bricks, National Seminar on Autoclaved Calcium Silicate Products, New Delhi,
January 8, 1990. Pages C-9-C-13.
9

Comparative Assessment of Energy Requirements and Carbon
Footprint for Different Types of Building Materials
and Construction Techniques
Abstract
Ashok Kumar, P.S.Chani, Rajesh Deoliya, Rajni Lakhani, and Naresh Kumar
CSIR- Central Building Research Institute, Roorkee
Corresponding Author, Email: kumarcbri@rediffmail.com
The building industry is responsible for about 30% of CO2 emission of the country. The
purpose of this paper is to provide insight into the challenges faced by building industry and
covers various approaches adopted to mitigate the CO2 emission. A study of the conventional
building materials and techniques is carried out to assess the current energy consumption and
associated CO2 emissions. Findings of the study suggest that proper sustainability in the built
environment is necessary to ensure climate security over the next decade and this can be
achieved by low carbon buildings which emit significantly less green house gases. Results
also reveal that there is a need for use of the available low – carbon & energy saving
technologies. This paper also explores a study of the innovative building materials and
techniques, to assess the current energy consumption and associated CO2 emissions. An
investigation into the energy consumed by the individual building materials as well as their
carbon emissions is computed to find out the total energy requirements and reduction in the
carbon footprint for a single storey house type to prove superiority of innovative construction
techniques developed by CSIR- CBRI, over conventional methods of construction.
Key Words: climate change, low carbon buildings, green house gases, CO2 emissions.
embodied energy,
1. Introduction
With growing concern towards climatic change and environmental pollution, various
strategies and activities have already started building up across the world [1]. It has been
identified by the International Panel of Climate Change (IPCC) that buildings are the major
contributors to global warming. In developing countries, the rate of building construction is
unprecedented, with little attention given to the impact, that the construction and operation of
these buildings will have on the environment, makes the situation even more worse [2].
Studies show that a person spends nearly 90% of his time indoor, thus building proves as the
main locus of human activities and is responsible for climate change. The main source of
green house gas (GHG) emissions from buildings is energy consumption. Energy is
consumed during the following processes: (i) manufacturing of building materials (‘embodied’
energy); (ii) transportation of these materials from production plants to building sites (‘grey’
energy); (iii) construction of the building (‘induced’ energy); and (iv) operation of the

uilding (‘operational’ energy) [3,4]. The process of construction of buildings consumes huge
amount of energy and in turn produces large volume of GHG. Construction sector in India is
contributing to 17% of the total CO2 emissions when both direct and indirect emissions are
considered. This emission comes from production and transportation of building materials
like brick, cement, steel, coarse aggregate, sand etc. Brick manufacturing using existing brick
kilns in India, which use coal as principal fuel, produces CO2 at the rate of 38 tons per one
lakh of brick. Apart from production of CO2, production of burnt clay bricks also results in
serious environmental degradation through exploitation of the top soil mainly from fertile
lands. Production processes of cement and steel are also energy intensive and huge amount of
CO2 is emitted during the process.
Emission from crude steel production in sophisticated plants is about 2.75 ton CO2 per ton of
crude steel or say 3.00 ton per ton of processed steel. Sand is another important material in
building construction and is available from natural sources like riverbeds or queries. But
transportation of the same by trucks requires energy and 0.00262 ton of CO2 is produced per
liter of diesel consumption. If it is considered that average transportation distance for sand
from the point of collection to point of use is 50 km then the CO2 emission per cubic meter of
sand will be 0.004 ton.
Considering diesel-operated machines at production point and transportation by diesel-run
trucks, we can find out that CO2 emission per cubic meter of use of stone chips is about 0.008
ton [5 -12] & [16]. Table 1 gives a brief glimpse of the environmental effects of a building.
It is transpired that the maintenance and life cycle of a building is the most harmful stage.
Hence, we have three different types of built environment to deal with i.e. new build, existing
buildings and supporting infrastructures (for transport, water/sewage, waste and energy
supply).The easiest sector to deal with first is the new build. As the buildings are built with
good life-cycle and the existing buildings are likely to remain for sometime, it is important
that they perform well in relation to CO2 emission.
Table 1. Environmental effect of buildings
Activity Environmental Effect
Mining/drilling Deforestation, land erosion, water pollution
Manufacturing/assembly Energy consumption, waste generation
Transportation/distribution Energy consumption,CO2 emission , resource use
Building CO2 emission, pollution and damage
Maintenance/life cycle Energy consumption, CO2 emission, wear and
tear and water pollution
Demolition Chemical contamination, toxicity
Recycle/waste Ground water contamination.
2. Low carbon buildings
Worldwide, the United States generates over 21% of the world's carbon dioxide emissions,
followed by China (17%), Russia (6%), Japan (5%) and India (4%). Keeping this huge

problem in mind low carbon buildings (LCB) are introduced to mitigate the climate change
[5]. The LCBs are designed to conserve resources, protect the environment and provide
healthy environment for the occupants. LCBs also provide a road map that will lead to zero
carbon building and recommends future development in relation to carbon emission and
energy in buildings. A zero carbon building has a reduced energy demand for thermal energy
and power and the supply is from renewable energy sources, integrated into buildings. Low
carbon building not only reduces its operating energy through the judicial use of renewable
resources but its embodied energy also gets offset.
It has been found by researchers [11-13] & [16] that production of building materials has a
major impact on environment. With the use of locally available materials, energy and carbon
dioxide emissions can be minimized. In India, where surplus labour force is available,
employment also increases with use the construction activities involving CO2 emission due to
labour intensive techniques. 2.1 Low Carbon Development in India. India firmly believes that
industrialized countries should fulfill the Kyoto Protocol commitment. To meet this Protocol,
there are five main policy targets to be followed: i) increase the efficiency of buildings; ii)
increase the energy efficiency of appliances; iii) encourage energy generation and distribution
companies to support emission reduction; iv) change the attitude and behavior towards
energy consumption; and v) promote the substitution of fossils fuels with renewable sources
of energy.
The enforcement of building codes is one of the policy frameworks. Results have shown that
current energy codes alone are not sufficient to achieve the reduction targets. Building codes
are always more successful when made mandatory rather than voluntary. The ongoing
research at CSIR – CBRI aims to promote the adoption and implementation of policies for
low-carbon development in India. The unplanned development in which rural villages have
been engulfed by low-quality housing and associated infrastructure, the researchers [16] have
involved strategies towards low carbon development. Modern methods of construction are
being developed, which result in efficient use of resources, less waste and better quality
control.
3. Energy intensity of building materials and carbon footprint
A carbon footprint is a total set of Green House Gas (GHG) emissions caused by an
organization, product or person. A carbon footprint is made up of the sum of two parts, the
primary footprint (home – gas, coal, electricity, oil, private & public transport etc.) and the
secondary footprint (buildings & furnishings, public & financial services, recreation &
leisure, food etc.). The primary footprint is a measure of our direct emissions of CO2 from
the burning of fossil fuels including domestic energy consumption and transportation (e.g. car
and plane). We have direct control of these. The secondary footprint is a measure of the
indirect CO2 emissions from the whole lifecycle of products we use, those associated with
their manufacture and eventual breakdown [16].
The energy requirements for production and processing of different building materials have
been studied by various researchers [4 – 14] , [16, 19] among many others and have
calculated the energy content of various building materials, and have found that for the
production or processing of different building materials, 16% of the total energy is consumed
for the raw material, 8% for manufacturing of the industrial raw material, 16% for the

manufacture of products, 10% for transportation of the products and people, 10% for human
energy, mainly workers' food, and the remaining 30% for heating.
Arabinda et.al. [12], Reddy & Jagdish [13], Rai [14], Kumar [16], and Chani [19] have
computed the energy usage of major building materials in India and have observed that
cement accounts for the highest percentage (25 - 30%), followed by bricks (10-15%), iron
and steel (7- 10%) and glass (7 - 9%) approximately. The studies reveal that the construction
cost per square meter of floor area is proportional to the energy consumption per unit area of
built space. About 0.098 ton of CO2 is produced per Giga joule of embodied energy i.e. 0.098
kg of CO2 per MJ of embodied energy and per one unit of carbon is 0. 27273. Hence, 1 Kg of
carbon burnt emits about 3.6 kg of CO2.
4. Regression equations for estimating the quantity of materials
CSIR- Central Building Research Institute (CBRI) has published equations for the estimation
of the major building material requirements (Table 2) with different floor areas for three
types of houses i.e. single storey, double storey load bearing wall residential buildings and
four storey framed structure residential buildings [12, 14, 16]. These equations are valid for
total floor area ranging from 30 to 300 m 2 for single and double storey structures, and from
120 to 400 m 2 for four storeyed structures. In order to establish a relationship between the
material requirement and the plinth area of different house types, other factors like the soil
condition, floor height, foundation etc. are kept the same. With the help of these regression
equations, the quantity of the major material required for the construction of the sub -
structure and superstructure has been estimated for a single and double storey house having
an area of 35m 2 [16]. Plan of a single storey house is shown in Figure 1.
Room
280 x 300
Room
280 x 250
Bath
110x 120
Loft above
Kitchen
210 x 180
Verandah
WC
90x120
All dimensions are in centimeters.
Ground Floor Plan
Figure 1. Typical Plan of a dwelling unit (Area 35m 2 )

Table2. Equations for material requirements in residential buildings
(A is the floor area in m 2 )
Materials Single Storey Double Storey
Bricks (1000 numbers) 2.26A + 66.8 2.15A + 63
Cement (ton) 0.153A + 0.57 0.145A + 0.54
Steel (kg) 21.3A - 314 21.97A - 305
Coarse Aggregate (m³) 0.176A - 0.21 + 0.145A + 0.178A - 0.21 + 0.075A
(all sizes)
1.5
+ 0.78
Brick Aggregate (m³) 0.113A - 0.83 0.056A - 0.42
Timber (m³) 0.019A + 0.23 0.019A + 0.23
Lime (100 kg) 0.145A - 0.35 0.073A - 0.17
Surkhi (m³) 0.052A - 0.37 0.026A - 0.18
Bitumen (kg) 1.836A - 9.0 0.918A - 4.0
Glass (m²) 0.064A - 0.73 0.064A - 0.73
Primer (1) 0.068A 0.068 A
Paint (1) 0.108A + 0.27 0.108A + 0.27
Note: The quantity of material required for the installation of electrical, mechanical,
plumbing, sewage and drainage systems is not included.
Similarly, based on the quantity of the major materials required for the construction of
different walling, roofing and other non structure items, the embodied energy and carbon
footprint has been computed [16]. The embodied energy and carbon emission computations
of the various innovative building materials and technologies are done based on the
procedure adopted by different researchers and compared with conventional materials to
prove their superiority and the values are given below in Table 3 [16]. After estimating the
quantities of major building materials required in the house, the energy cost of these materials
is assigned to the estimated quantities.
Energy consumed by these individual materials is, then, added to find out the total energy
requirement for a given floor area of single storey house. The procedure was repeated for
double storey type of house having the floor area of 35 m 2 .
The data generated through this method shows that energy used for constructing single storey
houses with load bearing structure using innovative materials and techniques (shown in
Figure 2 & Table 4, Sr. no. 5) is less than that the conventional materials used in single as
well as double storey [16, 18]. An investigation into the total quantity of the materials
estimated with the help of the CSIR - CBRI equations in the two types of houses shows that
the cost of building materials per unit of floor area decreases with an increase in the total
floor area for the two types of houses and the unit cost is lower for two storey residential
houses compared to the single storey houses [16, 17].

Table 3. Embodied energy and carbon emission of various materials and technologies
Item Description Embodied Energy Carbon Emission
Sr.
No
.
Item MJ / Kg,
MJ
/sq.m,
MJ/no.
MJ /
cu.m.
KgCO2 /
Kg/cu.m.
/no.
Carbon
Emission
Kg/unit
1. Cement average (bag 50 kg) 4.20 6300.00 0.412 0.11 kg/kg
2. Steel 42.00 330120 4.116 1.13 kg/kg
3. Cement sand mortar
(1cement : 4sand )
_ 1819.81 178.341 48.64kg/m 3
4. Cement sand mortar (1cement :
6sand )
_ 1226.15 120.162 32.77kg/m 3
5. Stabilized earth sand mortar
(1cement : 4soil : 8sand)
_ 632.21 61.957 16.90kg/m 3
6. PCC (1cement : 4sand : 8aggregate) _ 1274.30 124.882 34.06kg/m 3
7. Wire cut fire Brick Wall 23cm
thick
539.0 2345.00 229.810 62.68 kg/m 3
8. Concrete Block Wall 20 cm thick 235.0 1175.00 115.15 31.45 kg/m 3
9. Clay fly ash brick wall (22.9 x11.4
x7.6cm) and 23 cm thick in 1:6
cement mortar
372.10 1606.10 157.43 42.93 kg/m 3
10. Cement concrete block wall (30
x20 x15 cm) and 20 cm thick
268.25 1341.25 131.44 35.85 kg/m 3
11. Course Ruble stone wall (30 x20
x15 cm) and 30 cm thick
411.735 1372.45 134.500 36.68 kg/m 3
12. Sand lime brick wall (22.9 x11.4
x7.6 cm)
428.05 1861.1 182.38 49.74 kg/m 3
13. Cement concrete aerated block wall
(40 x20x 20 cm ) and 20 cm thick
170.75 853.75 83.66 22.82 kg/m 3
14. Fal – G – block wall (30 x20
x15cm)
212.25 1061.25 104.00 28.36 kg/m 3
15. R.B.C. slab roofing system (10cm
thick ) M20 Concrete
450.09 _ 44.10 12.03 kg/m 2
16. R.B. slab roofing system (10cm
thick )
480.10 _ 47.04 12.83 kg/m 2
17. Jack- Arch roofing system 515.466 _ 50.51 13.78 kg/m 2
18. RCC slab (12 cm. thick), grade of
concrete M20 (1:1.5:3)
543.63 _ 53.27 14.53 kg/m 2
19. R C. Plank and joist roofing
system(120 x 30 x 6 cm)
381.93 _ 37.42 10.21 kg/m 2
20. Brick panel roofing system size of
panel (120 x 53 x 7.5 cm) using
R.C.C. Joist of size 15 x 15 cm
427.39 _ 41.88 11.42 kg/m 2

The Figure 2 shows a comparison of the embodied energy calculations for five types of single
storey houses by using conventional and innovative materials & techniques developed at
CSIR- CBRI, Roorkee. Similar, study has been carried out for various other combinations to
prove the superiority of alternative materials developed across the country by different
organizations.
Figure 2. Comparison of embodied energy for five types of single storey houses using
conventional and innovative materials & techniques.
The Table 4 below shows the building materials and construction techniques used in
comparing the embodied energy.
Sr.
No.
Table 4. Computation of embodied energy for five types of single storey houses
Description of items / materials used in the house Embodied
energy
(MJ)
1. Traditional house using conventional materials such as brick masonry in
foundation & in walls and R.C.C. in roof. (Thickness of walls 23 cm).
2. Single storey house using stone masonry block in foundation, brick masonry in
walls and R.C. Planks and Joists in roof. (Thickness of walls 23 cm).
3. Single storey house using stone masonry block in foundation, Clay fly ash
brick masonry in walls, and Brick panel, R.C. Planks and Joists in roof.
(Thickness of walls 23 cm).
4. Single storey house using stone masonry block in foundation, stone masonry
block masonry in walls and Brick panel, R.C. Planks and Joists in roof.
(Thickness of walls 30 cm).
5. Single storey house using stone masonry block in foundation, concrete block
masonry in walls and Brick panel, R.C. Planks and Joists in roof. (Thickness
of walls 20 cm).
82178
61106
57484
50301
46395

5. Conclusions and recommendations
The review of different approaches towards reducing CO2 emission scenarios across the
world reveals that there is a lack of awareness about low cost energy efficiency measures and
lack of indicators to measure energy performance in buildings. Most of the occupants have
very limited or no knowledge about the energy saving potential of the building they are living
in. There is a gap between ‘as designed’, ‘as built’ and ‘as managed’ energy performance.
Thus, verifiable indicators are required which measure and compare energy consumption in
buildings. Study concludes that the energy efficiency improvement in buildings is considered
to be one of the major vectors of energy saving potential and mitigation of CO2 emissions.
The following recommendations, if implemented, would make a significant contribution to
about 80% reduction in emissions; i) Monitoring of private and public sector low carbon
domestic and non- domestic buildings including behavioral and occupier lifestyle monitoring
as well as energy efficiency, carbon foot print, temperature, ventilation etc. built both with
public funding and by public sector; and ii) Training and capacity building on using new
technologies, new products and new standards etc. Bricks, cement and steel are the three
major contributors to the energy cost of constructing a building.
Therefore, to reduce the indirect energy use in a building, the innovative and energy –
efficient materials and construction techniques developed by CSIR-CBRI need to be used in
all the projects and promoted by the government with additional incentives. The
investigations presented in this paper lead to the conclusion that there is a huge potential in
saving energy about 25-30% in single and double storey houses in India by using innovative
materials and techniques for the construction. This huge energy savings will contribute in
reducing the carbon footprint in the country. The outcomes of this study will be used for
furtherance of the research on multistorey and tall buildings. The results will also be used for
developing strategies for retrofitting existing buildings to achieve a certain degree of
greenness by using energy – efficient and green building materials as well as construction
techniques.
6. Acknowledgement
The research performed in this article is a part of CSIR- CBRI in - house research project on
“Development of a framework to reduce the carbon footprint and enhance the energy
efficiency in buildings”, and also forms a part of the Doctoral Research of Ashok Kumar, the
first author. The authors acknowledge the team members, especially Mr. Satypal Singh,
Project Assistant, for their contribution to the project. The work reported in this paper is
published with the permission of Director, CSIR- Central Building Research Institute,
Roorkee.
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walling elements in India”, Proceedings International conference on Civil Engineering
Practices for Sustainable Development, Pages 781 - 789.

Abstract
Construction and Demolition: Waste Recycling in India
Pinto Emerson* and Tejwant Singh Brar**
* Guru Nanak Dev University, Amritsar
**Sushant School of Art & Architecture, Ansals University, Gurgaon
Corresponding Author, Email: brartejwant@yahoo.com
Buildings are an integral part for development in any sector of economic growth and they
consume resources not only during their construction but also for operation throughout their
life. The design, construction, operation, maintenance, and ultimately the removal of
buildings consume large amounts of energy, water, and building materials, and generate large
quantities of waste, and pollute the air and water. The amount of resources consumed, waste
generated can be judged from the fact that in any development project, the component of
construction is quite large. The Indian construction industry has accounted for approximately
50% of the country's capital outlay in successive Five Year Plans, and projected investment
continues to show a growing trend. Out of 48 million tonnes of solid waste generated in
India, C&D (construction and demolition) waste makes up 25% annually. Despite this the use
of recycled material in construction is not much, which can largely be attributed to various
factors like lack of awareness on the part of designers/engineers, lack of awareness
campaigns and appreciation of using recycled materials, unorganized market of recycled
construction material, absence of a proper solid waste management system in urban areas,
lack of tax incentives and poor implementation of legislation on the use of recycled materials.
It is high time that the above said issues about the use of recycled material in construction in
our country be addressed so as to achieve economy in construction coupled with easing
burden on natural resources thereby resulting in cleaner environment.
Key Words: Sustainability, Construction and Demolition waste, Recycled materials.
1. Introduction
India having total population of over one billion and economic growth rate more than 8% is
witnessing increasing trend of urbanization due to which there is a dire need of “construction
of Roads, Railways, Airports and Power plants. India has a large and growing middle class
population out of which a large section is in need on new houses.”[1] The migration of people
from rural areas to cities result in consumption and generation of waste has put a considerable
strain on natural resources to meet the rising demand for food, water, energy, and goods and
services”[2]. With the prevailing conditions of rapid urbanization “the dependence on
energy is expected to increase further to achieve the targeted Gross Domestic Product (GDP)
growth rate of 8% during the Tenth Five-year Plan, the Government of India has granted high
priority to the energy sector. Increasing pressure of population and increasing use of energy
in different sectors of the economy is an area of concern for India. With a targeted GDP

growth rate of 8% during the Tenth Five-year Plan, the energy demand is expected to grow at
5.2%”[3]. Buildings are an integral part for development in any sector of economic growth.
Buildings consume resources not only during its construction but also for operation
throughout their life. The buildings which provide space for living, working, entertainment
and numerous other activities have direct or indirect bearing on our health and environment
in countless ways. The design, construction, operation, maintenance, and removal of
buildings consume large amounts of energy, water, and materials, and generate large
quantities of waste, and pollute the air and water. The amount of resources consumed, waste
generated can be judged from the fact that in any development project, the component of
construction is about 50%- 95%.
Table 1. Approximate Construction Component of Development Projects
S. Development project Approximate construction component
No.
expressed as %age of total project cost
1 Irrigation Head works,
dams, canals etc.
90 to 100
2 Roads and bridges 90 to 100
3 Shipyards, harbours, airports 45 to 55
4 Thermal power plants,
steelmills etc.
15 to 20
5 Shopping malls,
multiplexesetc.
35 to 40
6 Residential building 45 to 50
The share of construction industry in India’s GDP is approximately 10% and is growing
annually at a rate of 9.2%, Compared to global average of 5.5%. Although cities contribute
considerably to the economic growth of our country, urban growth and development are also
drivers of environmental degradation trends that include global warming, climate change and
biodiversity loss due to patterns of sprawling land consumption. In India the Building sector
is currently the third largest consumer of energy and building energy use is increasing by
over 9% which greatly outpaces the national energy growth rate of 4.3%. This trend has
already begun to strain the power sector with energy shortages of over 11.3% in peak demand
and a 7% supply deficit leading to power cuts and rolling blackouts that are endemic in most
cities and towns of our country. (CEA 2006)”[4] It is a general perception that industry and
transport consume maximum energy but the truth is that 30%-40% of the total energy
produced is consumed by buildings on account of lighting, HVAC etc. Another important
factor to be kept in mind is that in our country, high energy consuming materials like RCC,
Bricks, Glass, etc. are used which considerably strain the environment. Uncertain climatic
changes, ever widening gap between demand and supply of energy, dearth of resources and
green house gas (GHG) emissions are some of the ill effects the construction activity has
caused till date and the conditions are likely to deteriorate further if timely measures are not
taken. As stated earlier, there is a major boom in the construction Industry in our country
which is going to stay for another two decades. Current economic growth rate has
necessitated the development of infrastructure in a big way. “In property terms, this new
demand translates into over 12 million homes, 600 shopping malls, 80 million square feet of
offices and 200 townships, along with airports, hotels, hospitals and schools, all slated for
construction by 2010”[5] It is further projected that “the commercial sector will grow at 7%
annually up to the year 2030. Currently India has only 200 million square meters of installed
base and by 2030 it is expected that 869 million square meters of additional space will be

constructed. Or in other words 70% of the commercial buildings are yet to take place”[6].So
the rapid rate of urbanization coupled with increasing construction activity is bound to affect
the energy production. The above mentioned figures make it amply clear that there is a great
market potential for green buildings in India. “Considering the magnitude of construction
work (projected) in the next two decades, India has emerged as one of the world’s top
destinations for green buildings. This is opening up a wide range of opportunities in urban
planning, architecture and engineering design, building services, building materials and
equipment manufacture”[7]. Besides this, the cheap availability of labor from highly
unorganized labor sector is attracting people to construction Industry in India.
2. Components of green building [8]
Human efficiency is directly related to the environment he is living or working in, so green
buildings are a befitting reply to the spatial requirements to carry out various activities.
Objective of the Green buildings is to reduce the overall impact of the built environment on
human health and the natural environment by
1. Site planning using best suited orientation at a given site
2. Building Envelop design that that reduces energy requirements for space conditioning
(HVAC, Lighting etc.)
3. Integration of renewable energy sources to generate energy onsite.
4. Environment friendly Building Materials and Specifications.
5. Sustainable Construction methods.
6. Protecting occupants health and improving workers productivity
7. Reducing waste, pollution and environmental degradation, efficient water and waste
management
8. Efficiently using water and other resources
The Overall material/product selection criteria[9] for the construction of Green Buildings
include Resource efficiency, Indoor air quality, Energy efficiency, Water conservation and
Affordability, so recycled construction materials from Construction and Demolition waste are
the best option instead of going for the new materials. The recycling of the Construction
waste back into the new construction not only eases burden on the already depleting natural
resources but also will decrease the requirements of disposing off the waste by incineration
and other methods thereby reducing environmental pollution which is endemic to most of the
Indian cities. Currently the building Industry contributes about 22% of CO2 emissions The
current annual consumption in the manufacturing of building materials is 2500 X 106 GJ or ~
150 X 106t of coal equivalent and is likely to go up to 5000 X 106GJ by 2020[10]. The
greatest advantage of using recycled construction materials is that their embodied energy is
preserved. The energy consumed in making the construction and demolition waste fit for
reuse is considerably less than the energy used in the actual manufacturing of the same
material. Aluminum, for example, can be recycled for 15–25% of the energy required to
transform raw ore into finished goods [11]. Majority of the building materials like brick,
concrete, glass, plastics, metals and wood can be recycled. Further the recycling of the
construction waste back into the new construction or for manufacturing new construction
materials by using construction waste as raw material, involves the separation, storing and
final disposal requires manpower, so there is a tremendous opportunity for employment for
skilled as well unskilled people. Another added advantage of using the material salvaged
from construction waste over new construction material is highly economical as is clear from
the graph below.

The reuse of building materials commonly saves about 95% of embodied energy which
would otherwise be wasted. Some materials such as bricks and tiles suffer damage losses up
to 30% in reuse. The savings by recycling of materials for reprocessing varies considerably
with savings up to 95% for aluminium but only 20% for glass. Some reprocessing may use
more energy, particularly if long transport distances are involved” [12].
Table 2. Comparison of embodied energy content of common building materials from
Primary vs. Secondary sources. (All figures are for MJ/Kg)
Material Virgin Recycled
Aluminium 196 27
Polyethylene 98 56
PVC 65 29
steel 40 18
3. Construction waste generation in India
“Out of 48 million tonnes of solid waste generated in India, C&D waste makes up 25%
annually. Estimated waste generation during construction is 40 kg per m 2 to 60 kg per m 2 .
Similarly, waste generation during renovation and repair work is estimated to be 40 kg per m 2
to 50 kg per m 2 . The highest contribution to waste generation comes from the demolition of
buildings. Demolition of pucca (permanent) and semi-pucca buildings, on average generates
between 300kg per m 2 and 500 kg per m 2 of waste, respectively”[13]. The recycling of
construction waste in India to a great extent is in a very haphazard manner with some of the
building items from like bricks, tiles, wood, metal etc. which are easier to handle are re-used
and recycled, while the components like concrete and masonry whose removal and final
disposal is labor intensive, is not properly recycled and reused in India. The fine dust like
material (fines) from C&D waste is presently not being used and thus wasted [14].

Table 3. For materials not available locally, the transportation cost can form a significant
part of its embodied energy.
4. Scotland
Management of construction waste – International scene Denmark
Zero Waste Plan for Scotland has a long term Mission and vision which clearly states that
“This Zero Waste Plan is intended to create a stable framework that will provide confidence
for the investment necessary to deliver a zero waste Scotland over the next 10 years. It does
this by setting out a Mission and Vision for the long term.
Within that context the Plan sets strategic directions in the key areas of activity for the
medium term up to 5 years, with specific actions setting out immediate priorities.” and the
Mission is “To achieve a zero waste Scotland, where we make the most efficient use of
resources by minimising Scotland’s demand on primary resources, and maximising the reuse,
recycling and recovery of resources instead of treating them as waste” [16].

Table 3. Summary[15] of Measures used to Influence the Management of C&D Waste in
Denmark, Source: Symonds (1999)
5. Management of construction waste in India
The management of construction waste in India is not as organized as in the west. The
increasing pace of urbanization coupled with a steep increase in construction activity is
exerting significant pressures on already stretched Municipal Solid Waste Management
(MSWM) systems across cities in India. This problem is attaining gigantic proportions due to
lack of adequate capacity, institutional, financial capabilities and skilled resources in
collection, transportation, processing and final disposal. The owner or demolition contractor,
in order to get rid of the construction waste ( materials like concrete, bricks, and other such
items) from site, give these waste materials either free of cost or at throw away prices to be
dumped in low lying sites with scant regard to the environmental pollution. Most construction
waste goes into landfills, resulting in soil and water pollution. Despite the rise in construction
activity in most of the Indian cities there is hardly any site for the storage of Construction and
demolition waste. The existing Municipal Solid Waste (Management and Handling) Rules,
2000 clearly states that it will be the responsibility of generator of wastes to avoid littering
and ensure delivery of wastes in accordance with the collection and segregation system of the
concerned municipal authority, but still there is a lackadaisical approach as far as the
segregation, storage, recycling and disposal of C & D waste is concerned.

A brief comparison of Management of construction waste in different countries [17]
USA:
C&D waste accounts for about 22% of the total waste generated in the USA.
Reuse and recycling of C&D waste is one component of a larger holistic practice called
sustainable or green building practice.
Green building construction practices may include salvaging dimensional lumber, using
reclaimed aggregates from crushed concrete, grinding drywall scraps scraps for use as
soil amendment at the site.
Promoting ‘deconstruction’ in place of ‘demolition’.
Deconstruction means planned breaking of a building with reuse being the main motive.
Netherland:
More than 40 million C&D waste is being generated of which 80% is brick and concrete.
Number of initiatives taken since 1993, such as prevention of waste, stimulate recycling
promoting building material which have a longer life, products which can be easily
disassembled, separation at source and prohibition of C&D waste and landfills.
Factors which led to high recycling rate are:
o Separation at source
o Good market for recycled products
o Ban on landfills
Guidelines for using C&D waste in place of fresh aggregates
Japan:
Much of the R&D in Japan is focused on materials which and withstand earthquake and
pre-fabrication.
Concrete and composite materials constitute the main construction materials.
85 million tons of C&D waste was generated in 2000, of which 95% of concrete was
crushed and reused as road bed and backfilling material, 98% of asphalt+concrete and
35% sludge was recycled.
Singapore-C&D waste is separately collected.
A private company (Sembwaste) has built an automated facility with 3,00,000 ton per
annum capacity.
Singapore:
C&D waste is separately collected.
A private company (Sembwaste) has built an automated facility with 3,00,000 ton per
annum capacity.
Maharashtra has taken a pioneering step and notified the Maharashtra Non-Biodegradable
Solid Waste (Proper Scientific Collection, Sorting and Disposal in Areas of the Municipal
Corporation) Rules, 2006 wherein reuse of this waste is included in the action plan. The
Action Plan, inter alia, prescribes separate collection and disposal of debris and bulk waste. 18
Superintending Engineer, Municipal Corporation, Gurgaon reported that IL & FS Waste
Management and Urban Services Ltd (IWMUSL) entered into one year agreement with
Municipal Corporation, Delhi and establish First Construction & Demolition (C & D) and E-

Waste Management Facility plant which is functioning successfully for the last about one
year. Useful products like pavement blocks, curbstones, textiles, granular sub base and RMC
are being produced using the C &D Waste. Gurgaon is a premier city and the scientific
disposal of C&D waste is very essential to develop this city on world Class norms [19].
Delhi’s first scientific landfill site at Narela-Bawana Road became operational in 2011 and
has a capacity to handle 1200 metric tonnes of waste every day, the sanitary landfill (SLF)
site will take the load off other landfill sites, which are over-saturated. It has the provision of
a materials recovery facility (MRF) which accepts materials, whether source separated or
mixed, and separates processes and stores them for later use as raw materials for
remanufacturing and reprocessing. MRFs may be high and low technology facilities; the
main function of the MRF is to the main function of the MRF is to maximize the quantity of
recyclables processed, while producing materials that will generate the highest possible
revenues in the market [20]. Despite the development of above said facilities in most of the
metropolitan cities, the following table makes it amply clear lackadaisical approach of
building professionals towards the use of recycled construction materials.
Table 5. Current status of C & D waste Management in India
The above state of affairs regarding the use of recycled construction materials and products
from C & D waste at national level can largely be attributed to the following factors:
5.1 Lack of awareness on the part of designers/engineers
The green building movement in India has made the construction professionals aware of the
long term benefits of sustainability in design and construction but there is general lack of
awareness 21 on the use of recycled construction materials. This is due to the absence of
performance based data and Testing facilities to ensure recycled-content construction
materials meet performance specifications [22]. There is a dire need to establish the
infrastructure, where different construction materials salvaged from C & D waste could be
tested for structural strength, reusability etc. and a central data bank be created from the
results thus obtained for the reference of architects, planners, engineers, interior designers,
structural and other consultants, sculptors and environmentalists.
5.2 Lack of awareness campaigns by the Government/ Urban Local Bodies (ULB)
Concerted and vigorous advertising campaigns are required by Central and State
Governments about the long term benefits of recycled construction materials. Lessons can be
learnt from Solar Decathlon international competition in the US that challenges 20 collegiate
teams to design, build, and operate the most attractive, effective, and energy-efficient house
operated by solar power, the funds are provide by US Energy Department. The winner of the
competition is the team that best blends affordability, architectural aesthetics, and design
excellence with optimal energy production. The event is open to the public where the Solar

Decathlon gives the visitors a firsthand experience of energy efficient buildings. On the same
lines the state and national level competitions can be held where the use of recycled
construction materials and vernacular technologies can be demonstrated to the public.
5.3 Unorganized market of recycled construction material
The generation of recycled construction material is site specific and there is no centralized
information about the demolition of buildings and other infrastructure taking place. This
leads to the intermittent supply of recycled construction materials in the market. This lack of
guaranteed supply [23] of various recycled construction materials and components (in the
absence of established market of various recycled materials) they are unwilling to specify the
same in new construction. This is the reason that recycled construction materials cannot
compete with new materials in terms of cost and performance.
5.4 Lack of incentives for using recycled construction materials
The indigenous technology for manufacturing recycled construction materials from C & D
waste in India is lacking so there is great dependence on new materials which increases the
cost of buildings. Continuous rise in fuel prices in the recent times is another factor which has
increased the construction cost considerably. The users of the recycled construction materials
from C & D waste should be given relief by way of lowering the interest rates and the
completed buildings can be exempted from local taxes (till the time it achieves breakeven
point) in order to encourage the construction of energy efficient green buildings (from
recycled construction materials) and to make green building movement a success in India.
5.5 Modification of curriculum
Curriculum needs to be modified by upgrading the syllabi of building materials in the context
of Green buildings besides adding the subjects like building systems and energy modeling
tools. “To make the green building movement a success in India the ECO III project has
constituted an International Advisory Committee of 13 academics and 6 professionals to
make the existing architectural education curriculum green building friendly.” 24 The need of
the hour is to inculcate in the minds of students that due consideration should be given to
sustainability aspect from conception to commissioning stage of any building project. Despite
the fact that there is a growing awareness about the environmental issues and their long term
implications, but the research scenario in this field is dismal. This could be attributed to lack
of research facilities and qualified faculty in the field of environmental sciences and building
physics etc. in architectural institutes. Another factor is the lack of data on the performance of
recycled materials and components from C & D waste in different climatic zones of India. In
the survey conducted on doctorate degrees in Architectural Institutions the findings showed
that only “26% of faculty in environmental sciences and 35% faculty in building services had
doctorate degrees.” 25 There is a dire need of up gradation of curriculum which lays greater
emphasis on the use of recycled Construction materials from C & D waste and interaction of
faculty and students with the experts from the industry both from India and abroad. India has
approximately 400 qualified green building professionals today.
6. Conclusion
The tremendous potential of the use of recycled C & D waste can be exploited by city
specific salvaging and recycling plans and strict implementation of government legislation.

References
1. Urbanization and Sustainability, http://www.energy demand\Urbanization and
sustainability iJanaagraha.mht
2. Architecture curriculum in India- background paper, page 3,
http://www.eco3.org/downloads/007-
3. http:\energy demand\India Energy Portal 1.mht
4. Architecture curriculum in India- background paper, pages,
http://www.eco3.org/downloads/007
5. Cantgrel Emmanuel Green buildings: From concept to reality, http://profit.ndtv.com
6. Architecture curriculum in India- background paper, pages3,
http://www.eco3.org/downloads/007-
7. Turab Yusuf, Retrieved from: http://www.green-buildings.com/content/781958-leedindia-
what-market-size-and-growth- rate and Materials, p 265,266, McGraw Hill, 2010
8. Environmental Protection Agency. (October 28, 2009). Green Building Basic
information. Retrieved December 10, 2009, from http://www.epa.gov/
greenbuilding/pubs/about.htm
9. http://www.Green Building Materials Sustainable Building.mht
10. http://www.ese.iitb.ac.in/events/other/renet_files/21Session%203/Ene
rgy%20in%20buildings(B.V.V. Reddy).pdf
11 Kim J.J., Rigdon B, Sustainable Architecture Module: Qualities, Use, and Examples of
Sustainable Building Materials, p14, National Pollution Prevention Center for Higher
Education, 430 E. University Ave., Ann Arbor, MI 48109-1115, December 1998.
12 http://www.recovery-insulation.co.uk/energy.html
13 http://www.Rebuilding C&D Waste Recycling Efforts in India - Waste Mangagement
World.mht
14 Report of the committee to Evolve Road Map on Management of Wastes in India,
Ministry of Environment and Forests, New Delhi, March 2010, page 31, C &
D_waste_India.pdf.
15 Montecinos W, & Holda A, Construction And Demolition Waste Management In
Denmark, June 2006, p5, http://cowam.tech.net/Denmark_CD_Waste.pdf
16 Donnelley RR, Scotland’s Zero Waste Plan Source, p2, Scottish Government, June 2010
http://www.scotland.gov.uk/Resource/Doc/314168/0099749.pdf
17 Shankarnarayan M, Khandelwal PK, Rege S, Kaicker PK, Mazumdar NB, Vittal G,
Working Sub-Group on Construction & Demolition Waste, Delhi
Government,http://delhi.gov.in/wps/wcm/connect/b222d6804eed8b93abbdbbfe99daf05a/
C%26D_waste_14.1.09.pdf?MOD=AJPERES&lmod=1201996428&CAC HEID=b222d6
804eed8b93abbdbbfe99daf05a
18 http://moef.nic.in/downloads/public-information/Roadmap-Mgmt-Waste.pdf
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Bawana%20(English).pdf)
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205
22 http://moef.nic.in/downloads/public-information/Roadmap-Mgmt-Waste.pdf
23 http://moef.nic.in/downloads/public-information/Roadmap-Mgmt-Waste.pdf
24 Architecture curriculum in India- background paper, page 11.
http://www.eco3.org/downloads/007-
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Abstract
Value Added Insulating Materials from Wastes
S. P. Agrawal and B. M. Suman
CSIR-Central Building Research Institute, Roorkee-247 667 (U.K.)
Corresponding Author, Email: subodhagrawal@cbri.res.in
Heating and cooling of residential buildings are prime requirements in built environment for
comfort of residents/ occupants. Heating and cooling accounts for 50 -70% of the energy,
used in an average house. The best way to achieve the comfort zone temperature inside the
building is to put the barriers in the path of the heat is being transferred inside the building by
any mode i.e. conduction, convection, and radiation. Amongst all the methods, most
convenient and easy method to prevent incoming heat in a building is to provide the barrier as
thermal insulating materials, which impart resistance to flow of heat by conduction. Heat
conduction is the major source of heating of a building and contribute maximum. In this
paper a few insulating materials using agro-industrial wastes have been developed at CSIR-
Central Building Research Institute, Roorkee, which are eco-friendly as green materials are
described in brief.
Key Words: Thermal, Insulation, Insulation Materials, Alternative Insulation Materials
1. Introduction
The built environment is heated in different ways by external sources which include
conduction, convection, and radiation. These are the three modes of heat transfer and each
contribute significantly in raising the inside temperature of the built spaces which lead to
discomfort. The factors affecting the inside temperature of a building includes;
1. Influence of solar radiation on optimum plain shape and orientation.
2. Air-temperature cycles.
3. Placing and orientation of windows.
4. Solar shading
Heating and cooling of residential buildings are prime requirements in built environment for
comfort of residents/ occupants. Heating and cooling account for 50-70% of the energy used
in an average house. Inadequate insulation and air leakage are leading causes of energy waste
in most homes. Insulation saves money and our nation’s limited energy resources, makes our
house more comfortable by helping to maintain a uniform temperature throughout the house,
and makes walls, ceilings, and floors warmer in the winter and cooler in the summer. The
amount of conserved energy depends on several factors which include local climate, size,
shape, and construction of the house, living habits, type and efficiency of heating and cooling
systems, and the type of energy used. Heat flows naturally from warmer to a cooler space. In

winter, the heat moves directly from all heated living spaces to the outdoors and to adjacent
unheated attics etc. During the summer, heat moves from outdoors to the house interior. To
maintain comfort, the heat lost in winter must be replaced by heating system and the heat
gained in summer must be removed by used cooling devices. Insulating ceilings, walls, and
floors decrease the heating or cooling load by providing an effective resistance to the flow of
heat.
Heat loss during winter and heat gained during summer by a house are shown in figure 1 and
figure 2 respectively.
Figure 1: Heat Loss from a house during winter
Figure 2: Heat gained by a house during summer
The best way to achieve the comfort zone temperature inside the building is to put the
barriers in the path of the heat is being transferred inside the buildings by any mode i.e.
conduction, convection, and radiation. Materials used as barriers for conduction are named as
insulation materials, for convection the materials used as barriers are named as convective
heat barriers, and the materials used for radiant heat are named as radiant heat barriers. Batts,
blankets, loose fills, and low density foams all work by limiting air movement. The still air is
an effective insulator because it eliminates convection and has low conduction. Reflective
insulation works by reducing the amount of energy (heat) that travels in the form of radiation
by reflecting the radiant heat. Amongst all the methods, most convenient and easy method to
prevent incoming heat in a building is to provide the barrier as thermal insulating materials,
which impart resistance to flow of heat by conduction. Heat conduction is the major source of
heating of a building and contribute maximum. In this paper a few insulating materials using
agro-industrial wastes have been developed in CSIR-Central Building Research Institute,
Roorkee, which are eco-friendly as green materials are described in brief.

2. Thermal insulation board (bio-degradable) from forest wastes (leaves)
A product, a thermal Insulation board is developed using dried leaves of forest waste which is
suitable for acoustic cum thermal insulation purposes in rural houses. This board can also be
sandwiched between two laminating surfacing materials which can be used as paneling
material with better resistance to heat as well as acoustic purposes in buildings. The leaves
are cut into small pieces manually using scissors, soaked in 2.5 to 5.0 % solution of water
based binder (resin) for 8 h and then the soaked leaves are heat pressed in a hot press to
convert them into flat sheets after removing the excess resin solution. The typical sheets are
shown in Figure 3
Figure 3: Low Density Sheets made from Leaves of Forest waste
The developed product is characterized in the laboratory and the characterization values are
given in table-1.
Table 1. Characterization Values of Insulation Board from Forest waste (Leaves)
No. Property Value (Unit)-average
1. Dimensions L-150; W-150; T-6 to 10 in mm
2. Average Weight 200 g (approx.)
3. Density 234.35 kg/m 3
4. Initial Moisture (Temp. 28ºC, RH 42%) 12.28 % (by weight)
5. Bond Strength (between particles) 1.83 N/cm 2
6. Bio-degradability 6 – 12 months (being assessed)
7. Thermal Conductivity at 32.6ºC[1] 0.131 W/mK
8. Bio-degradability 4-8 months
9. Estimated unit cost Rs. 1.00
The mechanical strength (bending strength) of this developed board is low and for efficient
and effective use, the same should be sandwiched between two hard surfacing materials such
as MDF board, plywood, Hard Board etc.

3. Lightweight sandwich panels
The cellulosic refuse of paper industries are rich in small fibres and can be used to make
value added product, which can be used for acoustics, thermal insulation and false ceiling
purposes in buildings. The laboratory scale developed technology yielded a light weight
sandwich panel which is very much suitable for above mentioned purposes. These developed
panels have their end applications in partitioning, paneling, thermal insulation and false
ceiling with its unique aesthetics. The technology as well as product has been patented. The
estimated economic viable capacity is 2 tones per day and most suitable for paper industries
as a down stream process. Panels with different surface textures are shown in Figure 4.
Figure 4. Light Weight Sandwich Panels with Different Surface Textures
4. Coir-CNSL thermal insulation sheets
This is a composite material which utilizes the coconut fibres as reinforcing material and
CNSL as the natural binder. The density of the board is kept very low i.e. around 350-450
kg/m 3 . The product can be given suitable shape to be fitted with equipment or surface to be
insulated. The thermal conductivity is 0.0745 kcal/hr m 2 C. A prototype flat sheet made in
the laboratory is shown in Figure-5.
Figure 5. Light Weight Coir-CNSL Thermal Insulation Sheet

5. Low density thermal insulation board from paper industry waste
At present the cellulosic refuge from digester, recovery unit and ETP units of paper industries
is used as fuel within the industry or by outsiders (brick kilns etc.). A portion of this waste is
also used for making hardboard (gatta) by mixing some fresh pulp into it. This waste is used
to produce a value added product without mixing any fresh pulp. Paper industries are
generating waste around 10-15% of their production capacity. This low density board
technology is patented (patent no. 190173). A typical prototype of low density board is
shown in Figure 6. Properties of the board are given in Table 2.
Table 2. Characterization Values of Low Density Board from Paper Industry Waste
No. Property Value (Unit)-average
1. Density 537.2 kg/m 3
2. Initial Moisture (Temp. 24ºC, RH 38%) 4.46 % (wt)
3. Bending Strength 7.80 N/cm 2
4. Water Absorption after 2 h soaking in water 70.74 % (wt)
5. Thermal Conductivity at 32.6ºC 0.078 W/mK
Figure 6. Prototype of Low Density Board from Paper Industry Waste

6. Conclusion
Number of waste products and renewable materials are available which can be converted into
a value added products. These developed products can be used for thermal insulation
purposes in buildings as barrier for conductive heat transfer. These developed products are
cost effective, renewable, alternatives to conventional materials, and recyclable. Only there is
a need to produce them commercially and to make their availability in the market. These
technologies are available for transfer at laboratory level.
References
1. IS: 3346-1980, “Method for the determination of thermal conductivity of thermal
insulation materials (Two-slab, Guarded hot plate method).
2. Thermal Properties of Materials, Homsey, R. I., ENG 2000 series Chapter 9.
3. Principal Methods of Thermal Conductivity Measurement, a publication of TA Instruments,
Argentina.
4. http://en.wikipedia.org/wiki/Thermal_insulation
5. http://www.excellence-in-insulation.eu/site/fileadmin/user_upload/PDF/Thermal _ insulation
materials_made_of_rigid_polyurethane_foam.pdf

Impact of Sustainable Cements on the Conservation of Energy in
Buildings
Abstract
V. Sood, S.K. Agarwal and Ashok Kumar
CSIR-Central Building Research Institute, Roorkee
Corresponding Author, Email: sood65@yahoo.com
This article discusses the practicality of replacing Portland cements with alternative hydraulic
cements popularly called sustainable cements made with 0.5 or even lower clinker factor. The
use of high volume of fly ash & granulated blast furnace slag (GBFs) or both could result in
lowering total CO2 emissions per unit volume of concrete of equivalent performance because
most CO2 emissions result directly from the combustion of fossil fuels to produce usable
forms of energy. Thus, almost any approach to decreasing fossil fuel consumption should
have a similar beneficial effect in reducing CO2 emissions per unit of product. Currently, the
cement industry is responding rapidly to the perceived societal need for reduced CO2
emissions by increasing the production of blended Portland cements using supplementary
cementitious materials that are principally derived from industrial by-products, such as blastfurnace
slag and coal combustion fly ashes. Replacement of clinker with additive materials
like flyash / blast furnace slag etc. not only reduces the power consumption, protects the
environment, conserve the limestone and coal but also reduces the amount of GHG emission
to a great value. The work has been done at CBRI using admixtures like sodium sulfate and
super-plasticizer on the compressive strength of cement paste incorporating fly ash and slag
upto 70%. At 40% replacement of cement with fly ash (collected from first electro
precipitator) using 1% super-plasticizer gives 5% less strength at 28 days but at 90 days it is
at par with the control. However with 40% slag at 3, 7 & 28 day strength is at par and slightly
more at 90 days when 2% sodium sulfate is added. With 50% replacement the trend is same
as with 40% replacement except slightly lower strength upto 7days. With 30% each of fly ash
and slag it has been found that 28 & 90 day strength is similar to 50% replacement level. At
70% replacement the strength is low even at 90 days compare to control. However at 360
days compressive strength of cement paste without admixture at 60, 50 and 40% fly ash or
slag is at par with the control and with admixture it is more in all the cases.
Keywords: Flyash, super-plasticizer, GHG, metakaolin
1. Introduction
Sustainable cements with low clinker factor can be made using various SCM’s like fly ash,
metakaolin, silica fume and natural pozzolana. If these cements are judiciously blended with
proper selection of admixtures, mixture proportioning and curing can noticeably improve the
durability of concrete. Cement is the key material to satisfy the global requirement for
housing and infrastructure. CO2 emissions and consumption of material and energy is the area
of prime concern. Use of alternate materials and energy efficiency are the backbone of
cement producers. There is still a potential to use alternate materials to decrease the clinker

factor. Nevertheless, appropriate materials are limited in their regional availability. India is
the 2 nd largest producer of cement in the world, comprising of large and mini cement plants
and the quality of cement and standard of cement produced is par to any cement produced
elsewhere. Some of the major players are ACC Ltd., Guajarat Ambuja Groups, Ultra tech,
Grasim Industries, JK group, Lafarge, Jaypee group etc. In India likely production of cement
by the year 2011 – 12 will be around 250 Million tones. It is estimated that out of this total
cement production fly ash based cement will account for nearly 70%. Thus PPC will be able
to incorporate appox. 52% flyash. However this is possible if percentage of flyash in PPC
increases from 30 to 32% from the existing level of 25% (average). India presently stands as
the fourth largest emitter of GHG. Cement industry is one of the major industries releasing
appreciable amount of Green House Gases. Of the total national emissions, at present about
8% GHG emissions is due to this industry. The GOI has announced the reduction of GHG
emissions intensity by 20-25% of 2005 levels by 2020. This target can only be achieved when
all the segments of the economy strive independently to reduce their emissions and help the
nation to meet its commitments. Efforts should be made to reduce greenhouse gas emission
intensity by 20% from the present levels of 697 kg CO2 /ton of cement to 560 kg CO2 / ton of
cement. In cement plant the main sources of emission are calcination where conversion of
CaCO3 in the limestone to CaO and CO2, burning of fossil fuel, consumption of electricity
produced externally for manufacturing cement & transportation of raw material. For every
1% of increase in blended cement production, CO2 emission will be reduced by
approximately 2.2 – 6.0 kg/MT of cement keeping all the other parameters constant. Cement
industry is an energy intensive industry with about 35-45% of the total manufacturing cost. It
needs both electrical (mill drives, pumps, fans, conveyors, packer etc) as well as thermal
energy (kiln & pre-calciner) for its operation. Cement industry accounts for around 10% of
the coal and 6% of the electricity consumed by the Indian industrial sector. The Indian
cement plants on an average consume about 82kWh of electrical energy for producing 1 ton
of cement. Cement plants require 743kCal of thermal energy for making 1 kg of clinker. The
major use of thermal energy is in kiln and pre-calciner systems.
2. Materials
Ordinary Portland cement of 43 grade conforming to BIS 8112-2005 [14], Fly ash of first
field collected from thermal power plant near Delhi and slag were used for preparation of
cement cubes. The chemical composition of these cementitious materials used in the present
study is given in Table 1. Technical grade sodium sulfate was used as chemical activator.
Superplasticizer (SP) based on sulphonated naphthalene formaldehyde condensate (SNF)
conforming to BIS 9103 (2004) was used in the present study.
Table1. Chemical/Physical composition of Cementitious Materials
Composition,% Cement Fly ash Slag
SiO2 20.5 60.24 33.95
Al2O3 3.8 25.14 10.53
Fe2O3 2.6 4.75 1.25
CaO 60.5 3.10 40.40
MgO 3.2 8.65
Chloride content 0.03
SO3 2.5 1.35 0.10
CaO+MgO+ SiO2 - - 83.0
SiO2 + Al2O3 + Fe2O3 - 90.13 -
LOI 1.0 1.32 0.54
Fineness cm 2 /gm 3100 2850 4020

3. Experimental procedure preparation of blended cement cubes
Cement mixes incorporating fly ash/slag percentages, different mixtures were prepared in the
present study. The details of blending proportion are given in Table no. 2[34-35]. The
mixtures were blended in the powder mixture for 10 minutes. Cement cubes of 25mm of
various mixtures were cast with and without super plasticizer at the same consistency level.
After demoulding at 24 hours the cubes were cured at temperature 27+2 0 C with relative
humidity not less than 95% in the humidity chamber. The compressive strength of these
cubes was determined at different time interval of 3, 7, 28, 90 and 360 days. The results are
given in Table no. 3 & figure 4.
4. Results and discussion
X -ray of cement, flyash and slag are given in fig.nos.1-3. Where as X-ray of cement and fly
ash are normal, however in case of slag X-ray shows low crystallinity nature. A small peak of
Calcite, Merwinite (2CaO. Al2O3.SiO2) and Melilite (solution of gehlenite and akernite) is
visible in the X-ray. It is clear from the table no. 3 that when 40% cement is replaced by fly
ash compressive strength drops from 34, 20, 10% and at par at 90 days. When 1% SP is used,
drop in strength is 20, 13, 3% at 3,7 and 28 days. Thus at 28 days with the use of SP, strength
is at par compare to 10% drop when no SP is used. Similar trend has been found with 40%
slag without activator (sodium sulphate). However, when 2% activator is used 3 day strength
is slightly more than the control and at 28 and 90 days the strength is more than the control.
In case of 50% replacement when no admixture is used, the drop in strength is from 47%
(3days) to 17% (28 days) and 13% at 90 days. With 1% SP the drop in strength is from 33%
(3days) to13% (28days) and 3% at 90 days, suggesting thereby that with the use of SP the
drop in strength at 28 days is equivalent to 90 days when no admixture is used. In case of slag
drop in strength is 28% (3days) to 12% (28days) and 2.5% at 90 days. In case of 60%
replacement of cement by flyash/slag or blending of two, it is found that without any
admixture strength drops from 62% (3day), 52% (7day), 20% (28day) to 17% at 90 days.
However in case of fly ash with 1% SP the trend is from 42% to less than 10% at 90 days.
Similarly for slag it drops from 32% to less than 10% at 90 days. With 70% replacement the
drop in strength at 90 days is 35, 22 and 21% without admixture and with 1%SP and 2%
sodium sulphate the drop in strength is less than 15%. No synergic effect of superplasticizer
has been observed when sodium sulphate has been used as an activator in slag and fly ash
systems and vice versa for fly ash slag systems. Effect of additional dosage of SP and sodium
sulphate has not resulted in any gains. Further, it is clear from the table that at 360 days
compressive strength of cement paste without admixture at 60, 50 and 40% fly ash or slag is
at par with the control and with admixture it is more in all the cases. In 70% replacement the
strength is comparable to 90 days of control. Only exception found is when 4% sodium
sulphate and combination of SP and sodium sulphate is used. In both the cases 40% is slag.
Since slag is most like portland cement and least like a pozzolana. In contrast with early
strength development of the blended paste is better than the reference paste. The mechanism
of activation [15] by sodium sulfate on blended cement can be explained by assuming that the
sulfate ions reacts with the calcium ions dissolved from the cement minerals results in the
formation of gypsum, which act as nuclei for ettringite and CSH gel. During this process
calcium ions depletes and thus accelerates the dissolution of cement minerals such as alite
and belite. The function of sodium ions is to increase the pH of the paste, which helps in the
dissolution of amorphous silica oxide and aluminum oxide. The dissolved oxides react with
calcium hydroxide to form CSH gel.

It has been observed that the hydration properties of the blended pastes are function of water
to binder ratio, cement replacement level by pozzolanic materials and curing age. Further
pastes containing fly ash exhibited strongly reduced early strength, especially at higher levels
of replacement (>40%). In the case of increase in fly ash content, the hydration degree of
cement increases, but the pozzolanic reaction degree of fly ash reduces. The active effect of
fly ash is composed of pozzolanic activity of fly ash itself and promoting role of fly ash to the
hydration of cement. However, total hydration degree of the system reduces with the increase
of the fly ash content because the activity of fly ash is lower than cement [16-20].
Table 2. Mixture Proportions of Blended Cement Pastes
System Cement % Flyash % Slag % Admixture %
1
3
5
7
9
11
13
15
17
19
21
25
26
36
37
100
60
60
60
60
60
60
50
50
50
50
40
40
30
30
-
40
40
-
-
20
20
30
30
30
20
30
30
30
30
-
-
-
40
40
20
20
20
20
20
30
30
30
40
40
Table 3. Comparative strength of blended cement
-
-
1.0sp
-
2.0act
-
2.0act
-
2.0act
1.0sp
2.0act
1%sp
2.0Act
4.0%Act
2.0%sp+Act
System 3d 7d 28d 90d 360d
1 32.3 48.5 58.1 63.5 66.3
3 22.1 37.4 51.8 62.3 66.2
5 25.5 41.9 56.5 63.8 67.1
7 26.0 41.5 52.8 64.0 68.5
9 36.8 45.6 57.6 65.5 69.6
11 20.8 28.6 51.6 59.0 64.5
13 26.4 30.5 55.1 60.5 65.6
15 17.2 26.1 48.1 55.0 61.1
17 23.4 32.5 52.4 61.2 65.9
19 26.0 38.0 51.0 61.5 66.0
21 30.3 35.1 52.7 61.1 66.9

M
M
Q
C3
Q
C2S/C3
C2
C3
Figure 1. XRD profile of cement
C
M
M
H
Q
M
Q
M – mullite
Q- quartz
H - Hemitite
Figure 2. XRD profile of flyash
M
Ca - Calcite,
Mer - Merwinite
Me - Melilite
Figure 3. XRD profile of slag

5. Conclusion
It can be concluded from the present study that:
1. Fly ash collected from first hopper can be blended upto 50% (30% fly ash+20% slag) by
using admixture with strength at 90 days at par with control.
2. Similarly slag can be blended with 20% fly ash and use of activator the strength at 90 days
is equivalent to control.
3. 60% SCM’s can be blended considering difference of (23%) in 43grade and 33grade OPC
compressive strength when tested as per BIS 12269-2005 and 8112-2005.
4. Use of chemical admixtures can reduce the clinker and make the cement sustainable.
5. Thus with 50% replacement clinker factor of cement and equivalent amount of carbon
dioxide can be reduced. Further saving of 50% clinker will not only save our natural
resources but also precious thermal & electrical requirements. Hence sustainable cements
play an important role in the conservation of energy in the building sector. In the portland
clinker manufacturing process, direct release of CO2 occurs from two sources, namely the
decomposition of calcium carbonate (the principal raw material) and the combustion of
fossil fuels. The former accounts for about 0.6 kg CO2/kg clinker and the latter 0.25-0.35
kg CO2/kg clinker (depending on the carbon content of the fossil fuel); the global average
being 0.9 kg CO2/kg clinker. Alternate sources of energy other than fossil fuels are being
sought but, at present, they are too expensive.
6. Acknowledgement
This paper is part of ongoing R&D work in Central Building Research Institute and is
published with the permission of Director, CSIR-CBRI, Roorkee, India.
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80
70
60
50
40
30
20
10
0
m1 m3 m5 m7 m9 m11 m13 m15 m17 m19 m21
Figure 4. Test Mix giving comparable strength
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contribution to the system C3A-CaCO3-H2O & C4AF-CaCO3 H2O ZKG,18 (9).
21. Handoo SK, Gopal S, Gupta RS(1996). Investigation on the hydration characteristics of
multi component cement blends IV NCB Int. Sem. Cem. Build. Mater. New Delhi, India.
22. Sharma RL, Pandey SP(1999). Influence of mineral additives on the hydration
characterstics of ordinary Portland cement, Cem.Concr. Res.
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Xuebao pages 289-294.
24. Ramachandran VS, .Zang C(1986). Influence of CaCO3 on the hydration and
microstructural Characteristics of C3S, Il Cemento, pages 129-152.
25. Ramachandran R, Chun-Mei Z(1986). Dependence of fineness of CaCO3 on the
Hydration behaviour of C3S, Durability of Building Material, pages 45-66

26. European Committee for Standardization; Cement: Composition Specifications and
Conformity Criteria, Part 1: Common Cements, EN 197-1 (2000)
27. Ordinary Portland cement 43 Grade-Specifications BIS 2005
28. Zicho, W. & Naik.,T.R., “ Chemically Activated Cements” ACI Material Journal, pages
434 (2003)
29. Wang, A., Zhang, C., and Sun, W., “Fly ash effects Part II The active effect of fly ash”,
Cement & Concrete Res. Pages 2056-60 (2004)
30. Kosmatika, S.H., Kerkhoff, B., and Panarase, W.C., “Design and Control of Concrete
Mixes, 14th Edition, EB001.14T, Portland Cement Association, Skokie, IL (2002)”
31. Mehta, P. K., and Monterio, P.J.M., Concrete Microstructure, Properties and Materials,
3 rd edition, Mcgraw-Hill, New York, (2006)
32. Turanli, L., Uzal, B. and Bektas, F., “Effect of material characteristics on the properties of
blended cements containing high-volumes of natural pozzolanas”, Cement Concrete Res.,
pages 2277-82(2003)
33. Uzal, B. and Turanli, L., “ Studies on blended cements containing a high volume of
natural pozzolanas”, Cement Concrete Res., pages 1777-81(2003)
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650 (2011)
35. Wang, A., Zhang, C., and Sun, W., “Fly ash effects Part II The active effect of fly ash”,
Cement & Concrete Res. Pages 2056-60 (2004)
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Mixes, 14th Edition, EB001.14T, Portland Cement Association, Skokie, IL (2002)”
37. Mehta, P. K., and Monterio, P.J.M., Concrete Microstructure, Properties and Materials,
3 rd edition, Mcgraw-Hill, New York, (2006)
38. Turanli, L., Uzal, B. and Bektas, F., “Effect of material characteristics on the properties of
blended cements containing high-volumes of natural pozzolanas”, Cement Concrete Res.,
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natural pozzolanas”, Cement Concrete Res., pages 1777-81(2003)

Abstract
Embodied Energy and Digital Footprint of Buildings
Green Buildings Vs Vernacular Architecture
Mitul Kumari
Birla Institute of Technology Mesra, Ranchi
Corresponding Author, Email: mitul803@gmail.com
To achieve the required Indoor Environment Quality, green buildings use highly specialized
and effective equipments that generally use low operational energy, but have very high
production embodied energy. Therefore, the popularity of the green building movement
should be steered towards a vernacular movement, with emphasis given to shifting the bench
mark for comfort zone and Indoor Environmental Quality to what the locals are adapted to
regionally, rather than creating universally ideal psychrometric conditions. The benchmark
for rewarding points for Green Building Rating Systems is not Embodied Energy of
materials, but largely, the estimated post occupancy operational energy and how it is
minimized. The efficiency of the equipments (HVAC&R, building automation systems, etc.)
is definitely increasing; however, the historical trend of digital technology is toward more and
more energy intensive manufacturing processes. The concept of Indoor Environmental
Quality is becoming over hyped, and the buildings are changing into over-ventilated, overglazed,
and under-insulated, mechanically controlled micro environments. Due to urban
sprawl and changing climate, traditional construction techniques are being considered
obsolete. Need of the hour is to research on how vernacular materials as well as techniques
can be incorporated in the growing trend of high rise construction.
Keywords: green buildings, psychrometric, Vernacular, benchmark, Embodied Energy,
footprint
1. Introduction
The recent awareness created among the masses about the harmful effects of rampant
building construction is a remarkable task achieved by the joint efforts of the UN and the
various Green Building rating systems. However, as Green Buildings are becoming a new
trend among the emerging building construction projects, it is justified to ask whether the
prototype created by some developed countries should be universally replicated everywhere.
In developing countries like India, which enjoys a great history of traditional climate
responsive architecture, and where locals are adapted to the tropical climatic conditions, is it
necessary to go all the way green just to achieve some rating , or would it be enough to try to
go back to the basics of traditional Indian Architecture? The Green building movement
definitely has its pros, but on an average, if certain guidelines are followed, then, the

vernacular Architecture of this country might shine as the better solution to sustainability
woes.
2. Importance of building energy efficiency
Buildings are significant users of energy and building energy efficiency is a high priority
in many countries.
Efficient use of energy is important since global energy resources are finite and power
generation using fossil fuels (such as coal and oil) has adverse environmental effects.
The potential for energy savings in the building sector is large.
2.1 What is a green building?
Green building is the practice of creating structures and using processes that are
environmentally responsible and resource-efficient throughout a building's life-cycle from
sitting to design, construction, operation, maintenance, renovation and deconstruction.
In turn, green building reduces building impacts on human wellness and the environment by
implementing improved site location, design, construction, operation, maintenance, and
removal – encompassing the complete life cycle of building. Green buildings are designed to
reduce the overall impact of the built environment on human health and the natural
environment by:
• Efficiently using energy, water, and other resources
• Protecting occupant health and improving employee productivity
• Reducing waste, pollution and environmental degradation
A fundamental principle of sustainable development concentrates on keeping our planet in a
condition which will indefinitely support future generations. This is a tremendous challenge
due to the state of stress and overuse our global ecosystem is experiencing. Unfortunately,
finite sources of energy and materials are being depleted, and much of our environment is
being polluted or spoiled.
Green building aims to repair the damage that less sustainable building methods have had on
our environment and promote a system of building that enables us to live in a state of
equilibrium with our surroundings.
2.2 Reason why green building rating systems are becoming popular
Architects, real estate professionals, facility managers, engineers, interior designers,
landscape architects, construction managers, lenders and government officials all use Energy
Rating systems to help transform the built environment to sustainability.
Some salient points fuelling the popularity of rating systems are:
• Market recognition for low environmental impact buildings,
• Assurance that best environmental practice is incorporated into a building,
• Inspiration to find innovative solutions that minimize the environmental impact.
• A benchmark that is higher than regulation.
• A tool to help reduce running costs, Improve working and living environments
• A standard that demonstrates progress towards corporate and organizational

environmental objectives.
• What gets measured gets managed
2.3 Energy use in a building can be categorized into 2 major groups
• Energy needed for construction - generally the embodied energy of the materials is
concerned.
• Energy needed to operate the building – direct energy use drawn from the grid or
produced on site, in the form of electricity.
The construction industry plays a major role here as a primary consumer of materials and
energy. At the building scale, sustainable construction aims to provide long-lasting,
health-minded, useful buildings. This goal can be accomplished by conserving limited
material and energy resources by using durable, recyclable, and renewable materials
through energy-efficient design, and by using environmentally neutral energy sources
such as wind, sun, geothermal, and mechanisms including shading, simple evaporation
and cooling.
2.4 Salient features of green buildings
• Sustainable site selection
• Site planning
• Water efficiency
• Energy performance
• Environmental consciousness
• Material use
• Resource use
• Technologies
• Indoor environmental quality
• Innovation in design
Even though the benefits of a green building are infinite, both tangible and intangible, an
immediate tangible aspect could be readily observed once the green building starts operating,
which is the significant reduction in operating cost and water costs (up to 40% savings !).
Another tangible aspect would be the enhanced asset value. Intangible aspects would include
increased productivity, health and safety, and much more.
2.5 Reducing environmental impact
Green building practices aim to reduce the environmental impact of buildings, so some of the
basic rules of building green are:
• The greenest building is the building that doesn't get built because any type of new
construction almost always degrades the building site. So, not building is always a
preferred option.
• Every building should be as small as possible.
• Discouraging Urban sprawl. No matter how much grass is put on your roof, no matter
how many energy-efficient windows, etc., is used, if the construction contributes to

sprawl, it just defeats the purpose. Urban infill sites are preferable to suburban
"Greenfield" sites.
3. What is vernacular architecture?
Vernacular architecture is architecture without architects. It is the response to a society’s
building needs. It fulfills these needs because it is crafted by the individual and society it is
in. In addition, the building construction is trial-and-error story of the society in which they
are built until their building construction techniques get perfected to the climatic, aesthetic,
functional, and sociological needs of their given society. One of the most important things
that we can learn by looking at Vernacular architecture is the seemingly simple (almost lowtech)
methods of which we can create a building that is perfectly adapted to the building’s
users and the building’s locale.
At face value these may seem trivial yet are in fact quite complex and extremely effective
because they have been tested over time and have evolved to fit a society’s needs. Vernacular
architecture is perfect because it is derived through the application of local materials and
building techniques to create buildings that function as what they are meant to function as.
Because the building’s design and construction is intimately intertwined with the person who
will be using the structure, the final product functions exactly as intended. These building
maximize the local knowledge of how buildings can be effectively designed as well as how to
effectively use local materials and resources
4. The concept of embodied energy
4.1 Embodied energy
Embodied energy is the sum of all the energy required to produce goods or services,
considered as if that energy was incorporated or 'embodied' in the product itself. The concept
can be useful in determining the effectiveness of energy-producing or energy-saving devices
of buildings, and, because energy-inputs usually entail greenhouse gas emissions, in deciding
whether a product contributes to or mitigates global warming.
Embodied energy is an accounting method which aims to find the sum total of the energy
necessary for an entire product life-cycle. Determining what constitutes this life-cycle
includes assessing the relevance and extent of energy into raw material extraction, transport,
manufacture, assembly, installation, dis-assembly, deconstruction and/or decomposition as
well as human and secondary resources. Different methodologies produce different
understandings of the scale and scope of application and the type of energy embodied.
There are two forms of embodied energy in buildings:
• Initial embodied energy; and
• Recurring embodied energy
The initial embodied energy in buildings represents the non-renewable energy consumed in
the acquisition of raw materials, their processing, manufacturing, transportation to site, and
construction. This initial embodied energy has two components:

Direct energy the energy used to transport building products to the site, and then to construct
the building; and
Indirect energy the energy used to acquire, process, and manufacture the building materials,
including any transportation related to these activities.
The recurring embodied energy in buildings represents the non-renewable energy consumed
to maintain, repair, restore, refurbish or replace materials, components or systems during the
life of the building.
As buildings become more energy-efficient, the ratio of embodied energy to lifetime
consumption increases. Clearly, for buildings claiming to be "zero-energy" or "autonomous",
the energy used in construction and final disposal takes on a new significance.
4.2 How is it measured?
Typically, embodied energy is measured as a quantity of non-renewable energy per unit of
building material, component or system. For example, it may be expressed as Mega Joules
(MJ) or giga Joules (GJ) per unit of weight (kg or tonne) or area (square meter). The process
of calculating embodied energy is complex and involves numerous sources of data. Refer to
the Related Resources + References page for further information on embodied energy.
Implicit in the measure of embodied energy are the associated environmental implications of
resource depletion, greenhouse gases, environmental degradation and reduction of
biodiversity. As a rule of thumb, embodied energy is a reasonable indicator of the overall
environmental impact of building materials, assemblies or systems. However, it must be
carefully weighed against performance and durability since these may have a mitigating or
compensatory effect on the initial environmental impacts associated with embodied energy.
[1]
4.3 Embodied energy of construction materials
The building industry arguably has a claim to being the birthplace of the whole idea and it is
certainly one area where the concept has been widely embraced. It is, for instance, not
uncommon to see articles in the construction trade magazines and journals discussing the
relative merits of different materials in terms of their embodied energy, or the closely related
embodied carbon, values. As the whole idea of eco-building has grown to become
increasingly mainstream within the industry, novel insulating fabrics, for example, such as
flax, hemp and cellulose, have gained ground on their more conventional counterparts, often
on the basis of their low embedded energy. Strictly speaking, embodied energy is an
accurately calculated value of the amount of energy hidden away inside products and given in
mega-joules per kilogramme (MJ/kg), though it is often used more loosely by builders
themselves, without giving any hard numbers. Although this may offend the purists, in many
ways it’s no bad thing, since it has led to the widespread general awareness of the idea that
some types of materials, say concrete, have ‘high’ embedded energy levels, while others,
such as wood have ‘low’ ones. [2]
4.4 Embodied energy of digital technology [3]
When we talk about energy consumption, all attention goes to the electricity use of a device
or a machine while in operation. A 30 watt laptop is considered more energy efficient than a
300 watt refrigerator. This may sound logical, but this kind of comparisons does not make

much sense if you don't also consider the energy that was required to manufacture the devices
you compare. This is especially true for high-tech products, which are produced by means of
extremely material- and energy-intensive manufacturing processes. How much energy do our
high-tech gadgets really consume? The energy used to produce electronic gadgets is
considerably higher than the energy used during their operation. For most of the 20th century,
this was different; manufacturing methods were not so energy-intensive. An old-fashioned
car uses many times more energy during its lifetime (burning gasoline) than during its
manufacture. The same goes for a refrigerator or the typical incandescent light bulb: the
energy required to manufacture the product pales into insignificance when compared to the
energy used during its operation. Advanced digital technology has turned this relationship
upside down.
A handful of microchips can have as much embodied energy as a car. And since digital
technology has brought about a plethora of new products, and has also infiltrated almost all
existing products, this change has vast consequences. Semiconductors (which form the
energy-intensive basis of microchips) have also found their applications in ecotech products
like solar panels and LEDs. While it is fairly easy to obtain figures regarding the energy
consumption of electronic devices during the use phase (you can even measure it yourself
using a power meter), it is surprisingly hard to obtain reliable and up-to-date figures on the
energy consumed during the production phase.
Especially when it concerns fast-evolving technologies, a life cycle analysis of high-tech
products is extremely complex and can take many years, due to the large amount of parts,
materials and processing techniques involved. In the meantime, products and processing
technologies keep evolving, with the result that most life cycle analyses are simply outdated
when they are published. Figures show that the embodied energy of the memory chip alone
already exceeds the energy consumption of a laptop during its life expectancy of 3 years
4.4.1 Why are microchips so energy-intensive to manufacture?
One of the reasons becomes clear when you literally zoom in on the technology. A microchip
is small, but the amount of detail is fabulous. A microprocessor the size of a fingernail can
now contain up to two billion transistors - each transistor less than 0.00007 millimeters wide.
Magnify this circuit and it becomes a structure as complex as a sprawling metropolitan city.
The amount of materials embedded in the product might be small, but it takes a lot of
processing (and thus machine energy use) to lay down a complex and detailed circuit like
that. While the electricity requirements of machines used for semiconductor manufacturing
are similar to those used for older processes like injection molding, the difference lies in the
process rate: an injection molding machine can process up to 100 kilograms of material per
hour, while semiconductor manufacturing machines only process materials in the order of
grams or milligrams. Another reason why digital technology is so energy-intensive to
manufacture is the need for extremely effective air filters and air circulation systems (which
is not included in the figures above).
When you build infinitesimal structures like that, a speck of dust would destroy the circuit.
For the same reason, the manufacture of microchips requires the purest silicon (Electronic
Grade Silicon or EGS, provided by the energy-intensive CVD-process). Every 18 months the
amount of transistors on a microchip doubles (Moore's law). On one hand, this means that
less silicon is needed for a certain amount of processing power or memory. On the other

hand, when transistors become smaller, you need even more effective air filtration and purer
silicon. Since the structure also becomes more complex, you need more processing steps.
4.4.2 Recycling is no solution for micro-electronics
Encouraging recycling is often proposed as a way to lower the embodied energy of products.
Unfortunately, this does not work for micro-electronics (or nanomaterials). In the case of
conventional manufacturing methods, the energy requirements of the manufacturing process
(1 to 10 MJ per kilogram) are small compared to the energy required to produce the materials
themselves. In the case of semiconductor manufacturing, this relation is reversed. While it
takes 230 to 235 MJ of energy to produce 1 kilogram of silicon (already quite high compared
to many other materials), chemical vapour deposition (an important step in the semiconductor
manufacturing process) requires about 1,000 MJ of electricity and thus 3,000 MJ of energy
per kilogram. That is 10 times more than the energy consumption of material extraction and
primary processing. In the case of conventional manufacturing techniques, the use of recycled
material is an effective way to lower overall energy use during manufacture. In the case of
semiconductors, it is not. Recycling is not a solution for energy consumption if all your
energy use is concentrated in the process itself.
5. Embodied energy of green buildings
After a thorough study of IGBC LEED NC and GRIHA manuals, it was observed that the
benchmark for rewarding points is not Embodied Energy of materials, but largely, the
estimated post occupancy operational energy and how it is minimized. While Lifecycle
Assessment of every equipment and material might not be a practical solution for rating
individual buildings, it should have been an integral part of forming the guidelines. The
efficiency of the equipments (HVAC&R, building automation systems, etc.) is definitely
increasing, however, the research of Timothy Gutowski shows that the historical trend of
digital technology is toward more and more energy intensive manufacturing processes.
5.1 Indoor environment quality
Indoor Environment Quality is a fairly new concept that originated barely 20-30 years ago.
As the name implies, it simply refers to the quality of the air in an office or other building
environments. Workers are often concerned that they have symptoms or health conditions
from exposures to contaminants in the buildings where they work. One reason for this
concern is that their symptoms often get better when they are not in the building. While
research has shown that some respiratory symptoms and illnesses can be associated with
damp buildings, it is still unclear what measurements of indoor contaminants show that
workers are at risk for disease. Indoor environments are highly complex and building
occupants may be exposed to a variety of contaminants (in the form of gases and particles)
from office machines, cleaning products, construction activities, carpets and furnishings,
perfumes, cigarette smoke, water-damaged building materials, microbial growth (fungal /
mold and bacterial), insects, and outdoor pollutants.
Other factors such as indoor temperatures, relative humidity, and ventilation levels can also
affect how individuals respond to the indoor environment. Green building rating systems
emphasize strongly upon the need to fulfill some prerequisites to ensure a minimum standard
of Indoor Environmental Quality.

This is in direct conflict with the sustainability issues, as largely, these prerequisites are being
met by mechanically controlled environments that are highly energy intensive. Also, even, in
case of natural ventilation being provided in the buildings, sensors need to be installed to
monitor CO2 levels. To achieve the required Indoor Environment Quality, green buildings
use highly specialized and effective equipments that generally use low operational energy,
but have very high production embodied energy. The energy savings realized by digital
technology barely absorbs its own growing footprint.
5.2 Adaptability of the locals
Therefore, the popularity of the green building movement should be steered towards a
vernacular movement, with emphasis given to shifting the benchmark for comfort zone and
Indoor Environmental Quality to what the locals are adapted to regionally, rather than
creating universally ideal psychrometric conditions. At the London School of Hygiene and
Tropical Medicine, a group of 32 students were asked to record their sensations of comfort
under precise air-temperature, humidity, and airspeed conditions. They included
approximately equal numbers of students from Great Britain and the United States, and from
tropical countries. A summary of the student responses at 22.2°C (72°F) dry-bulb
temperature, 16.1 °C (61 °F) wetbulb temperature, 56% relative humidity, and 0.25-0.38 m/s
(50-75 ft/min) airspeeds is given in table 6. Although this is a preliminary, and by no means
conclusive, experiment with only a small number of subjects, it indicates some fundamental
difference between people from tropical and temperate countries with regard to comfort
sensation. [4]
Table 2. The values for the ambient and most appreciated air-conditioning temperatures and
humidity in four tropical cities [4]
Dry Bulb
Temperature
Wet Bulb
Temperature
Dew
Point
Ambient conditions:
Delhi, India 43.3 (110) 24.4 (76) 16.1
(61)
Abadan, Iran 46.1 (115) 26.7 (80) 19.4
(67)
Bombay, 32.2 (90) 27.7 (82) 26.7
India
(80)
Lagos, 35.0 (95) 28.3 (83) 27.8
Nigeria
Most desired
conditions
(82)
25.6 (78) 19.4 (67) 15.6
(60)
Relative
Humidity
Effective
Temperature
21% 30.4 (86.8)
22% 31.9 (89.5)
72% 29.0 (84.2)
62% 30.2 (86.3)
55% 22.5 (72.5)
5.3 Therefore, the popularity of the green building movement should be steered towards a
vernacular movement, with emphasis given to shifting the benchmark for comfort zone and
Indoor Environmental Quality to what the locals are adapted to regionally, rather than
creating universally ideal psychrometric conditions.
6. Conclusion

While the building construction industry is definitely adopting the Building Energy Rating
Systems, one may ponder that it is more out of financial concern - in terms of post occupancy
energy savings, than out of environmental sensibility. The concept of Indoor Environmental
Quality is becoming overhyped, and the buildings are changing into over-ventilated, overglazed,
and under-insulated, mechanically controlled micro environments.
Sustainability is not a new movement or revolution; it is how things were meant to be.
Vernacular Architecture of any region is a testimony to this fact. However, due to urban
sprawl and changing climate, these traditional construction techniques are being considered
obsolete. Need of the hour is to research on how vernacular materials as well as techniques
can be incorporated in the growing trend of high rise construction.
References
1. Cole, R.J. and Kernan, P.C. (1996), Life-Cycle Energy Use in Office Buildings, Building
and Environment, Vol. 31,No.4,pp.307-317
2. Comparing the Environmental Effects of Building Systems, Wood the Renewable
Resource Case Study No.4, Canadian Wood Council, Ottawa, 1997
3. Kris De Decker, (2009) , Low-tech Magazine
4. Fathy, Hassan (1986), Natural Energy and Vernacular Architecture,
The United Nations University

Abstract
Energy Efficiency and Sustainability in Skyscrapers
A Historical Timeline Analysis
Shankha Pratim Bhattacharya
Indian Institute of Technology, Kharagpur (West Bengal)
Corresponding Author, Email: spd@arp.iitkgp.ernet.in
High rise buildings are not considered as a ecologically sustainable building. But
population pressure in the present urban hubs considers the tall building an essential part
of the city development. The development of skyscrapers has many influencing factors.
This paper highlights the energy use and conservation criteria of development of tall
building since its birth. This paper is supported by study of various literature including
recent articles in reputed journals. The trend of energy conscious sustainable high rise
architecture is presented in a historical timeline. The merits and demerits of the tall
building construction in energy consumption perspective are discussed initially. The
hundred twenty five years of skyscrapers development spectrum categorically subdivided
into five generations. The turning points or the linking events are also critically analyses.
Finally the paper tells about the present status of modern fifth generation skyscrapers and
its discussed its physical energy friendly features.
1. Introduction
The birth of high rise building was initiated in the last phase of nineteenth century. The
Home Insurance Building at Chicago was known as the first high rise building 1 . Over the
past hundred twenty five years the high rise building constructions undergone an array of
modifications. There are many factors identified as parameter for the advancement of
high rise building to today’s modern skyscrapers. Development of new material and
technology, regulatory changes by civil bodies, change in demography in urban areas,
modern economic and commercial impact to the society are the major influencing factors
to be responsible for parametric shift in the growth of tall building. High rise architecture
became popular in the urban centers because it caters the high density population and
maximizes the financial returns over a fixed plot size. UN report, in the year 2010
estimated that, urban population will exceed rural population within next twenty years.
Sixty percent of the world population will live in urban areas by 2030 10 . These changes
will be clearly visible in Asian countries where the economy is increasing rapidly. In
modern context, the climate change and global worming are the burning issues. It is a fact
that, the built environment made a significant contribution on the global green house
effect. UNEP environmental programme, 2007 found that, the building materials and its
present construction system are accountable for 30 to 40 percent of the primary energy
used in the world 8 . Recently, the rate of high rise buildings construction becomes

unprecedentedly high all over the world. In this notion, all attention is presently given
towards the environmental impact and sustainable features of tall buildings.
2. Energy issue of high rise buildings
Generally, Skyscrapers are not considered as an ecological building. The skyscrapers
require more energy and high embodied material resources to build. It also requires quite
a high energy during the operation and demolition. There are many factors that influence
the high level energy requirement of tall building. On the other hand in a comprehensive
city and regional planning point of view the group of tall building has certain advantages
also. According to the Roaf et al. 6 the drawbacks and according to Wood 9 the advantages
of the tall building and its impact to energy consumption are listed below:
2.1 Disadvantages of tall buildings
Higher embodied energy building materials are used high rise construction
High energy consumption in building operations and services.
Gradual increase in the wind loading at higher level of the building requires higher
size of structural and facade elements
Both maintenance and cleaning operation in skyscrapers required high energy.
A complete closed environment at higher level requires efficient HVAC system and
artificial lighting.
High degree of safety requirement is essential during construction of high rise
building, especially post 9/11 and terrorist threats in urban regions.
Higher cost involves in effective foundation system.
Internal environment, spatially in residential high-rise housing may lack open,
recreational, social interaction spaces.
High rise buildings become problematic for the people suffering from vertigo.
Overpopulation in certain localities provide greater demand on existing urban
services and infrastructure
2.2 Advantages of tall buildings
Denser cities reduced transportation demands and provide less travel time, which lead
to less consumption of automobile fuel.
Efficient land use in population concentration provides reduction in spreading in
suburban areas. Concentrated cities reduce size of infrastructure networks, like
power, water supply, waste water etc.
By virtue of its smaller footprint it will have considerably less impact on productive
agricultural land.
High rise buildings standardized the use of building materials. It also provides the
scope of use of prefabricated units for constructions.
Higher wind velocities at height have potential for natural ventilation through stack
effect and also generate a scope for wind power.
Space in the higher floors has the potential for recreational spaces, away from traffic
noise, air pollution.
Skyscrapers increase the access to view.

Thus, the above two comparative analysis shows that, there is a possibility to have a
viable, energy efficient ecologically sustain high rise built form. Presently the
architectural and technological advancement gradually justify the need and necessity of
green skyscrapers.
3. Energy generation of skyscrapers
The recent advancement in software technology, particularly in designing, modeling,
detailing, and management highly influence the construction of skyscrapers. However, it
is also interesting, and necessary, to look at the energy consumption characteristics of tall
buildings through the historical timeline. It is required to study and examine how and
why these changed has incorporated in the design and to learn possible lessons for the
future. Historically, the development of high rise building can be clustered into five
energy generations. These five generations are separated by each other with a connecting
event. Four such connecting event are recognized as (i) Introduction of 1916 New York
zoning law, (ii) Innovation and use of curtain wall as building façade, 1951 (iii) The
energy crises in 1070s and (iv) Rise of an environmental consciousness in 1997 5 . The
first energy generation is considered the time between the birth of tall building in 1885 to
the 1916. The construction of high rise building was made possible those days due to the
development of structural steel and invention of elevators. The Home Insurance building
in Chicago, Illinois, (ten storied with 42 meter in height) is generally referred as the first
high rise building. The architect William Le Baron Jenney, was used the method known
as ‘skeleton construction’, using structural steel. Ventilation was achieved naturally
through windows and artificial lighting levels were very low. The concept of large
window and high ceiling was provided to allow higher daylight penetration to the
interiors. The physical envelope of construction was influenced by traditional loadbearing
system. External walls were often quite thick with normal masonry providing
high degree of exposed thermal mass. It creates comfortable indoor thermal environment
by maintaining relatively warm and cool temperature during winter and summer months.
The Equitable building, a 38 storied office building in New York was completed in 1915.
A total 176000 Sqm floor area of the building contribute a FAR (Floor Area Ratio) of
30 3 . This building does not have any set-backs and rising vertically to its full height from
the edge of the sidewalk. This massive building created a controversy, as it block both the
light and views from the surrounding buildings. The volume of the building cast day time
shadow on the adjacent streets. Many New Yorkers feared that further construction of
buildings of this kind, would turn Manhattan into an unpleasant and dark patch in streets.
Finally, City authority of New York established a landmark zoning law 1961 restricting
the vertical structures in Manhattan. The law established limits in building massing at
certain heights, usually interpreted as a series of setback in horizontal directions. Figure 1
shows the impact of zoning law on the massing of tall building. For a constant volume,
the surface area of the building increases to accommodate the vertical setbacks. The
bulky nature of first energy generation buildings becomes slender with more surface
exposure. Finally, the zoning law indirectly made an impact on building energy use. The
energy requirement for heating and air-conditioning is proportionally increases with the
increase of building surface area. This zoning law in 1916 become a mile stone in the
history of skyscraper development. It initiates the “second energy generation” and
continues till 1951. However, at the higher floor levels, the slender buildings have
reduced floor plans compared to the first generation buildings. This parametric change in
building design results, greater natural light penetration and considerably reducing the

demand of artificial lights. The traditional building materials like brick, stone and thick
plaster are continued to use as previous generation, offering comfort to the occupants.
Figure 1. Impact of Vertical set backs in Tall Buildings
The third energy generation started in 1951. After the Second World War, technological
innovations gave rise to the use of fully-glazed tall building. This development of curtain
glazing dramatically changed the high-rise typology. Tall buildings completed prior to
the war had 20 to 40% glazing within their facades. Whereas ‘third generation’ buildings
had a significantly higher ratio, between 50 to 75% (Lake Shore Drive Apartments,
Chicago, 1951: 72%; Lever House, New York, 1952: 53%) 5 . Rectangular glass facade
buildings quickly become popular around the world, regardless of building’s site location
and climatologically consideration. It becomes a symbol of economic wealth and
towering glazed office blocks became fashion as company headquarters. The large
amount of single glazing initiate the problem related to thermal insulation, internal spaces
experience vast heat losses in the winter, but also overheats from excess solar gain in the
summer. Internal heating and cooling can be compensated by HVAC systems but it
directly leads to extremely high primary energy consumption 4 . Another interesting
feature of third generation was evolution of black skyscrapers in various parts of the
world, influenced by van der Rohe’s ‘International Style’. Black or gray colour surface
having high value of solar absorption with compare to the buildings with masonry or light
colour facade. The uses of dark curtain wall increase the building’s primary energy
consumption in two folds. Despite of the high quantities of glazing in the facade, low
amounts of natural light would actually penetrate into the office spaces, due to the poor
light transmission properties of the dark-coloured glass (44 percent with respect to 86 in
normal glass). It increases dependence on artificial lighting and consumption of energy.
Figure 2. Impact of Energy Crisis in Black Skyscrapers Construction in US
The popularity of the single-glazed curtain wall facade high rise building construction
was abruptly interrupted by the energy crises that evoked in 1973 and 1979 (triggered by
the two global oil crises). The amount of primary energy used in the third generation

uildings suddenly became a major issue of concern. The mass people gradually become
concuss of using energy in buildings. Many developed nations brought in building energy
performance codes, forcing switch over to double-glazing. The construction of singleglazed
curtail wall was strongly criticize. The industry and research house led to develop
more effective thermal insulation, solar heat control glass with higher degree of
transparency. A noteworthy improvement in tall-building facade design and energy
performance was initiated the fourth energy generation from 1973. The construction
industries also move away from dark-tinted glazing to effectively minimize artificial light
loads. Another reduction in lighting load was achieved by American National Standard
Practice for Office Lighting revision in 1982. They proposed roughly a 25–50% decrease
in office illumination levels, due to the rising energy costs and environmental concerns
brought about by the energy crises 7 .Some of the building was redesign with the energy
efficiency perspective. The black skyscrapers in general became increasingly unpopular
due to their inherent energy efficiency flaws [Refer Figure 2].
3. The present fifth energy generation eco-skyscrapers
The majority of the building constructed since 1970 followed the ‘fourth generation’
characteristics. The requirement of environmental sustainability and further reduction in
primary energy demand in buildings was noticed in late twentieth century buildings. In
1956 Frank Lloyd Wright’s Price Tower in Oklahoma shows many features which was in
future rationalized as sustainable one 2 . In 1984, Skidmore Owings & Merrill (SOM)
constructed National Commercial Bank, Jeddah where sustainable approach is followed.
The glass curtain walls blocks are placed in introverted manner to stay away from direct
sun in the hot solar extreme of the Saudi Arabian desert. The introverted glass facade
with monolithic stone block with a triangular plan shielded the strategically position of
interior sky gardens from outside set an excellent examples of ‘environmental’
skyscrapers and introvert nature of Islamic culture as well 9 . Some literature would of
course, claim that the early work of Geoffrey Bowa in Sri Lanka (Mahaweli office tower,
Colombo, 1976), Charles Correa in India (Kanchanjunga Apartments, Bombay, 1983), or
Harry Seidler in Australasia (Riverside Centre, Brisbane, 1986) are more indicative of the
first prototypes for eco-skyscrapers. The first significant tall building reflecting these new
environmentally conscious principles was the Commerzbank in Frankfurt designed by
Norman Foster and Partners, 1997. This will become the landmark point between the
fourth and present fifth generation buildings. The building is also considered the first
'ecological' skyscraper due to its use of sky gardens and energy-saving technologies 11 .The
Commerzbank incorporates a high degree of primary energy-reducing design strategies
and technologies that include:
A central atrium of full height of the building was designed to provide natural lighting
and ventilation to internal office spaces.
Open to sky, large gardens are infusing in the various vertical levels to further
increase the natural light quantity in interiors.
A facade allows for natural ventilation for over half the year through operable
windows.
A water-based cooling system was designed for chilled ceilings.
During the last ten years there are many tall building shows the ecological and
sustainable characters. Some of the characters of those buildings are highlighted below:

The Bank of America tower in New York (2009) was set the tone for the future
skyscrapers that will built in US. This is one of the skyscrapers that were built using
largely recycled material. A sophisticated rain water capture system is also in place. The
windows are so designed to maximize the sunlight along with the smart and efficient
LED lighting. In Okhta Tower at St. Petersburg, Russia (2007), double layer outer shell
or skin of the needle like building is designed in such a way so as to maximize the
amount of sunlight penetration in the interior of the building. It ensures the trapping of
most of the heat energy inside the building during harsh cold winter. Chicago’s 340 on
the Park (2007) feature high tech insulation and rain water capturing system. Two storey
winter gardens starting on the 25 th floor that makes great use of the special windows
designed for optimal sunlight dispersion throughout the building. Three large (29meters
in diameter) wind turbine 225KW each in The Lighthouse Tower, Dubai (2012,
Proposed) will be implemented in the building façade. It also proposed to clad with 4000
solar panels to generate additional electricity. The Co-operative Insurance Solar (CIS)
Tower, Manchester, UK (2006-Renovated) set a new benchmark by retroactively
installing renewable energy technology onto the service tower during renovation in
2006. In 2004 the deteriorating mosaic tiles in the façade was replaced by 575 KW of
building integrated photovoltaic cells.
5. Conclusion
The tall buildings are not recognized as an ecologically sustainable building. The effects
of climate change and the urgent need for more sustainable building types and patterns of
living has been realized today. The development of skyscrapers and shown a positive and
gradual shift towards a sustainable and energy efficient practices. Since last two decades,
quite a large number of professionals and institutes are working on appropriate
environmental responses in the domain of tall building design. We hope, in future
vocabulary of skyscrapers will take a green turn with the invention of new materials and
modern technology.
6. References
1. Ali, M.M., and Moon, K.S., Structural Developments in Tall Buildings: Current Trends and
Future Prospects, Architectural Science Review, Vol 50(3), 2007, pages 205-223
2. Alofsin A (ed.). 2005. Prairie Skyscraper: Frank Lloyd Wright’s Price Tower.
Rizzoli: New York; Price Tower Arts Center: Bartlesville.
3. C. Willis, Form follows Finance: Skyscrapers and Skylines in New York and Chicago
(New York, Princeton Architectural Press, 1997).
4. D. Arnold, ‘Air Conditioning in Office Buildings after World War II’, ASHRAE
Journal (July, 1999), pages33–41.
5. Oldfield, P., Trabucco, D and Wood, A., Five energy generations of tall buildings: an
historical analysis of energy consumption in high-rise buildings, The Journal of
Architecture, Vol.14 (5), 2009, pages 591-613.
6. Roaf, S., Crichton D, Nicol F. 2005. Adapting Buildings and Cities for Climate
Change: A 21st Century Survival Guide. Architectural Press: Oxford.
7. Stein, R.G., Observations on Energy Use in Buildings, Journal of Architectural
Education, Vol.30 (3), 1977, pages 36–41.

8. UNEP, Buildings and Climate Change: Status, Challenges and Opportunities,
Nairobi, United Nations Environmental Programme, 2007.
9. Wood, A., Sustainability: A New High-Rise Vernacular, The Structural Design of
Tall and Special Buildings, Vol.16, 2007, pages 401-410.
10. World Population Prospects: The 2006 Revision and World Urbanization Prospects:
The 2007 Revision, http://esa.un.org/unup, Population Division of the Department of
Economic and Social Affairs of the United Nations Secretariat, (Website visited on
January 2008).
11. Yeang, K. and Powell, R., Designing the Eco-Skyscrapers: Premises for Tall Building
Design, the Structural Design of Tall and Special Buildings, Vol.16, 2007, pages 411-
427.

Life Cycle Analysis and Energy Saving Potential of EPS and XPS
Abstract.
Amol Desai
Supreme Petrochem Limited, Mumbai
Corresponding Author, Email: amol_desai@spl.co.on
More effective insulation is one of the easiest routes to improved building energy efficiency,
both in new build constructions and in the renovation of existing buildings. Loss of energy
through walls and roofs is 30 to 40%. There are many ways to insulate a building, and there
are dozens of insulation assemblies. Here we discuss two insulation types in this paper. These
are popular in a variety of installations for the entire building envelope: EPS and XPS
1. Introduction
Buildings are reported to be responsible for 40% of energy consumption in developed
countries, more than industry or transport, and for 36% of total CO2 emissions. Roadmap for
moving to a competitive low carbon economy also highlights the need for further
improvements to the energy performance of buildings. More effective insulation is one of the
easiest routes to improved building energy efficiency, both in new build constructions and in
the renovation of existing buildings. Loss of energy through walls and roofs is 30 to 40%.
Taking measures to insulate the walls and roofs of the building stock could result in a
substantial cut in CO2 emissions through reduced energy use, their by increasing the energy
efficiency of buildings. Insulation is a product that blocks heat transfer, and the resistance to
heat flow is measured as R-value, therefore, the higher the R-value, the better the insulation.
There are many ways to insulate a building, and there are dozens of insulation assemblies.
There are two insulation types that are popular in a variety of installations for the entire
building envelope: EPS and XPS.
2. Description
Expanded polystyrene (EPS) foam is closed-cell insulation; the appearance is typically a
white foam plastic insulation material. Extruded polystyrene (XPS) foam is a rigid insulation
formed with polystyrene polymer, using an extrusion process. While EPS and XPS are two
different products, they do have some similar characteristics and fall under the same
manufacturing standard: ASTM C578 Standard Specification for Rigid, Cellular Polystyrene
Thermal Insulation. The use of EPS and XPS insulation in building construction offers great
flexibility, compatibility, and thermal efficiency for use at all areas of a building envelope.
Picking between the two will depend on particular use; choosing the appropriate type is
critical for proper insulation performance. Expanded polystyrene (EPS) does not experience
thermal drift, meaning its R-value remains constant throughout the life of the building. EPS
can provide compliance with ASHRAE 90.1-1999. Additionally, this material’s use in
insulating concrete forms (ICFs) and structural insulated panels (SIPs) also contribute to
increased energy efficiency without compromising comfort levels for occupants. Extruded
polystyrene (XPS) can help achieve high energy efficiencies by providing stable, long-term

insulation value, as well as blocking thermal shorts that may occur in roof, wall, and belowgrade
assemblies. EPS insulation can return up to 200 times the amount of energy required to
produce it, and reduce emissions by up to 100 times the volume produced during the
manufacturing process.
3. Life cycle analysis
conducted by Franklin Associates for the EPS Molders Association, USA – to quantify the
energy savings and greenhouse gas reductions provided by the use of EPS foam insulation in
single ‐family residential construction, demonstrate an average savings of over 36 times the
amount of energy expended when adding EPS insulation to the exterior walls of a home in
the U.S, and a reduction in global warming potential by nearly 60 times the CO2 equivalent
of the emissions produced. This represents an energy payback period of less than17 months
and a recapture of greenhouse gas emissions in less than 10 months for adding EPS insulation
to America’s homes. It is worth noting that the payback period for energy in all of North
America is no greater than 2 years (The EPS insulation modeled has a density of 1.0 lb/ft3
and an R-Value of R-3.85 per inch for R-6 insulation in U.S. Zone 5). In Canada, the results
were even more pronounced, returning the energy invested in less than 6 months, and the
emissions in just less than 1 year. Payback period is as little as 3 months (for R-4 insulation
in the Northwest Territories of Canada). This is an excellent return on investment (ROI) by
any measure. In Europe, in the construction sector, EPS has a long established reputation for
its exceptionally high insulation qualities. Its BRE ‘A-plus’ rating means it is the perfect
choice for use in under-floor, between-floor, walling and roofing applications where it is able
to give a constant insulation value across the full service life of the building. Thermal
conductivity testing of EPS to DIN52612, under the auspices of the Forschungs institute für
Warmeschutz in Munich, confirmed that its insulation efficiency at 0.0345W/mK was well
within the originally specified standard requirement of 0.04W/mK. For those seeking
material higher performance for the Code for Sustainable Homes (CSH), low lambda material
is available – which is typically grey in color. The thickness of high performance, low
lambda EPS can be as little as 70mm, making possible a total floor thickness of 135mm.
4. Conclusion
These results present a powerful case for the significant contributions of EPS insulation in
making homes more efficient, comfortable and environmentally sustainable. The benefits of
insulation vary with the climate and are generally more pronounced in colder regions where
significant energy is used to heat a home. The exceptional performance of EPS as an insulator
for the built environment offers the construction industry the tools and technology needed to
achieve superior thermal performance while making a significant and restorative contribution
to the reduction of global warming. Architects, designers and material specifires can be more
confident than ever that they are providing an environmentally responsible choice when
selecting EPS to insulate their buildings.

Role of Reflective Insulation Roof Coatings for
Improving Thermal Performance of Buildings
A field Study in Bangalore
D. E. V. S. Kiran Kumar and Minni Sastry
The Energy and Resources Institute (TERI) - Southern Regional Centre, Bangalore
Corresponding Author, Email: d.kumar@teri.res.in
Abstract.
Reflective roof coatings play a vital role in improving indoor conditions in naturally
ventilated buildings and energy performance in air conditioned buildings. Currently there
is a wide range of reflective coatings available in Indian market as one of the solutions
for improving energy efficiency in buildings. A recent advancement in this field is-
reflective coatings that can also provide good insulation. These reflective coatings consist
of ceramic nano particles as fillers which form an insulation layer. This paper discusses
the micro structure, mechanical properties and advantages of such reflective coatings. An
experimental study was carried out by the authors to observe the thermal performance of
such insulation reflective paints coated on the roofs of two existing buildings in
Bangalore. Hourly surface and air temperatures were monitored for a few weeks in
summer using infrared gun. The maximum surface temperature difference observed
between coated and uncoated roof is 27degC over deck and 8degC under the deck. The
paper also addresses issues related to long term maintenance of these coatings and
highlights a solution that enhances their performance.
Keywords: Thermal performance, Reflective roof coatings, Insulation, Ceramic nano
particles, Heat flux
1. Introduction
Surface reflectance property of building envelope is one of the most important parameters
that influence thermal performance of buildings. High reflective surfaces are effective in
reducing radiant heat transfer in buildings especially in tropical climates. They create a
kind of thermal barrier by refracting, reflecting and dissipating the heat. Typical
construction of roof in most of the Indian cities is using concrete slabs. The surfaces of
these roofs are covered with moss and become dark over the time; in turn decrease their
solar reflectance and remain at higher temperatures. In this context, the application of
reflective coatings is one of the simple and economically viable solutions especially
while retrofitting buildings for improving energy efficiency. A recent advancement in this
field is insulation reflective coating which not only reflects incident solar radiation but
also insulates the roof surfaces. It consists of ceramic nano particles suspended in a base
reflective paint. It results in lowering the radiant heat flux entering into the buildings and

thus helps to provide more comfortable indoors. It can reduce energy demand in air
conditioned buildings and improve thermal comfort in un conditioned buildings. It plays
a prominent role to reduce urban heat islands and thus help to mitigate the climate change
effects. Insulation reflective coatings reflect more light and heat from the solar radiation
and cut off envelope surface heat gains. A laboratory test carried by Guo et al (2011)
shows that the insulation coating performs better than the non-insulation coating and the
insulation temperature difference increases by 0.73⁰C. It is also understood from their
study that by applying insulated coatings energy savings are about 5.8kWh/m 2 month
possible in air conditioned buildings. Studies carried by Shen et al (2011) highlights the
impact of reflective coatings on the indoor environment. They found that exterior and
interior surface temperatures can be reduced by upto 20⁰C and 4.7⁰C respectively.
2. Methodology
Cities like Bangalore where the solar radiation intensity is usually strong, insulation alone
might not have the best impact. Hence, the application of the insulation reflective coatings
foresees a new trend in the field of roof coatings for improving thermal performance of
buildings. This paper presents an application of insulation reflective coatings on the roofs
along with the measured data. Temperature monitoring has been carried out on R C C roofs
of two buildings in Bangalore city during summer. Two local suppliers supported the study
by providing two different ceramic reflective coatings on the selected building roofs. Air
temperatures were monitored for a few days in April and in June using thermohygro data
loggers. Parallelly, instantaneous readings were taken for surface temperatures (over and
under the deck) using infrared gun at 1 hour interval during the daytime. The readings on
coated roof were compared with the readings of uncoated roofs in the same building. Finally
results of the experiments carried in both building I and II were compared. Coating on
building II is based on nano mica as well as ceramic particles whereas on building I it
consists ceramic particles alone. The chemical composition and the physical properties of the
coating on building II has been studied using microscopic images. Advantages of these
paintings have also been highlighted. Figure 1 show schematic sections of the buildings and
the parameters recorded during the measurement.
Figure 1. Schematic sections of the buildings selected for the study

3. Results & discussions
3.1 Building I
In building I, maximum surface temperature of the uncoated RCC roof, over the deck is
found to be 61 o C at 13:00hrs when the corresponding air temperature is 30.1 o C. The
maximum surface temperature of the coated RCC roof recorded over the deck is 34 o C
surface temperature under the deck, shows an interesting profile as it increases drastically
from 32 o C at 15:00hrs to 36 o C at 17:00hrs in case of uncoated RCC roof. However, the
surface temperature under the deck of the coated roof remains at 27-28 o C throughout the
day. Surface temperature comparison between coated and uncoated RCC roofs is
presented in figures 2 & 3. The difference between the mean temperatures recorded over
the deck and under deck of coated and uncoated roof is 17degC and 3.3degC
respectively. It is understood that due to this significant difference in temperatures,
amount of heat flux in this case is almost 77% less compare to the uncoated RCC roof
during the peak hour. More solar reflectance and less absorbance it leads to lower surface
temperatures over the deck. As mentioned, it is also to be noted that the roof coating
provides both reflection as well as insulation. The higher surface and air temperatures
results in more heat flux through the RCC slab and results in sudden rise in temperature
under the deck. There is 1 degC difference in indoor air temperature found for coated and
uncoated roofs. Figure 4 shows the image of the coated roof of Building I.
Figure 2. Over deck surface temperature profile with the RCC of roof of
building I with and without insulation reflective paint
Figure 3. Under deck surface temperature profile with the RCC of roof of building I with
and without insulation reflective paint

Figure 4. RCC roof of Building I coated with insulation reflective coating
3.2 Building II
During the monitoring process, it is also observed that the white coating loses its
performance when the dust gets collected over it. It is thus important to address the issues
related to maintainability of white roof coatings to enhance their performance in the long
run. Use of roof coatings with glossy finish similar to ceramic / mosaic tiles is a solution
for easy maintenance. So, a coating is selected considering these parameters and applied
on another building near to building I. The coating surface has a thin coat of epoxy resin
been applied over the major white coating to provide the glossy finish. The experiment
has been carried for about a week in June to collect air temperature and surface
temperature data. The sky condition was cloudy for a few hours in the afternoon of the
experimented day. Figure 5 shows the comparison of surface temperatures taken for
conventional as well as coated roofs both over the deck. The difference in mean surface
temperature over the deck between the coated and uncoated roofs is 10degC.
Figure 5. Over deck surface temperature profile with the RCC of roof of building II with
and without insulation reflective paint

The mean surface temperatures recorded under the deck for coated and uncoated RCC
roof of building II are 29.8˚C and 26.3˚C respectively. As observed in building I, the
under deck temperature of the coated roof remains constant throughout the day. However,
the surface temperature over the deck drastically rises after 12:00hrs (figure 6). Mean
room air temperature recorded for coated and uncoated roof is 27.3⁰C and 28.6⁰C when
the mean ambient temperature is 32.7⁰C. Table 1 presents a summary of temperatures
recorded in building I and building II.
Figure 6. Over deck surface temperature profile with the RCC of roof of building II with
and without insulation reflective paint
Overdeck
Underdeck
Table 1. summary of temperatures recorded in building I and building II
Building I Building II
Coated Uncoated Coated Uncoated
Mean Surface temperature 29.1 46.2 30.8 39.7
Mean Ambient air
temperature
Mean Surface temperature
Mean Room air
temperature
30.2
32.7
26.7 30.1 26.3 29.8
30.2 31.0 27.3 28.6
4. Microstructure, mechanical properties and advantages of insulation reflective
coatings
Micro structure of the mica and ceramic based paint coated on building II was studied using
Scanning Electron Microscope (SEM) images. Figures 7 show the structure of ceramic and
mica particles on surface and the cross-section of paint respectively. Size of the ceramic
particles present in the coating varies from 0.5 to 2 microns. These sphere like particles which
are hollow microscopic ball filled with air or inert gases add insulation property to the coating.
Proper mixture of these particles with the polymer matrix helps uniform dispersion of coating.

It is observed that the size of the mica particles is as small as 2 microns on the surface.
However, its size varies from 10 to 100 microns in the cross section of the paint which
improves the insulation property of the paint. Due to the homogeneity in its composition, the
tensile strength and the impact resistance of the coating seems to be good. Table 2 presents a
few mechanical properties of the coating as provided by the manufacturer. Thermal properties
of this kind of coating are usually referred with the R value Equivalency (RvE). However, due
to unavailability of the testing facility for RvE, the manufacturer of the coating was unable to
provide the same.
Figure7. SEM images of insulation reflective coating (with ceramic and mica particles)
for surface and cross showing ceramic particles and mica pellets
4.1 Advantages
1. Compared to other conventional insulating materials like fiberglass and rigid polysterene
boards, these nano coatings don’t not appear to raise environmental and health concerns.
2. As mica is a natural and mined source material the product is known as green product.
3. Reflects the incident solar radiation by almost 75% and resistant to UV light.
4. Good water proofing and protection against moss and algae due to glossy surface.
5. Coefficient of linear thermal expansion (CLTE) matches with concrete CLTE and due to
which good adhesion is possible.
Table 2. Chemical composition and physical properties of mica and ceramic based
insulation reflective coating
Chemical Composition Polyamide cured epoxy resin with ceramic
and mica fillers+ UV resistant acrylic
aliphatic coating with high reflective pigments
Tensile strength 26.5 N/mm 2
Compressive strength 93N/mm 2
Young’s Modulus 63N/mm 2
Coefficient of Linear thermal expansion 12.5 to 14X10-6/˚C
Reflectivity Upto 75%
Colour White

5. Conclusion
The importance of insulation reflective coatings for improving thermal performance of
buildings is understood through field measurements. The maximum surface temperature
difference observed between coated and uncoated roof of Building I is 27degC over deck and
8degC under the deck. In Building I, difference between the mean surface temperatures
recoded over and under the decks of uncoated and coated roof is 17degC and 3.3degC
respectively. In case of building II it is 10deg C and 3.5degC. It is understood that due to
insulation reflective coating, amount of heat flux through roof reduced by 80% in case of
building I and 65% in case of building II. The difference in mean room air temperature of
coated and uncoated roofs of Building I & II are 0.8 degC and 1.3degC respectively. This
improvement in the indoor conditions predicts a good potential for energy savings in air
conditioned buildings. Thus, the thermal performance of insulation reflective coatings
building roofs is significant in Bangalore where the ambient air temperatures are moderate
and solar radiation intensity is high. It is also understood the necessity of addressing
maintainability issues of white roof coatings to enhance their performance in the long run.
Use of roof coatings with glossy finish similar to ceramic / mosaic tiles is a solution for easy
maintenance. An attempt has been made to study the micro structure of the roof coating. It is
thus concluded that there is a good research potential in the area of developing nano
insulating materials for buildings.
6. Acknowledgement
Authors would like to thank Mr. Aditya and Mr. Rammohan for providing insulation coatings
on the buildings selected for the study. Also like to specially mention the help extended by
Dr. Sailaja Bhattacharya and Ms. Deepthi for getting SEM images.
References
1. Balakrishna B. (2011), “Ceramic insulation paints: the need for insulating construction
materials”, The Masterbuilder,Vol 13-12, Pages 60-62.
2. Mohammas S. Al-Homoud (2005), “Performance characteristics and practical
applications of common building thermal insulation materials” Building and
Environment, Vol 40, pages 353-366
3. George Elvin (2007), “Nano technology for Green Building- Research report by Green
Technology Forum”, Pages17-20.
4. Guo W, Qiao X, Huang Y, Fang and X Han M (2012), “Study on energy saving effect of
heat- reflective insulation coating on envelopes in hot summer and cold winter zone”,
Energy ans Buildings, Vol 50, Pages 196-203
5. Shen H, Tan H W, Tzempelikosa A (2011), The effect of reflective coatings on building
surface temperatures, indoor environment and energy consumption- an experimental
study; Energy and Buildings Vol 43, Pages 573-580

Energy Efficiency through ICT Adoption for Sustainable Habitat
Abstract
Amit Kush*, Amod Krishna** and P.K.Bhargava*
*CSIR-Central Building Research Institute, Roorkee
**Roorkee Institute of Technology, Roorkee
Corresponding Author, Email: amitkush@cbri.res.in
India is the second most populated country in the world, accommodating over 120 crore
people in diverse climatic zones. Owing to the rapid growth in infrastructure, especially in the
commercial sector and the substantial rural to urban shift of the population, India’s building
sector is expected to grow at a brisk pace. Commercial and residential sectors of buildings
consume substantial quantum of energy throughout the lifecycle of buildings, contributing to
around 6% of India’s total Green House Gases (GHG) emissions. Various initiatives have
been introduced in the recent past, both at economy level and specifically for habitat sector
that aim to increase energy efficiency and sustainability. The study focuses on exploring
potential GHG reduction opportunities and energy efficiency opportunities enabled through
Information and Communication Technology (ICT) solutions. On an average, it is estimated
that the implementation of energy efficient options through ICT solutions would help in
achieving around 30% electricity savings in new residential buildings and around 40%
electricity savings in new commercial buildings. ICT based solutions for sustainable habitat
in the areas of planning, energy efficiency, water and waste management, environmental
pollution, building materials and technologies, roads and transportation, and impact of
habitation on climate change can play a critical role in this transition towards higher energy
efficiency, and low carbon emission habitats have been reported in this paper.
Keywords: GHG, ICT, environmental pollution, energy efficiency, carbon emission
1. Introduction
Several ICT based technologies have an important role to play in enhancing the efficient use
of energy in buildings, with the green building technologies. Building management systems
(BMS) to automatically manage and reduce energy consumption and control heating,
ventilation and air conditioning systems, lighting systems play a crucial role. With climate
change posing a global challenge, adopting ICT solutions in various industries would be a
win-win way to cut India’s carbon foot print.
The study attempts to quantify the energy savings potential through the use of currently
available ICT solutions and their contribution in reducing the green house gases (GHG)
emissions in various sectors. ICT options for achieving increased energy efficiency are
economically viable and available in the market. Report [1] says that total cost of ICT
implementation in identified sectors – considering moderate penetration of ICT solutions in

2020 and 2030 – is estimated at INR 49,700 crore and INR 156,100 crore, respectively.
These investments correspond to cost savings of around INR 7,300 crore per annum and
INR29,200 crore per annum respectively. Identified ICT solutions can potentially lead to
GHG emission savings of up to 450 million tonnes CO2 p.a. in 2030 – approximately 10% of
estimated GHG emissions in 2030 for the sectors covered in the study, as well as energy cost
savings of around INR 137,000 crore p.a. in 2030, which is approximately 2.5% of India’s
current GDP. Road Transport and Power Sector have the maximum saving potential of 42%,
30% and 16% respectively.
Globally, transport is the second largest CO emitting sector after electricity and heat
2
production, while the building sector accounts for more than 40% of energy use. ICT driven
applications across transportation have the potential to achieve a reduction in total global
emissions by software systems to optimise transportation systems to reap big energy savings.
Although efficient technologies are being developed worldwide and deployed in the sector on
a continuous basis, the total energy consumption has still been rising.
2. Energy consumption and green house gas emission for sustainable habitat
Sustainable habitats aim to make cities sustainable through improvements in energy
efficiency in buildings, shift to public transport for commuting and management of solid
waste with focussed target of reduction in carbon emissions. Energy consumption and ICT
enabled solutions in the areas of planning of habitats facilitate energy efficiency, water and
waste management, better control on environmental pollution, and better use of resources for
building materials and technologies, roads and transportation.
2.1 Buildings sector
Worldwide, the building sector accounts for more than 40% of energy use; although
progressively efficient technologies are being developed and deployed.
Figure 1. World CO 2 emissions by sector
Figure 2. Consumption of petroleum
products in 2006 by the transport sector

According to a recent study [2], the worldwide energy consumption for buildings will grow
by 45% from 2002 to 2025 – where buildings account for about 40% of energy demand out
of which 33% is from commercial buildings. In many countries, specially developed
countries, buildings are the largest contributors of CO 2 emissions.
2.2 Transport sector
The urban population of India, which constitutes 28% of the total population, is
predominantly dependent on road transport. In India, around 80% of passenger and 60% of
freight movement depends on road transport. The transport sector accounts for nearly
one-quarter of global energy-related CO2 emissions and it can be inferred that road transport
is responsible for the highest share of emissions globally (around two-thirds).
The transport sector is a major contributor to air pollution as well as CO2 emissions in
densely populated urban India. Passenger mobility in urban India relies heavily on its roads,
as rail-based and air-based transport services are available in only selected cities. Various
energy sources used in this sector are coal, diesel, petroleum (gasoline) and electricity.
Transportation through road, rail and air are responsible for CO2 emissions of around 80%,
13% and 6%, respectively [3].
2.3 Municipal solid waste
Municipal solid waste management continues to be one of the most unprofitable and
neglected areas of urban development in India. However, considering the health, and
environmental (including GHG emissions) implications of the sector on the population, it is
imperative for the country to focus on the wide range of operations of solid waste
management to ensure efficiency of collection and disposal. With regard to direct ICT
implications on the sector, it is worthwhile to mention that more than 332,000 tonnes of
e-waste was generated in India in 2007 and is likely to increase to 800,000 tonnes by 2012.
The ICT equipment segment is fast growing with regard to its contribution to e-waste. In
India, e-waste is mostly generated in large cities like Delhi, Mumbai and Bangalore.
However, there is no large-scale organized e-waste recycling facility in India, which can
accommodate this quantum of e-waste. Among the top 10 cities generating e-waste, Mumbai
ranks first followed by Delhi, Bangalore, Chennai, Kolkata, Ahmedabad, Hyderabad, Pune,
Surat and Nagpur. Mumbai generates 23,000 tonnes of e-waste every year while Bangalore’s
innumerable IT (information technology) and related companies produce 11,000 tonnes of
e-waste every year. ICT may prove to be cost effective proposition for waste disposal and
adequate governance by using RF ID Tags connected with recycling, billing and incentive
schemes.
3. ICT Solutions in buildings
ICT applications can contribute to the reduction of the carbon footprint for buildings, both
during construction and during operation stages. The construction process is a highly energy
and GHG intensive process owing to the high degree of embodied energy of materials used in
construction (e.g. steel and concrete). Further, ICT solutions can also deliver energy savings
by way of simulation, modeling, analysis, monitoring and visualization at design stage and
building management at operation stage.

Incorporation of ICT solutions in new buildings to achieve energy efficiency are easier but in
existing buildings to incorporate identified ICT solutions are difficult and expensive.
3.1 Design phase
Software tools can be deployed for purposes such as temperature modeling and fluid dynamic
modeling, and can be used to plan buildings that are able to extract the maximum benefit
from their surroundings. They help builders to determine the most optimal and efficient
design of a building, bearing in mind the various factors that contribute to efficiency in terms
of health and comfort, building costs, energy performance, etc. The analysis and simulation
software and design tools such as Trnsys, EnergyPlus and eQUEST/DOE-2 etc. can help
designers in selecting building materials, construction methods, building orientation and
equipment types to optimize energy consumption. They also aid designers and builders in
system sizing and cost optimization.
3.2 Operation phase: building management systems (BMS)
During the operation phase of buildings, ICT solutions like BMS can be used to
automatically control and adjust heating, cooling, lighting and energy use, and regulate the
buildings’ behaviour and performance to changes in the external environment and needs of
the users. These systems constitute the most promising technology for enabling energy
savings by optimizing operation and output of equipment and reducing excess energy
consumption. BMS typically is a computer system that can control connected loads of a
building according to the pre-set requirements of the building as well as by way of acting on
information received from its sensors. Its inputs, such as temperature sensors and outputs,
such as on/ off signals are connected to control centres around the building. A modem may
also be connected to the system to allow for remote access. BMS can also help in monitoring
in real-time, as well as recording and preserving past records of data, which can help in
diagnosis of failure. A BMS typically is guided by the information through the sensors to get
the status of temperature, heat, light level, movement of occupants, smoke and gas, air
quality, open window and glass break etc.
3.3 Remote management systems
Remote management systems remotely control digital devices, such as computers, security
systems and appliances like ACs, heat pumps, and lighting. Remote management systems
when integrated with the smart grids will allow consumers and utility companies to more
closely monitor power grid activity and appliance power usage. For example, it can allow
users to set appliances to run at a certain time of day (off-peak). With the implementation of
remote management systems, around 10% of energy consumption can be reduced. By using
Smart Occupancy Controls, Intelligent Building Controls and Intelligent Street Lighting
Management, Illumination Level Detection, and Time Scheduling, it is possible to set the
utility features and services adroitly. By adopting such techniques, we can accomplish
significant impact on energy utilization without sacrificing services and may substantially
reduce GHG emissions from buildings.

3.4 ICT solutions in transport
Road, rail and air are responsible for 80%, 13% and 6%, respectively, of total transport GHG
emissions. Although, as a long-term strategy, reducing GHG emissions will eventually
require decarbonizing the transport sector, however, for the short-term, relatively economical
reductions can be achieved through the implementation of ICT solutions. One of the
solutions for GHG emission reduction from the transport sector is to augment public transport
so that road space can be used more efficiently to carry passengers at greater speed. ICT can
play a vital role in promoting the cause of public transportation by enhancing road movement
efficiency. ICT solutions can provide relatively economical answer for the sustainable
development of this sector.
Mobility management systems encompassing a broad range of wireless and wired ICT
solutions have the potential to significantly enhance the effectiveness and efficiency of
surface transportation systems through advanced applications in information systems,
communication channels and sensors. Designed to provide continuous stream of information,
utilities like intelligent traffic management systems (ITMS) can stabilize traffic flow by
providing real-time data on incident locations, travel times, congested corridors and transit
vehicle information at multi-modal centres. ITMS encompasses a wide range of ICT enabled
tools to enable authorities, operators and individual travelers to make better informed and
more coordinated decisions. These systems vary in technologies applied, from basic
management systems, such as car navigation, traffic signal control systems, variable message
signs, automatic number plate recognition or speed cameras to monitoring applications, such
as security CCTV systems. More advanced applications may integrate live data and feedback
from a number of other sources, such as parking guidance and information systems including
weather information systems. Although reducing congestion and increasing the carrying
capacity by mobility management initiatives may induce additional traffic, in many
circumstances, overall traffic emissions are likely to reduce due to optimization of operating
speeds.
Features that are part of a basic intelligent public transport system include vehicle tracking
systems, real time passenger information system (GSM/GPRS, GPS), central control station
(cluster of servers), communication sub systems (GPRS, display units, GPS vehicle mounted
unit), travel demand management, and incident and emergency management system. The key
ICT solutions are GSM/GPRS, geographical positioning system, DGPS, dead reckoning,
track circuits, odometers and different combinations of these technologies, electronic display
systems and vehicle mounted units, among others.
3.5 Data centres
The continued development and adoption of more efficient ICT, which includes PCs and
peripherals, data center servers and cooling technologies, telecommunications devices and
infrastructure, is expected to improve energy efficiency of products produced within the ICT
sector. Globally, these improvements are projected to reduce the in-use energy consumption
of ICT products by 895 billion kWh in 2015. "Continuing developments and adoption of
energy saving technologies, specific to computers and peripherals amounts to well over 30%
in energy reduction by 2015, compared to 2010 consumption," said Carr[4]. "This includes
the increasing sales of these products globally."
To effectively manage the operation-phase energy consumption of data centres, one needs to

focus on both the IT and Infrastructure energy consumption of data centres, given the fact
that less than half of the total electricity consumed by a facility actually goes towards
powering IT equipment, such as servers and networking devices, the rest being consumed by
environmental control systems and power delivery components. These environmental control
systems include cooling system components, such as chillers, computer room air conditioning
(CRAC) units, direct expansion (DX) air handler units, pumps, cooling towers, lighting, fire
protection system, etc. Power delivery systems include UPS’, switch gears, generators, power
distribution units (PDUs), batteries and distribution losses external to the IT equipment.
Fig. A green IT strategy typically entails progress and improvement in the following aspects:
The EPA estimates that servers and storage hardware account for almost 50% of total power
usage of data centres and measures aimed at increasing their energy efficiency can result in
considerable savings in space, power and cooling requirements.
4. Barriers to improved energy efficiency through ICT adoption
• Lack of awareness
• Lack of skilled man power
• High Cost of ICT Solutions
• Unavailability of benchmarks
• Lack of incentives for builders to consider ICT for energy efficiency
• Demand side constraints of urban transport sector
• Demand side constraints of municipal waste management
• Lack of standardization
• Limited alternatives on the supply sides
5. Conclusion
Energy efficient, eco friendly buildings for people and the earth promising low carbon
footprint may be accomplished by adopting ICT based solutions through coordinated efforts
of government, industries and research with adequate mixing of plans, policies and funding.
Effects of CO2 reduction through the suggested methods may be whopping; up to 93% in
certain areas (e.g. through e-learning where the participant is not commuting regularly) by
optimizing the usage of ICT equipment, office/home space, movement of human beings and
resource consumption.

References
1. Bedi Rahul,( Aug 26, 2011), “ Shaping sustainability in business via ICT tools” The
author is Director, Corporate Affairs at Intel South Asia.
2. Source: ASHRAE, US Department of Energy- Building Technologies Program
3. ICTs contribution to India’s National Action Plan on Climate Change (NAPCC), A
report by CII-ICT Centre of Excellence for Sustainable Development, 2010 and Digital
Energy Solution Consortium.
4. Shelley Carr, (Tue, Aug 28, 2012 ), Information & Communications Technologies Boost
Energy Efficiency: SBI Bulletin Press Release: SBI – AM EDT

Thermal Performance of Rural Architecture in Jharkhand
Case-Study of a Typical Mud House
Abstract.
Janmejoy Gupta and Manjari Chakraborty
Birla Institute of Technology, Mesra, Ranchi
Corresponding Author, Email: profmanjari@gmail.com
This paper aims to assess passive solar design techniques and the extent to which they
promote high thermal comfort in a vernacular rural mud house in the state of Jharkhand in
India. The study of this mud house provides an insight for designing an energy efficient rural
house that provides thermally comfortable conditions, as well as leaving behind a very low
environmental footprint. The existing realities of the mud house are studied and a few
reforms have been suggested after a thorough study. Jharkhand has, as per the 2011 census,
75.9 % of its total population living in rural areas, and it is in this context that the
development of proper rural architecture is important. With the energy crisis deepening, the
role of the built environment becomes more significant because buildings use nearly 50% of
the energy produced. Mud has a number of properties which make it a perfectly suitable
material for constructions which aim at achieving thermal comfort and energy efficiency at a
low cost specially in a climate like that of Jharkhand. All these properties are studied with
respect to the mud houses, which had been built in the wattle and daub construction method.
The various parameters which are considered in the study of the existing mud houses are –
orientation, plan-form, building exposure, surface-volume ratio, wall thickness, openings,
shading building envelope material, roofing materials, color, texture, etc. As a tool for
studying the thermal comfort conditions inside the mud house and in order to simulate
different thermal conditions, the software ‘Autodesk Ecotect Analysis sustainable design
analysis’ is used.
This software based analysis gives detailed breakups of heat gained from different sources,
thermal comfort levels, radiation levels and other facets, all of which will be described in
detail in the full length paper. These software generated simulations are then validated
through on-site measurements and survey of occupants, other that self-estimation. Once the
existing realities of the mud house under the existing conditions is studied, the paper intends
to suggest reforms and a few passive design strategies through which existing conditions in
the hut can be improved. It also strives to suggest ways based upon completed and ongoing
research in mud architecture, as to how to increase build-ability and durability of mud houses
along with doing away with certain negative aspects commonly found in mud houses like
high humidity during monsoons and negative properties of hatch.
Key Words: Mud architecture, Passive Design strategies, Thermal Comfort, Environment
Friendliness, Simulation, Thatch,

1. Introduction
Jharkhand has, as per the 2011 census, 75.9 % of its total population living in rural areas, and
it is in this context that the development of proper rural architecture is important. With the
energy crisis deepening, the role of the built environment becomes more significant because
buildings use nearly 50% of the energy produced. Jharkhand predominantly has two different
styles of vernacular houses: huts and havelis. These houses were constructed, without any
mechanical means, in such a manner as to create micro-climates inside them to provide high
thermal comfort levels. Hence the study of thermal comfort levels in these buildings in
relation to built environment in today’s context is significant. Of these two primary
categories of vernacular houses in Jharkhand this paper studies the first category, i.e. a mud
hut in rural and suburban settings. Out of these two, while research is going on w.r.t creating
high thermal comfort in buildings in urban areas, it is the dwellings in the rural area which
are not getting enough attention. These mud houses have a lot of potential to provide both
reasonable living conditions and thermal comfort at affordable prices for the rural people if
properly dealt with. The Passive Solar House is an ancient concept in architecture. Earth as
mud bricks have been used in the construction of shelter for thousands of years. From olden
days, Indian buildings used the environment, climate-responsive design, and local and
sustainable materials in their design and construction. Even in recent times, 30% of the
world’s total population live in earthen structures as reported by Cofirman et al. (1990).Since
the Iron Age, Jharkhand has been a land of thirty different tribes on the Chotanagpur plateau.
Before British colonization in 1870, Jharkhand had an agrarian society. Huts made of mud
walls and thatched roofs were the standard construction. Along with a thermally-responsive
construction, the architecture of Jharkhand also responded to interactive social life by
creating community courtyards. According to available data, these buildings constituted 48%
of total residential construction until 1960 (Das & Pushplata, 2005). Mud house has natural
air-conditioning effect, resulting in cooler rooms during day and warmer at night. It also
controls room air temperature. (Duffin & Knowles, 1981) There are numerous advantages of
mud in hot developing countries. It suits different weather and geographical conditions as
temperatures inside the mud houses remain temperate throughout the year and they display
very good thermal behaviour. Besides, mud houses are very economical to construct and mud
is abundantly available.
A study by P. R. Reddy and B. Lefebvre (1993) showed that traditional mud houses create
thermal comfort. The study investigates thermal comfort attitudes of those dwelling in
traditional mud houses. Their survey shows that 90.6% inhabitants of mud houses find them
to be comfortable without artificial cooling and ventilation. The study also shows, however,
that due to the high maintenance, these dwelling in mud houses would prefer burnt clay
bricks over traditional mud walls. Shaviv (2001) suggested using high thermal mass
materials in buildings along with natural ventilation at night to keep buildings cool. Peleg
and Robinson (1964) stated that thermal comfort levels can be achieved inside a house with
rational use of natural ventilation: preventing hot air from penetrating the house during hot
hours of the day and allowing exchange of air and heat during the cool outdoor hours.
Thulasi Narayan concluded that high thermal mass creates a shift in thermal lag and keeps
the heat out in summer months. Narayan also concluded that high thermal mass, natural
ventilation and evaporative cooling are good passive strategies to achieve thermal comfort in
warm climates. All these studies suggest using natural ventilation to cool the structure at
night and using high thermal mass to keep heat out of the structure during the day, which can
be possible in rightly designed mud houses.

1.1 Typical existing vernacular mud huts in Jharkhand in rural and suburban areas
1.1.1 Size and layout
An average hut measured approximately 5 to 6 meters (15 to 18 feet) long and 3 to 4 meters
(10 to 12 feet) wide (Dhar, 1992). The huts vary in size. There are huts that extend up to 12
to 14 meters in length and 8 to 9 meters in width. These huts were arranged in a linear pattern
along the main street of a village, usually amidst a group of bamboo trees. The houses were
normally surrounded by a fence made of bamboo, shrubs, or twigs that defined the boundary
between the public street and the semi-public courtyard area in front and at the rear of the
hut. This open-to-sky courtyard acted a prime space for the house, especially during the day
in winter and in the evenings in summer. Most day to day activities occurred in this space.
Often there was a well in this courtyard that served as the source for water for drinking,
bathing, washing, and cooking. (Refer Figure 1) People used this courtyard to dry clothes,
crops, and eatables during the day time. The aged of the house used this as a rest area,
supervising the children at play. The house often sat on a raised platform made of compacted
earth. The high thermal mass helped keep the house cool in the evenings in summer which
made it pleasant for people to rest in the evenings. The huts normally had minimal
fenestration. Often the only opening on the external walls was the main door. Some houses
had windows, but they were small and placed high to ventilate the indoors while, at the same
time, acting as a visual barrier for the private spaces. The small windows also served to keep
the hot summer sun and cold winter winds out.
Figure 1. Courtyard Type Planning
Figure 2. Attic of hut
Occupants of the huts believe the attics (where present) made the hut more thermally
comfortable as per a Masters Level Dissertation, titled, ‘Climate Responsive Vernacular
Architecture : Jharkhand, India (Avinash Gautam). (Figure 2).

1.1.2 Typical mud huts in Jharkhand – construction & details
The four types of mud-house construction employed in Jharkhand are:
1. Cob: Fresh lumps of mud [soil & water & local fibre materials] stacked on each other.
Stacking lumps of mud.
2. Wattle and Daub: Woven work of sticks intertwined with twigs or bamboo covered with
mud.
3. Rammed Earth: Damp earth laid between formwork and moulded and compacted by
ramming.
4. Straw-bale: Plastering the bundle of hay with mud.
Out of these, the Cob method & Wattle and Daub method is the most commonly used in
Jharkhand huts. Wattle and Daub was the method used in the hut studied.
Figure 3. Cob Construction Figure 4. Wattle & Daub Figure 5. Special mud blocks
Construction left with vegetable waste matter
to mature for wall construction
The hutments were originally built of mud, sticks, grass, and pebbles. These houses were
mostly self-built by family members, sometimes aided by neighbours. Their modest beauty
lay in being less influenced by self-conscious decorative attempts than from pure, practical
shapes produced by adapting local material as economically as possible to mitigate hostile
environmental elements and to use beneficial ones (Cooper & Dawson,1998). Traditional
architecture developed its individuality by tapping nearby resources and exploiting them to
confront problems posed by the local environment (Cooper & Dawson, 1998). The huts were
made of local materials. Timber, bamboo, clay, straw, cow dung, and a special variety of
grass were used to build houses (Dhar, 1992). The walls was made of a special type of mud
obtained by souring earth by adding vegetable waste and leaving it to mature (see Figure 3).
The decaying waste produced tannic acid and other organic colloids, greatly improving the
mud’s plasticity (Cooper & Dawson, 1998). This mud was then mixed with cow dung,
chopped straw, and gravel or stones to make the raw material for the walls. In the Middle
East fibrous ingredients like straw are used to improve tensile strength of mud bricks. Binici
et al (2007) investigated the thermal isolation and mechanical properties of fibre reinforced
mud bricks as wall materials. The walls were formed by applying a thick coat of the mixture
on both sides of bamboo mesh that wrapped around the posts (see figures 6 and 7).
Sometimes the mesh was made of wooden logs obtained from saal trees that grow in
abundance in this region. The walls are approximately 450 mm (18 inches) thick.

Figure 6. Mud wall with
wooden-posts of typical hut
–plan & detail Reproduced
from Dhar, 1992)
The roof rested on nine wooden posts erected in three rows, with three posts per row, as
shown in Figure 6 (Dhar, 1992). These posts were sunk into the raised platform and tied with
wooden beams and purlins that supported the roof structure. The huts usually had a gabled
thatch roof. Bamboo sticks formed the mullions to support the thatch. The thick thatch used
as roofing material prevented rain from entering the house and at the same time provided
insulation to the building. While providing some benefits to the house, thatch had its own
drawbacks. It tended to house parasites, rodents, and birds (see Figure 8). Over time, as an
effect of industrial hybridization, the thatch in the huts was replaced by sun-dried or burnt
clay Mangalore tiles that are today more commonly used as roofing material for the huts as
has been done in the house studied.
2. Method
2.1 Study and analysis of existing mud hut
Figure 7. Mud wall with
wooden-posts of typical
hut
Figure 8. View of
decayed thatch roof in a
hut over a period of time.
The hut is located in Mesra village, 16 kms from Ranchi. Its dimension is 12 meters in length
by 7 meters in breadth. (FIG 10 A, B, C) It is made of mud walls and has a Mangalore tiled
roof. It has 450 mm thick mud walls and was constructed by wattle and daub construction.
Ranchi has a Sub-Tropical Humid type of climate as per Koppen’s Classification of Indian
Climates. (FIG 9)
Figure 9. Jharkhand Climatic Zone Figure 10a. Study Hut Plan

2.1.1 Orientation
Figure 10b. Recreation of study hut, Figure 10c. Recreation of Study Hut
The mud house has its longer side oriented along East-West Axis. The two doors are placed
in the southern side. (FIG 11)The solitary small window like opening is placed on the
northern wall.
Figure 11. Study Hut, photographs
Figure 12a. Ecotect software analysis of simulated study-hut – solar heat gain at 9 a.m,
30 th june. Solar heat gain in watts.

Figure 12b. Ecotect software analysis of simulated study-hut – Mean radiant temperature
inside mud hut at 9 A.M, 30 th June.
Figure 12c. Ecotect software analysis of simulated study-hut – solar heat gain at 4 P.M, 30 th
December. Solar heat gain in watts.
Analysis
The best orientation for least heat gain for rectangular
built form with one side longer than the other is the
longer sides facing the East-South and North-West
direction making an angle of about 40 degrees or 45
degrees with the East-West Axis, rather than the longer
side of the building aligned along the East-West Axis as
done in the mud house studied. With the longer side
orientated along NW-SE direction heat gained would be
even lesser. With proper orientation, the heat gained by
the mud house would be even lesser. (Figure 13)
Figure 13. Ideal orientation of
hut for least solar heat gain in
summer & ventilation

2.1.2 Surface area to volume ratio(S/V)
The total surface area (excluding ventilation opening & including roof area) is 185 square
meters in mud hut studied. The total volume is 210 meter cube. The ratio comes to be 0.88.
In composite or sub-tropical humid type climate the S/V ratio should be as low as possible as
this would minimize heat gain.
Analysis: The Surface Area to Volume Ratio can be reduced further by using a domical or
vaulted roof and a more square plan overall. A domical roof & vaulted roof would further
reduce direct heat gain.
2.1.3 Ventilation
The portion through which cool air at night could come in at the top portion of the roof and
through which warm air can go out by convective process has been blocked in this particular
hut due to rain water coming inside the hut during rains. This causes lack of ventilation in
summer and convective air flow at evening and night. A probable solution is to let the
openings remain and cover them by bamboo mesh like surface to stop rain water coming in
monsoons. (Figure 14)
Figure 14. Extended Eave projection &
bamboo meshing to prevent rain ingress &
allow ventilation
2.1.4 Building materials
The building material for the walls is mud and the roof material is Mangalore Tiles. The U
value for mud is 0.35 W/sq m K & the U value for Mangalore Tiles is 3.1 W/sq m K.
Analysis
Figure 15. Ideal nocturnal ventilative
cooling carried out with small gap to allow
air-flow.
Though U value of Mangalore/Clay Tiles and khapra used is not that high, the insulating
property of thatch is much more, as its U value is even lesser. So in summer, it keeps the
inside of the hut even cooler than clay tiles do. The disadvantages with thatch as mentioned
before in this paper can be mitigated with modern day industrially improved hatch use.
Modern day thatch treated and improved industrially can also be used for mass use in rural
areas, being low cost and having very good thermal properties. Thatch is a natural reed and
grass which, when properly cut, dried, and installed, forms a waterproof roof. The most
durable thatching material is water reed which can last up to 60 years. A water reed thatched
roof, 12 inches thick at a pitch angle of 45 degrees meets the most modern insulation

standards. The U-value of a properly thatched roof is 0.35 W/sq m K, which is equivalent to
4 inches of fibreglass insulation between the joists. Only in the last decade have building
codes begun to demand this level of roof insulation. Yet, thatch has been providing insulation
since much longer.
Figure 16a. Passive heat gains breakdown in studied hut
Figure 16b. Model hut-different temperature gains – sources
2.1.5 Shading: There is no shading except for the projection of the roof.
Analysis: If shading is increased by having greater eave projections and also sunken window
or chajjah then heat gained can be reduced. (Fig 16)
2.2 Results of occupant-survey
The occupants of the hut moved outdoors during the evenings in summers because of air
movement; air movement inside the house was nearly non-existent.
Occupants of other huts preferred to stay indoors in summers even in the evenings.
Despite spending most of their time indoors, washing, bathing, drying of clothes, praying
were done in the courtyard early in the morning when the temperature outside was cooler
than in the afternoon.
The users slept inside the huts throughout the year.

Occupants of the entire hut felt more comfortable all day inside the house during summer
because it was relatively cooler inside than out.
Some occupants said temperature was most uncomfortable in summer and winter. They
also felt humidity and lack of air movement were uncomfortable in summer.
Occupants of the huts said that the rainy season was the most uncomfortable season
because they could not perform day-to-day activities as usual.
Temperature measurements results indicate that the selected hut exhibited lower ambient
temperature than outside during the day and a higher ambient temperature at night.
3. Conclusion
The Mud house studied reinforced the fact that mud as a building envelope keeps the inside
of the hut cooler in summer. However the cooling effect of these traditional mud houses can
be further improved by proper building orientation, surface-volume ratio minimisation, and
proper design of huts to facilitate nocturnal ventilative cooling, shading devices being used
and proper building material selection which can be economically viable for rural areas as
well as have proper insulation properties. For example thatch as used before by the villagers
had problems like tending to host rodents thus decaying and result in rain water seepage. But
modern day industrially improved thatch can be used with all the good thermal properties
intact and the disadvantages gone.
References
1. Krishan Arvind, Baker Nick, Yannas Simos, Szokolay S.V. (2001), Climate Responsive
Architecture – A Design Handbook for Energy Efficient Buildings, Tata McGraw-Hill
Publishing Company Limited, New Delhi.
2. Olgyay Victor (1963), Design With Climate- Bioclimatic Approach to Architectural
Regionalism, Van Nostrand Reinhold, New York.
3. Majumdar Mili.(2001), Energy-Efficient Buildings In India, Tata Energy Research
Institute, Ministry of Non-Conventional Energy Sources.
4. Givoni Baruch(1969), Man, climate, and architecture, Elsevier.
5. Chel,Arvind, Tiwari G.N. (2009), Case study of vault roof mud-house in India, Thermal
performance and embodied energy analysis of a passive house , Energy, Volume 86,
Issue 10, October.
6. Srivastava A., Nayak J.K., G.N. Tiwari, Sodha M.S. (1984), Design and thermal Design
and thermal performance of a passive cooled building for the semiarid climate of India,
Energy and Buildings, Volume 6, Issue 1, January.
7. Garg H.P, Sawhney R.L (1989), A case study of passive houses built for three climatic
conditions of India, Solar & Wind Technology, Volume 6, Issue 4.
8. Gautam Avinash(2008), Climate Responsive Vernacular Architecture: Jharkhand, India,
Masters Of Science Thesis, Department of Architecture, Kansas State University,
Manhattan,Kansas.

Abstract
Heritage Buildings
An Inspiration for Energy Efficient Modern Buildings
Neeta Mittal
CSIR- Central Building Research Institute, Roorkee
Corresponding Author, Email: neeta.mittal20@gmail.com
India is known for rich Architectural and cultural heritage. Thermal performance and air quality
inside the buildings can be improved substantially and energy can be saved through
understanding the ancient design concept. Mugal architecture of India is known worldwide for
the wonderful monuments.. Landscaping was an integral part of Indian palaces and
monuments. Trees, green areas and water body around a building improve the physical
comfort along with the visual pleasure. In monumental buildings passive techniques used for
the comfort in different climatic region. Jali is the ornamental feature provided in most of the
palaces in Rajasthan, Taj Mahal and Agra fort which increase the ventilation and comfort.
Study of historical city of Jaipur shows that in desert areas where water is in short supply step
wells are built which improve the microclimate of the place. Courtyard was also an important
design element in old residential buildings in hot dry climate called Havelis. It was an element
of passive cooling for regular fresh air supply. One of the modern buildings designed in Jaipur
on this concept using these factors is also discussed. The paper highlights the ancient passive
techniques to improve the thermal comfort and ventilation through examples of heritage
buildings which may prove an inspiration for energy efficient modern buildings design.
Key words: Passive, Landscaping, Jali, Water, Step well, ventilation, thermal, microclimate.
1. Introduction
Indian vernacular architecture reflects the environmental realities. The architectural quality
makes a building a heritage building. Hindus & Mughals built magnificent monuments.
Traditional architecture is the outcome of centuries of optimization of climate consideration, of
material use, construction techniques. Landscaping elements water body and trees provided in
monumental buildings, temples improves the microclimate of the place and increase the
comfort level in the buildings.
Environmental degradation, technology advancement and development of urban centers have highly
influenced energy consumption in buildings. Energy is the important component for economic
development of the country. The modern equipment and materials used in construction and to

maintain indoor thermal environment consumes significant amount of our national energy. In
view of the shortage of energy it is very much essential to review the historical origin of
Architecture &Technology to restore the comfort inside the building. Climate responsive
architecture is the need of the day. Today most building structures are designed to separate man
from the outside environment and require application of significant energy quantities to create
an acceptable indoor environment. Energy consumption can be reduced in heating & cooling
from 50-80% if the buildings are designed and planned considering the microclimate,
topography of the place, and other external features. Modern buildings are being built with little
consideration of the climate. An overview of vernacular architecture will help to understand the climatic
or technological limitations of the past . Control Of the microclimate around the building was
always important in indigenous design. This happened not only for the palaces but for simple
dwellings as well.
2. Passive techniques of heritage buildings design
Ancient buildings demonstrate the passive architecture of India. Without mechanical means
these buildings are better than the newly designed buildings. Natural ventilation and advantages
of solar direction was taken in those buildings. Materials are chosen for construction according
to the climatic characteristics of the place. The Palaces in Rajasthan also demonstrates the
natural ventilation techniques. Water body in temple premises, keeps the environment cool and
improve the microclimatic conditions. Havelis of Rajasthan & Gujrat are good examples of
passive architecture. The Mughals constructed excellent mausoleums, mosques, forts, gardens
and cities. Taj mahal, Agra fort and, Fatehpur Sikri are few monumental buildings near Agra.
Mugals laid out many beautiful gardens with water bodies in the centers in the neighborhood of
Agra & Lucknow. These buildings are designed in such a way that all people are comfortable
inside a building during the hot summer.
Indian architecture was greatly influenced by Persian styles. The Mughals constructed excellent
mausoleums, mosques, forts, gardens and cities. Mughals built magnificent monuments. They
also laid out many beautiful gardens with water bodies in the centers in the neighborhood of
Agra and Lahore. Some gardens like Shalimar and Nishat gardens in Kashmir have survived to
this day.
2.1 Landscaping
Mugal gardens are famous for planned landscaping. The general theme of a traditional Islamic
garden is water and shade. Unlike English gardens, which are often designed for walking,
Islamic gardens are intended for rest and contemplation. For this reason, these gardens usually
include places for sitting with trees. Water greatly influence the microclimate of the place and
improve the environment.
2.1.1 Water
Water is an architectural element which is extensively used in our ancient buildings and in
garden of the Mugals. Water not only delighted the eye on a hot summer day but also provide
the passive cooling. Water improves the physical comfort by the evaporative cooling of the

surrounding air. Rate of heat loss from the moving air depends upon the area of water in contact
with the air and careful zoning of the sheltered spaces so that strips of the water could be
strategically placed around the structure [1].The beauty of Taj Mahal and Chota Immambada,
Lucknow is enhanced by provision of water in front and built environment is comfortable in hot
summer (Figure 1,2. ) [2].
Figure1. Water body in front of Taj Mahal, Figure2. Chota Immambada ,Lucknow
In 1579, Guru Ramdas, the fourth Guru of the Sikhs founded the city of Amritsar in the Punjab.
He first constructed a pool and named it Amrit Sar or 'Pool of Nectar' on a stretch of land gifted
to him by Akbar. The golden temple is built in the water which reduce the outdoor air
temperature through evaporation ( Figure 3.4. ) [2].
Figure 3. Golden temple Figure4. Golden temple gate, Amritsar
2.2 Baoli
This method was employed over 1,500 years ago by local Rajasthanis, who built "baoli" or
stepwells -- bodies of water surrounded by a descending set of steps, helping to create a
microclimate in the surrounding structure. Chand Baoli is a famous step-well situated in the
village of Abhaneri near Jaipur. It was built in the 9th century and has 3500 narrow steps in 13
stories and is 100 feet deep (Figure 5)[3].

Figure 5. Chand Baoli -Step well in Jaipur
Among the various attractions at the Bada Imambada, the five storied baoli (step well),
belonging to the pre-Nawabi era is the most captivating structure. Generally called as the
Shahi-Hammam (royal bath), this well is connected with Gomti river. Only the first two-stories
of the baoli are above water and the rest being perennially below water. Step wells reduces the
temperature of surrounding areas.
2.3 Ventilation techniques in heritage buildings
2.3.1 Jali
In monumental buildings Jali is the ornamental feature provided in most of the palaces In
Rajasthan, In Taj Mahal , Agra fort etc ( Figure 6.7) [2]. Fresh air enters in the building through
jali with speed as well as stone jali protects the enclosure from direct solar radiation. Jali cast
the decorative shadow in buildings which is also helpful in reducing the inside temperature.
Figure 6. Inside view of Taj Mahal Jali Figure 7. Outside view of Jali-TajMahal

2.3.2. Ventilator
Natural ventilation is very important for comfort. Ventilation system provided in Bada
Imambada Lucknow is the example to improve the natural air circulation ( Figure 8)[2] .
2.4 Courtyard
Figure 8. Bada Immambada , Lucknow
Courtyard was also an important design element in old residential buildings in hot dry climate
including palaces. It was an element of passive cooling for regular fresh air supply and for day
lighting. These interior courts - a common feature of Rajasthani architecture -optimize circulation of air
during the 50°C summers ( Figure 9.10) [4].The rooms around courtyard are comfortable for use.
Figure 9. Haveli of Shekhawati Rajasthan Figure 10. Haveli- Rajasthan

3. Modern building -pearl academy of fashion Jaipur
Very few buildings in India are designed following the concepts of the ancient architecture.
One of the building recognized globally for the passive design is Pearl Academy Jaipur built in
the arid suburbs of Jaipur, Rajasthan by Architect Manmit Rastogi[5]. The Pearl Academy of
Fashion combines modern exterior styling with ancient Rajasthani architecture -designed to
keep temperatures down without artificial cooling systems.The passive features used are
Double skin, derived from traditional "jaali" structure ( Figure 11)
Concrete screen runs the length of the building to provide a cooling outer skin.
Traditional step wells often go many stories below ground level, here it is just four
meters down (Figure 12 )[5].
Reversed earthen pot kept on the roof which act as insulator
At the height of summer, in the sweltering industrial suburbs of Jaipur, Rajasthan in north-west
India, the Pearl Academy of Fashion remains 20 degrees cooler inside than out -- by drawing
on Rajasthan's ancient architecture.
Figure 11. Double skin Exterior- Concreta Jali Figure 12. Water Body in the centre
The central water body act as step-well and keeps the surrounding area cool.This modern
building is inspired by the traditional passive techniques.
4. Conclusion
Energy is precious and to save this energy is a matter of prime concern. It is the time to learn
and adopt the passive design techniques to maintain the comfortable environment inside
without much use of active systems of cooling or heating. Ancient monumental buildings,
palaces are still a place to relax without fan, coolers and air conditioners. There is a need to
study the traditional buildings because they are time tested. it is important to investigate the
effectiveness of the passive environment control system of Indian traditional architecture and
identify its potential for contemporary application. Let us go back and review the science
behind the architectural design of heritage buildings. Today green Building designalso provide

the opportunity to adopt our age old passive techniques. Awareness should be created to design
the modern buildings on the traditional building design concept.
5. References
1. Mittal Neeta,Energy Conservation Ancient Techniques for Effective Planning of Buildings,
Seminar on Conservation of Energy in Buildings and Architecture, 15-16 Feb. 2002
Calcutta organized by Institute of Energy Environment and Waste Management
2. Mittal Neeta-courtesy,Figure./ Photos ( 1, 2, 3, 4, 6, 7, 8 )
3. en.wikipedia.org/wiki/Chand_Baori
4. rangdecor.blogspot.com/.../havelis-.
Smiriti Saraswat,Understanding court yard design through Havelis of Rajasthan, 2011
5. Ancient 'air-conditioning' cools building sustainably,From Nick Glass and George
Webster, CNN,March 8, 2012 -- Updated 1725 GMT (0125 HKT)

Planning and Energy Conservation Strategies
in Small Settlements
S.K. Negi* and V.Srinivasan**
*CSIR-Central Building Research Institute, Roorkee
** CSIR-Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai.
Corresponding Author, Email: e-mail:sknegicbri@rediffmail.com
Abstract.
The importance of energy efficient buildings has assumed great urgency today. In developing
countries like India, rising population, increasing standards of living and rapid urbanization
result in an increase in building construction activities. The need of energy is also increasing
manifold, particularly with the coming up of MNCs & Real Estate developments. Design &
planning of buildings and settlements can play a major role to curtail the energy demand and
thus can help in achieving the global objective of sustainable development. In India the
majority of the areas come under composite climate and our buildings are often designed
without taking enough consideration of climate. The methodology adopted involves finding
out the physical requirements for a settlement of 5000 population for which energy
requirements are to be analyzed. In a study for Delhi region, the orientation of buildings if
kept with longer axis as East –West i.e. major façade facing North & South and shorter
facades on East & West, the building performs best for thermal comfort. If it is tilted 15 to 20
degree north then it also gets the advantage of air movements. Further having higher building
blocks on south side rows, we get the advantage of the shadow on north side blocks by the
movement of sun from east to west.
Keywords: energy conservation, orientation, simulation, shadow pattern, planning patterns,
density of population
1. Introduction
Rapid urbanization, rising population, and increasing standards of living results in an increase
in building construction activities. Globally, buildings are responsible for approximately 40
percent of the total world annual energy consumption. Most of this energy is used for the
provision of lighting, heating, cooling and air conditioning. The demand for electrical energy
by residential building in India is growing at a disproportionate and increasing rate. However,
the design and construction of modern residential buildings, which are heavily reliant on
electrical appliances for control of the internal built environment, are causing greater concern.
As a result, local attention is focused on improving energy efficiency for residential
buildings. Apart from general lack of norms and regulations, one reason that buildings are
poorly adapted to the climate is lack of knowledge among building designers, whether an
architect or engineer or town planner. In the field of passive solar architecture related to
individual buildings many research works have been done. Some studies have been carried
1

out on tree shade effects on residential energy use at California using different type of trees
(e.g. shape, size) and location around buildings. Tree shade reduces summer air conditioning
demand and increases winter heating load by intercepting solar energy that would otherwise
heat the shade area. Similarly studies are available on shading of windows, their designs etc.
In all studies the effects have been limited to single building only. Few buildings with passive
features and other concepts of non-conventional sources of energy have been constructed at
Delhi, Gurgaon & Hyderabad etc. to save the energy loads. In this background a project was
under taken to achieve energy conservation through design and planning of small settlements.
In this paper the impact of energy conservation has been discussed at a settlement level with
different planning patterns through design of buildings, their orientation and distances among
the buildings of different heights for shading effect.
2. Energy conservation in small settlement
2.1 Methodology
The methodology adopted involves finding out of energy requirements for different
orientation of buildings and these are adopted in the layout planning for the physical
requirements of a small settlement. The requirement includes the various types of residences,
education facilities, recreation facilities and shopping facilities. Then area of the site has been
estimated considering an assumed density of population. In this case a density of 125 persons
has been taken for a population of 5000 persons only. This gives a housing density of 50
dwelling units / acre assuming 5 persons per family and total requirement of land comes out
to be 40 acres or approximately 16 hectares only.
Requirements
1. No of houses @ 5 persons / family - 1000
2. Economically weaker sections i / Low income group ii houses - 600
3. Middle income group iii houses - 230
4. Higher income group iv houses - 170
5. Primary school - 1
6. Nursery school - 2
7. Convenient shops - 20
The total requirement of houses comes out to be 1000 dwellings. The number of low category
houses has been taken as 60 per cent of the total houses as majority of the population in India
belongs to this section of population and government policy also advocates that in any urban
housing scheme major share of houses should be assigned to low income group people. The
other building requirements are also kept as per prevailing planning norms in India.
Accordingly a plot of 400m x 400m has been theoretically selected for the study point of
view. To calculate the energy requirements of a settlement the number of residences, their
design, specifications, orientation and design of other buildings like shopping, schools etc.
are all important.
2.2 Architectural design & specifications
To calculate the energy load of a building their architectural design and specifications are
important consideration so the designs for various categories of houses, a primary school, a
nursery school and a shopping center have been developed. The areas for LIG, MIG and HIG
2

houses have been taken as 36.00 sq.m., 72.0 sq.m. and 108.0 sq.m. respectively. The areas for
primary and nursery schools are 421.65 sq.m. and 90.74 sq.m. respectively. Shopping
complex with 20 Nos. of shops has been designed with area of one shop as 12.00sq.m. The
specifications for energy calculation point of view have been taken as follows.
Brick work in cement mortar for 23cm thick brick walls and 11.5cm thick brick with
10mm thick cement plaster on both sides.
10 cm RCC roof with 10cm thick mud fuska including insulating layer of tar felt, & 5cm
brick tiling.
4 cm thick cement concrete flooring on 7.5 cm lean concrete in two room set.
5 cm thick cement concrete flooring including 1.5 cm thick moisac finish and 7.5 cm
thick lean concrete.
Windows with plane glass of 3 mm thickness with wooden frame.
2.3 Energy aspects
The above designed buildings have been assessed for energy flow for 22nd June temperatures
putting these buildings in eight cardinal directions and having two and four Storey
developments by using TRNSYS software. The energy simulation curves have been prepared
for Delhi Region. During temperature simulation process shading factor on the building
surface is also required. For this purpose, software/program has been developed using
FORTRAN programming language to calculate the shadows. It calculates the height of
shadows on the opposite buildings placed at a given distance at different orientations of the
building for different altitudes and azimuth of the sun at different hours of the day.
2.4 Settlement plans
Three plans have been developed, two with normal / traditional type of clusters & road
patterns having 4 storeyed walkup apartments for LIG group and 2-4 storey apartments for
MIG & HIG group. Here the buildings have been placed in all the directions as depicted in
figure 1 & 2. The other layout has been developed considering orientation of all the buildings
in E-W direction as longer side (facing north & south) because it consumes minimum energy.
The depicted from the cooling load in table 1.
The cooling load histogram for LIG houses is shown in fig. 3. In this layout the height of
blocks on the northern side rows have been reduced while of the blocks on the southern side
has been increased to get the maximum advantage of the sun movement. It is reflected in the
different design of residential clusters. Then these clusters have been grouped in a plot area of
400 m x 400m i.e. 16.00 hectare plot giving a density of 315 person / hectare or 126 persons /
acre approximately. The development has been envisaged from 2 to 12 storeyed. The
plantation of trees has been proposed on western side of clusters with a continuous belt of
trees all round the boundary line of the site.
The energy conservation in a settlement is a function of many things because a settlement
comprises of houses, community buildings and services. As the study was specifically to
conserve energy through planning patterns and land uses, it is important to understand the
concept of planning pattern and land uses taken in the study.
3

Table 1. Cooling Loads (kw) for Houses in Different Directions
Direction LIG MIG HIG
two four two four two four
Storey Storey Storey Storey Storey Storey
N 3.32 4.846 5.751 7.759 8.301 11.054
NE 3.795 5.826 6.282 8.845 8.919 12.305
E 3.686 5.618 6.088 8.434 8.598 11.652
SE 3.73 5.7 6.238 8.753 8.874 12.217
S 3.258 4.757 5.719 7.694 8.263 10.978
SW 3.811 5.858 6.302 8.884 8.933 12.342
W 3.687 5.62 6.089 8.437 8.6 11.656
NW 3.772 5.785 6.209 8.855 8.916 12.32
Figure 1. Settlement layout plan for a
neighborhood of 5,000 population,
Alternative – I
Cooling Load KW
2.5 Concept of planning patterns
7
6
5
4
3
2
1
0
3.32
4.85
3.80
5.83
2_storey 4_storey
3.69
5.62
3.73
5.70
3.26
4.76
Planning pattern at city level may be taken as an out come of major road patterns i.e. linear, grid,
radial or a combination of these. At a small settlement level-planning pattern in general is the
disposition of various buildings, in a locality in different fashion. It is shown in figure 4. This is the
4
3.81
5.86
3.69
5.62
3.77
N NE E SE S SW W NW
Direction
Figure 2. Settlement layout plan for a
neighborhood of 5,000 population,
Alternative – II
Figure 3. Histogram for cooling load (kw) for LIG houses
5.79

type of development in terms of height, number of storeyes and orientation of building blocks. The
height or number of storeyes plays an important role in conserving energy because in a multi-storeyed
building more number of floors are in shade. The top floor can be provided with proper insulation.
Placing the buildings with respect to each other in a space in terms of distances and directions is also
very important because of various patterns of shadows displayed on the opposite or side buildings.
Orientation also plays a role as north & south surfaces get negligible quantity of sunrays.
The land use is a direct result of type of development or planning pattern. As we go higher we
consume less space on ground and we reduces the land area for a particular land use like residential
and get more open area as a more green/open land use for recreational activities i.e. parks,
playgrounds, landscaping etc. for a better environment.
The distances and direction becomes significance because in a particular direction the building
consumes less energy as compared to other direction. Further the distance & direction changes the
shadow pattern of the blocks and the advantage of the shadows of higher buildings can be taken on
the other buildings if higher blocks are placed in a fashion giving maximum shadow on the other
blocks.
2.6 Discussions and findings
Figure 4. Site View of Small settlement planning Pattern
The results of the studies through temperature simulation curves drawn using TRNSYS for
22nd June indicate that orientation having longer sides on E-W direction is the best for
energy considerations. So the orientation of the blocks of a building should be with E-W as
longer side and facing north or south. The results for cooling load calculations for a LIG
cluster planned in a traditional fashion of four storeyed development having 64 houses
required a load of 40.78 KW while a cluster of similar houses planned in the proposed
fashion requires a cooling load of 30.05 KW only i.e. a saving of 25% of cooling load. In
these calculations the impact of shading has not been considered, if it is also taken in to
account a saving of 35-40% of cooling load can be achieved easily. Shadow pattern studies
show that maximum shadow on the buildings can be obtained on east & west surfaces placed
against each other. This indicates that the surfaces of the building facing east and west should
be put closer to each other to get the maximum advantage of the shadow. On north and south
faces of the buildings there is hardly any shadow of opposite buildings. The shadows on
south east & south west direction of blocks are generally thrown from the side blocks placed
at an angular position on south side. Further the higher blocks of buildings / residences can be
put on southern side of the other buildings so that advantage of the shadow of these blocks
from movement of sun from east to west can be taken on the southern side by the blocks
situated at angular position i.e. blocks which are on the E / W sides of the immediate north
side blocks.
5

3. Conclusions
The importance of energy is well known. The scarcity of it is felt particularly due to the
increasing population and more per capita consumption. Fast depleting energy resources are
other matter of concern. By proper planning and design of settlements energy of the order of
40 percent or more can be saved easily using proper specifications and orienting the building
blocks in suitable direction. Study for Delhi region shows that if residential blocks are placed
in east –west direction with 15 to 20 degree tilt on north side, the advantage of sun and air
movement taken together and providing some insulation in roof finish can save the energy
bill upto 35- 40 percent. This saving can further be increased if southern side blocks in the
layout are taken of more height than northern side blocks which may provide shadow on
northern side low height blocks with movement of sun from east to west. Thus we can
contribute in achieving the broad objective of global sustainability by way of planning and
design of buildings and settlements.
4. Acknowledgements
The substance presented in this paper has been taken from in-house R&D project on ‘Energy
conservation through planning pattern and land uses.
References
1. Agarwal, S.S. Singh, R.D. and Chand Ishwar, Design and Study for Energy Efficient
Building, Proceedings of the conference on Indian Habitat and Infrastructure – Need for
Innovative Approach 25-26 Sept (2003), CBRI, Roorkee, pages 19-25.
2. Hans Rosenlund, Climate Design of Buildings using Passive Techniques, Building issues,
volume 10 (2000)
3. Papadakis, G. Tsamis, P. & Kyritsis, S., An experimental investigation of the effect of
shading with plants for solar control of buildings, Int. journal of Energy & Buildings,
volume 33 (2001), pages 831-36.
4. Radu Zmeureanu, Paul Fazio, Sebastiano Depani & Robert Calla, Development of an
energy rating system for existing houses, Int. journal of Energy & Buildings, volume 29
(1999), pages 107-119.
5. Ripudaman Singh, V.Srinivasan, Energy Efficient Design & Planning of Small
Settlements as A Sustainable Building Approach, Proceedings of the International
Conference on Sustainable Building (SB08), 21-25 Sept, Melbourne (2008).
6. Simpson, J.R. and Mcpherson, E.G., Simulation of tree shades impacts on residential
energy use for space conditioning in sacraments, Atmospheric Environment, volume
32(1998), pages 69-74.
7. Simpson, James R., Improved estimates of tree-shade effects on residential energy use,
Int. journal of Energy & Buildings, volume 34(2002), pages 1067-76.
8. Teri, Energy efficient buildings in India (Mili Majumdar ed.), Tata energy research
Institute (2001), New Delhi.
9. Vildan, Ok., A procedure for calculating cooling load due to solar radiation: the shading
effects from adjacent or nearby buildings, Int. journal of Energy and Buildings, volume
19 (1992), pages 11- 20.
10. Yakakura, T., Kitade, S. & Goto, E., Cooling effect of greenery cover over a building, Int.
journal of Energy Buildings, volume 31(2000), pages 1-6.
6

Abstract
Green Initiative through Energy Conservation of Building
Biman Ghosh
Berger Paints India Limited, Shibpur, Howrah
Corresponding Author, Email: bimanghosh@bergerindia.com
Buildings are responsible for at least 40% of the used energy in most of the countries and the
figure is rising as the construction booms. But pace of energy saving in building is much
lower in India as compared to developed countries. So, there is an immediate need to open up
new techniques to address the issue and also progress in the area of actual implementation
should be accelerated immediately because both knowledge and techniques are available
today to slash the energy usage in a building. Our focus is mainly on the modification of
building envelope to reduce the energy used for cooling in A/C building and to reduce the
temperature of the interior of non- A/C building. Berger has developed different systems such
as EIFS for wall, Roof insulation and Heat reflecting paint for both wall & roof. The
efficiency of these systems in terms of energy saving and cooling has been tested at Howrah
and also has been tested by CBRI at Roorkee, through actual field study for two years. The
test results revealed that the maximum energy saving of 32.33% can be achieved for A/C
building. For non A/C building, maximum temperature difference of 6.4 0 C between outdoor
and indoor air of the room can be achieved.
Keywords: EIFS, Roof Insulation, Energy saving, TSR, Energy efficiency, Thermal
resistance.
1. Exterior insulation finishing system
1.1 Introduction
Exterior Insulation Finishing System is a type of building exterior wall cladding system that
provides exterior wall with an insulated finished surface and waterproofing in an integrated
material system. In Europe, these systems are also known as ETICS (External Thermal
Insulation Composite Systems). EIFS was invented in Germany in the late the 1940s to
insulate existing masonry buildings while retaining a classic appearance. The technology was
brought to North America in 1960s. Building code agencies issued evaluation reports in
1970s, setting the stage for large- scale acceptance in 1980s. Since then, EIFS have become
one of the most thoroughly tested wall systems ever produced. After a comprehensive review,
members of the International Code Council (ICC) voted to include EIFS in the 2009 update
of the International Building Code and International residential code. The system comprise
pre-fabricated insulation product (Expanded Polystyrene) bonded on to the wall by a
combination of adhesive and mechanical fastener. The other side of the insulation material is
coated with cement based adhesive layer reinforced with fiber glass mesh embedded into the
adhesive layer. The systems include special fittings like starter strip, corner bead etc, to

connect these to the building structures. On top of the reinforcing layer primer is applied
followed by top coat.
1.2 Description of the system
components
The sectional view of a typical
EIFS has been shown in the Fig
1. All the components are part
of the whole system and have
different functions to fulfill
different requirements of the
system.Installation of EIFS
starts with the fixing of
insulation board (EPS) to the
wall with the use of adhesives. Figure 1. Components of EIFS [10]
After thorough drying of the
adhesive, the insulation boards are mechanically attached to the wall with the help of
mechanical fasteners. The gaps in between the EPS boards are filled with PU foam and the
joints are sealed with silicone sealer wherever there is possibility of water penetration or
seepage. Then sanding of the whole surface of the EPS board is done before application of
the reinforcing layer which consists of adhesive and fibreglass mesh. After thorough curing
of the reinforcing layer, priming is done on it followed by application of top coat (paint).
1.3 Advantages of EIFS
EIFS has the following advantages [10]
1) Highly efficient thermal insulation which results in saving energy.
2) Makes the building durable, weather resistant and provides a pleasant look.
3) Reduces the power consumption resulting in lowering the costs for heating/cooling.
4) Prevent contractions and mechanical damage of walls due to temperature fluctuation in
construction layer.
5) Highly water repellent walls (reduction in moisture absorption of the exterior surface of
the system).
6) Environment protection and mitigation of green house effect, as a result of reduced CO2
emission, caused by lower energy carrier consumption.
However, the above advantages can be broadly described from the two important points of
view namely Energy Efficiency of Building and Durability of Building.
1.3.1 Energy efficiency of building
Control of the flow of thermal energy and moisture through the building envelope is key to
energy conservation, preservation of the construction and its contents and occupant’s
satisfaction. The choice of exterior cladding and the quality of installation is critical for
achieving the desired performance.
1.3.1.1 Thermal insulation of walls
Heat transfer takes place from higher temperature to lower temperature in three different
ways namely conduction, convection and radiation. However, the extent of energy efficiency

of building largely depends on thermal insulation of exterior walls. The technical parameter
that characterizes this quantity is the overall heat-transfer coefficient U.
Overall heat-transfer coefficient (U): U value denotes the amount of heat transferred in one
second per unit surface area of wall (1 m 2 ) assuming that the difference in air temperature on
both sides equals to 1K (1°C). The value is calculated according to following equation:
U = 1/( Rsi + Rt + Rse) = 1/RT (1)
Where Rt is the sum of thermal resistances of all the layers, Rsi & Rse are the exterior and
interior surface thermal resistances and RT is the total thermal resistance of the system.
1.3.1.2 Comparison of theoretical R&U values of a typical EIFS Vs cavity wall
Table.1 below shows calculation of RT and U on the theoretical basis. The values show that
RT of EIFS(with 120 mm EPS) is much higher than that of cavity wall (with 120 mm air
gap) and U factor is much lower than that of cavity wall. So it can be concluded that EIFS is
more efficient system in terms of energy saving of a building as compared to cavity wall.
Table 1. RT & U of a typical EIFS and a typical cavity wall [6,8]
EIFS Cavity Wall
R1 (m 2 .K/W): Resistance of 230
Brick Wall
(Density = 1920 Kg/m 3 ) &
(Thermal Conductivity= 0.81
W/mK)
R2(m 2 .K/W): Resistance of
120 mm EPS Board
(Density=15 Kg/m 3 ) &
(Thermal Conductivity=0.036
W/m.K)
R3(m 2 .K/W): Resistance of
10mm Render/Mortar
Rse(m 2 .K/W): Exterior
Surface Thermal Resistance
Rsi(m 2 .K/W): Interior Surface
Thermal Resistance
RT(m 2 .K/W)= Rsi + R1 + R2 +
R3 + Rse
0.284 R1(m 2 .K/W): Resistance of
230 mm Brick Wall
(Density = 1920 Kg/m 3 ) &
(Thermal Conductivity =
0.81 W/m.K)
3.330 R2(m 2 .K/W): Resistance of
120 mm AIR GAP
0.020 R3(m 2 .K/W): Resistance of
115mm Brick Wall
(Density=1920 Kg/m 3 ) &
(Thermal Conductivity=0.81
W/m.K)
0.040 Rse(m 2 .K/W): Exterior
Surface Thermal Resistance
0.130 Rsi(m 2 .K/W): Interior Surface
Thermal Resistance
3.804 RT(m 2 .K/W) = Rsi + R1 + R2
+ R3 + Rse
0.284
0.180
0.142
0.040
0.130
0.776
U (W/m 2 .K) = 1/ RT 0.262 U (W/m 2 .K) = 1/ RT 1.288
The Table 2 shows the requirements of building envelope as per different guide line.

Table 2. Opaque wall assembly u-factor and insulation r-value requirements [6, 11]
Parameters Climatic Zone ECBC User Guide V-
0.2 (Public)-2009
Maximum U-factor of
overall assembly
Minimum R-value of
Insulation alone
1.3.2 Durability of building
1 .Composite
2 .Hot & dry
3.Warm & humid
4. Moderate
5. Cold
1 .Composite
2 .Hot & dry
3.Warm & humid
4. Moderate
5. Cold
1. U-0.440
2. U-0.440
3. U-0.440
4. U-0.440
5. U-0.369
1. R-2.10
2. R-2.10
3. R-2.10
4. R-2.10
5. R-2.20
IGBC Green
Homes Rating
System Ver 1.0
1. U-1.10
2. U-1.10
3. U-1.25
4. U-1.25
5. U-0.50
------
There are various environmental agents considered as affecting the durability and service life
of construction materials. However, following two factors are considered to be most
important [12].
1.3.2.1 Water/Moisture
Water or moisture enters building materials due to rain, condensation, melting of snow etc.
Water contributes to the deterioration of building materials due to dimensional change of
building materials, corrosion of metals, Freeze-thaw effects, decay, leaching of calcium from
cement, blistering, efflorescence, displacement of wall cladding materials etc.
1.3.2.2 Temperature
Building materials change volume with the change in temperature. The expansion and
contraction of building material due to the fluctuation of temperature in the day and night
time results development of micro cracks. Water gets into the structures through these defects
and slowly damages the building.
2. Heat reflective paint
2.1 Introduction
Heat reflective paints are a new type of paint which is applied on the exterior surface (e.g.
roof, exterior wall etc.) of the building to reduce the absorption of solar radiation. These
types of paint are also known as solar reflective paint or albedo paint. Two types of such
paints are available for building, one is for wall and the other is for roof [1-4]. Composition
of these paints varies depending on the application and also the requirements.

2.2 Solar radiation
The surface of sun, estimated to be at a temperature of about 5500 0 C, emits electromagnetic
radiation. The spectrum of electromagnetic radiation striking the Earth’s atmosphere spans a
range of 100 nm to about 1 mm. This can be divided into three regions in increasing order of
wave lengths. These are Ultraviolet range(100 to 400 nm),Visible range spans( 380 – 780
nm) and Infrared range (700 nm to 1 mm). The infrared light from Sun accounts for 49 % of
heating of the earth, with the rest being caused by visible light that is absorbed and then reradiated
at longer wave length.
2.3 Some definitions
2.3.1 Solar reflectivity
Solar reflectivity is the fraction of the incident solar energy which is reflected by the surface
in question. The best standard technique for its determination uses spectrophotometric
measurements, with an integrating sphere to determine the reflectance at each different
wavelength.
2.3.2 Emissivity
Emissivity is a parameter between 0 and 1 which measures the ability of a warm or hot
material to shed some of its heat in the form of infrared radiation.
2.3.3 Solar reflective index (SRI)
The Solar reflectance Index (SRI) is a measure of the substrate’s ability to reject solar heat.
Materials with the highest SRI values are the coolest choices.
2.3.4 Total solar reflectance (TSR)
The TSR value quantifies solar radiation which has not been absorbed by the surface and it is
important indicator of structural heat build up due to solar radiation.
2.4 Technology
There are various ways to make heat reflective paint. However these approaches are broadly
based on either by use of additive (e.g. ceramic or glass hollow microsphere) that has the
ability to reflect the heating component of solar radiation or by use of IR reflective pigments
(both white and coloured). Roughly 50% of the solar radiation is absorbed at the earth
surface. Black surfaces usually absorb up to 90% of this energy and white surfaces, on the
other hand, absorb only up to 25%. So, White pigments are most efficient in terms of cooling.
However, coloured pigments with higher TSR value than ordinary pigments are available.
These are called complex inorganic colour pigments (CICP). The TSR value of these
pigments lies between 11% to 25% [1,2]. When the paint formulated with hollow tiny glass
beads dries, the microsphere form a fine layer on the surface to which they are applied. The
beads produce a radiant barrier and reflect the heating components (IR, visible type) back to
the atmosphere.

3. Field study of the products developed by Berger Paints
Field studies of different systems developed by Berger Paints such as EIFS, Roof Insulation
and Heat Insulating Paints (both for Roof and Wall) were conducted at Howrah and at CBRI,
Roorkee, for energy saving (for A/C building) and cooling (for non A/C building).
3.1 At Howrah site
Two identical rooms (each having two windows and one door) with same orientation and
specification (Table 3) were built and same air conditioning machines (1.5 ton capacity,
automatic) were installed in both the room with separate electrical energy meter connected to
each machine. In the first phase, EIFS was installed on the exterior wall of one room and
hence forth this room will be called “treated room”. The other room was only painted with
water based exterior primer followed by white coloured acrylic textured paint and hence forth
this room will be called “untreated room”.
The job was initiated with fixation of starter strip on the wall surface at 10 to 12 cm from the
ground level with the help of metal screw with plastic covers. The EPS Boards were installed
with the help of cement adhesive followed by fixing of Fasteners after 24 hours of curing of
adhesive. PU foam was used to seal the gaps between EPS Boards. But prior to fixation of
fibre-glass mesh, corner beads were placed at the corners of the walls, doors, windows and
opening of A/c machine. The surface was smoothened with the help of long float with grater
followed by application of adhesive. The fibre-glass mesh was then fixed and encapsulated
with adhesive. It was ensured that the overlapping of meshes are at least 8 to 10 cm. Finally
water based exterior primer followed by acrylic textured paint was applied.
The A/c machines were set at 23 0 C. The energy saving was calculated from the difference in
energy meter reading between the untreated room and the treated room. The energy meter
readings were recorded initially at 24 hrs intervals for several days and later on for 7 days
intervals. The outside air temperature was recorded by employing data logger and
thermocouple system on hourly basis.
Table 3. Dimension of rooms
Size of room(m) Size of window(m) Size of Door(m) Wall/Roof thickness(m)
3.66 x 3.05 x 3.35 1.22 x 0.99 1.88 x 0.91 0.254/0.114
Photo 1. Rooms before application Photo 2. Rooms after application
After completion of the experiments in the first phase, the work was initiated for second
phase of experiments. In the second phase, insulation was installed on the roof of treated
room and the roof of untreated room was kept bare. Measurements of energy savings and
recording of outside air temperature was done in the same way as done in the first phase.

3.1.1 Results & discussion
The energy saving due to the installation of EIFS on the wall of the room and also the same
due to the combined effect of EIFS on wall and Roof Insulation on roof against the untreated
room was calculated from the energy meter readings. The maximum temperature of a
particular day was obtained from the temperature data logger. The Fig 2 shows how the
energy saving of the treated room (with and without roof insulation) against the untreated
room changes with the ambient temperature.
Figure 2 . Energy saving (%) Vs ambient temperature ( 0 C)
From the Fig 2, it is observed that in both the cases (i.e. with only EIFS and with the
combined effect of EIFS and roof insulation), substantial energy saving was achieved.
However, the amount of energy saving was found to be dependent on the ambient
temperature in both the cases and it was found to increase with the increase of ambient
temperature. It was found that at ambient temperature above 34 0 C, there was a sharp increase
of the energy saving due to roof insulation.
3.2 At CBRI site
Two pair of rooms with each pair having the same orientation and specifications were
selected for the study. Each room of one pair were installed with 1.5 ton automatic A/c
machine those were connected to separate electrical energy meter and A/c machines were set
at 23 0 C. The other pair of rooms were selected for measuring the temperature differential and
cooling efficiency.
The outside temperature, indoor air temperature and wall surface temperature of both these
rooms were recorded by employing data logger and thermocouple system. The temperatures
were recorded on hourly basis continuously for a week. The rooms selected for application of
different systems will hence forth be called as “Treated Room” and the other rooms on which
only conventional paint was applied will be called as “Untreated Room”. The Table 4 and
Table 5 below show the different systems applied for study at CBRI and the dimension of
each pair of rooms.

Table 4. Different systems evaluated at CBRI
System Treated Room Un-treated Room
Wall Roof Wall Roof
1 Weathercoat Heat Nil Conventional Nil
Insulating Paint
White paint
2 Weathercoat Heat
Insulating Paint
3 Berger External
Insulation Finishing
System
4 Berger External
Insulation Finishing
System
5 Berger External
Insulation Finishing
System
Weathercoat
Kool &Seal
Paint
Conventional
White paint
Nil Conventional
White paint
Weathercoat
Kool &Seal
Paint
Berger Roof
Insulation
System
Table 5. Dimension of two pair of rooms
Conventional
White paint
Conventional
White paint
Size of each pair No of Size of Size of door(m) Thickness of
of rooms (m) windows window(m)
wall/roof (m)
5.79 x 3.66 x 3.66 - - 2.1 x 0.9 0.255/0.115
3.2 x 2.94 x 3.05 1 0.45 x 0.3 2.0 x 0.9 0.255/0.115
3.2.1 Results & discussion
The extent of cooling in terms of temperature difference and the energy saving recorded
during the experiment with the above systems are given in the Table 6 and Table 7.
System Energy
Saving
(%)
Table 6. Energy saving and temperature drop by paint coated on rooms
Maximum Indoor Air
Temperature difference
between the treated
room and the untreated
room ( 0 C)
Maximum Temp
difference
between Exterior
and Interior Wall
surface for the
treated room( 0 C)
Nil
Nil
Nil
Nil
Maximum Temp
difference
between outdoor
and indoor air of
the treated room
( 0 C)
1 5.56 2.8 4.9 5.3
2 12.73 3.9 7.5 6.4
Table 7. Energy Saving by insulation and paint
System Energy saving against untreated room(%)
3 20.51
4 25.66
5 32.33

The solar reflectivity and emissivity of both the paints (Wall & Roof ) developed by Berger
are given in the Table 8.
Table 8. Solar reflectivity & Emissivity of Paint
Parameters Weathercoat Heat
Insulating paint
Reflectivity for solar
radiation
Emissivity for
thermal Radiation
(Long Wavelength)
0.83
Weathercoat Kool
& Seal
0.73 ≥ 0.70
0.93 0.92 ≥0.75
ECBC
Requirements (for
Roof paint only)
In case of system 1(Wheathercoat Heat Insulating Paint), 2.8 0 C temperature reduction and
5.56% energy saving was recorded against the untreated rooms. For system 2, both the
temperature reduction and energy saving increased to 12.73% and 3.9 0 C respectively against
the untreated rooms due to the coating (Weathercoat Kool & Seal) applied on the roof. The
high solar reflectivity and emissivity of both the paints are responsible for this performance.
Weathrcoat Kool and Seal also was found to conform to the requirement of ECBC (Table 8).
However, it is to be noted here that if the comparison of the performance of Weathercoat
Heat Insulating Paint is made against an unpainted building, higher saving and temperature
reduction may have been achieved.
When the same evaluation was carried out for system 3, 4 and 5, it was found that the
maximum energy saving of 32.33% can be achieved by application of EIFS on wall and roof
insulation. Only EIFS contributed 20.51% savings in electrical energy and together with Kool
& Seal roof coating, the energy saving increased to 25.66%.
4. Conclusion
From the above field evaluation, it is observed that Berger External Insulation Finishing
System and Berger Roof Insulation System together produced the maximum benefit in terms
of saving in electrical energy. So, this combination of systems would be ideal for building
where A/c machine runs continuously (e.g. cold storage) in a day or runs maximum in the day
time (e.g. centrally A/c Office buildings). However the material cost as well as the cost of
installation of these systems is higher than those of paint. The maximum contribution of Roof
insulation in energy saving is found to vary from 12% -16%. Hence, considering the
maximum savings contributed by roof paint (W/C Kool & Seal), which varies from 5%-7%,
it can be recommended as a cheaper alternative of roof insulation. Weathercoat Heat
insulating paint contributed 5.56% saving in energy and if this is applied on EIFS, the
efficiency of EIFS is expected to increase by certain extent.
For non-A/C building, system 2 would be the most preferred combination for reducing the
temperature of the room. With this combination the room temperature can be reduced by
approximately 4 0 C more than what any conventional white paint and the maximum
temperature difference between outdoor and indoor air temperature that can be achieved is
6.4 0 C.

5. Acknowledgement
I owe my gratitude to Mr. B.Bera, Senior Vice President-R&D (Berger Paints India Ltd), Mr.
S.Samanta, Chief Technical Manager-R&D (Berger Paints India Ltd) and Dr. B.M. Suman,
Sr. Tech. Officer, CBRI, Roorkee for their valuable suggestion and constant inspiration. I am
also grateful to my colleagues for helping me at various stages of this project work.
References
1. Zielnik, A. "Hot topic, concepts: Energy-efficiency mandate continues to drive
technology advances in coatings, building envelope systems ", Durability + Design, the
Journal of architectural coating, Vol 1,No 4, July/August- 2011, Page 36-47.
2. Zubielewicz, M. “Making keeping cool easier”, European Coatings Journal,
01/2012,Page 24-29
3. Brenk,B., Helsel,J.L., “Restoration role powers the sustainability prowess of reflective
roof coatings”, Durability + Design, the Journal of architectural coating, Vol 2,No 2,
March/April 2012, Page 36-40
4. Scarborough, W., “ Roof coatings study builds knowledge base on performance
questions”, Durability + Design, the Journal of architectural coating, Vol 1,No 6,
Nov/Dec- 2011, Page 22-28
5. Raskin, R., “ Innovations in thermal reflective and barrier coatings”, Polymer Paint
Colour Journal, Vol 201,No 4563,August 2011,Page 31-32
6. Energy Conservation Building Code User Guide V-0.2, 2009(Reprinted 2011)
7. Zeng, X., Zhu, D., "Review of Building Energy Saving Techniques", Proceedings of the
Sixth International Conference for Enhanced Building Operations,Shenzhen,China, Nov
6-9,2006.
8. Guide Line for European Technical Approval of External Thermal Insulation. Composite
Systems with Rendering ,ETAG 004 Edition March 2000.
9. Guide To Exterior Insulation & Finish System Construction , EIMA Issue 6/07.
10. Technical Manual No. IB/01/2001, Bolix EIFS Technology Insulation Systems.
11. IGBC Green Homes Rating System Ver 1.0, April 2009.
12. Durability Guidelines For Building Wall Envelopes, PWGSC,RPS, Technology and
Environment.

Abstract.
Energy Conservation under Solar Control – An Analysis
Abhinav Chaturvedi
Aayojan School of Architecture,
Corresponding Author, E-mail: abhinavdavinci@gmail.com
The Existing built up structures are consumers of 40% of the global primary energy and
generator of 24% CO2 emission. But this Built environment itself offers enormous
opportunities in scaling down this energy consumption. In history buildings do not artificial
systems of cooling or heating. These buildings, especially in Arid and Semi Arid Climate, are
provided with Solar Passive Design Techniques that is the reason of comfort inside the
buildings. Present paper describes Various Solar Passive design techniques used in past, and
the same could be used in present to reduce the consumption of energy.
Keywords: solar passive design technique.
1. Introduction
There is an increasing recognition of the earth to absorb the impacts of human activities is not
infinite. Present level of energy consumption in the industrialized countries are unsuitable
and cannot be continued without depleting the earth’s natural capital beyond repair.
Considering the role and importance of energy as a major driver of economic growth with
limited availability of conventional and non renewable resources and ever rising demand and
market prices, issues related to energy consumption, energy conservation and promotion of
non conventional and alternate energy sources of energy have assumed global concerns. With
rapid urbanization and growth of population, more and more buildings would be require to be
constructed to meet the increasing demand of the shelter. With the increase in the in the
demand of house hold will result in increase in the demand of the energy for different usages
such as heating, lighting cooling etc. So it is like that around 40% of our national energy
consumption is used in building sector to heat, cool and illuminate our buildings, to
manufacture building products and to construct buildings. As much as one half of the energy
could be saved by proper building design, construction and use. Making building energy
efficient have distinct advantage in terms of not only saving money on energy cost but also
reduction of adverse impact on the environment through reduced use of fossil fuel , and
increase the use of renewable energy sources to conserve energy. We have several
techniques and methodologies available for us, involving the application of science and
technology, by which objective can be met to suit the local climate. Infact it would not be an
exaggeration to state that these techniques which had grown through the practice of science
and through generation of experience during various stages of our historical past have by and
large been forgotten and we have followed the convenient and safe path of basing our design
and construction methods of architecture practice in developed countries. In order to

construct a building, the first step is to know the climatic condition on which we are planning
to build a building.
1.1 Arid and semi arid climate
These climates tend to have hot, sometimes extremely hot, summers and mild to warm
winters. Arid climatic regions are characterised by very high radiation levels, ambient
temperatures and relatively low humidity. Therefore it is clear by observing the
characteristics of the Arid and Semi Arid climatic zone it is very difficult to create comfort
conditions in a building without using mechanical systems. An answer to such kind of
situation is Solar Passive Design techniques.
2. Solar passive design techniques
Solar Passive design techniques are the methods used to design a building in order to achieve
thermal and visual comfort by using natural energy sources. the solar passive design
strategies should vary from one climate to another climate.
3.Building design and solar passive design techniques
Main feature of energy efficient design of a building will revolve around the following
parameters.
3.1 Site
Knowledge about the site is the starting point of the building design. Climatic conditions,
existing vegetation, surroundings etc.
3.1.1 Landform
Regions in this zone are generally flat and heat up uniformly. In case of an undulating site,
constructing on the leeward side of the slope is preferred.
3.1.2. Waterbody
Figure 1: Diagram of Leeward Side and Windward Side
Water absorbs relatively large amount of radiation. They also allow evaporative cooling. As
a result, during day time area around water bodies are generally cooler. At night, however,
water bodies release relatively large amount of heat to the surroundings. In hot-dry climates,

water bodies can be used both for evaporative cooling as well as minimizing heat gain.
Figure 2. Diagram showing air movement through water body
3.1.3. Street width and orientation
Streets must be narrow so that they cause mutually shade the buildings. Streets need to be
oriented in the north-south direction to block solar radiation.
3.1.4. Open spaces and built form
Figure 3. Diagram showing Width to height Ratio Cuts off sun
Open spaces such as courtyards and atria promote ventilation. They can be provided with
ponds and fountains for evaporative cooling. Courtyards act as heat sinks during the day and
radiate the heat back at night. Grass can be used as ground cover to absorb solar radiation and
aid evaporative cooling. Earth berming can help lower the temperature and also deflect hot
summer winds. Open spaces gain heat during the day. If the ground is hard and building surfaces
are dark in colour, then much of radiation is reflected and absorbed by the surrounding buildings.
If however, the ground is soft and green, then less heat is reflected
Figure 4. Diagram showing Effect of grass on a building.

3.2 Orientation
Orientation has the greatest impact on the energy conservation by the building. Orientation of
the site and the Building play an important role in attempt of reducing the undesirable effects
of climate and other sources of discomfort and to create the comfortable living condition
inside the building.
South and north facing walls are easier to shade than east and west walls. During summer, the
south wall with significant exposure to solar radiation in most parts of India, leads to very
high temperatures in south-west rooms. Hence, shading of the south wall is imperative. The
surface to volume (S/V) ratio should be kept as minimum as possible to reduce heat gains.
Artificial heating and cooling are the biggest consumer of the energy in a building , which is
placed at 26% of the average energy utilize by buildings. A major principle of the energy
efficiency is to orient the building in a manner that maximizing sun heat gain during the
winter while exluding it during the long hot days during the summer. In summer sun rises
early in the North – East and climbs high in the south before setting in North – West and heat
gain is mainly through the roof and east and west windows of the building. In winter sun rises
late in south of east stay low in south before setting in south of west. South windows and the
walls receive the maximum winter sun. So north and south facing walls should be 1.5 to 2
times the length of East and West.
3.3. Internal layout
Figure 5. Diagram showing proper orientation of the building.
Not only placing of internal walls are critical but also rational allocation of internal spaces in
the buildings for achieving the desired level of energy efficiency. Space required cool
comfort condition during the summers should be kept either in South and East.
3.4 Windows placement sizing and shading
For evolving energy efficient design solutions appropriate placement, sizing and shading of
the window is necessary. In hot and dry climates, reducing the window area leads to lower
indoor temperatures. More windows should be provided in the north facade of the building as
compared to the east, west and south as it receives lesser radiation throughout the year . All
openings should be protected from the sun by using external shading devices such as chhajjas
and fins. Ventilators are preferred at higher levels as they help in throwing out the hot air. he
use of 'jaalis'(lattice work) made of wood, stone or RCC may be considered as it they allow
ventilation while blocking solar radiation. Scheduling air changes (i.e. high ventilation rate at
night and during cooler periods of the day, and lower ones during daytime) can significantly

help in reducing the discomfort. The heat gain through windows can be reduced by using
glass with low transmissivity. The use of 'jaalis'(lattice work) made of wood, stone or RCC
may be considered as it they allow ventilation while blocking solar radiation. Scheduling air
changes (i.e. high ventilation rate at night and during cooler periods of the day, and lower
ones during daytime) can significantly help in reducing the discomfort. The heat gain through
windows can be reduced by using glass with low transmissivity. Large size windows should
be used at North facade only.
3.5 Insulation
Acting as barriers, insulation makes space more comfortable by reducing heat loss in winter
and heat gain in summer. Insulation of ceiling, roof, external walls and air gaps would be
critical to achieve the desired objective of energy efficiency. Bulk and reflective are the two
major kind of insulation used Bulk insulation work by trapping small cell or layer of air
within the insulating materials which are effective in retarding the heat transfer, whereas in
case of reflective insulation, reflection of light and heat are used. Effective use of insulation,
treating roof for regulating solar radiation, using cavity walls are other methods by which
thermal insulation could be done.
3.5.1 Roof
Flat roofs or vaulted roofs are ideal in this climate. Nonetheless, a vaulted roof provides a
larger surface area for heat loss compared to a flat roof. The material of the roof should be
massive; a reinforced cement concrete (RCC) slab is preferred to asbestos cement (AC) sheet
roof. External insulation in the form of mud phuska with inverted earthen pots is also
suitable. A false ceiling in rooms having exposed roofs is favourable as the space between the
two acts as a heat buffer. Thermal insulation over false ceiling further increases the buffer
action. Insulation of roofs makes the buildings more energy efficient than insulating the
walls. Evaporative cooling of the roof surface and night time radiative cooling can also be
employed. Increase of evaporative cooling, it is better to use a roof having high thermal
transmittance.
3.5.2. Walls
Figure 6. Diagram showing vaulted roof
In multi-storeyed buildings, walls and glazing account for most of the heat gain. The control
of heat gain through the walls by shading, thus, becomes an important design consideration.
A wall that transmits less heat is hence feasible.

3.6. Courtyards
Courtyards have been considered critical in promoting energy efficiency in the buildings.
They facilitate not only nature air light into the inner area but also high degree of cross
ventilation. Courtyard makes building safe from large heat intake and glare. Acting as large
evaporator cooling during summer, courtyard promotes enormous cooling without
mechanical aids. Courtyard with water fountains have been considered as great
environmental moderator.
3.7. Landscaping
Effective use of landscaping as a part of building design can help considerably in lowering
energy consumption in the buildings. Garden can act as a significant climate moderator. Use
of evergreen creepers and trees along Western walls can help in considerable reduction of
heat intake in the summer. The landscaping act as a screen to the building and reduce the
radiation and heat gain in the building.
3.8. Materials
Choice of building material have important bearing on energy consumption level of the
building .Using energy materials efficient structural design and reduction for energy used for
transportation can help in achieving high degree of energy efficiency. Choice of locally
available material and innovative construction technique has clearly demonstrated their
usefulness in reduction of energy consumed by the buildings during construction and
operations.
3.9 Colour and texture of the external facade
External finish of the building needs a careful choice in order to regulate the heat gain loss by
wall. As a tendency light colour has a tendency to reflect the sun’s heat, while dark colour
absorb it. During summer choice of light colour would be critical to minimize heat gain and
to keep inside space cooler by reflecting heat from the sun. The surface of the wall should
preferably be textured to facilitate self shading. Colours that absorb less heat should be used
to paint the external surface.
3.10 Use of energy efficient appliances
80% of the energy consumed by the building over entire life cycle is during the operational
phase of the building .Energy consumed at the operational phase should be minimized. The
appliances which consume less energy or which could work on solar or some renewable
source should be used to minimize the consumption and thereby conserving the valuable
energy.
4. Case study
4.1 Site
The site is slightly contoured and this palace is located on the bank of the river Chambal. It is
an historic building, so there by no mechanical ventilation or lighting is possible at that time.

Only solar passive techniques, done historically made this building environment comfortable.
4.1.1. Water body
Water absorbs relatively large amount of radiation. They also allow evaporative cooling. This
is the major source of cooling inside the building. Wind direction in Kota is N-W to S-E. and
this wind direction also helps in introducing evaporative cooling.
4.1.2. Open and covered spaces
Since it is a palace so we can easily find number of courtyards and covered spaced related to
each other. This is another source of comfortable conditions inside the building despite of
severe heat in summers.
4.1.3.Vegetation
Figure 7. Areal view of Garh Palace, Kota
Figure 8(a). Open and closed spaces. Figure 8(b). Presence of water body
in North West direction of the site
Southern and western facade is densely occupied by trees . This will help to reduce the sun
radiation inside the building through western facade.

4.2. Site planning and orientation
We can easily observed that the orientation of the majority of the building is close to the
desired orientation for this climatic zone. That is E-W orientation. This also reduce the heat
load in the summers and gives passive warmness in the winter.
4.3 Windows placement
We can easily see in the following diagram the majority of the windows in the palace
buildings are in North direction which is desired orientation which is reducing the heat load
and imparting proper ventilation.
The Size of the window is large in all directions except the west facade and totally covered
with stone jaalis. These windows are covered with Jharokhas as a shading device. So it
further increases the comfort level inside the building.
4.4 Insulation:-
Figure 1. Vegetation
Figure 2. Orientation of the buildings
Figure11. North Facade of the palace.

The roof of the Garh palace is domical at several edges. This domical character of the roof,
does not allow solar radiation to pass through it, and thereby reducing the heat load inside the
building. This is the main reason by which we can easily feel coolness inside the building in
severe hot weather. The wall is made up of stone and is plastered with lime. So this
combination will act as a strong shield from the hot air.
4.5 Colour and texture of the external façade
As we can see in the above photograph the light coloured paint is applied on the external
facade which always have a tendency to reflect the sun’s heat.
5. Conclusion
Solar passive design techniques should be used in order to make a building energy efficient.
Use of local material along with modern materials should be incorporated, in order to make
the building cost effective and climate responsive design. Proper orientation and proper
shading devices should be used because it has a significant effect on reducing the energy
load. Although, our life style is changed as compared to historic times, but we should
incorporate some of the design characteristics of the buildings of historic period, in order to
have proper energy conservation design of a building. Proper landscaping and choice of
colour of External facade will reduce the heat load of the building. Garh palace Kota,
Rajasthan, is a historic building but still we can easily analyse the presence of solar passive
design techniques which is the reason by which we can feel the comfortable conditions inside
the building. This building acts as role model historic building which is a good example
showing phenomenon of energy conservation.
Refrences
Figure12. Thermal Insulation by roof.
1. Gary Steffy, Architectural Lighting Design, John Wiley and Sons (2001) ISBN 0-471-
38638-3
2. Lumina Technologies, Analysis of energy consumption in a San Francisco Bay Area
research office complex, for (confidential) owner, Santa Rosa, Ca. May 17, 1996
3. GSA paves way for IT-based buildings [15]
4. The official homepage for the European Intelligent Metering project. [3]
5. Energy conservation in residential building dissertation by Renu Phasin.

Development of Integrated Solar Photovoltaic - Thermal System
Abstract.
Rajiv Kumar* and Vinod Kumar**
*CSIR- Central Building Research Institute, Roorkee
** Retired Scientist, CSIR- Central Building Research Institute, Roorkee
Corresponding Author, Email: rajivkgoel@gmail.com
Solar Photovoltaic is a key technology option to realize the shift to a decarbonized energy
supply and is projected to emerge as an attractive alternate electricity source in the future.
The solar PV manufacturing base in India comprises primarily of cell and module
manufacturing. Solar PV applications in India have followed a different trend from global
practices. While globally, there has been higher focus on grid connected applications, the
Indian PV market has predominately focused on off-grid applications. In the Indian context,
the power scenario and the nature of energy demand is highly skewed, with huge differences
seen between the per capita electricity consumption in the urban and the rural areas. For a
high cost resource like PV, the relevance and scope of its applications would, therefore, be
vastly different from that of a developed western economy. However, the socio-economic
and the geographical features of the country provide ample scope to use new, renewable
energy resources like SPV. In several cases, SPV appears to be not only the most relevant
option, but also a viable alternative even at the prevailing price. Now a days, SPV modules
are being manufactured having the various types of solar cell using different semiconductors
such as Single / multi / ribbon crystalline Silicon, Thin film Silicon, a-Si, m-Si, Gallium
Arsenide, Cadmium Telluride, etc. However, Si (mono / multi crystalline) continues to be
the most preferred material because it is one of the most thoroughly studied and understood
material available in abundance in the purest form which allows commercial manufacturing
of large area cells on a large scale. But Solar Photovoltaic cells have an inherent
disadvantage of loosing their efficiency with the rise in temperature. Even a stage comes
when the conversion efficiency becomes zero. In view of this fact, the study reported in the
present paper, was carried out for the development of Integrated Solar Photovoltaic -
Thermal System for electrical and thermal use in buildings with objective to enhance the
efficiency of photovoltaic conversion by cooling SPV module with water as well as obtain
hot water. It was considered that SPV module be attached to a heat exchanger to develop an
integrated system The radiations falling on the SPV modules are converted to electrical
output by photovoltaic cells while unutilized radiations are absorbed by the heat exchanger
and cool the module for enhanced PV conversion efficiency while the heat removed is
utilized for thermal use. The developed Integrated SPV/T system consists of SPV module of
33 Silicon cells in glass to glass moulding with a peak electrical output of 29 Watts
generating 15 V at 2.2 V. The module has the circular solar cells area and the rest of the area
is transparent. The incident solar radiation which falls on the cells generates electrical power
and the rest is allowed to pass through transparent area and is collected by a selectively
coated copper receiver which is just below and in close contact of the SPV module. A simple
mathematical model has been described in this paper. A typical day observation has been
1

plotted and an improvement of 10 to 15% in electrical output of integrated system is
achieved as compared to the output of SPV module without cooling under similar condition.
1. Introduction
Energy is most vital for economic development. There is huge gap between demand and
supply of electricity in India (13% at peak demand). Nonrenewable sources like oil, coal, gas
etc are fast depleting. According to Ministry of Coal, the coal reserves of India will deplete
by next fifty years. There is need to explore alternative source of energy. Atomic energy is
one such alternative but which apart from being hazardous is also expensive. Present day
answer to the problem is harness solar energy which is available in abundance. India being
the tropical country has more than 300 sunny days with 4-7 kWh/ m 2 solar insolation daily
(amounting to 5000 PetaWatt hr per year (PWh/year). If solar energy is harnessed properly,
India can become self-reliant in energy. Solar Photovoltais cells can be used to convert solar
energy into electrical energy. Tremendous amount of work has been done on Solar
Photovoltaics in the past and still in progress. However Photovoltaic cells have an inherent
disadvantage of loosing their efficiency with the rise in temperature, Even a stage comes
when the conversion efficiency becomes zero. Keeping this in view, development of an
autonomous integrated system for electrical and thermal use in buildings has been taken up at
CBRI, Roorkee with a view to enhance efficiency of photovoltaic conversion and obtaining
hot water supply by circulation of water for cooling the system. The objective was to
integrate solar thermal and solar photovoltaic conversion and design an efficient composite
panel to deliver thermal / electrical power. Now a days, SPV modules are being
manufactured having the various types of solar cell using different semiconductors such as
Single / multi / ribbon crystalline Silicon, Thin film Silicon, a-Si, m-Si, Gallium Arsenide,
Cadmium Telluride, etc. However, Si (mono / multi crystalline) continues to be the most
preferred material because it is one of the most thoroughly studied and understood material
available in abundance in the purest form which allows commercial manufacturing of large
area cells on a large scale. Commercially available type in India is Single Cryatalline Silicon
Cells. Normally the efficiency of silicon cell is 8-10% at 25 o C but rise in temperature has an
inverse effect and drops to zero at 270 o C. The integrated photovoltaic / thermal system has
the advantage that the water which is used as coolant for photovoltaic modules becomes hot
and can be stored in proper storage tanks for domestic use.
2. Design and fabrication of prototypes
SPV efficiency goes down with the increment in temperature hence the cooling of the SPV
cells is desirable. Conceptually integrated SPV/T panel will be having a SPV module whose
bottom surface will either be attached to a suitably designed heat exchanger or would itself
form a part of the heat exchanger. So two processes i.e electrical conversion and thermal heat
exchange (cooling) are integrated to increase conversion efficiency as well as deliver hot
water.
2.1 Design methodology
Autonomous integrated system is one in which two process -electrical and thermal
conversion of solar energy are combined without any power source. Electrical part is
obtained by Photovoltaic conversion by Solar cells and thermal part is obtained by
remaining solar energy which is not converted to electrical by SPV cells but heat up solar
cells. This heat energy is removed by cooling of cells to enhance the cell efficiency. Thermal
2

part also includes the solar insolation falling on the transparent area without solar cell, of
SPV module and transferred to the coolant flowing through the heat exchanger. Thus coolant
is heated up and cools the SPV module. While designing photovoltaic/thermal system the
two fragments are to be considered separately and designed accordingly. Both SPV electrical
conversion and cooling parts are designed separately as given below.
2.1.1 For Photovoltaic conversion
The cell area is available from the manufacturer and the panel area can be chosen from cell
characteristics. The daily AH to be fed to the battery from PV panels is the sum total of
(a) Load requirement
(b) Losses in cables and wires
(c) Losses in instrumentation electronics
(d) Losses due to dust accumulation
(e) Losses due to mismatch of the cells
(f) Possible degradation due to ageing
The basic block schematic is given in figure below
The basic PV conversion schematic diagram is given in Figure 1.
2.1.2 Design Methodology for Thermal System
The total solar radiation incident on the collector will be sum total of:
(i) Heat transferred to the fluid
(ii) Heat losses from top, side and bottom.
Since the main aim is to increase the efficiency of SPV system. Thermal aspect is added to
extract the solar energy which are not being utilized for SPV conversion.
2.1.3 Design Methodology of Integrated SPV/T system
One Glass to Glass SPV module with 33 solar cells of 100mm dia, was used for design and
fabrication of integrated SPV/T system. The module has a peak electric output of 29 watts
generating 15 volts at 2.2 amperes. The module has circular solar cells accounting for 60% of
the panel area and the rest is transparent. Two types of heat exchanger to be fixed below the
SPV module for cooling water circulation were designed for fabricating the integrated SPV/T
systems – Water jacket type and conventional pipe-header type. On comparison, the
conventional pipe-header type heat exchanger was found better due to ease in fabrication and
fixing below lower glass of the module. In jacket type heat exchanger, problem of bulging
and bending because of welding and consequent leakage was encountered. So it was decided
to design and fabricate pipe – header type heat exchanger.
3. Mathematical model
The solar energy incident on the SPV/T panel will be sum of energy received by two
component system. One component of the energy is received by cell area of the module
which is opaque. While the remaining area without cell is transparent. The solar energy
incident on the transparent area is not utilized for PV conversion, it is directly transmitted to
3

absorber copper plate of heat exchanger below the bottom glass of the module. The thermal
energy absorbed is transferred to the fluid flowing in pipe fixed below the absorber plate of
the heat exchanger. This flowing fluid becomes hot and thermal energy except the losses is
extracted away from the module delivering hot water. The solar radiations falling on opaque
cells area of the module are partially converted into electrical energy and its thermal
component is passed to the fluid by way of conduction through the cells. Thus reducing the
solar cell temperature resulting into a better PV conversion efficiency.
Based on the above analogy, the design of the integrated SPV/ Thermal system is done in the
following paras
We define the p
Where and are the solar cell area and collector area, respectively. If the solar
insolation I is falling on the panel, then the energy absorbed by the solar cells is
Where
= Absorptivity of the solar cells
= Transmittance of the glass cover
= The solar Insolation
The solar energy converts into two components- electrical ( ) and thermal ( ) and given
by
(3)
Thermal component in solar cell area which is conducted to absorber through cell
Where = conversion efficiency of solar cell
is Solar cell temperature of the order of 270 o C where solar cell efficiency is zero
is 25 o C where solar cell efficiency is 10%.
The energy received by heat absorber ( ) through transparent area given by (7)
= Absorptivity of absorber plate
= Transmittance of upper glass
4
(1)
(2)
(4)
(5)
(6)

= Transmittance of lower glass
Useful energy gain through transparent area of the module
Useful energy gain through opaque cell area is
Where,
Where, and are the absorber plate and ambient temperatures, respectively. , ,
and are the thickness and , , and are the conductivities of absorber
plate, solar cell , upper and lower glass, respectively plate
Total useful thermal gain absorbed by integrated panel
Useful gain extracted by the system
5
(8)
(9)
(10)
(11)
(12)
NL (13)
Where
W = Centre to Centre distance of copper tubes (riser pipes)
D = Diameter of the riser pipes
= Energy absorbed
= Number of tubes
= (14)
= (15)
= (16)
4. Fabrication of integrated SPV/T system
A 3 mm thick copper plate was fixed at the bottom glass plate of the glass to glass module as
shown in Figure 2. This copper plate which is selectively coated with Silicon, acts as
absorber. Silicon compound was used to make the thermal contact with glass as close as
possible for maximum energy absorption. The incident solar radiations, which falls on the
cells, generate electrical power and the radiations falling on transparent area are collected by
this selectively coated copper absorber plate. The copper plate is connected to a pipe type

heat exchanger consisting of 20 mm dia header pipe and 10mm dia riser pipe for heat
removal when the water is allowed to flow as the media (Figure 2).
5. Instrumentation
Copper Constantan thermocouples were mounted to observe the temperature of water inlet,
water outlet upper glass plate, copper surface of the heat exchanger and storage water tank
etc. The thermal data is obtained through a multichannel data logger with printer and
electrical parameters were also recorded simultaneously with the help of millimeter. The
whole assembly is enclosed in wooden tray filled with glass wool to insulate the heat
exchanger. The inlet and outlet of the header are connected to insulated m.s. storage tank of
inner size 310 mm x 310 mm x 300 mm in such a way that thermo-syphon action may take
place. The whole system is mounted in a angle iron frame placed above the ground.
Another SPV module without heat exchanger (cooling) is also mounted adjacent to the
SPV/T system for comparison. It was instrumented for measurement of surface temperature
and electrical out put.
6. Data generation
The electrical and thermal parameters were recorded for about two weeks. However due to
cloudy sky conditions, the pattern of solar insolation had abrupt changes. The data for SPV/T
system and SPV module without cooling are observed simultaneously for comparison. A
typical one day observation is depicted below in Table 1. On the basis of the observations
shown in Table 1, the curves plotted for thermal performance and improvement electrical
efficiency are shown in Figure 3 to Figure 5.
7. Conclusion
The various curves for temperature were plotted and compared with the observation taken for
a panel without heat exchanger and the efficiencies were computed from the curves it is
concluded
(1) The percentile improvement in the efficiency of the hybrid system as compared to the
normal PV system is about 10 to 15%
(2) The temperature of hot water available is of 40 o C.
References
1. Remme et al. "Technology development prospects for the Indian power sector"
International Energy Agency France; OECD, February 2011
2. http://powermin.gov.in/indian_electricity_scenario/introduction.ht
3. ‘Solar PV Industry 2010 :Contemporary scenario and emerging trends’, Report prepared
by India Semiconductor Association, Bangalore and supported by the Office of the
Principal Scientific Adviser to the Government of India, May, 2010.
4. http://en.wikipedia.org/wiki/India's_energy_policy
6

5. Chopra, K.L. “Application of Sottp://en.wikipedia.org/wiki/India's_energy_policylar –
Photovoltaics in Buildings”, CSIR Foundation Day Lecture, CSIR-CBRI, Roorkee
(India), September, 26, 2010.
6. Muneer, T.; Asif, M.; Munawwar, S). "Sustainable production of solar electricity with
particular reference to the Indian economy". Renewable and Sustainable Energy Reviews
9 (5): 444, 2005.
Time in
HRS.
9.30
10.00
10.30
11.00
11.30
12.00
12.30
13.00
14.00
15.00
15.30
Solar Insol
mW/cm 2
Table 1. Observed Data
Temperatures in °C
Elect Power O/P
Watts(EP) % IMP
T1 T2 T3 T4 T5 T6
EP
With
cooling
Bare
66 31 33 35 32 51 54 27.70 24.00 15.4
68 30 35 40 33 54 57 26.00 23.75 9.4
76 32 36 42 35 58 60 27.00 25.00 8.0
80 33 38 44 37 61 62 27.00 25.35 6.5
82 35 41 44 40 60 64 26.60 25.65 3.7
84 38 42 46 40 59 63 29.00 26.60 9.0
40 33 43 47 42 59 65 16.20 15.20 6.5
84 40 44 47 42 58 63 28.00 24.70 13.3
74 40 44 50 42 57 61 24.00 22.80 5.2
58 40 42 46 44 55 54 21.50 19.50 10.2
43 44 44 47 41 50 53 16.20 16.65 --
16.00 30 38 42 46 42 48 52 11.40 12.35 --
16.30
22 40 41 45 43 44 48 9.25 7.00 32.1
T1 -Intlet water temperature, T2 -Outlet water temperature, T3- Storage water temperature, T4 –
surface temperature of heat exchanger, T5- surface temperature of SPV module of integrated
system,
T6 – surface temperature of SPV module without cooling
7

Single crystalline
silicon solar cell
Selectively Coated
Copper Absorber
Plate
PV Array
Electronics and Master
Control Panel for Charging
Battery Storage
Load Management System
and Distribution Board
Figure 1. SPV Schematic
Figure 2. Integrated SPV/T System for Glass to Glass module
8
Inversion Electronics
Load Management System
and Distribution Board
Transparent
Glass Cover
Copper Pipe
Insulation

Solar Insolation, mW/cm 2
100
90
80
70
60
50
40
30
20
20
8 10 12 14 16 18
100
90
80
Solar Insolation, mW/cm 2
70
60
50
40
30
Solar Insolation
T1
T2
T3
T4
T5
T6 Solar Insolation
Time, Hrs.
Figure 3. Solar Insolation and Thermal Performance
Solar Insolation
Elect output (with cooling)
Elect. output (without cooling)
Solar Insolation
Electrical output
20
0
8 1012 14 16 18
Time, Hrs.
9
100
90
80
70
60
50
40
30
100
90
80
70
60
50
40
30
20
10
Temperature, o C
Electrical Output, Watt

Solar Insolation, mW/cm 2
100
90
80
70
60
50
40
30
20
Figure 4. Solar Insolation and Electrical Output
Solar Insolation
Improvement in Electrical output
8 10 12 14 16 18
10
Solar Insolation
Improvement in Electrical Output
Time, Hrs.
Figure 5. Percentage Improvement in Electrical Output
100
90
80
70
60
50
40
30
20
10
0
Improvement in Electrical Output,%

Abstract.
Interaction of Solar Radiation and Earth Atmosphere
Shree Kumar
Former Scientist, CSIR-Central Building Research Institute, Roorkee
Corresponding Author, Email: shreekumar_5031@rediffmail.com
In this paper various aspects of interaction of solar radiation with earth atmosphere with
specific focus on characteristics of light scattering and absorption and phenomena of green
house effect along with natural air movement are discussed. All of the above natural
processes are very important for a physicist involved in solar energy utilization in building.
This article is based on the references listed at the end of the paper.
1. Introduction
Solar radiation and earth atmosphere are two most important factors that are necessary for the
existence and sustaining the life on the planet. In the absence of solar radiation or atmosphere
one can’t imagine the life on earth. Solar radiations are emitted by the sun which is at
1.5x10 11 m away from earth by thermonuclear process. When radiation reaches the earth
surface it passes most of the distance through space which is almost vacuum, without any
modification and only a small part of the path is crossed through the atmosphere. During the
traverse through this region many process taken place, most important of these are absorption
and scattering. As the atmosphere is not a homogeneous medium of constant concentration.
Its constituents vary largely with location and height from the earth surface. The atmosphere
has been divided into various layers namely biosphere, troposphere, stratosphere,
mesosphere, ionosphere or exosphere depending on varies features like height, temperature,
state of constituent’s particles. The atmospheric ozone has been formed by converting the
atmospheric oxygen in the presence of ultraviolet solar radiation. Many natural
phenomenon’s such as blue color of sky, during daytime reddish color of sun disc at the time
of sun rise and sunset changing color and pattern of clouds are mainly due to interaction of
solar radiation with the atmospheric particles. The diminishing visibility during haze and fog
are due to scattering of radiation with the suspended molecules of water in the atmosphere.
The average Earth surface temperature (about 16°C), is regulated by the solar radiation and
the greenhouse effect of the atmosphere, this allows water to exist naturally in all its three
phases -- solid, liquid, and gas.
The solar radiation is absorbed by air and earth surface both, but the absorption of radiation
by earth surface is at different rates at different locations. Large bodies of water will get
warm and cool at a slower rate than large bodies of land. This creates a disparity in the
atmosphere above and this causes horizontal movement of air or wind.

2. Atmospheric effects
A considerable portion of solar radiation is reflected back into outer space upon striking the
uppermost layers of the atmosphere, and also from the tops of clouds. In the course of
penetration through the atmosphere, some of the incoming radiation is either absorbed or
scattered in all directions by atmospheric gases, vapours, and dust particles. Scattering of
solar radiation is either selective and non-selective depending on the particle size of the
atmosphere.
Selective scattering is caused by atmospheric gases or particles that are smaller in dimension
than the wavelength of radiation. It is inversely proportional to the wavelength of radiation it
follows the pattern: far UV > near UV > violet > blue > green > yellow > orange > red >
infrared. Selective scattering of violet and blue light by the atmosphere causes the blue color
of the sky. At noon time, the sun appears white because sunlight passes through minimum
thickness of atmosphere. At sunrise and sunset, however, sunlight passes obliquely through a
much thicker layer of atmosphere. This results in maximum atmospheric scattering of violet
and blue light, with only a little effect on the red rays of sunlight. Hence, the sun appears to
be red in color at sunrise and sunset.
Non-selective scattering occurring in the lower atmosphere is caused by dust, fog etc, of
particle sizes more than ten times the wavelength of solar radiation. Since the amount of
scattering is equal for all wavelengths, clouds and fog appear white. The degree of absorption
of solar radiation passing through the outer atmosphere depends upon the their wavelengths.
The gamma rays, X-rays, and ultraviolet radiation less than 200 nm in wavelength are
absorbed by oxygen and nitrogen. Most of the radiation with a range of wavelengths from
200 to 300 nm is absorbed by the ozone (O3) layer in the upper atmosphere. Solar radiation in
the red and infrared regions of the spectrum at wavelengths greater than 700 nm is absorbed
to some extent by carbon dioxide, ozone, and water present in the atmosphere in the form of
vapour and condensed droplets (Table 1). In fact, the water droplets present in clouds not
only absorb rays of long wavelengths, but also scatter some of the solar radiation of short
wavelengths.
Optical phenomena involving reflection, scattering, and absorption of radiation, the quantity
of solar energy that reaches the earth's surface is much reduced in intensity. The amount of
reduction varies with the radiation wavelength, and depends on the length of the atmospheric
path through which the solar radiation traverses. The intensity of the direct beams of sunlight
thus depends on the altitude of the sun, and also varies with such factors as latitude, season,
cloud coverage, and atmospheric pollutants.
The total solar radiation received at ground level includes both direct radiation and indirect
(or diffuse) radiation. Diffuse radiation is the component of total radiation caused by
atmospheric scattering and reflection of the incident radiation on the ground. Reflection from
the ground is primarily visible light with a maximum radiation peak at a wavelength of 555
nm (green light). The relatively small amount of energy radiated from the earth at an average
ambient temperature of 17°C at its surface consists of infrared radiation with a peak
concentration at 970 nm. This invisible radiation is dominant at night.
During daylight hours, the amount of diffuse radiation may be as much as 10% of the total
solar radiation at noon time even when the sky is clear. This value may rise to about 20% in
the early morning and late afternoon.

3. Characteristics of scattering
Scattering is the process, by which a particle in the path of an electromagnetic wave
continuously do the following action
(1) Abstracts energy from the incident wave.
(2) Reradiates that energy in to the total solid angle centered at the particle.
The particle is a point source of the scattered energy. For scattering to occur, it is necessary
that the refractive index of the particle be different from that of the surrounding medium. The
particle is then optical discontinuity, or in homogeneity, to the incident wave. When the
atomic nature of matter is considered it is clear that no material is truly homogenous in a
fine-grained sense. As a result, scattering occurs whenever an electromagnetic wave
propagates in a material medium. In the atmosphere the particles responsible for scattering
run the size gamut from gas molecules to rain drops, as listed in Table 1. The wide ranges of
size and concentration are noteworthy.
Table 1. The size and concentration of atmospheric particles
Type Radius (μm) Concentration (cm -3 )
Air molecules 10 -4
Aitkin nucleus 10 -3 – 10 -2
10 4 – 10 2
Haze particle 10 -2 – 1 10 3 - 10
Fog droplet 1 - 10 100 – 10
Cloud droplet 1 -10 300 -10
Rain drop 10 2 – 10 4
10 -2 – 10 -5
About each particle the intensity of the scattered radiant energy, here after called the scatter
intensity, forms a characteristic three dimensional pattern in space. . If the particle is
isotropic, the pattern is symmetric about the direction of the incident wave. The form of the
pattern depends strongly on the ratio of particle size to wave length of the incident wave, as
illustrated by the three examples in figure. In figure (a) the relatively small particle tends to
scatter equally in to the forward and rear hemisphere. When the particle is larger, as in figure
(b), the overall scattering is greater and is more concentrated in the forward direction. For a
still larger particle, as in figure (c), the overall scattering is even greater. Most of it is now
concentrated in a forward lobe, and secondary maxima and minima appear at various angles.
Further increases in particle size produce patterns of even greater complexity. In all cases the
form of the pattern is influenced by the relative refractive index, that is, the ratio of the
refractive index of the particle to that of the medium surrounding the particle.
3.1 Types of scattering
The wide range of particle size in table, covering orders of magnitude suggests that scattering
itself may show large variations. This is indeed a fact, as can be seen in figure 1. When the
particle is far smaller than the wavelength, the scattering is called Rayleigh scattering. This
name commemorates the man who developed the theory of scattering by very small isotropic
particles. Scattering of this type varies directly as the second power of the particle volume
inversely as the forth power of the wavelength. Equal amounts of flux are scattered in to the
forward and back hemispheres, as in figure 1(a). The principal Rayleigh scatterers in the
atmosphere are the molecules of atmospheric gases.
10 19

Figure 1. Angular distribution of scattered intensity from particle of three sizes. (a) Small
particle, (b) large particle, (c) larger particles
When the particle diameter is greater than about one –tenth of the wavelength, Rayleigh
theory is not adequate to explain the phenomena. The greater overall scattering and pattern
complexity, as in figure 1(b) and 1(c), require for their explanation the theory developed by
Mie. Although his theory is strictly applicable only to isotropic spheres, it is customary to
employ the term Mie scattering even though the particles may be somewhat irregular in
shape. The full Mie theory is expressed as a mathematical series embracing all particle sizes;
the first term of the series is equivalent to the Rayleigh expression. For spheres of great
relative size, such as rain drops illuminated by visible light, the Mie theory can be closely
approximated by the principles of reflection, refraction and diffraction. Every particle in the
atmosphere is actually a Mie scatterer, but we apply the term only to particles larger than
Rayleigh scatterers.
Attention is called to a third type of scattering which, under certain conditions, accompanies
Rayleigh scattering. As noted previously, Rayleigh scattering occurs without change in
frequency. However, when the incident light is nearly monochromatic, or alternatively
consists of line spectra, a careful analysis of the scattered light reveals weak spectral lines not
present in the incident light. Such changing in frequency is the result of changes in the
energy level of the molecules. The changes or transitions take place concurrently with
Rayleigh scattering and produce frequencies greater and less than the frequency of the
principally scattered light. The frequency shifts are related to the differences between the
permitted energy level, and they provide data for identifying the molecular species. This
phenomenon is Raman scattering, named for the Indian physicist who first investigated it.
3.2 Scattering by many particles
In many particles cases we are concerned with the scattering by all the particles within a
given volume of space. When the average separation distance is several time the particle
radius, each particle is considered to scatter independently of all the others. This means that
each scattering pattern (such as those shown in figure 8.1) is unaffected by the neighboring
scattering. This is called independent scattering. The separation criterion is easily satisfied in

all the metrological conditions typified by the particles listed in Table 8.1. Consequently,
independent scattering prevail in the atmosphere. The criterion is not met by the closely
packed atoms and molecules of high-pressure gases, liquid, and solids. Therefore
independent scattering does not obtain in such media.
We are mostly concern with independent scattering. When the particles are randomly
arranged and randomly moving, no coherent phase relationships exist between the separately
scattering waves. Hence no interferences among these waves can be discerned, and their
intensities rather than their amplitudes are additive. This is incoherent scattering. If the
particles are identical, the composite or resultant intensity pattern is the same as that from a
single particle. The randomness requirements are met by all atmospheric conditions. The
requirements are not met by more regularly arranged atoms and molecules of liquid and
solids, so their scattering has coherent aspects. In a liquid, for example, mutual interferences
suppress most of the lateral scattering. The scattering of x rays by the atoms of a crystal
lattice provides a more striking example. Here the interferences are sufficiently strong to
produce major maxima and minima of intensity at certain angles, giving rise to the term x ray
diffraction.
In the discussion to this point it has been tacitly assumed that the particle is exposed only to
the light of incident or direct beam. That is, single scattering has been assumed. No account
has been taken of the fact that each particle in a scattering volume is exposed to and also
scatters a small amount of the light already scattered by the other particles. The intensity of
this light, will be very weak in comparison to that of the direct beam, reaches a given particle
from many directions, as suggested by figure 8.1. Hence some of the light that has been firstscattered
may be re-scattered one or more times before emerging from the scattering volume.
This is called secondary or multiple scattering. Although removed from the direct beam, it
may significantly alter the composite pattern of scattered intensity due to all the particles.
This characteristic of multiple scattering can be appreciated from figure 1(a b c). For
example, as visualized that the pattern in figure(c) is overlaid with a multitude of similar but
far weaker patterns having all orientations in the plane of the figure. It becomes clear that the
composite pattern, while still retaining the principal features of the original, exhibits fewer
and smaller variations in intensities as a function of angle. In the extreme, as with a very
turbid medium, all sense of the direction of beam is lost, and the scattered lights tend to reach
an observer rather uniform from all directions. This tendency is manifested in a dense fog.
The simple mechanism of scattering and absorption is depicted in fig 2 and mathematically it
is expressed by equation 1 and it called Bougure’s Lambert Law.
I / Io = exp (-αL) (1)
The coefficient α usually varies with wavelength, and for Rayleigh scattering is proportional
to 1 / λ 4 . This is used for calculations of the solar constant. For this the logarithm of Hλ, the
relative spectral power distribution of sunlight, is plotted verses the air mass m, m is related
with the solar altitude θ in radians.
m = 1/ [sin θ + 0.15 (h + 3.885) -1.253 ] (2)
here h is solar altitude in degrees. Each wavelength gives a nearly straight line, the more so
for clearer and more stable atmospheres. By extrapolation to m = 0, the lines give the
extraterrestrial values Hoλ required for solar constant calculations, and their slopes varying
with wavelength provided the atmospheric extinction coefficients. It is desirable to extend

Figure 2. Scattering and absorption mechanism of solar irradiance through the earth’s
atmosphere
the lines as far as possible. Some observations have been made up to m = 10 or more, where
z the zenith angle of sun is nearly 90 0 and sec z is no longer nearly proportional to m owing
to refraction in the air. Correction factors are used in such cases.
More commonly an empirical approach has been found sufficient. For example, Fowle
expressed extinction by the formula:
I/Io = exp [-(a1 +a2) m] (3)
Here a1 refers to molecular scattering and a2 other causes with air mass m. It was realized
that, as particles in a cloud or aerosol increased in size the scattering became less dependent
on wavelength as in a jet of cooling stream which scatters light, first blue, then more and
more white. The Rayleigh exponent could be considered to change from 4 to zero.
3.3 Distinctions between scattering and absorption
Scattering must be distinguished from absorption. Both processes remove flux from a given
beam of light, but the similarity ends there. As already noted, scattering is explained in terms
of the wave theory of light, and it produces no net change in the internal energy state of the
molecules. In contrast, absorption requires quantum theory for its explanation and does
produce change in the energy states. Three forms of such internal energy exist: rotational,
vibrational and electronic arrangement. These forms are additional to the kinetic energy of
molecular translation, which plays an indirect but essential role in absorption and also in the
associated process called emission.
Within the small domains of molecular space and action, each forms of internal energy is
quantized to discrete, permitted values or levels. The incident radiant energy also must be
regarded as quantized and only whole quanta can be accepted by the molecule. In absorbing a
quantum of energy the molecule thereby undergoes a transition from a lower to a high state
of one of the three internal energy forms. Time-wise, absorption is a discontinuous process
because of the quantization. Spectrally the process is selective, not continuous, because only

those quanta can be absorbed whose energies are equal to the differences between the
permitted levels.
Absorption is only the first part of a cycle which is completed by emission. As a consequence
of molecular motion and collisions molecules endless exchange internal energy for
translation energy, and vice versa. Molecules already excited to upper level are de-excited or
relaxed to lower levels, on a statistical basic. Conversely, molecules at lower are excite to
upper level by collisions, again on a statistical basis. Most of the upper are inherently
unstable, however, and molecules occupying these levels undergo transitions to lower by
emitting quanta of radiant energy. These downward transitions may be either spontaneous or
stimulated. The first type predominates in the atmosphere, while the second type is the
operation basis of lasers; the emitted quanta have energies equal to the differences between
the initial and final levels, so emission is as spectrally selective as absorption. Being
quantized, emission by an individual molecule is a discontinuous process.
From above, several basic distinctions between scattering and absorption-emission become
apparent. These distinctions should be kept in mind. Absorption and emission by gases are
not discussed further in this volume. Absorption by particles, however, is dealt with to the
extent that several quantities developed in scattering theory are employed as measures of
absorption. This allows both scattering and absorption by particles to be considered jointly as
a process called extinction.
4. Green house effect
Over thousands of years the temperature on the Earth has been more or less constant with
seasonal variations. This is possible only if the energy received from outer space is same as
dissipated from Earth. Otherwise earth will either become too cold or too Hot for life to
survive.
The amount of energy received at the edge varies according to location and season. When the
sun's rays are perpendicular to a location at the edge of the atmosphere, that area receives the
maximum amount of radiation. Because of the earth's curvature the equator receives a
greater amount of solar energy than the poles. The position of the earth relative to the sun
also affects the amount of radiation received. When the northern hemisphere experiences
summer the North Pole is tilted toward the sun, resulting in a longer period of daylight and
more perpendicular rays. Though the earth in its elliptical revolution is actually at its farthest
distance from the sun, the amount of energy and the length of daylight compensates for the
distance. When the earth is closest to the sun, the North Pole is tilted away and the northern
hemisphere experiences winter, short days and oblique rays.
The transfer of energy from the sun to the earth's atmosphere is through radiation. These
waves are classified according to their wavelength - the distance between peaks in the waves
- from shorter to longer. Differing wavelengths causes differing interactions with the
atmosphere; the amount of energy that enters the atmosphere is greatly reduced due to
absorption, reflection, and scattering before it reaches the earth's surface. Absorption causes
energy to be captured and retained by a substance, and by retaining energy the substance
heats up and reradiates. X-rays and gamma rays, which have the shortest wavelengths, are
absorbed by oxygen and nitrogen molecules in the upper atmosphere and transformed into
ions, which form the ionosphere. Ultraviolet rays of slightly longer wavelength are absorbed
by ozone in the stratosphere. Infra-red rays, at the other end of the spectrum, are slightly
absorbed by carbon dioxide and water vapor in the troposphere. Wavelengths that are visible

to the human eye - violet, blue, green, yellow, orange, and red - are affected by reflection and
scattering. Reflection occurs when particles and surfaces that are larger than the incoming
waves meet and turn back solar energy. Clouds, snow, and light-colored sand are all
reflectors. Scattering occurs when particles the same size as the wavelength of the radiation
meet. Scattering causes energy to be redirected in all directions, some of which returns to
space. The sky appears blue because the short, blue wavelengths are more easily scattered.
Without scattering the sky away from the sun would appear black, similar to outer space.
Scattering is also the reason the sun appears red at sunrise and sunset. Because the sun's path
through the atmosphere is much longer at this time of day, more of the blue wavelengths are
scattered out of its beam, leaving more red light.
Only about one-fifth of energy warms the atmosphere directly. Most of the energy that
warms our atmosphere comes indirectly from the heated earth. A small amount of the energy
absorbed by the earth warms the atmosphere through a process called conduction. More heat
is transferred from the surface to the atmosphere through convection.
Almost all convection energy is absorbed by the atmosphere. The difference in temperature
between atmosphere and earth changes the wavelength of the predominant wavelength.
Lower the temperature, the longer the wavelength. The shortwave visible light rays which
passed down through the water vapor and carbon dioxide without obstruction return upward
as long wave radiation and are for the most part absorbed by those same clouds. The clouds
heat up and reemit energy back to earth as counter radiation - in effect recycling radiation
from the earth. This process of trapping long wave radiation has been called the greenhouse
effect, and is one of the important ways the atmosphere's temperatures remain within a
livable range.
Amount of energy absorbed by the earth-atmosphere system over the entire globe in a year is
equal to the amount emitted by the system.
At different latitudes an imbalance exists between the outgoing and absorbed radiation of the
earth-atmosphere heating system. The poles should be getting colder and tropical regions
warmer, but this is not happening. Heat is being transported pole ward from areas of surplus
radiation, almost equally, by ocean and air. The atmospheric balancing act is achieved by
wind systems.
5. The mechanism of atmospheric air motion or winds
Heat is transferred vertically from the earth to the air by convection. But wind is defined as
the horizontal movement of air relative to the earth's surface. Air temperature varies because
the earth's surface heats up at different rates. Latitude and season cause temperature
variations. Large bodies of water will get warm and cool at a slower rate than large bodies of
land. This creates a disparity in the atmosphere above. Because heat decreases with altitude,
mountain peaks are cooler than cities at sea level. Differences of temperature cause
differences in pressure. A difference in pressure across distances is called a pressure gradient,
and is the driving force behind wind. Once the air has begun to move (surplus heat to the
poles and surplus cold to the equator) another force comes into play. This is called the
Coriolis force, and is caused by the rotation of the earth. The earth rotates on its axis at the
rate of 1666 km per hour at the equator. The speed decreases with increasing latitude until it
is virtually zero at the poles.

6. Conclusion
Following are some important conclusion that may be drawn from the above article.
1 Solar radiations are emitted by the Sun which is generated by thermo nuclear process
mainly fusion of hydrogen nuclei into Deuterium and other chain reactions.
2 The solar radiations cover a wide spectrum ranging from gamma rays to micro wave
region. It includes Ultraviolet, Visible, Infrared, Radio waves etc. The peak of the
spectrum lies in visible region centered at 500 nm in the green yellow region of visible
part.
3 The amount of solar radiation reaching at the earth surface depends on site latitude and
longitude, solar position, atmospheric condition i.e. whether the atmosphere is clear or
polluted.
4 There is a long history of evolution earth atmosphere and the present atmosphere is third
generation atmosphere. It constitute permanent gases molecule like Oxygen, Nitrogen
and Argon and trace gases such as CO2 and Methane etc. which are evolved due to
anthropogenic (human-produced) activities.
5 During the traverse of solar radiation from sun to earth it passes through almost vacuum
in the inter space part beyond the atmosphere without any major but when it enters the
atmosphere of the earth many processes take place such as absorption, scattering. Which
in turn causes chemical changes in some gases e.g. convert Ozone to Oxygen and vice -
verse.
6 The atmosphere work as a blanket for the living being by keeping the mean temperature
of the earth in a range that avoids harsh cold or hot.
7 Various types of scattering takes place which depends on the relative size of scattering of
the molecules and the wave length of solar radiation. These are mainly classified into
Rayleigh scattering, Mie scattering and Large particle scattering.
In conclusion, therefore, it is evident that in cloudy weather the total radiation received at
ground level is greatly reduced, the amount of reduction being dependent on cloud coverage
and cloud thickness. Under extreme cloud conditions a significant proportion of the incident
radiation would be in the form of scattered or diffuse light. In addition, lesser solar radiation
is expected during the early and late hours of the day. These facts are of practical value for
the proper utilization of solar radiation.
7. Acknowledgement
I sincerely acknowledge the interest shown and encouragement given by my former
colleagues Dr. P.K.Bhargava and Dr. B.M.Suman in completing this article.
References
1. Robinson .N. (editor), Solar Radiation, Chapter 4 by W. Schuepp, Elsevier, Amsterdam
(1966).
2. Coulson.K. L., Solar and Terrestrial Radiation, Acadamic Press, New York (1975).
3. Angstrom, “Techniques of Determining the Turbidity of the Atmosphere”, Tellus 13(2),
214-233 (1961).
4. King R., and Buckius. R.O., “Direct Solar Transmittance for a Clear Sky”, Solar Energy
22, 297-301 (1979)

5. Navvab. M., Karayel M., Ne’eman E. and Selkowitz S., “Analysis of Atmospheric
Turbidity for Daylight Calculations”, Energy and Buildings, no. 6, 293-303 (1984).
6. Mani Anna and Chacko Oommen, “Attenuation of Solar Radiation in the Atmosphere”,
Solar Energy 24, 347-349, (1980).
7. Kasten F., “A new table and approximate formula for relative optical air mass”, Arch.
Meteorol. 8, 955-962 (1969).
8. Penndorf R., “Tables of the Refractive Index for Standard Air and the Rayleigh
Scattering Coefficient”, J. Opt. Soc. Am., 47,176 (1957).
9. Malik Q., “Estimation of Atmospheric Ozone for Association of South East Asian
Nations (ASEAN) Countries”, Renewable Energy 12, no. 2, 193-202, (1997).
10. Leckner, “The spectral distribution of solar radiation at the earth’s surface elements of a
model”, Solar Energy 20, 143-150 (1978).

Abstract.
Energy from Cloud-to-Ground Lightning Discharge
Manoj Kumar Paras and Jagdish Rai
Indian Institute of Technology Roorkee
Corresponding Author, Email: mkparas.iitr@gmail.com
In this paper, we calculated dissipated heat energy and radiated energy due to the current
flowing in the body of lightning channel. The energy loss by means of heat and radiation
come out to be around 1.58×10 6 J and 3.23×10 3 J respectively. It is found that the energy
loss due to lightning in the form of radiation is much low as compared to the dissipated heat
energy.
1. Introduction
Lightning is one of the most dangerous natural disasters in earth’s atmosphere. It is a
transient, high-current electric discharge in air. The most common source of lightning is the
thundercloud or cumulonimbus cloud in which electric charge regions of opposite polarity are
separated due to certain mechanisms. The upper and lower parts of the thundercloud have
positive and negative charges respectively. The mechanisms of thundercloud electrification
include drop-breakup, ion charging, convective and induction [1]. There are commonly four
types of lightning discharges known as intracloud, cloud-to-cloud, cloud-to-air and cloud-toground.
Intracloud lightning occurs more than half times of all lightning discharges.
However, cloud-to-ground lightning has been studied more extensively than other lightning
forms because of its practical interest (e.g., as the cause of injuries, deaths and forest fires)
[2]. A lucid model of the formation of lightning in atmosphere is still missing in spite of the
fact that many features of this spectacular phenomenon have been studied in detail. The
modern concept regarding generation of atmospheric electricity is based on the potential
gradient between the cloud and ground, and between various regions of the cloud. When the
potential gradient i.e. electric field reached beyond the dielectric strength of air (3×10 6 V m -1 )
lightning takes place. Cloud-to-ground lightning flash originates near the cloud base in the
form of “stepped leader”, which moves downward toward the earth in discrete steps. Each
step lasts for about 1 μs during which time the stepped leader advances about 50 m. The time
interval between steps is about 50 μs. Stepped leader carries the cloud charge to the earth. As
soon as the stepped leader nears the ground it induces the positive charges on the ground,
especially on protruding objects, and when it is 10-100 m from the ground a travelling spark
moves up from the ground to meet it. After the contact is made between the stepped leader
and travelling spark, large number of electrons flow to the ground and a highly luminous and
visible lightning stroke known as “return stroke” propagates upward in a continuously
fashion along the path followed by the stepped leader. Return stroke is responsible for the
brightness of lightning channel. Following the first stroke, which carries the largest current,
subsequent strokes, may occur along the same main channel, provided that additional

electrons are supplied to the top of the previous stroke. Cloud-to-ground lightning are of two
types depending on the nature of stepped leader. If stepped leader carries negative charge it is
called as negative cloud-to-ground lightning and if it carries positive charge it is called as
positive cloud-to-ground lightning discharge. Positive cloud-to-ground lightning discharges
are much stronger than the negative cloud-to-ground lightning discharges. In this paper,
energy loss in the form of heat and radiation has been calculated from cloud-to-ground
lightning discharge.
2. Heat energy in the lightning channel
Cloud-to-ground lightning discharge contains two different types of current. The first one and
most intense is the return stroke current. It can ranges from 10-100 kA with duration of 100-
200 μs [3]. The estimated peak current of first return stroke has been reported about 300 kA
in temperate region and about 450-500 kA in tropics [4]. The other one is called lateral
corona current. Lateral corona current will be discussed in next section. The heat energy
dissipated in the lightning channel is mainly due to the return stroke current. The maximum
temperature in the lightning channel can reach up to 30,000 K [5,6]. The highly ionized core
of return stroke forms the plasma. The velocity and current expressions for return stroke are
given by [7,8]
-at -bt
-t
-t
V
rs
() t V
0
e -e
(1)
Irs () t I
0
e -e
(2)
where, V0=9×10 7 m/s; a=3×10 4 s -1 ; b= 7×10 5 s -1 ; I0=22 kA; α=1.6×10 4 s -1 ; β=5×10 5 s -1 .
The thermal power in the lightning channel can be written by
P I2 rs()
t R() t
(3)
th
where, R(t) is the resistance of the conducting channel. R(t) is given by
Rt ()
Lt ()
(4)
r2
where, σ=10 4 mho/m [9], the conductivity of lightning channel; r=2 cm, the average radius of
cross section of the lightning channel [10]; and L(t) is the distance travelled by the lightning.
L(t) is given by
t
L() t Vrs() t dt
(5)
0
The total dissipated heat energy in the lightning channel is given by
W P dt
th (6)
0
th
The total dissipated heat energy in the conducting channel comes out to be around 1.58×10 6 J.

3. Radiated energy
In this section we have calculated the amount of total radiated energy from tropospheric
cloud-to-ground lightning discharge. We have discussed about the return stroke current in
previous section. Below the tip of the return stroke, the whole channel up to ground surface is
at high potential than the surrounding medium left by the stepped leader. The negative ions
and electrons along the entire channel from tip to the ground move towards the highly
conducting return stroke core and constitute a current which immediately flows to the ground
through this channel. Since this current is developed due to the radial movement of negative
ions and electrons, it is known as “lateral corona current”. The mathematical expression is
given by [8]
2
KV V
0 -2t 2 2
I
lc
( t) ( b- a) exp - bexp - a t aexp -b
t
ab CR
CR
CR
Where,
K=Corona constant (10 -16 AV -2 m -1 s -1 ); V=Potential difference between the return stroke and
the leader sheath in volts and can be taken as 10 8 Volts; C=Distributed capacity of the leader
sheath-return stroke core in farads/m; R=Distributed resistance of the above configuration
(CR=5.3865 ms for I0=22 kA). Both currents flow simultaneously in the cloud-to-ground
lightning channel and they are not separable. Therefore, the total current is written by
Itot () t Irs() t I () t
lc
(8)
The Electric and magnetic fields have been calculated due to an arbitrary oriented lightning
discharge channel using a vector potential “A” associated with the return stroke current [11].
Fig. 1 shows the orientation of an arbitrary lightning channel in spherical-polar coordinates.
The general expression for “A” is given by
0 It (')
A '
4
dz (9)
r
where, μ0 is the permeability of the medium; r is the distance between the observation point
and the source; dz’ is the retarded elemental length of the channel; t’ (= t-r/c) is the retarded
time; and I(t’) is the total current flowing through it. They did not consider the lateral corona
current in their calculation. On the other hand we added this term to the return stroke current
for better outcomes. The vector potential “A” can be written by
A 0 A Ft (')
(10)
4
r 0
In equation (10), “A0” and “F(t’)” can be found with the help of current distribution and
velocity of the lightning discharge. The magnetic field components are given by [11]
Hr 0
(11)
A
0 sin sin( - )
1
( ')
1
H Ft
Ft ( ')
(12)
41 1 r2 cr t
(7)

Fig. 1. Schematic diagram shows the orientation of lightning channel. A(r1,θ1, 1)
and P(r,θ, ) are the lightning position and point of field observation respectively.
A
H -0-sincos sin coscos( - )
1
Ft ( ')
1
Ft ( ')
4
1 1 1
r2
rc t
Similarly, the electric field components are given by [11]
(13)
2A
0 cos cos sin sin cos( )
1
( ')
1
Er
F t dt F( t')
4
1 1 1 3
(14)
2
0
r r c
A
0 sin cos cos sin cos( )
1
( ')
1
( ')
1
E
F t dt F t F( t')
(15)
4
1 1 1
3 2 2 t
0
r r c rc
A
0 sinsin( )
1
(')
1
(')
1
E F t dt F t
F(') t
4 1 1 3 (16)
2 2 t
0
r r c rc
Since, the RS-LC system is vertical (θ1=0). So, the above expressions of magnetic and
electric fields become
Hr 0
(17)
H 0
(18)
A
0 sin
1
( ')
1
H Ft
Ft ( ')
(19)
4r2 rc t
2A
0 cos
1
( ')
1
Er F t dt F( t')
4 3
(20)
2
0 r r c
A
0 sin
1
( ')
1
( ')
1
E F t dt F t
F( t')
4 3
(21)
2 2 t
0 r r c rc
E 0
(22)

The radiated energy by a source is determined by the Poynting vector “S”, which describes
the direction and magnitude of electromagnetic energy flow. The Poynting vector “S” is
given by
S=E×H (23)
where, E and H are the calculated electric and magnetic fields at point (r,θ, ). All the terms
in equation (23) which decrease much faster than (1/r 2 ) will have zero contribution to
radiation energy at large distances. The survival components of electric and magnetic fields at
large distances are given by
A sin
E 0
F(') t
rad 4 rc2
t
0
A sin
H 0
F(') t
rad 4
rc t
Erad and Hrad are the radiated electric and magnetic fields respectively.
Imagine the source is at ground surface, the total radiated power passing through the upper
hemispherical shell having radius “r” is given by
(24)
(25)
/2 2
P () t r
2
sin d d
rad S
(26)
00
The total radiated energy is given by
W P () t dt
rad
t0
rad
(27)
Using equations (23), (24), (25) and (26), “Wrad” becomes
A 2 2
0 F
W
dt
rad 12 c3
0
t 0
t
The values of “A0” and “F(t')” for the RS-LC system have been given by [8].
where,
(28)
V
A 0
(29)
0 ab
F(') t F 1
(') t F
2
(') t
(30)
F
1
( t') I
0
exp(- t') - exp(- t')
-2t ' 2 2 ;
i 0 ( b- a) exp - bexp -a t' aexp -b t'
CR
CR
CR

KV
2
V
F
2
( t') aexp-bt'- bexp-at' (
b- a)
; and i
0
0
;
ab
where, I0, V0, a, b, α, β, V, K and CR are constants which has been discussed earlier.
The total radiated energy due to RS-LC system comes out to be around 3.23×10 3 J.
4. Results discussion and conclusion
The energy dissipation in the form of heat and radiation from cloud-to-ground lightning has
been calculated. It is found that most of the energy of lightning is dissipated in the resistive
part of the air column, which appears as the heat or thermal energy to raise the temperature of
the channel. The temperature of the column is so high and produces acoustic disturbances
known as “thunder”. The calculated total dissipated thermal energy comes out to be of the
order of 10 6 J. Most lightning return stroke contains heat energy approximately 3 kJ/m based
on a peak current of 20 kA [12]. Experimental studies have shown that the return stroke
channel length is ≤ 1.3 km [13], so the maximum heat energy for 20 kA current becomes of
the order of 10 6 J, as we have calculated. Similarly, the energy loss in the form of radiation
comes out to be around 3.23 kJ. It is found that energy loss in the form of heat is much more
as compared to the radiation losses. The above calculated energy is from a single lightning
stroke. There are 44±5 flashes (both cloud-to-ground and intracloud combined) occurring
around the globe every second [14]. This much enormous amount of energy generating from
lightning discharge may be used for mankind as an alternative source of energy, for example
in buildings. Buildings account for roughly 40% of all energy use in the world. Energy
consumption in buildings is divided mainly in two ways, residential and commercial.
Residential and commercial energy use involves in computers, cooking, electronics, lighting,
room heating, cooling, refrigeration, ventilation and office equipment etc. One can also use
this atmospheric electricity to heat the water, consequently hydrogen and oxygen gases will
be produced. Hydrogen gas can be used as a fuel and oxygen will be beneficial in the
hospitals. If the energy from the lightning channel becomes storable, it may help us to fulfill
our demands up to certain limits. Further, we can avoid the lightning strikes on sensitive
airborne operations and ground based experimental set-ups by using these techniques.
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Solar energized Liquid Desiccant Air Conditioning – A review
Abstract
Nagesh B. Balam and PK Bhargava
CSIR – Central Building Research Institute, Roorkee
Corresponding Author, Email: nagesh.balam@gmail.com
A review on Liquid Desiccant based cooling technologies with special focus on advances in
liquid desiccant materials and configurations of heat and mass exchangers have been
discussed. Performance comparison and energy saving potential of a hybrid liquid desiccant
cooling system based on vapour compression based sensible cooling and liquid desiccant
based dehumidification in comparison to conventional vapour compression system has been
reviewed. Hybrid liquid desiccant cooling system has enormous energy and cost saving
potential especially in hot and humid regions like India. The ability of Liquid Desiccant
cooling technology to be energized by Solar thermal makes it an attractive alternative to high
electrical energy intensive conventional vapour compression based cooling for residential and
commercial HVAC applications.
Keywords: Liquid Desiccant, Dehumidification, Vapour Compression, Solar Thermal.
1. Introduction
India is a tropical country and more than 80% of Indian Sub continental area falls under
Warm humid or Composite Climatic zone [1]. These climatic zones are characterized by high
annual average temperatures and high humidity. With rapid urbanization and industrialization
in India, there is sharp rise in air conditioning load in Industrial, commercial as well as
residential buildings.
The Air conditioning load could be broadly classified as sensible load and latent load.
Conventional vapour compression Air conditioners (VAC) meet the total air conditioning
load by cooling the air below the dew point temperature and thus condensing the moisture.
These systems require evaporator temperatures to be maintained much lower than required to
achieve sensible cooling alone. The dew point temperature is much below the set temperature
level and hence process air requires further heating to bring its temperature to set temperature
level. This requirement increases the capacity rating of the compressors and requires high
electricity and consequently operates at reduced coefficient of performance (COP) [2].
There is a necessity to separate the latent cooling load and sensible cooling load and handle
them separately so as to improve the COP of the air conditioners. The desiccant cycles can be
used to reduce the moisture content of air by partially converting latent cooling load to
sensible cooling load and then meeting the load by VAC’s. These systems with vapour
compression cycle for meeting sensible cooling load and liquid – desiccant cycle for latent
cooling load are called hybrid systems.

2. Liquid desiccant dehumidification and air conditioning
A desiccant material has a strong attraction for water vapour. Desiccants are commonly used
in industrial applications where low dew-point air is needed. The strength of a desiccant can
be measured by its equilibrium vapour pressure (i.e., pressure of water vapour that is in
equilibrium with the desiccant). This equilibrium vapour pressure increases roughly
exponentially with the temperature of the desiccant/water system. It also increases as the
desiccant absorbs water (a dilute liquid desiccant will have a higher equilibrium vapour
pressure than a concentrated liquid desiccant). When the absolute humidity of air that has
come into equilibrium with a liquid desiccant of fixed concentration is plotted on a
psychometric chart, the equilibrium line closely follows a line of constant relative humidity
and the Fig1. illustrates this behaviour for solutions of lithium chloride.
Figure 1. Psychrometric performance of LiCl at
different concentrations
Figure 2. Examples of Wet-bulb temperature
and brine-bulb temperature
As shown in the Fig 2., the brine-bulb temperature for a 43% solution of lithium chloride and
air at 30.0/25.6°C dry-bulb/wet-bulb will be 47.8°C. With an ambient wet-bulb temperature of
25.6°C, a typical cooling tower might supply water at29.4°C. It’s impractical to cool the
ambient air using this cooling water in a conventional heat exchanger, because the cooling
water is only one degree below the air temperature. However, a strong cooling effect could be
achieved by wetting the surfaces of the heat exchanger with the 43% lithium chloride. Of
course, one does not get this enhanced cooling for free. If the cooling process is to be
continuous, energy must be expended to regenerate the desiccant back to its original
concentration. If ambient air from the preceding example is brought into equilibrium with
43% lithium chloride at 85°F (29.4°C), the air will have a dew point of 33.5°F (0.8°C), a wetbulb
of 57.8°F (14.3°C), and its enthalpy will be reduced from 41.5 Btu/lb (96.3 kJ/kg) to
24.9 Btu/lb (57.8 kJ/kg). This large cooling effect, both in terms of latent cooling and total
cooling, and low dew point—both of which are achieved without a compressor—demonstrate
the potential for liquid desiccants to become an important part of HVAC systems. Liquid
desiccants have been successfully used to produce dry air for a surprisingly long time. Dr.
Russell Bichowsky, working for the Frigidaire Division of General Motors, first used
solutions of lithium chloride to dry air in the 1930s. Also in the 1930s, the Niagara Blower
Company introduced a liquid desiccant technology that used glycol solutions to prevent frost
from forming on low-temperature evaporators. Both lithium chloride and glycol continue to
be used today in liquid-desiccant dehumidifiers, but their use is limited primarily to industrial
applications[3].

3. Hybrid configuration: desiccant de-humidification and vapour compression based
cooling
An example of desiccant cooling application is represented in fig. 3 [4].
Figure 3.Schematic of Hybrid Liquid Desiccant aided Vapour compression air conditioning
Here, the cool strong desiccant solution is sprayed onto the top of the dehumidifier through
spraying nozzles. By gravitation, it trickles through the structure of the dehumidifier where it
gets contact with the process air stream blown perpendicularly to its trickling flow direction.
Since, the cool and strong desiccant solution vapour pressure is less than that of the air vapour
pressure, water vapour migrates from the air stream to the desiccant solution and condenses
therein. Consequently, the heat of condensation and mixing are liberated causing an increase
in the solution’s temperature. The process air stream is slightly cooled down due to its contact
with the cold desiccant solution. The dehumidified and rather warm process air stream then
passes successively through the evaporative cooler and the evaporator of the traditional
refrigerant vapour compression air conditioner, before being delivered into the conditioned
space. The diluted desiccant solution, exited from dehumidifier, is circulated through the
regenerator where it is heated and the moisture absorbed in the dehumidifier is now lost to the
scavenger air stream. In order for the system to keep functioning continuously and effectively,
an equal amount of water vapour absorbed from the humid air and condensed to the desiccant
solution in dehumidifier must be evaporated from the desiccant solution in the regenerator.
The hot and strong desiccant solution is thereafter cooled down in the pre-cooler and then
cooled further in the heat exchanger (HX) before being ready again to dehumidify the
incoming process air.
The lowest limit temperature attainable by the evaporative cooler is the process air wet bulb
temperature which decreases with the decrease of the relative humidity and increases with the
elevation of the dry bulb temperature. The essential role of the desiccant solution in this

example is to lower the relative humidity of the incoming air stream in order to enable the
evaporative cooler to function more effectively.
Here, the desiccant assisted evaporative cooling is associated with the traditional vapour
compression air conditioning to reduce its size and enhance its coefficient of performance.
Because the latent load is handled independently by the desiccant dehumidifier, the need of
cooling the ventilation air below its dew point is obviated. The temperature of evaporation can
thus be lifted up to 15 °C from its generally practiced level of 5 °C for the traditional vapour
compression system. The increase in evaporation temperature will entail the increase of the
system’s coefficient of performance (COP).
This assemblage can be useful in humid climates where the wet bulb temperature is fairly
high. In such climates, a significantly downsized vapour compression air conditioner can be
supplemented with a desiccant assisted evaporative cooler in order to reach the desired indoor
temperature, thus enabling costs and energy savings and improving the indoor air quality.
4. Liquid desiccant materials
Liquid desiccants such as Glycols and solutions of halide salts are routinely used in industrial
de-humidifiers. Commonly used liquid desiccant materials include lithium chloride, lithium
bromide, calcium chloride, triethylene glycol and mixture of salts etc. The choice of desiccant
will have a profound effect on the design of desiccant de-humidifiers.
The desirable properties of liquid desiccants include large saturation absorption capacity, low
regeneration temperature, Low Viscosity, Good heat transfer, non volatile, non – corrosive,
odourless, non toxic, non flammable, stable and inexpensive. Surface Tension of liquid
desiccants is an important parameter of liquid desiccants as it plays important role in static
hold up and wetting of the surface of heat and mass exchanger of Liquid desiccant system.
Halide salts such as lithium chloride and lithium bromide are very strong desiccants. A
saturated solution of lithium bromide can dry air to 6% relative humidity and lithium chloride
to 15% but halide salts are corrosive in nature. Lithium Chloride has good desiccant
characteristics and does not vapourize at ambient conditions but droplet filters are necessary
to prevent any mixing of the liquid droplets with process air. Cost of halide salts are relatively
high except calcium chloride whose cost is comparatively low compared to LiCl, LiBr and
TEG. Another advantage of Calcium chloride is its low viscosity which reduces the pumping
power. But the CaCl2 salt is highly corrosive in nature and can be used in non metallic
systems only [5].
The least expensive alternative to lithium chloride is calcium chloride. Unfortunately, calcium
chloride is a relatively weak desiccant. A 42% solution, which is about as strong as can be
used without encountering crystallization, will dry air to about 35% rh. (For comparison, a
43% lithium chloride solution can dry air to a 15% rh.).
Glycols are the second class of liquid desiccants now used in industrial equipment. Both
triethylene and propylene glycol have low toxicity, and their compatibility with most metals
has led several researchers to use them in LDACs designed for HVAC applications. However,
all glycols have one undesirable characteristic that they are volatile and any evaporation into
the supply air makes it unacceptable for air conditioning for occupied buildings [6].

Salts of weak organic acids, such as potassium or sodium formate and acetate, have been
explored as less corrosive alternatives to halide salts that are also not volatile. Although it is a
significantly weaker desiccant than lithium bromide or lithium chloride, the ability to dry air
below 30% relative humidity could make potassium formate a good alternative desiccant in
some applications. Another less expensive alternative is potassium acetate. While potassium
acetate could dry air to about 25%, its viscosity becomes very high. At 70% concentration and
27°C, a potassium acetate solution has a viscosity of about 28 cp. This is almost twice has
high as a 43% lithium chloride solution at the same temperature. Water at 27°C has a
viscosity of close to 1.0. [3].
Studies were also conducted on mixtures of calcium chloride and lithium chloride solutions to
take the advantage of good desiccant properties of LiCl and low cost CaCl2 [7].
4.1 Advantages of using liquid desiccants include
1. Lower air pressure drop in process air stream.
2. Liquid desiccants are capable of providing equivalent dehumidification as solid desiccant
systems with lower regeneration temperature(mostly 70 - 80°C) due to the internal cooling
provided by cooling tower water or chilled water and allowing utilization of solar heat or
waste heat.
3. Pumping of liquid desiccants is possible makes it possible to connect several small
desiccant dehumidifiers to a larger regeneration unit which is especially beneficial for
large multi zonal commercial buildings.
4. Liquid desiccants have high COP’s as highly efficient liquid-liquid exchangers could be
employed.
5. Simultaneous air dehumidification and desiccant regeneration is not necessary as it is
possible to store dilute saturate liquid until regeneration heat is available.
6. Liquid desiccants are highly beneficial for their ability to filter microbial contamination,
bacteria, viruses, and moulds from process air stream.
5. Heat and mass exchangers for Liquid desiccant de-humidification
The Heat and mass exchanger of a desiccant dehumidification unit is where the liquid
desiccant comes in direct contact with the process air.
The desirable characteristics for heat and Mass exchanger for high-performance liquid
desiccant dehumidifiers
1. High heat and mass transfer rates
2. Low pressure drop in process air flow
3. Small liquid-side resistance to moisture diffusion
4. Large contact transfer surface area per unit volume
5. Compatible desiccant/contact materials (non corrodible with high wetting coefficient)
6. Zero carryover of liquid desiccant droplets into process air
7. Use of common materials and inexpensive manufacturing techniques
8. Classified various thermally activated Desiccant cooling technologies as shown in fig. 4

Figure 4. Heat and mass exchanger configurations for various desiccant cooling technologies
The packed-bed conditioner has been the focus of many R&D projects on Desiccant Dehumidifiers.
More recent R&D on packed-bed heat and mass exchangers includes the work of
[9] in which the performance of packed-bed heat and mass exchangers flooded with lithium
chloride solutions were experimentally measured. The researchers first implemented their
conditioner and regenerator as internally cooled units using either copper tubes or
polypropylene tubes as the contact surface. However, the copper tubes were too easily
corroded by the desiccant, and the polypropylene tubes were too difficult for wetting.
[10] modelled and experimentally measured the performance of packed-bed, lithium chloride
heat, and mass exchangers that used a random, polypropylene packing with a volumetric
surface area of 210 m 2 per m 3 . They reported that the lithium chloride solution did not
uniformly wet the packing because of its high surface
tension.
High flooding rates are necessary to keep the desiccant
cool and complete wetting. But High flooding rates may
cause carryover of liquid desiccant droplets into air stream
and also is responsible for pressure drop in air flow.
Conditioners that are internally cooled do not have to
operate at the high flooding rates of packed-bed units as
the desiccant temperature is maintained close to coolant
temperature [11]. A cross flow heat exchanger is shown
inthe Fig. 5 which is internally cooled by coolant where
the process air flow and desiccant flow contact at right
angles. A coolant liquid provided from a cooling tower or
chilled water enters through the pipe section throughout the heat exchanger and hence
internally cooling desiccant.
Figure 5.Internally cooled
Cross flow heat exchanger
At low liquid desiccant temperature the vapour pressure also remains low and thus allowing
more moisture absorption into the liquid desiccant.

6. Solar Hybrid Desiccant Cooling System
[12] has investigated the solar hybrid desiccant cooling system (SHDCS) shown in Fig. 7 for
its applicability and performance in commercial premises with high latent cooling load in
subtropical Hong Kong. Vapour compression chiller was used to provide chilled water to a
supply air cooling coil. Desiccant wheel was adopted and its regenerating heat primarily came
from the solar thermal gain of the evacuated tubes. The desiccant wheel dehumidified the
fresh air to the required level and the supply air coil provided the sensible cooling. For
commercial premises with high latent cooling load (60% RH) It is observed that SHDCS had
more superior cooling and energy performances than the conventional centralized airconditioning
(AC) system in the subtropical Hong Kong. The annual primary energy
consumption saving could be around 49.5% in comparison to conventional vapour
compression systems.
Figure 7. Solar Hybrid Desiccant Cooling system with solar heating for desiccant regeneration,
Desiccant Dehumidification and compression based cooling
[13] simulated a hybrid desiccant cooling system comprising the conventional vapour
compression air conditioning system coupled with a liquid desiccant dehumidifier which was
regenerated by solar energy. The study suggested that, when the latent load constitutes 90% of
the total cooling load, the system can generate up to 80% of energy savings. [14] conducted a
comparative study of a standalone VAC, the desiccant-associated VAC, and the desiccant and
evaporative cooling associated VAC as shown in following figure. The authors found an
increase of cold production by 38.8–76% and that of COP by 20–30%. [15] have studied the
performance of three possible hybrid system configurations in supermarket applications and
have compared their performance with traditional VAC system. As reported, a total air
conditioning saving ranging from 56.5% to 66% could be achieved for specified design
conditions (ambient conditions: 30 °C, 16 g/kg.da; indoor conditions: 24 °C, 10.4 g/kg.da;
room sensible heat ratio: 0.35). [16] have modelled the performance of a desiccant integrated
hybrid VAC system. The waste heat rejected from a VAC cycle is utilized to activate a solid

desiccant dehumidification cycle directly. The performance sensitivity of a first generation
prototype hybrid VAC system to variable outdoor conditions has been studied and compared
to the performance of conventional VAC systems. Results showed that the performance
improvement over VAC systems could be 60% at the same level of dehumidification under
ARI summer conditions. [17] have simulated the transient performance of a hybrid desiccant
VAC system for the ambient conditions of Beirut. The annual energy consumption of the
hybrid system in comparison with the conventional VAC system has been studied for the
entire cooling season. A payback period less than five years was achieved.
[18] has reviewed various thermally activated cooling technologies and has tabulated a
summary of the main features of up-to-date thermally activated cooling technologies which is
shown in table 1. It is observed that of all the technologies liquid desiccant cooling
technologies has lowest regeneration temperatures and has better COP value compared to
other technologies.
7. Conclusion
Liquid Desiccant dehumidification systems although limited to industrial applications, but
could exhibit huge potential energy and economic savings for HVAC industry by
Reducing the peak electricity demand created by compressor – based AC’s
Improving the indoor air quality and reduce the indoor humidity levels that could be
difficult to be controlled by conventional air conditioners.
Hybrid liquid desiccant cooling technology has demonstrated its superior performance for hot
and humid climatic conditions and could save more that 50% operational energy saving
compared to conventional vapour compression cooling technology. One of most important
advantages of desiccant cooling systems undoubtedly lies in the possibility of using solar
energy which can be effectively utilized to regenerate saturated liquid desiccants by using
relatively low-cost solar thermal collectors. LDAC’s have low regeneration temperatures (60 -
90°C) and have high COP values (0.5 – 1.2) compared to other thermally activated cooling
technologies.
Future research should include development of non corrosive desiccant materials having
lesser regeneration temperatures, developing control strategies to prevent mixing of liquid
desiccant droplets in the process air stream and design of small and compact systems for
application in residential buildings.

References
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India”,Tata Mc Graw Hill Pvt. Ltd., New Delhi.
2. Kaushik S.C, (1989), “Solar Refrigeration and Space-Conditioning”, Geoenviron
Academia Press, Jodhpur, India
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HVAC& R research, 14(6):819 - 839.
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Review,” Renewable and Sustainable Energy Reviews, Vol. 10, pp. 55-77
5. Lowenstein, A. Slyzak, E. Kozubul, (2006) National Renewable Energy Laboratory, A
Zero carry over liquid desiccant Air conditioner for Solar Applications. ASME
International Solar Energy Conference (ISEC 2006) Denver, Colarodo.
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desiccant cooling system for commercial premises with high latent cooling load in
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supermarket applications. ASHRAE Transactions;91(Part 1B):457–68.
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172 – 203.

Abstract
Design and Thermal Performance Studies
of a Domestic Cooker – cum - Drier
J. S. Puri
Former Technical Officer, CSIR-Central Building Research Institute Roorkee
Corresponding Author, Email: purijs@rediffmail.com
Major part of the energy used for cooking is met from fire wood, agricultural wastes, cow
dung and cooking gas etc. Solar cookers have become much popular to some extent. But the
target of their using, is not much achieved, despite efforts made by various agencies working
in the areas. Similarly in case of drying, hardly anybody take the advantage of drier for
drying the chillys, potato etc. People dry the material in open sky but suffers drawback on it,
such as no control on drying rate, slow drying, no uniform drying, no protection from
rains/dust storms. To make more popular utilization of solar energy particularly for cooking
and drying is much needed. CBRI has designed and developed a solar cooker cum drier for
domestic use for a small family for both cooking and drying. The cooker has been made with
G. I. sheet of 24 SWG having 5cm insulation all around between inner and outer boxes with
double glazing on its inclined front. Necessary opening has been provided to facilitate
cooking & drying operation. The thermal performance study was carried out of both cooker
and drier. In addition to this, study was also carried out for cooking various foods and drying
of various fruits and vegetables both in winter and summer. The cooker cum drier has been
found more effective and efficient. This paper gives more details about its design,
construction and thermal performance.
1. Introduction
More than fifty of energy consumption on domestic sector has been used for cooking
purpose. This energy generally traps from agricultural wastes, cow dung and cooking gas etc.
(1). Larger use of these sources causes ecological and population problems (2). In view of
acute shortage and steel growing higher prices of fuel etc. there is a great need for utilizing
solar energy for cooking and drying. Due to sufficient availability of this energy, it can be
used as alternate source of energy. The different types of cookers and driers have been
designed and developed by different agencies and institutions in India and abroad (3, 4, 5, 6).
Solar radiation has important role in solar devices. In India solar radiation on horizontal
surface is on an average 5.5 K.Watt/m 2 /day (7, 8). To make cooking & drying more popular
and attractive CBRI has designed and developed a cooker cum drier for a small family. The
performance study of cooker was cried out measuring plate temperature, inside air
temperature; water temperature in winter as well as in summer in both the cookers (CBRI
cooker and conventional cooker) made by means of thermal couples. The performance was
also checked by cooking various foods in cooker. The performance study of drying was

carried out by measuring inlet air temperature, plate temperature and outlet air temperature of
CBRI drier and inside temperature, plate temperature and air temperature at the opening of
conventional cooker both in winter and in summer. In additional to this various vegetables
have been dried measuring initial weight, moisture and duration of period for drying.
2. Design and construction details of cooker – cum – drier
A domestic cooker –cum-drier has been designed and developed particularly for a small
family taking into consideration for cooking as well as drying. Earlier many driers have been
designed and developed of larger capacity (9, 10, 11, 12, 13). In this cooker one can cook two
items at a time Dal-rice etc. or can also dry small quantity of vegetable/fruits. This box type
cooker cum drier has been made up with 24 SWG GI sheet. The size of inner box 50X35 cm
with 7X23 cms height on its front and rear side of 60cm. the total area of inside box (base and
walls), is 0.5m 2 . The insulation of 5cms has been provided all around between two boxes. For
drying purpose, seven nos. of holes with G.I. nipples 2.5cms dia. have been provide for inlet
air and a Pipe of dia. 7.5 cms with 19cms. Height has been used as chimney for outlet hot air.
A wire mesh tray of size 45X20cms with 5cm height has been used during drying. There is a
door on its rear side size 45X20cms to facilitate cooking and drying operations. Inner box is
painted with dull black paint and covered with 4mm air tight double glazing with slope 35 o
with horizontal. Castor wheels have been provided at the bottom of the unit for easy motion
for tracking the sun during cooking or drying. The provision has also been made for closing
and opening of inlet and outlet accordingly during cooking or drying.
3. Performance studies of cooker cum drier
The performance study was carried out by measuring the temperature in both CBRI cookers
and conventional cookers, on plates, inside sir, and in water by means of thermocouples
(Cooper-constantan) with the help of digital temperature recorder in both winter and summer.
During experimental study 500ml. Water was placed in each cooker. This is shown in Figure
1. For the comparison of thermal performance, the hourly temperature was measured from
9AM to 3PM. This is shown in table 1.
Table 1. Observed hourly variation of temperature during cooking in summer and
winter (Load 500 ml water in each cooker)
Summer Winter
CBRI Cooker Conventional Cooker CBRI Cooker Conventional Cooker
Time Water Plate Inside air Water Plate Inside air Water Plate Inside air Water Plate Inside air
(hrs) Temp. temp. temp. Temp. temp. temp. Temp. temp. temp. Temp. temp. temp.
( o C) ( o C ) ( o C) ( o C) ( o C ) ( o C) ( o C) ( o C ) ( o C) ( o C) ( o C ) ( o C)
9 21 44 43 20 40 35 11 14 15 9 13 12
10 54 81 67 64 93 82 27 46 41 35 60 52
11 75 96 81 88 110 110 50 70 61 67 86 80
12 83 102 83 88 130 112 65 77 67 81 92 85
13 83 101 83 87 125 103 73 81 71 87 86 90
14 83 100 86 85 118 96 57 51 46 61 52 47
15 83 95 82 85 112 95 51 39 37 55 40 43

We have also studied the performance of cooker by cooking various items such as rice-dal,
rice-channa & rice-rajma etc. Figure 1. shows the cooker with two pots during cooking. The
efficiency (14) of cooker has also been calculated and found approximately of the same order
as in the case of conventional cooker. We have also compared the thermal performance of
CBRI cooker-cum-drier with conventional cooker used as drying purpose. We have
compared with conventional cooker because most of the people take the advantage of this
cooker by drying the material by slightly opening the lid to escape the moist air. The
temperature at inlet, plate and outlet were measured in CBRI drier whereas inside air
temperature, plate temperature and air temperature at opening were measured in conventional
unit from 9AM to 3PM both in winter and summer. The temperature comparison has been
shown in table 2.
Table 2. Observed hourly variation of temperature during drying process in summer
and winter (No Load)
Summer Winter
CBRI drier Conventional Unit CBRI drier Conventional Unit
Time Water Plate Inside air Water Plate Inside air Water Plate Inside air Water Plate Inside air
(hrs) Temp. temp. temp. Temp. temp. temp. Temp. temp. temp. Temp. temp. temp.
( o C) ( o C ) ( o C) ( o C) ( o C ) ( o C) ( o C) ( o C ) ( o C) ( o C) ( o C ) ( o C)
9 31 61 53 45 67 71 12 15 15 12 11 11
10 32 78 57 50 93 84 20 33 30 37 53 49
11 32 85 57 52 106 90 19 46 39 48 77 72
12 34 84 55 55 137 112 20 50 43 57 87 83
13 32 82 53 54 131 102 25 50 43 58 88 81
14 31 80 52 60 122 95 15 25 24 29 35 35
15 31 72 50 60 92 85 15 21 20 22 27 28
The performance of drier has also been checked by drying potato chips in summer and
tomato in winter. The hourly temperatures have been measured during two days for potato
chips and 5 days for tomato, shown in table 3 & 4 respectively.
Time
(hrs)
Table 3. Observed Hourly Variation of temperature during drying in summer (With
Load 400 gm potato chips)
1 st Day 2 nd Day
Inlet air Plate Outlet air Inlet air Plate Outlet air
temp. ( o C) temp. ( o C) temp. ( o C) temp. ( o C) temp. ( o C) temp. ( o C)
9 29 29 35 25 29 32
10 26 31 40 25 33 39
11 29 37 43 23 47 45
12 30 38 41 28 55 48
13 26 33 49 32 58 50
14 23 33 38 25 54 48
15 22 29 36 23 47 44

Time (hrs)
9
10
11
12
13
14
15
Table 4. Table 4. Observed Hourly Variation of temperature during drying in winter
(With Load 400gm tomato)
Inlet air Temp ( o C)
11
13
13
21
19
14
13
1 st Day 2 nd Day 3 nd Day 4 th Day 5 th Day
Plate Temp( o C)
9
16
25
34
34
20
17
Outlet air Temp ( o C)
12
24
27
34
33
20
17
Inlet air temp ( o C)
10
12
16
12
14
13
12
Plate temp( o C)
9
19
16
30
33
19
16
Outlet air temp ( o C)
10
23
30
32
35
19
16
Inlet air Temp ( o C)
10
12
12
16
18
12
12
Plate temp( o C)
8
15
26
31
30
18
16
Outlet air Temp ( o C)
12
22
27
32
32
18
15
Inlet air Temp. ( o C)
11
17
20
27
28
19
16
Plate temp ( o C)
8
21
23
29
30
18
15
Outlet air Temp
( o C)
Inlet air Temp ( o C)
During drying a wire mesh tray has been used, shown in Figure 1. Further, some more
vegetables and fruits have also been dried in winter and summer measuring moisture content,
weight of material, and duration of period (hours/days). This is shown in table 5. The
efficiency of drier has also been calculated.
12
12
12
12
14
12
11
Table 5. Drying Details of Vegetables and Fruits
Vegetables and Weight of material Moisture content Duration of time of drying
Fruits (gms). %(Initial) (Days) (hrs)*
Initial Final
Onion 300 60 80 3 15*
Potato 400 70 82.5 2 10
Cauliflower 400 35 91.5 5 20
Tomato 400 30 92.5 5 20
Chilies 500 100 80 5 20
Banana 130 20 84.6 3 12
Guava 215 50 76.7 3 12
Grapes 165 60 63.6 7 8
* Solar radiation is available on cooker/drier surface, about 4 to 5 hrs daily. The rest of
time it is shaded by side standing ling trees.
10
12
12
12
14
12
11
Plate temp ( o C)
8
21
27
30
32
19
16
Outlet air Temp ( o C)
9
26
26
31
33
19
15

4. Results & discussion
Figure 1: Solar Cooker-cum-Drier and Conventional Cooker
During the study in comparison of temperature of two cookers, it is observed that I summer,
the max. Plate temperature 102 o C in CBRI cooker and 130 o C in conventional cooker was
obtained. Similarly the max. Water temperature 83 o C and 88 o C and inside air temperature
86 o C and 112 o C were obtained in CBRI cooker and conventional cooker respectively. During
winter observations, the max. plate temperature 81 o C and 92 o C, water temperature 73 o C &
87 o C and inside air temperature 71 o C and 90 o C in both CBRI cooker and conventional cooker
respectively were obtained.
Higher temperature in all cases was observed in conventional cooker than the CBRI cooker
because of additional provision of reflector in conventional cooker. The various foods have
also been cooked such as rice dal, rice channa, rice rajma etc. It has been observed that rice
could be prepared between 1 and ½ to 2 hours and hard dals etc. could be prepared between
2-3 hours. The study has also been carried out for drying during summer.
In CBRI drier it was observed that the maximum air temperature at inlet 34 o C and max. air
temperature at outlet 57 o C through chimney and max. plate temperature 85 o C were obtained
in typical summer and in case of conventional unit maximum air temperature at opening
60 o C, plate temperature 137 o C and inside air temperature 112 o C were obtained. During
winter also we have obtained maximum inlet air temperature 25 o C, plate temperature 50 o C
and outlet air temperature 43 o C in CBRI drier and in case of conventional unit maximum
temperature at opening 58 o C, plate temperature 88 o C and inside air temperature 83 o C were
obtained. In addition to this, the performance has also been checked by drying potato in
summer and tomato in winter measuring inlet temperature and outlet temperature for
consecutive two days and five days respectively.
Apart from this more vegetables fruits have been dried measuring hourly temperature initial
moisture, initial and final weight and duration of period for drying the materials. The cost of
cooker cum drier has been calculated and it comes out to Rs. 800/- whereas the cost of
conventional cooker is Rs. 1700/-.

5. Conclusion
The cooker designed by CBRI is more efficient and effective. In this cooker both the facilities
of cooking & drying have been provide. It is very useful for a small family for cooking ricedal
or drying small quantities of vegetables or fruits. The efficiency of cooker is calculated
and found almost the same as in case of conventional cooker even after elimination of
reflector. To make more efficient, certain modifications in design and more investigations are
required.
6. Acknowledgement
This paper is a part of research activities of Central Building Research Institute, Roorkee and
is published with the permission of Director. Author is thankful to Ishwar Chand and Dr.
Manik Chandra for their faithful suggestions and Shri Har Sagar for the help during
experimental measurements.
References
1. Ganguly R. et al. (1987) “Solar option for Rural India” Proceeding of seminar on Rural
Build and Environment, CBRI Roorkee.
2. Murugesan, R./, et al., (1987), “Testing and performance analysis of an indirect type solar
cookers”. National solar energy convention, New Delhi.
3. Gupta, C.L., (1977), “The Indian Sun Scene” Sun World, Vol. 3.
4. Hoda, M.M. (1977), “Solar cookers” Proceeding First International Conference Building
Tech. London Vol.2, pages 817-823.
5. Malhotra, K.S., et al., (1983) “Development of Solar cookers in India”. Sun world Vol.
6(6).
6. Garg, H.P. and Thanu K.P. (1976) “Simple hot box type solar cooker” Research &
Industry, 21 (3), 184-186.
7. Mani. A. (ed) (1980), “Handbook of Solar Radiation data from India” Allied Publisher
Pvt. Ltd., New Delhi.
8. Garg. H. P. et al. (1969), “Design data for Direct Solar Utilization devices Part II-Solar
Radiation” Indian Journal of Meteorology and Geophysics Vol. 20(3) pages 221-226.
9. Pande, P.C. (1980) “Performance Studies on improved solar cabinet drier” National Solar
Energy Convention pages 1-5 at Annamalai University, Annamalai Nagar.
10. Garg. H. P. (1988), “Solar Drying” Summer School Energy Application at IIT New
Delhi, pages-1-19.
11. Low ward. T.A. (1966), “A Solar Cabinet Dries” Journal Solar Energy Vol. 10 (4), pages
158-164.
12. Soda, M.S. et al (1982), “AN Experimental Solar Drier” National Solar Energy
Convention at IIT New Delhi, pages 4.018-4.021.
13. Sharma V. K., Colangelo, A & Spagna, GA (1995), “Experimental Investigation of
Different Solar Dryers suitable for fruit and vegetables drying”, Renewable energy 6(4)
pages 413-424.
14. Jerman, B., (1981), “Light Weight Portable Solar Cooker” Proceedings of International
Solar Energy Congress Brightan England.

Partial Replacement of Conventional Heat Energy by Solar
Energy in the Production of Gypsum Plaster
Abstract.
Narendra Kumar*, S. K. Saini**, Sameer*
*CSIR-Central Building Research Institute, Roorkee
** Former Scientist, CSIR-Central Building Research Institute, Roorkee
Corresponding Author, Email: nkumar247@rediffmail.com
Gypsum is one of the important industrial minerals. It is hydrous calcium sulphate
(CaSO4.2H2O) having a composition of 79% calcium sulphate and 21% water. Gypsum in its
natural form finds applications in the manufacture of hydraulic cements, ammonium sulphate
fertilizer, sulphuric acid and soil reclamation for agriculture purposes. When calcined into the
form of plaster of Paris and enriched with additives like accelerators, retarders, fillers and
binders, the use of gypsum are varied and extensive. The calcined gypsum or plaster of Paris
is used in building, pottery, ceramic and surgical according to its grade plaster.
A batch type energy efficient gypsum calcinator has developed few years back in Central
Building Research Institute with the primary aim of replacing the traditional open pan method
with an energy efficient system using fossil fuel. The primary source of energy is the fossils
fuels and mostly being used for the energy consumption today. The reserves of fossils fuels
are limited and they will not sustain for a long time. The widespread use of fossil fuels
increasing the environmental degradation day by day particularly global warming, urban air
pollution etc. Hence the need was felt to explore the use of renewable energy sources to meet
the growing demand of energy. For calcining the gypsum, the temperature required is around
160 o C inside the shell and this can be achieved by Solar energy. Solar energy is the most
appropriate renewable energy that is collected from the radiations of Sun with the help of
Solar thermal system. India is a sunny country with most parts receiving about 4 to 7 kilowatt
hours of solar radiation per square meter per day with 250 - 300 sunny days in a year. This
makes solar energy a very attractive option for generating both power and heat.
An experimental set-up of capacity 40 kg per batch for the calcination of gypsum has been
designed and installed. The trials of the experimental set-up have been carried out using
thermic oil heated by an alternate heating method.
Keywords: Gypsum, Calcination, decompose, solar radiation, thermic oil
1. Introduction
Gypsum is the sulphate of calcium (CaSO4. 2H2O). The available gypsum can be grouped into
three main classes based on their mode of origin - quarry gypsum, marine gypsum and by
product phospho gypsum. India is rich in the deposits of quarry gypsum and the mines are

located mainly in Rajasthan, Gujarat, Jammu & Kashmir, Andhra Pradesh and Uttar Pradesh.
About 90% of annual production of quarry gypsum is from Rajasthan alone. Marine gypsum
is produced during separation of ordinary salt from seawater when the latter is evaporated in
shallow pits. Huge quantity of phospho gypsum is produced from phosphoric acid plants as
by-product of the wet process of phosphoric acid manufacture by acidulation of rock
phosphate with sulphuric acid. The phospho gypsum, however, contains impurities like
phosphates, fluorides and organic matter but after processing, the phospho gypsum is calcined
into plaster of Paris and used for building and other purposes in the same way as the plaster
produced from quarry gypsum or marine gypsum.
Gypsum in its natural form used in the manufacture of hydraulic cements, ammonium
sulphate fertilizer, sulphuric acid and in soil reclamation. After calcination it converts into
plaster of Paris and enriched with additives like accelerators, retarders, fillers and binders, the
uses of gypsum are varied and extensive. The calcined gypsum used in building, moulding
and casting plasters of many kinds; dental and surgical plasters; plaster for bedding plate glass
while grinding and polishing; pottery mould plaster; dehydration of oil; filtering; and
manufacture of many special products.
2. Manufacture of gypsum plaster
Gypsum as such does not posses proper setting and binding properties. Industrial importance
of gypsum is attributed to its dehydrating ability on heating. Manufacture of gypsum plaster
of different grades like surgical, building and pottery grades requires the gypsum to be
calcined to hemi-hydrate commonly called plaster of Paris. On heating at 120-160 o C, gypsum
releases one and a half molecule of water of crystallization forming hemihydrate.
The calcination or conversion of gypsum (CaSO4.2H2O) to the hemihydrate (CaSO4. 1/2H2O)
involves a reduction in water content from 20.9% to about 6.2%. This 14.7% water is lost in
the form of steam, the escape of which from the powder gypsum gives an appearance similar
to that of a boiling liquid. For producing gypsum hemihydrate (or plaster of Paris), gypsum is
ground and heated to 120-160 o C. Because of the
boiling liquid appearance at this temperature, the
trade name of hemihydrate gypsum is first boil.
The hemihydrate or the result of the first boil,
known as ‘first settle plaster', sets rapidly when
mixed with a suitable amount of water. When,
however, gypsum is burnt at temperatures much
in excess for 200 o C, the product is said to be
'overburnt' and the rate of setting is considerably
delayed depending on the temperature employed.
The need for careful control in the calcination of
gypsum is therefore manifest; indeed, an unduly
hurried calcination with bad distribution of heat
may easily result in an unwelcome mixture of
several calcined products plus some unaltered
gypsum. Not only does the temperature require
careful control, but also relative uniformity of
temperature has to be achieved by constant Figure 1. Energy Efficient Gypsum
mechanical churning of the gypsum charge

during calcination. The different methods commonly employed for calcination of gypsum
include: kiln or oven, open pan, gypsum bhatti, rotary kiln and kettle etc.
Amongst the above methods, open pan system was mostly used in India earlier and now
gypsum bhatti for reasons of simplicity in design, operation and low initial cost of installation.
However, these systems have several drawbacks; heat is wasted, dust losses and the plaster
produced is not of uniform quality being sometimes under burnt or over burnt in different
portions of the charge. As a result of growing awareness towards energy conservation in
production units and to meet the requirements of the industry, a new system named as Energy
Efficient Gypsum Calcinator was developed by CBRI which can be run using fire wood, coal,
liquid fuel.
After successful in-house trials on the prototype plant at the Institute, the technology of the
calcinator was licensed to several manufacturers. Commercial units of this calcinator are
successfully producing plaster of Paris for industrial use. The innovative calcinator (Fig. 1) is
basically a deep pan type calcinator with improved design of furnace for higher fuel
efficiency and with the facility of power operated stirring system. It is free from all the
drawbacks of open pan system and can be installed at low initial cost.
3. Thermal energy required for calcining gypsum
During storing, the powdered gypsum picks up some moisture because of its hygroscopic
nature. The free moisture thus picked up may vary 3% to 7% but it may go up to 10% in
certain cases. In addition to the free moisture, the gypsum (CaSO4.2H2O) contains two
molecules of water in the combined form. For converting gypsum into plaster, gypsum losses
1.5 molecules of water besides the free moisture present in the gypsum. The heat consumed
during calcination comprises of followings:
Heat required to evaporate the free moisture content from the gypsum charge.
Heat required for bringing gypsum charge to its decompose temperature.
Heat required to decompose gypsum for conversion into gypsum plaster.
Heat required for bringing temperature of gypsum to its calcination 130 to 160 0 C and
maintain it to evaporate water molecules released in decomposition gypsum for
conversion gypsum into gypsum plaster.
4. Solar heating system for calcination
For producing gypsum plaster (or plaster of Paris),
gypsum is ground and heated to 120-160 o C for a
certain period and at this temperature it releases
one & half molecules of water of crystallization
forming hemihydrate. Such solar heating system is
required which can raise the temperature of
gypsum powder to 120-160 o C by circulating the
hot thermic oil (heated by Solar System) around the
calcination pan. The different solar heating systems
are available by which the temperature can be
achieved for different applications.
Figure 2. Parabolic Trough Concentrator

The heart of a solar thermal system is a `solar collector'. As the name implies, it's main
function is to collect solar thermal energy and transfer it to the oil to be heated. There are four
different types of solar collectors i.e. flat plate collector (FPC), evacuated tube collector
(ETC), CPC collector (stationary concentrator) and parabolic trough concentrator
The FPC, ETC & CPC collectors are suitable for applications that require a maximum
temperature of about 80 - 85 O C which is not sufficient for the calcinations process. Parabolic
Trough Concentrators are the most suitable for the application in gypsum calcination system
as it may raise the temperature of thermic oil up to 350°C. A parabolic trough consists of a
linear parabolic reflector that concentrates solar radiations on to a receiver positioned along
the reflector's focal line. The receiver is a tube positioned directly at the focus of the parabolic
mirror and filled with a working oil. The reflector follows the sun during the daylight hours
by tracking along a single axis. The oil is heated to 150–350 °C as it flows through the
receiver and is then used as a heat source for the required system (Fig. 2).
5. Experimental set-up of gypsum calcinator
An experimental set-up is designed and installed for the calcination of gypsum utilizing solar
energy as partial replacement of
heat energy required for
calcination process. In the design
system the heat energy is
transferred to the gypsum powder
by the hot thermic oil which is
heated by solar energy system i.e.
parabolic trough concentrators is
the most suitable for the
calcinations system which may
raise the temperature of thermic
oil up to 350 O C. The experimental
set-up of calcinator having
capacity 40 kg per batch consists
of the calcinations pan, powered
churning system, supporting
structure and a hot thermic oil tank
with hot oil circulation system
(Fig. 3).
5.1 Calcination pan
Fig. 3 Schematic Diagram of Experimental Set-up
of gypsum Calcinator
The cylindrical insulated calcination pan has the capacity of 40 kg per batch. The shape of the
bottom of the pan is convex type and a cylindrical jacket is provided around the cylindrical
shell as well as at the bottom of the pan for the circulation of hot thermic oil during
calcination process. Provision has been made on the lower side & upper side of the pan for the
inlet & outlet of the thermic oil respectively. The thermocouples have been provided on the
inlet, outlet of the pan to monitor the temperature of the thermic oil and inside the pan at level

to monitor the temperature of gypsum powder during calcination. An insulated top cover is
also provided on to pan to minimize the thermal & dust losses.
5.2 Churning mechanism
The churning mechanism comprises of electric geared motor, stirrer shaft and churning
blades. Two pairs of churning bladed have been provided on to the stirrer shaft and the lowest
pair of churning blades is fixed with the bottom end of the stirrer shaft. A flange is fitted at
one end of the stirrer for the mounting of stirrer with the geared motor. The churning system
helps in proper agitation and intermixing of the gypsum charge in the pan during calcination.
5.3 Temperature sensing and monitoring
To calculate the heat transfer for the replacement of heat energy, the temperature of the
thermic oil at inlet and outlet of the calcination pan was observed as well as the temperature
of the charge during calcination was also observed with the help of thermocouples provided at
different points and digital temperature indicator.
5.4 Operation of the gypsum calcinator
Due to non-availablity of parabolic trough concentrator, the thermic oil was heated by the
alternate energy source i.e. electrical power. The heating element of 6 KW is fitted in the
heating tank to heat the thermic oil. The heating of the thermic oil was started & the
circulation of hot thermic oil was also started for initial heating of empty calcination pan.
When the inside temperature of the pan is started increasing, the gypsum powder (passing
through IS-60 Mesh Sieve) is loaded in the calcination pan in stages and the total charge of 50
Kg loaded within 30 minutes. The temperature of the thermic oil at inlet & outlet was
recorded as well as temperature of the charge inside the pan was recorded at different interval
during calcination process with the help of thermocouples provided and digital temperature
indicator.
6. Observations
The maximum temperature of the thermic oil was increased up to 219 o C and with the
continued circulation, the temperature of the gypsum charge achieved up to max 124 o C in the
pan during calcination. The heat required for producing 1 kg of gypsum plaster from gypsum
having 10 % free moisture is 189.22 kCal. The total heat calculated on the basis of the
temperature gain of the charge and it is 105.89 kCal / Kg of gypsum. Thus, the replacement of
heat energy is about 56%. The saving in heat energy may be increased if the temperature of
the thermic oil increased and with the result the increase in the temperature on the gypsum
charge to be calcined.
7. Acknowledgement
The paper is published with the permission of Director, Central Building Research Institute,
Roorkee and forms the part of the R&D program of the institute.

8. References
1. Chopra, S.K. Taneja, C.A. and Kaushish, J.P. etc., ‘A Kettle for Improved
Calcination of Gypsum’ , Research and Industry, Vol. 16, No.2, pages. 123-124, 1971.
2. Report on, ‘ Energy Efficient Gypsum Calcinator’ , sent to NRDC, New Delhi in June
1988 for NRDC Award Competition.
3. Riddell, wallace, C, "Kettle Process of Calcination", Rock Products, Vol.48, NO.8, Aug.
1945, pages 88,89, and 152.
4. Lewis R., "Improved Calcining Process for Gypsum", Zement-Kalk-Gips (ZKG), Vol.38,
NO.5, May 1985, pages.250-255.
5. Indian Mineral Year Book, Ministry of Steel and Mines, Vol. 2, 1986, pages 488-501.
6. Kaushish J.P., Bhagwan Dass, Saini S.K., etcc., ‘ An Energy Efficient Gypsum
Calcinator’. Invention Intelligence, Vol. 24 No.7 July 89, pages 321-327.

Abstract.
Solar Photo-Voltaic Systems – A Review
Paresh Goel
Indian Institute of Technology Guwahati (India)
Corresponding Author, Email: p.goel@iitg.ernet.in
India needs 600-1200 GW electric power generation capacity before 2050 (that’s 20-
40GW/year) [1].India’s per capita consumption of energy is far lower than that of the world
average. Even with such low per capita consumption, the power deficit is about 11% in total
demand and a deficit of more than13% in peak load demand. This clearly signifies that the
available fuel is not sufficient to meet the rising demand for energy of India. The 56.65%
proportion of installed electric energy (205GW in June 2012) comes from coal, which is a
polluting and a non – renewable source [2]. India’s coal reserves are fast depleting and will
last only up until 2040 or so. About 10% of the total power is sourced from oil & gas. A
significant portion of oil used to generate energy in India is imported. It is imperative that the
country reduces dependence on foreign oil. The other sources are hydro and nuclear power.
Hydro electric power generation also comes with certain disadvantages such as human
displacement, soil erosion, diminished forest cover and wildlife habitats.
Similarly, nuclear power is costlier and takes longer time to start and faces nuclear waste
management problems. Also, India's nuclear power generation potential has been stymied by
political activism since the Fukushima disaster in Japan as can be seen by the opposition to
the Kudankulam Atomic Power Project. In view of electricity market liberalization and
international pressure to reduce CO2 emissions as well as problems associated with the above
sources of power generation, a renewable energy source is best and most practical alternative
address the persistent demand supply gap in the power industry.
India is blessed with abundance of non-depleting and environmentally friendly renewable
resources, such as solar, wind, biomass, hydro and geothermal. At present, renewable energy
accounts for about 12% of India’s installed generation capacity [2]. Much of this capacity is
wind-based (about 60%), with the share of solar power being very small. India has an
abundance of solar radiation, with the peninsula receiving more than 300 sunny days in a year
[3]. So Sunlight is the most reliable and viable source of renewable energy in the long run.
Solar cells are such devices which converts sunlight directly to clean, pollution free and high
grade electrical energy. The associated technology is termed as “Solar Photovoltaic (SPV)”,
or just “Photovotaics (PV)”. It is a method of generating electrical power by converting solar
radiation into direct current electricity using semiconductors that exhibit the photovoltaic
effect [4]. The present paper discusses the state of art status of Solar Photovoltaic and
reviews the various SPV technologies, its relevance and application particularly in context of
India.
1

1. Introduction
India is positioned on the threshold of a new era of possibilities and opportunities. The
exponentially growing demand for resources in both rural and urban India is creating new
possibilities every day. It is a well-known fact that the rapidly growing population and
businesses are placing considerable pressure on India’s power resources. India’s per capita
consumption of energy is far lower than that of the world average. Even with such a low per
capita consumption, the power deficit is about 11% in total demand and a deficit of more than
12% in peak load demand [3]. About 17% of the villages in India are non-electrified, which
would translate to about 450 million [3]. With a growing economy, the demand for power is
growing at about 6% every year and the peak load demand is expected to cross 778 GW by
2031-32.The Indian power sector is highly dependent on coal as fuel. With 56.65% of the
total installed capacity being coal based generation [2].According to the Ministry of Coal, the
existing coal reserves are estimated to last for another 40-45 years. To meet the 778 GW
demand for power by 2031-32, the Government of India is planning heavy investments in
coal based and nuclear power generation [3]. But electricity market liberalization and
international pressure to reduce CO2 emissions have led to new architectures of the future
electricity networks with a large penetration of distributed energy resources, in particular
from renewable sources. Renewable energy source is also a practical solution to address the
persistent demand supply gap in the power industry. At present, renewable energy accounts
for about 12% of India’s installed generation capacity [2]. Much of this capacity is windbased
(about 60%). India has an abundance of solar radiation, with the peninsula receiving
more than 300 sunny days in a year [3]. So solar energy can be best alternative in the
renewable energy sources. The sun is perpetual source of solar energy available to mankind
in abundance. In different part of the earth, the solar energy received varies spatially as well
varies with time of day [5]. The 89 PW of sunlight reaching the Earth's surface is plentiful –
almost 6,000 times more than the 15 TW equivalent of average power consumed by
humans.[6]Several methods are available to harness or convert the solar energy into thermal,
chemical, electro chemical, biochemical. Photosynthesis, photo catalytic and electrical
process / energy. The efficiency of conversion varies from a maximum of 4% for
photosynthesis to over 30% for conversion to thermal energy. Solar cells are such devices
which converts solar energy directly to clean, green and high grade electrical energy. The
associated technology is termed as “Solar Photovoltaic (SPV), or just Photovotaics (PV). It is
a method of generating electrical power by converting solar radiation into direct current
electricity using semiconductors that exhibit the photovoltaic effect[4].In photovoltaic effect,
photons of light excites electrons into a higher state of energy, allowing them to act as charge
carriers for an electric current. The photovoltaic effect was first observed by Alexandre-
Edmond Becquerel in 1839 [7]. Photovoltaic power generation employs solar panels
composed of a number of solar cells containing a photovoltaic material. Materials presently
used for photovoltaic include monocrystalline silicon, polycrystalline silicon, amorphous
silicon, cadmium telluride, and copper indium gallium selenite/sulfide[5]. Due to the growing
demand for renewable energy sources, the manufacturing of solar cells and photovoltaic
modules and arrays has advanced considerably in recent years[8, 9, and 10].Originally this
technology was a costly source of power for satellites but it has steadily come down in price
making it affordable to power homes and businesses/ industries.
2. Solar photovoltaic
Solar Photovoltaic power generation employs solar cells, solar module, solar panels and
arrays [11] as shown in Figure 1.
2

2.1 Solar cells
Figure 1. Solar Photovoltaic
The solar cell is the elementary building block of the photovoltaic technology. A single PV
cell is a thin semiconductor wafer made of two layers generally made of highly purified
silicon (PV cells can be made of many different semiconductors but crystalline silicon is the
most widely used). The layers are doped with boron on one side and phosphorous on the
other side, producing surplus of electrons on one side (Phosphorous doped) and a deficit of
electrons on the other side (Boron doped). So phosphorus doped side acts as n-type and
boron doped side becomes p-type and both are in intimate contact with each other. A p-n
junction is established and a diffusion of electrons occurs from the region of high electron
concentration (the n-type side) into the region of low electron concentration (p-type side).
When the electrons diffuse across the p-n junction, they recombine with holes on the p-type
side. However, the diffusion of carriers does not occur indefinitely, because the imbalance of
charge immediately on either sides of the junction originates an electric field. This electric
field forms a diode that promotes current to flow in only one direction. Ohmic metalsemiconductor
contacts are made to both the n-type and p-type sides of the solar cell, and the
electrodes are ready to be connected to an external load. When photons of light fall on the
cell, they transfer their energy to the charge carriers. The electric field across the junction
separates photo-generated positive charge carriers (holes) from their negative counterpart
(electrons). In this way an electrical current is extracted once the circuit is closed on an
external load. [12]. The PV cell has no storage capacity, it simply acts as an electron pump.
The amount of current is determined by the number of electrons that the solar photons knock
off. Bigger cells, more efficient cells, or cells exposed to more intense sunlight will deliver
more electrons. There are several types of semiconductor material used for manufacture of
solar cells. However, more than 90 % of the solar cells. Currently made worldwide consist of
wafer-based silicon cells. They are either cut from a single crystal rod or from a block
composed of many crystals and are correspondingly called mono-crystalline or multicrystalline
silicon solar cells. Wafer-based silicon solar cells are approximately 200 μm thick.
Another important family of solar cells is based on thin-films, which are approximately 1-2
μm thick and therefore require significantly less active, semiconducting material. Thin-film
solar cells can be manufactured at lower cost in large production quantities; hence their
market share will likely increase in the future. However, they indicate lower efficiencies than
3

wafer-based silicon solar cells, which mean that more exposure surface and material for the
installation is required for a similar performance.
3. Solar modules
In order to avoid any type of damage during manufacturing, transportations, and protect from
heat, cold, moisture, rains, hails and wind impact while in practical use at site, the solar cells
are packaged tightly behind a glass sheet and interconnected to give higher current and
voltage than a single cell delivers. These are interconnected in parallel to increase current and
in series to produce a higher voltage. This assembly of packaged cells is called Solar
Photovoltaic module. 36 cell modules are the industry standard for large power production.
For constructing modules, the cell is created on a glass substrate (lower layer) or superstrate
(top layer) , and the electrical connections are created in situ, a so called "monolithic
integration". The substrate or superstrate is laminated which is encapsulated with tempered
glass (or some other transparent material) on the front surface, and with a protective and
waterproof material on the back surface (usually another sheet of glass). The edges are
sealed for weatherproofing... The structural (load carrying) member of a module can either be
the top layer (superstrate) or the back layer (substrate) and is often an aluminum frame
holding everything together in a mountable unit. In the back of the module there is a junction
box, or wire leads, providing electrical connections [11]. Today’s photovoltaic modules are
extremely safe and reliable products, with minimal failure rates and projected service
lifetimes of 20 to 30 years Most major manufacturers offer warranties of twenty or more
years for maintaining a high percentage of initial rated power output. Many crystalline silicon
module manufacturers offer a warranty that guarantee electrical production for 10 years at
90% of rated power output and 25 years at 80% [13].
There are currently following commercial production technologies for PV Modules:
I. Crystalline silicon modules
Most solar modules are currently produced from silicon PV cells. These are typically
categorized into either monocrystalline or multicrystalline modules
(a) Single Crystalline
This is the oldest and more expensive production technique, but it's also the most efficient
sunlight conversion technology available. Module efficiency averages about 10% to 12%
[11]
(b) Polycrystalline or Multicrystalline
This has a slightly lower conversion efficiency compared to single crystalline but
manufacturing costs are also lower. Module efficiency averages about 10% to 11% [11]
II. String Ribbon
This is a refinement of polycrystalline production; there is less work in production so
costs are even lower. Module efficiency averages 7% to 8% [5]
4

III. Thin Film
In Thin Film solar cell / module technology, very thin layers of a chosen semiconductor
material (ranging from nanometer to several micrometers in thickness) are deposited on to a
substrate of superstrate made of either coated glass or stainless steel or a polymer. The thin
film modules are called rigid or flexible depending upon rigidity or flexibility of used
substrate or superstrate. Amorphous silicon Thin Film solar cell is the earliest device
developed in this area. Other types of Rigid Thin Film cells that followed are Cadmium
Telluride (CdTe) and Copper Indium Gallium Diselenide (CIGS) solar cells. .The
commercially available (in MW quantities) flexible module uses amorphous silicon triple
junction cells. Although these module have lower conversion efficiency of 5% to 7% yet the
cost per watt is lower than any other. . The production rate of these modules is higher using
less comparatively lower energy consumption processes. Thin Film modules generate power
even under diffused light and hence can generate more electricity per unit of installed power
than crystalline silicon modules of similar power rating [14]. After nearly two decades of
technology development efforts, the share of the Thin Film solar cell technology is still low.
With the obvious advantages of low material cost per Watt, technology development efforts
are focused on improvements in efficiency, deposition rates, yield levels and scalability of the
processes involved So photovoltaic panels based on crystalline silicon modules are
encountering competition in the market by panels that employ thin-film solar cells (CdTe,
CIGS, amorphous Si, microcrystalline Si) [14], which had been rapidly evolving and are
expected to account for 31% of the global installed power by 2013[15].However, precipitous
drops in prices for polysilicon and their panels in late 2011 have caused some thin-film
makers to exit the market and others to experience severely squeezed profits [16].
4. Photovoltaic panels
A PV panel consist of one or more PV modules assembled as a pre-wired, field-installable
unit to generate and supply electricity in commercial and residential applications as a part of
larger photovoltaic system. Modules of different manufacture can be intermixed without any
problem, as long as all the modules have rated voltage output within 1.0 volt difference. Most
solar panels are rigid, but semi-flexible ones are available, based on thin-film cells.
5. Photovoltaic arrays
A PV Array consists of a number of individual PV modules or panels that have been wired
together in a series and/or parallel to deliver the voltage and amperage a particular system
requires. An array can be as small as a single pair of modules, or large enough to cover acres.
A photovoltaic installation typically includes an array of solar panels, an inverter, batteries
and interconnection wiring.
5.1 Rated out put
The performance of PV modules and arrays are specified in terms of rated output. Rated out
output refers to their maximum DC power output (watts peak) under Standard Test
Conditions (STC) also called Photovoltaic power capacity. Standard Test Conditions are
defined by a module (cell) operating temperature of 25 o C (77 F), and incident solar irradiant
level of 1000 W/m 2 and under Air Mass 1.5 spectral distribution [11]. The actual power
5

output at a particular point in time may be less than or greater than this standardized, or
"rated," value, depending on geographical location, time of day, weather conditions, and
other factors in the field, actual performance is usually 85 to 90 percent of the STC rating.
Other parameter to specify the electrical characteristics [10] which include nominal power
(PMAX, measured in W), open circuit voltage (VOC), short circuit current (ISC, measured in
amperes), maximum power voltage (VMPP), maximum power current (IMPP), peak power,
kWp, and module efficiency (%). Nominal voltage refers to the voltage of the battery that the
module is best suited to charge; this is a leftover term from the days when solar panels were
used only to charge batteries. The actual voltage output of the panel changes as lighting,
temperature and load conditions change, so there is never one specific voltage at which the
panel operates. Nominal voltage allows users, at a glance, to make sure the panel is
compatible with a given system [11]. Open circuit voltage or VOC is the maximum voltage
that the panel can produce when not connected to an electrical circuit or system. VOC can be
measured with a meter directly on an illuminated panel's terminals or on its disconnected
cable [17]
The peak power rating, kWp, is the maximum output according to STC (not the maximum
possible output) [18]
5.2 Out put of PV array
The DC output of panel or array of panels is a product of the rated output times the number of
panels times the insolation times the number of days The capacity factor, or duty cycle, of
photovoltaic is relatively low, typically from 0.10 to 0.30 as the output of a photovoltaic
depends upon the area, the efficiency, and the insolation. The insolation changes with latitude
and prevailing weather, and is location specific from about 2.5 to 7.5 sun hours/day. [19]
5.3 Efficiency of PV modules
Solar cell efficiencies vary from 6% for amorphous silicon-based solar cells to 43.5% with
multiple-junction concentrated photovoltaic. But the efficiency of available solar panel varies
from 5-18% in commercial production, typically lower than the efficiencies of their cells in
isolation.
6. Current development / methods to improve efficiency of PVS
Several new technologies are being pursued mainly from the point of view of achieving high
conversion efficiency and cost reduction possibilities through cheaper and abundantly
available materials.
1. Panels are often static and set to latitude tilt, an angle equal to the installation’s latitude,
but performance can be improved by adjusting the angle for summer or winter depending
upon the sun path in the sky [11].
2. Panels with conversion rates around 18% are in development incorporating innovations
such as power generation on the front and back sides [11].
3. Casting of cell instead of sawing of wafers will reduce manufacturing cost [11].
4. To increase the efficiency of panels, sun light is focused by concentrator using lenses or
mirrors onto an array of smaller cells This enables the use of cells with a high cost per
unit area (such as gallium arsenide) in a cost-effective way [11]. More complex parabolic
reflectors and solar concentrators are becoming the dominant technology particularly for
6

use in commercial establishment R&D work is in progress to set up and test a new highconcentration
1 000 times photovoltaic system to develop high-efficient concentrating
photovoltaic to reach the system minimize the cost [12].
5. Multi-junction solar cells are developed to increase conversion efficiency. Triple-junction
cells are being developed which can give efficiency of 35.8% by Sharp Corporation [19]
and 40.7 % (Boeing Spectrolab) without concentrators. The most efficient solar cell so far
is a multi-junction concentrator solar cell with an efficiency of 43.5% produced by the
National Renewable Energy Laboratory in April 2011 [20].
6. Micromorph technology (a-Si + μ-CSi), a combination of amorphous silicon and
microcrystalline silicon, is a relatively new development over multi-junction (double and
triple junction) Amorphous Silicon technology [3]. It is projected to evolve as a potential
competitor to CdTe in the Thin-Film family. Carbon nanotubes, quantum dot cells, dye
sensitized cells and organic semiconductor based cells are typical examples in this
direction. [12]
7. PV panels does not produce electricity from an entire wavelength range of solar radiation
(including ultraviolet, infrared and low or diffused light) except visible light portion.
Hence much of the incident sunlight energy is wasted by solar panels, and they can give
far higher efficiencies if illuminated with monochromatic light. Therefore another design
concept is to split the light into different wavelength ranges and direct the beams onto
different cells tuned to those ranges. [21] This has been projected to capable of raising
efficiency by 50%. The use of infrared photovoltaic cells has also been proposed to
increase efficiencies, and perhaps produce power at night. A March 2010 experimental
demonstration of a design by a Caltech group led by Harry Atwater which has an
absorption efficiency of 85% in sunlight and 95% at certain wavelengths is claimed to
have near perfect quantum efficiency [22] however, absorption efficiency should not be
confused with the sunlight-to-electricity conversion efficiency.
8. The sunlight received by the array is affected by a combination of tilt, tracking and
shading. Solar trekking system can be used to move PV panel to follow the sun to
increase the amount of energy produced per panel so tracking increases the yield but also
the cost, both installation and maintenance. A dual axis tracker can increase the effective
insolation by roughly 35–40%, while temperature effects can reduce efficiency by 10%.
The increase can be by as much as 20% in winter and by as much as 50% in summer. [23]
9. Panels mounted above each other in ladder on a turnable disk may be used to follow sun
exactly if the zenith distance of the Sun is greater than zero, During a day it is only
necessary to turn the panels around this axis to follow the Sun. [11]
10. The AC output is roughly 25% lower due to various losses including the efficiency of the
inverter [24]. So a photovoltaic system consisting of module-integrated inverters can be
used to achieve the highest output [12]. It enables performing Maximum Power Point
Tracking (MPPT) for each module individually, and the measurement of performance
data for monitoring and fault detection at module level. The AC output is roughly 25%
lower due to various losses including the efficiency of the inverter [24].
7. Status of Solar Photovoltaic Generation
7.1 Global scenarios
Solar electric generation has the highest power density (global mean of 170 W/m 2 ) among
renewable energies.[6] Solar photovoltaic is growing rapidly, albeit from a small base, to a
total global capacity of 67,400 megawatts (MW) at the end of 2011, representing 0.5% of
7

worldwide electricity demand. [25] as shown in Table 1.The 2011 European Photovoltaic
Industry Association (EPIA) report predicted that, “By 2015, 131–196 GW of photovoltaic
systems could be installed around the globe [26] and by the year 2030, 1,864 GW of PV
systems would be fulfilling the electricity needs of about 14% of the world's
population.[27][Approximately 2,646 TW of electricity].
7.2 Indian scenario
Table 1 Year End Capacities
Photovoltaic power worldwide GWp
2005 5.4
2006 7.0
2007 9.4
2008 15.7
2009 22.9
2010 39.7
2011 67.4
India is positioned on the threshold of a new era of possibilities and opportunities. The
exponentially growing demand for resources in both rural and urban India is creating new
possibilities every day. It is a well-known fact that the rapidly growing population and
businesses are placing considerable pressure on India’s power resources. In the present
scenario, renewable resources emerge as the best alternative. At present, renewable energy
accounts for about 11%of India’s installed generation capacity. Wind energy sector, which
has shown tremendous growth in the recent year, dominates the renewable energy sector in
India. The amount of solar energy produced in India in 2007 was less than 1% of the total
energy demand [28]. The grid-interactive solar power as of December 2010 was merely
10 MW [29]. Government-funded solar energy in India only accounted for approximately
6.4 MW-yr. of power as of 2005[28].However, India is ranked number one in terms of solar
energy production per watt installed, with an insolation of 1,700 to 1,900 kilowatt hours per
kilowatt peak (kWh/KWp) [30]. 25.1 MW was added in 2010 and 468.3 MW in 2011[31].By
May 2012, the installed grid connected photovoltaic had increased to over 979 MW, and
India expects to install an additional 10,000 MW by 2017, and a total of 20,000 MW by
2022[32].
Table 2. Status of Installed Solar Plants in India (state wise) in June 2012 [32]
State MWp %
Andhra Pradesh 21.8 2.2
Chhattisgarh 4.0 0.4
Delhi 2.5 0.3
Gujarat 654.8 66.9
Haryana 7.8 0.8
Jharkhand 4.0 0.4
Karnataka 9.0 0.9
Madhya Pradesh 2.0 0.2
Maharashtra 20.0 2.0
Orissa 13.0 1.3
Punjab 9.0 0.9
8

Rajasthan 197.5 20.2
Tamil Nadu 15.0 1.5
Uttar Pradesh 12.0 1.2
Uttarakhand 5.0 0.5
West Bengal 2.0 0.2
Total 979.4 100
8. Applications
Photovoltaic systems are used for either on- or off-grid applications. First practical
application of PV systems was done to power orbiting satellites and other spacecraft.
Globally, more than 90 % of photovoltaic systems are being used to generate grid-connected
power, while in India, Solar PV applications have followed a different trend from global
practices and are predominately focused on off-grid applications. In the Indian context, the
power scenario and the nature of energy demand is highly skewed, with huge differences
seen between the per capita electricity consumption in the urban and the rural areas. The
socio-economic and the geographical features of the country provide ample scope touse new,
renewable energy resources like PV. In several cases, PV appears to be not only the most
relevant option, but also a viable alternative even at the prevailing price. So a significant
market has emerged in off-grid locations for solar-power-charged storage-battery based
solutions, particularly in India. These often provide the only electricity available [33].Some
of the major “grid or off grid” applications of Solar Photovoltaic ranging from milliwatts to
megawatts are
1. Small stand-alone power packs for street lighting, community services, small
refrigerators in hospitals, lanterns, watches, radio, TV, Solar battery charger, Solar cell
phone, Solar lamp, Solar notebook, Solar-pumped laser and other small power electronic
equipment’s,
2. Off-grid power for remote dwellings, Small transport Vehicles, boats, recreational
vehicles, electric cars, roadside emergency telephones, remote sensing, and cathodic
protection of pipelines etc.
3. Water pumps for Irrigation for Agricultural Support
4. Telecommunication systems
5. Cathodic protection of pipe lines
6. Energy storage through charging of batteries, stored water, hydrogen generation by
electrolysis
7. Uni- and Bi- directional grid: grid support
8. Electronic security system
9. Dedicated industrial applications
10. Building Integrated photovoltaic (BIPV)
11. Rural Electrification
8.1 Advantages of SPV
The advantages of solar power are significant enough for India to accelerate the generation of
solar energy and make it one of its top priorities. The following will be the major advantage
of SPV.
9

1. Solar power is pollution-free during use. Production end-wastes and emissions are
manageable using existing pollution controls. End-of-use recycling technologies are
under development [34] and policies are being made that encourage recycling by
producers [35].
2. PV installations can operate for many years with little maintenance or intervention after
their initial set-up, so after the initial capital cost of building any solar power plant,
operating costs are extremely low compared to existing power options.
3. Grid-connected solar electricity can be used locally thus reducing
transmission/distribution losses.
4. Solar power, when fed into the grid, can be used as an economical substitute for high cost
peak hour supply and as a means to ease grid loading.
5. Compared to fossil and nuclear energy sources, very little research money has been
invested in the development of solar cells, so there is considerable room for improvement.
Nevertheless, experimental high efficiency solar cells already have efficiencies of over
40% in case of concentrating photovoltaic cells [36] and efficiencies are rapidly rising
while mass-production costs are rapidly falling. [37]. Though still an expensive form of
power generation, solar systems on the whole are becoming more cost – effective as
technology improves and economies of scale begin to have an impact. It is anticipated
that solar electricity will cost less and less as technological advances make energy
conversion more efficient.
6. Although the process of manufacturing solar energy equipment is environmentally
degrading to a certain extent, the use of solar power systems and devices is not. Hence,
solar energy contributes to a reduction in carbon emissions.
7. Solar electricity is sometimes the only energy alternative in isolated locations, which are
not connected to the conventional electricity grid. Many far flung villages in India, which
were without electricity earlier, now have the facility of solar power. It also serves as an
alternative to local battery power.
8.2 Disadvantages
Solar power, however, does not come without disadvantages.
1. If home owner moves to another home, the relocation of home mounted SPV system from
one home to another is costlier.
2. Solar power can be used directly only in daylight. Locations that do not receive adequate
sunlight or are cloudy for most of the year cannot derive maximum benefits from solar
power without proper storage solutions.
3. Proper backup powers plants are required for the grids to function properly even during
the periods when solar energy stations do not generate electricity. This requires
considerable energy costs since these plants usually run on fossil fuels such as coal.
4. Solar energy needs to be converted into AC power before it is used in conventional
electricity transmission grid systems because solar cells produce DC power. This results
in a 5 – 10% energy penalty, which reduces the output of solar panels to that extent.
5. As regards vehicles, solar power cannot be used directly but must be converted into a
form of energy that is compatible with motorized transport. This again results in energy
losses.
6. The amount of land required for utility-scale solar power plants—currently approximately
1 km 2 for every 20–60 megawatts (MW) generated [28]—could pose a strain on India's
available land resource. So highly distributed set of individual rooftop power generation
systems, all connected via a local grid[28] will prove to be a practical solution to this
10

problem. This could be possible in future as with the advancement of technology, erecting
such an infrastructure by an individual and average family size household consumer will
become economical.
9. Conclusions
Due to its proximity to the equator, India receives abundant sunlight, averaging
approximately 3000 hours a year. India's theoretical solar power reception, on only its land
area, is about 5000 Petawatt-hours per year (PWh/yr) (i.e. 5000 trillion kWh/yr or about 600
TW) [38.39].With daily average solar energy incident on India being 4 to 7 kWh/m 2 at
different locations. Assuming the efficiency of PV modules as low as 10%, this would be a
thousand times greater than the domestic electricity demand projected for 2015[38]. Solar PV
solution has the potential to transform the lives of 450 million people living in 17% of
villages without electricity and rely on highly subsidized kerosene oil and other fuels,
primarily to light up their homes. Renewable energy source is a practical solution to address
the persistent demand supply gap (8-12% at peak times) in the power industry. It is estimated
that India need to add between 600-1200 GW of generating capacity before 2050 (that’s 20-
40GW/year). Solar energy can contribute immediately and significantly to meet India’s
urgent and growing energy needs. With the launching of Jawaharlal Nehru National Solar
Mission (JNNSM) by Government of India [40], the growth of PV industry in India is
expected to accelerate and make India emerge brightly in the global PV scenario.
References
1. Remme et al.. "Technology development prospects for the Indian power sector"
International Energy Agency France; OECD, February 2011
2. http://powermin.gov.in/indian_electricity_scenario/introduction.ht
3. ‘Solar PV Industry 2010: Contemporary scenario and emerging trends’, Report prepared
by India Semiconductor Association, Bangalore and supported by the Office of the
Principal Scientific Adviser to the Government of India, May, 2010.
4. http://en.wikipedia.org/wiki/India's_energy_policy
5. Chopra, K.L. “Application of Sottp://en.wikipedia.org/wiki/India's_energy_policylar –
Photovoltaics in Buildings”, CSIR Found. Day Lecture, CSIR-CBRI, Roorkee Sep, 2010.
6. Smil, Vaclav, “Energy at the Crossroads. - Global Perspectives and Uncertainties”.
Published by The MIT Press (2005-02-11).
7. The photovoltaic effect. Encyclobeamia.solarbotics.net.
8. German PV market. Solarbuzz.com.
9. BP Solar to Expand Its Solar Cell Plants in Spain and India.
Renewableenergyaccess.com. March 23, 2007.
10. Bullis, Kevin. Large-Scale, Cheap Solar Electricity. Technologyreview.com June , 2006.
11. Solar Cell From Wikipedia, the free encyclopfile:///E:/Solar/Photovoltaic_cell.htm
12. A Report on photovoltaic solar energy- Development and current research in European
Union by European Commission, 2009, ISBN 978-92-79-10644-6 doi: 10.2768/38305
13. "CTI Solar sales brochure". Cti-solar.com. http://www.cti - solar.com/ user files/ file/
brochette %20CTI- SOLAR%20vers%20EN.pdf.
14. The technology at a glance. Wuerth-solar.de (2012-03-30). Retrieved on 2012-06-03.
15. "Thin-film's Share of Solar Panel Market to double by 2013"Renewable Energy World.
16. Cheyney, Tom (29 July 2011). "Exit strategy: Veeco's departure from CIGS thin-film PV
equipment space raises questions, concerns" PV-Tech.
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17. "Introduction to Solar Electricity and Residential Solar Panels - AltE". altestore.com.
http://www.altestore.com/howto/Getting-Started-Renewable-Energy-Sustainable-
Living/Introduction-to-Solar-Electricity/a89/.
18. Luque, Antonio and Hegedus, Steven. Handbook of Photovoltaic Science and
Engineering, John Wiley and Sons. ISBN 0-471-49196-9, 2003.
19. Sharp Develops Solar Cell with World's Highest Conversion Efficiency of 35.8%.
Physorg.com. October 22, 2009.
20. "Update: Solar Junction Breaking CPV Efficiency Records, Raising $30M". Greentech
Media. 2011-04-15.
21. STO: Very High Efficient Solar Cells
22. "Caltech Researchers Create Highly Absorbing, Flexible Solar Cells with Silicon Wire
Arrays".California Institute of Technology. February 16, 2010. Retrieved 7 March 2010.
23. Effect of Panel Temperature on a Solar-Pv Ac Water Pumping System. Ars.usda.gov. R.
24. Calculator for Overall DC to AC Derate Factor. Rredc.nrel.gov. Retrieved on 2012-06-03.
25. European Photovoltaic Industry Association (2012). "Market Report 2011"
26. "Global Market Outlook for Photovoltaics until 2015". European Photovoltaic Industry
Association (EPIA). May 2011. p. 39.
27. Solar Generation V – 2008. Greenpeace.org
28. Roul, Avilash. "India's Solar Power: Greening India's Future Energy Demand"15 May
2007. Ecoworld.com.
29. Estimated medium-term (2032) potential and cumulative achievements on Renewable
energy as on 30-06.2007
30. Chittaranjan Tembhekar (26 October 2009). "India tops with US in solar
power"Economic Times.
31. Generation of Solar Power
32. Grid Connected Solar Capacity Increases from 2.5 MW in 2011 to 1040.67 MW In 2012
33. http://en.wikipedia.org/wiki/Solar_power_in_India
34. Nieuwlaar, Evert and Alsema, Erik. “Environmental Aspects of PV Power Systems”, IEA
PVPS Task 1 Workshop, 25–27 June 1997, Utrecht, The Netherlands
35. McDonald, N.C.; Pearce, J.M. (2010). "Producer Responsibility and Recycling Solar
Photovoltaic Modules". Energy Policy38 (11): 7041. DOI:10.1016/j.enpol.2010.07.023
36. World Record: 41.1% efficiency reached for multi-junction solar cellsFraunhofer ISE
37. Study Sees Solar Cost-Competitive In Europe by 2015 Solar Cells Info (2007-10-16).
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with particular reference to the Indian economy". Renewable and Sustainable Energy
Reviews9 (5): 444. doi:10.1016/j.rser.2004.03.004
39. Renewing India - Under Heading: Solar Photovoltaics
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Projects. Govt of India, Ministry of New and Renewable, No. 5/17/2009-P & C, July 2010
12

Integration of Daylight and Artificial Lighting along with PV
Conversion System for Energy Efficient Lighting of Buildings
Abstract.
B. K. Saxena* and Tushar Saxena**
*Former Dy. Director CBRI Roorkee & Coordinator IDMP
**TERI University, New Delhi
Corresponding Author, Email: tusharsaxena.8@gmail.com
Visible range of solar energy as daylight and sunlight provides an attractive and viable option
of efficient lighting in buildings. Integration of energy efficient CFL and LED with day
lighting can provide optimal solution to energy efficient lighting of buildings. Daylight data
collated by Central Building Research Institute(CBRI) in India under International Daylight
Measurement Program (IDMP) of CIE and WMO can be suitably used for computation of
daylight availability indoors. This can be effectively utilized for judicious design of window
glazing with appropriate glazing material, such as heat absorbing glass, heat reflecting glass,
or double glazing. For this purpose Task-Ambient lighting approach satisfying task
illuminance requirement along with desired ambient brightness provides a rational basis for
day lighting and artificial lighting design as well as for integration of artificial light with day
light. Also, possibility of photovoltaic conversion of sunlight for indoor artificial lighting
need to be explored further for lighting applications in buildings. The paper presents rational
approach for energy efficient lighting of buildings through utilization of IDMP data on
daylight and conventional photovoltaic and organic photovoltaic conversion for artificial
lighting.
1. Introduction
Solar energy radiated by sun contains a sizeable part of visible radiation within the range 400 to
700 nm. The peak sensitivity of human eye corresponds to 555 nm which tapers down to zero at
lower and upper extremes of 400 nm and 700 nm respectively. Direct beam of sun is called
direct solar radiation or beam radiation and the solar radiation scattered by the atmosphere is
called diffuse radiation. Thus daylight comprises direct sunlight and diffuse sky light. Lighting
is an essential requirement for performing the entire gamut of visual activities to be carried out
in industrial, educational, institutional, commercial and office buildings. During day time
hours the available daylight outdoors can be optimally utilized for indoor lighting in
conjunction with artificial lighting. For use beyond daylight hours sunlight can be suitably
converted by photovoltaic panels and stored in a system of batteries. Latest energy efficient
light sources not only help in energy conservation in lighting of buildings but also enhance
feasibility of use of photovoltaic conversion for artificial lighting using energy efficient light
sources as well as for energy efficient integration of artificial lighting with daylight.Taskambient
lighting approach not only ensures satisfactory task illuminance but also well balanced

visual surroundings, which can be achieved through optimal day lighting and its integration
with artificial lighting.
2. Terms, Notations, Units and Definition
The International Commission on Illumination (CIE) has published [1] International Lighting
Vocabulary (ILV). Some of these terms are as follows.
Solid Angle ω (Steradian)
It is the angle subtended by a surface at a point and is defined as the ratio of projected area of
the surface to the square of its distance from the point in question. Thus 1 m 2 of the surface
area of a sphere of 1m radius subtends unit solid angle (1 steradian) at the centre.
Intensity I (Candela)
Intensity of a light source in a given direction is the luminous power emitted per unit solid
angle in that direction.
Luminous Flux Φ (lm or Lumen)
It is the light flux or luminous power. 1 lumen is the light flux emitted by a light source of 1
candela intensity within unit solid angle.
Luminance L (Candela/m 2 )
It is the brightness of a surface defined as the light intensity per unit projected area of the
surface in a given direction.
Illuminance E (Lux)
It is the level of lighting at a point on a surface and is defined as light flux (lumen) incident
on a square metre area of a surface around the point in question.Thus 1 LUX is 1 lumen per
square metre.
Luminous efficiency η (Lumen/watt)
It is the light flux emitted by a light source per watt of electric power consumed.
Uniform diffuser
A matt surface diffusing light uniformly in all directions is called a uniform diffuser, such a
large uniform diffuser or a hemispherical diffuser of 1 candela/ m 2 brightness produces
illuminance of π Lux on a parallel or a diametric plane. Another convenient unit of brightness
for assessing the resulting illuminance is known as Apostilb where a large uniform diffuser of
brightness 1 Apostilb produces illuminance of 1 Lux on a parallel plane or a diametric plane
of hemispherical diffuser.

Sky factor (SF)
It is indoor illumininance on a plane (generally horizontal plane) due to uniform sky (i.e.
having constant luminance throughout) expressed as percentage of the horizontal illuminance
outdoors due to the entire sky.
Brightness factor (BF)
It is the ratio of mean sky luminance as seen from an indoor point through the window
opening and equivalent uniform sky luminance corresponding to actual outdoor sky
illuminance (or diffuse illuminance) on horizontal plane. Sky component is equal to the
product of brightness factor and sky factor. Accordingly SC = BF x SF
Daylight factor (DF)
It is the sum of sky component (SC), inter-reflected component (IRC) and external reflected
component (ERC) where the later are respectively the contribution of internal reflection and
external reflection to the indoor illuminance expressed as percentage ratio of the outdoor sky
illuminance (diffuse illuminance) on a horizontal plane due to the entire sky. Accordingly DF
= SC + IRC + ERC. Thus Daylight Factor at an indoor point on a plane is the ratio of total
daylight due to sky, inter-reflection and external reflection expressed as percentage of the
outdoor sky illuminance (diffuse illuminance) on a horizontal plane due to the entire sky.
3. Fenestration percentage
It is the total area of window opening expressed as percentage of floor area.
3.1 IDMP Data
Saxena et al [2(a), (b)] have collated precise daylight data at several stations in India under
International Daylight Measurement Program (IDMP) launched by International Commission
on Illumination (CIE) and World Meteorological Organization (WMO). These include sky
luminance distribution and horizontal diffuse illuminance and normal direct solar illuminance
(sunlight) from which direct solar illuminance have been derived on horizontal and vertical
surfaces. These data form basis for computation of daylight availability indoors and are of
considerable significance in quantitative estimation of photovoltaic conversion of sunlight
into electricity for lighting purposes.
3.2 Task-ambient lighting
Task-ambient lighting design approach emphasizes need of not only satisfying task
illuminance [3] (e.g. required illuminance on horizontal work plane) but also ensures
desirable ambient brightness. Ambient brightness [4]has been suggested as 100 Apostilb (32
Candela/m 2 ). This value of illuminance or general illuminance of 100 lux can be obtained
from multi reflection formula [5]
[M.EO.F.A.RAV] / [100.Ar.(1-RAV )] = 100 (1)
Where,

EO Illuminance on window plane which is obtainable from IDMP data
A Floor area of room
Ar Total internal surface area of room
RAVAverage reflectance of room
M Reduction factor due to glass transmittance, maintenance and reduction due to
louvers and reduction due to area obstructed by window sashes.
F Fenestration (window opening) as percentage odd floor area
Taking EO as 6000 lux from IDMP data and for a room of 5m x 3m x 3m
A = 15
Ar = 78
RAV = 0.6 (For a light finished interior)
M = 0.62 (For 3mm thick clear glass of transmittance as 0.85 and accounting for
reduction of 0.9 each due to maintenance, louvers and sashes)
F=[ 100 x 100 x Arrx (1-RAV)] / [M x EO x A x RAV ]= 9. (2)
It may be noted that if the interior finish is dull off-white of average reflectance as 0.5
instead of 0.6 as in the above example, the ambient brightness will be reduced by a
factor of 1.5 resulting in general illuminance as 70 lux ( instead of 100 lux ).
For determination of total workplace illuminance Sky Factor (SF) protractor and Brightness
Factor (BF) protractor (figures 1 , 2 ) have been provided which may be used on plan of room
and elevation of window respectively for obtaining sky component [6] as follows
Sky Component = (BF) x (SF) (3)
Since sky component values will be obtained as percentage of outdoor horizontal sky
illuminance (diffuse illuminance) therefore for outdoor diffuse illuminance of 8000 lux (8
klux) 1 %, 1.5% or 2% sky component will be 80, 120 or 160 lux indoor illuminance
respectively due to sky.
Artificial lighting design utilizing energy efficient light sources can be based on conventional
Lumen method for ensuring required task illuminance. However, for detailed analysis of
distribution of workplace illuminance point by point method may be followed so as to ensure
the task illuminance.
4. Energy efficiency of light sources
The development of fluorescent light sources have provided manifold energy efficient lamps
as compared to incandescent lamps (10 – 18 lumen/watt). The latest CFL and LED lamps [7]
have energy efficiency of 50-80 lumens/watt. Energy efficiency of various light sources are
given in Table1. For energy efficient artificial lighting of buildings CFL and LED provide
best options particularly for use with photovoltaic conversion. Mirror optic luminaires and
semi-direct luminaires further boost up incident light on the working plane. Therefore, use of
energy efficient light sources together with efficient luminaries and adequate provision of day
light provide reliable solution of energy efficient lighting design of buildings.

5. Photovoltaic conversion of Sunlight
Solar photovoltaic technology enables the direct conversion of sunlight into electricity
through semiconductor devices called solar cells without involving any moving part or
causing environmental pollution. PV modules are presently crystalline silicon PV modules
with minimum power output of 37W or 74W (depending upon configuration) at 16.4 V load
voltage ( Vld) and open circuit voltage (VOC) as 21 V.
12 V flooded electrolyte type tabular plate low maintenance lead acid batteries of 40 or 75 Ah
capacity depending on the configuration are deployed for storage. Sample testing and
certification of the PV lighting systems is presently undertaken by Solar Energy Center
(SEC) of the Ministry of New and Renewable Energy (MNRE) in the vicinity of Gurgaon
(Haryana) and other authorized test centers are Central Power Research Institute (CPRI)
Thiruvananthapuram, Electronics Regional Test Laboratory Kolkata and Electronics Test and
Development Center (ETDC), Bangalore.
The next generation organic solar cells provide further possibilities of extended use in
artificial lighting. The conventional (inorganic) silicon devices are called minority carrier
materials, wherein the diffusion of carriers in the built in electric potential creates the
photovoltaic current on excitation by sunlight. On the other hand, organic cells are majority
carriers because the excitons dissodiate only at the interface so that holes exist primarily in
one phase and electrons exist primarily in the other phase and their movement results directly
in the flow of current

Table1. Luminous Efficiency of Light Sources
Light Source Luminous Efficiency Average Life
Lm / w Hours
GLS Incandescent lamps 8 – 18 1000
25 – 1000 w
Tungsten Halogen lamps 22 – 27 2000
500 –2000 w
Cool Daylight Fluorescent Tubes 61 5000
(diameter 38 mm) 20 - 80 w
Warm White Fluorescent Tubes 67 5000
(diameter 38 mm) 20 – 80 w
Slim Line Fluorescent Tubes 70 7000
(diameter 26 mm) 36 w
Compact Fluorescent Lamps 50 – 82 8000
(CFL) & LED lamps
* Recommended : Mirror Optic Luminaires / Efficient Semi-direct Luminaires

6. Conclusion
1. Utilization of daylight in buildings based on latest IDMP data needs to be ensured.
2. Latest energy efficient light sources should be utilized for energy efficiency in buildings.
3. Selective artificial lighting units should be energized by photovoltaic conversion systems.
4. Further researches need to be carried out for enhancing efficiency of solar cells in order to
make them cost effective.
7. Acknowledgement
The authors are grateful to former CBRI scientists of Illumination Group, especially Mr.
Shree Kumar and Mr. S. S. Aggarwal for useful interaction and valuable discussions on latest
development in the field of day lighting and artificial lighting design.
References
1. CIE standard S 017/E { 2011} ILV International Lighting Vocabulary
2 (a). Saxena, B.K.. Aggarwal, S..S. , Shree Kumar {1999}, Methodology for estimation of
daylight availability on horizontal and vertical surfaces for day lighting design of
buildings, PRAKASH 99, pages 247-251. (b). Saxena, B.K.{1999}, Day lighting and
IDMP data, Directory of Lighting Industry in India, PRAKASH 99, published by ISLE
(Indian Society of lighting Engineers), pages.75-92
3. BIS National Building Code ( 2001), Bureau of Indian Standards, New Delhi
4. Saxena,B.K..Narasimhan,V.(1977),EnergyEconomic I Design for day-time lighting, ISI
Bulletin,Volume 9, No.6, pages 195 –198
5. Arndt, W. (1953), Proceedings of CIE Daylight Committee.
6. BIS SP 41 (S & T) – (1987), Handbook on Functional Requirements of Buildings, Bureau
of Indian Standards, New Delhi.
7. Valia, A. (2012), LED Lighting Systems, International Lighting Academy, Mumbai.

Abstract.
Energy Efficient Lighting
An Approach towards Sustainable Development
Keerti Mishra and Seepika Chandra
Amity School of Architecture and Planning, Amity University, Noida
Corresponding Author, Email: ar.keertidixit@gmail.com
Why lighting matters? The quantity and quality of light around us determine how well we see
and perceive things. Light affects our health, mood, efficiency, morale and comfort level.
Energy-efficient lighting is a hot topic in today’s discussions on climate change. In Indian
context, the energy sector assumes critical importance in view of the ever-increasing energy
needs, widening of supply–demand gaps, and also huge investments required to meet them.
In the Indian context, the current peak demand shortage is 14% and the energy deficit is
8.4%. In certain areas, this could be as high as 25%. Very simply, energy efficiency means
using less energy to perform the same function. Lighting accounts for 15% of the total energy
consumed in a developing country as against about 7%–10% in developed countries. For
optimal lighting solutions, the total system (active and passive) involving day lighting,
lamps, fixtures, controls, configuration, materials, and furnishing needs to be considered
holistically. The objective is thus identifying and analyzing the barriers being faced in the
quest towards efficient lighting. The aim of this study is to analyze the criteria for energy
efficiency, resulting in a series of feasible active and passive design solutions that can make a
contribution in the field of architecture, towards the knowledge of developing and designing
energy-efficient residential buildings. The study also aims at identifying changes in the
design process that can affect energy efficiency in residential buildings, taken as a case. The
paper also aims to study the role of architects, interior designers, clients/land owners and
residents that can promote energy efficiency in the residential buildings.
Keywords: lighting principles, the barriers, Natural & artificial lighting, Day Lighting,
Policies
1. Introduction
India’s installed capacity of power generation is about 112 058 MW (CEA 2004). According
to an estimate of the share of electricity used and the lighting component for major sectors
(Table 1), about 15% of the total electricity generated is used for lighting purposes in various
sectors. The paper has been broadly covered under four phases: the first phase discusses the
lighting principles and terminology. Second phase is to identify the barriers for adopting
energy efficient lighting solutions in a residential building. Thirdly various Natural and
Artificial solutions for lighting are analyzed and the fourth phase includes discussing the
possible techniques / methods, planning / design considerations to be taken by the Architects,
Developers, Interior Designers & the users in the Indian context

Table 1. Electricity used and the lighting component for major sectors
Sector Electricity used
Lighting component
(% of total)
(% of total electricity used
Industry 49 4-5
Commercial/ Public 17 4-5
Domestic 10 50-90
Other 24 2
2. Lighting principles and terminology
Light is the electromagnetic waves in space. Light is emitted through: Incandescence, Electric
discharge, Electro luminescence and Photo luminescence. 1 Lumen = the photometric
equivalent of the watt. 1 lumen = luminous flux per m2 of a sphere with 1 m radius and a 1
candela isotropic light source at the centre. 1 watt = 683 lumens at 555 nm wavelength. Lux
metric unit of measure for illuminance on a surface: 1 lux = 1 lumen / m2. Lux therefore
takes into account the area over which the luminous flux is spread. For example, 1000
lumens, concentrated into an area of one square meter, lights up that square meter with an
illuminance of 1000 lux. The same 1000 lumens, spread out over ten square meters, produce
a dimmer illuminance of only 100 lux. Luminous intensity I: the unit of luminous intensity is
the candela. Luminous flux We talked about how one lumen is determine using a sphere with
one meter in radius. The area of a sphere of radius r is calculated using formula
4r2Therefore, a sphere whose radius is 1m has 4 of area. Thus the luminous flux emitted
by an isotropic light source of intensity I is given by: Luminous flux (lm) = 4 × luminous
intensity (cd). Room index is the ratio for the plan dimensions of the room. Target load
efficiency is the installed load efficacy considered achievable under best efficiency. Its unit is
Lux/W/m². Utilization factor is a measure of the effectiveness of the lighting scheme.
E = I / d 2
E1.d1 2 = E2.d2 2 ,
Where,
E= Illuminance
I= Luminous Intensity
d= Distance
3. The Barriers
India’s energy intensity per unit of gross domestic product is higher when compared to the
rest of Asia, Japan, and the US by 1.47, 3.7, and 1.55, respectively. Though this indicates
inefficient use of energy, it also implies substantial scope for energy savings. However, many
barriers are being faced in the drive towards energy-efficient lighting. The common problems
and barriers are:
Emphasis on minimization of first cost by end-users
Capital availability constraints
Manufacture of inefficient products in parts of the unorganized sector

Aversion to taking risks associated with new technologies
Shortage of skilled staff
Lack of information.
Technical problems: It is generally observed that in certain areas/seasons/ installations,
power quality are poor. Both planned and unplanned interruptions happen; line voltage
varies up to 30%. Besides, spikes and surges are common. All these problems contribute
to the reduced lamp/ballast life and lead to an increased need for lamp/e-choke
replacements and hence higher O&M (operation and maintenance) costs. In addition to
power quality issues, poor and inefficient designs of lighting systems also pose problems
for most facilities.
Energy efficient fluorescent lamps have starting and flickering problems at low
temperatures.
While very efficient, low pressure sodium lamps are monochromatic and do not
reproduce colours well.
Standard HPS lamps do not produce acceptable colour for merchandising areas.
If a power interruption occurs, HID sources can require four to ten minutes to re-strike.
Based on the experience of the real estate market and on the way architects, developers and
interior designers work and how the clients behave, the roles of these actors involved in the
process of designing energy efficient building are scrutinized below to identify the barriers.
Role of Architect: They need more information and technical skills to design energy efficient
buildings. Even if the architects are well-informed about energy efficient design features,
they might still not be able to use all the energy efficient design features, because the
architect is not the only actor in the design process who can bring changes. Architects are
appointed or hired as consultants by the developers and the architects are under constant
pressure from the developers and the clients to maximize space utilization with minimum
construction costs.
Role of Developer: Developers are primarily interested in maximizing the net saleable area
and in the speedy completion of the building. Future operating costs, which are borne by
prospective occupants of the building, are not key considerations because the developers do
not take long term responsibilities; their role is limited to the moment the flat is handed over
to the client.
Role of Interior Designer: The interior designers are hired by the owners of the flats and they
work in alliance with the owners, without any sort of collaboration with the architects who
designed the building. They too are unaware of the necessity and potentials of energy
efficient design solutions.
Role of clients (land owner) and residents: Clients too are unaware of the role they can play
in mitigating the energy crisis. Barriers in the form of behavioural characteristics of residents,
their lifestyle and split incentives can also hamper the energy efficiency of residential
buildings and are discussed as follows:
Behavioural characteristics of residents: Small, but easy practices such as switching off
the lights when leaving a room is often ignored.

Lifestyle of residents: The lifestyle of the higher income groups contradicts with the
notion of energy efficiency. In such cases, a well-designed energy efficient building can
fall short of its endeavour.
Split incentives: Split incentives occur when costs and benefits of investing in energy
efficiency improvements are split between two parties
Because of these and other similar potential problems, it is essential that lighting designers
and consultants know the advantages and disadvantages of each of the major lighting sources.
Only by understanding the basics of lamp characteristics and applications can the designer
assure that the system will perform as desired.
4. Lighting
Lighting or illumination is the purposeful use of light to achieve a practical or aesthetic
effect. Lighting includes the use of both natural lights by capturing daylight & artificial light
sources like lamps and light fixtures as well.
4.1 Natural lighting
Natural lighting (using windows, skylights, or light shelves) is sometimes used as the main
source of light during daytime in buildings. This can save energy in place of using artificial
lighting, which represents a major component of energy consumption in buildings. Proper
lighting can enhance task performance, improve the appearance of an area, or have positive
psychological effects on occupants.
Day lighting is the oldest method of interior lighting. Day lighting is simply designing a
space to use as much natural light as possible. This decreases energy consumption and costs,
and requires less heating and cooling from the building. Due to a lack of information that
indicate the likely energy savings, day lighting schemes are not yet popular among most
buildings.
Basic principles in energy efficient Day lighting in residential buildings during Planning &
Design process
Planning aspect
Site analysis: Analysis of the building site should be made to determine the following:
- Wind breaks
- Shade from existing buildings and trees
Ratio of Built form to open spaces: The volume of space inside a building that needs to be
lighted will be directly depending on the ratio of open space around the building.
Building orientation: Properly oriented buildings take advantage of solar radiation and
prevailing wind contributing to the natural day light.
Room orientation & arrangement: The arrangement of rooms depends on their function and
according to the time of the day, they are in use. A house can be made more energy efficient
if it is planned according to solar orientation and prevailing wind direction.

Landscaping: it is an important element in altering the microclimate of a place. Proper
landscaping reduces direct sun from striking and heating up of building surfaces. It prevents
reflected light carrying heat into a building from the ground or other surfaces. Landscaping
creates different airflow patterns and can be used to direct or divert the wind advantageously
by causing a pressure difference.
Building envelope and fenestration: which includes Surface finishes, Roof Windows: size,
orientation, shading device, natural ventilation and daylight.
Natural light is admitted into a building through glazed openings. Thus, fenestration design is
primarily governed by requirements of heat gain and loss, ventilation and day lighting.
4.2 Artificial lighting
Types of Artificial lighting Systems: they are as follows:
Incandescent lamps Tungsten Halogen Lamps
Fluorescent lamps High pressure sodium lamps
Low pressure sodium lamps Mercury vapour
Metal halide Blended and LED lamps
Assessment of lighting systems: Every task requires some lighting level on the surface of the
body. Good lighting is essential to perform visual tasks. Better lighting permits people to
work with more productivity. Typical book reading can be done with 100 to 200 lux. The
question before the designer is hence, firstly, to choose the correct lighting level.
Recommended lighting levels for various tasks are given in the chapter, which are also
included in national and international standards for lighting design. The second question is
about the quality of light. In most contexts, quality is read as color rendering. Depending on
the type of task, various light sources can be selected based on their color-rendering index.
5. Performance characteristics of artificial light
Efficacy: It is a measure of how effectively a lamp transforms electricity into light (or
luminous flux) in lumens per Watt. Efficacy varies, depending on a number of factors
including wattage, operating frequency and type of phosphor coating, so the results are
displayed in bands. However, it should be noted that the amount of light reaching the
occupant will depend heavily on the direction of the light and the characteristics of the
complete light fitting (luminare). Average life: Lamp life can be measured in different ways.
Frequent switching of lamps can also affect operating life, particularly in the case of
fluorescent lighting (although specialist fluorescent lamps are now available with are
designed to withstand such use). Although switching may affect operating life, it is not true
that fluorescent lamps consume large amounts of energy every time they are switched on –
they should always be turned off when not required. Colour rendering and colour
temperature: Colour rendering is a measure of how accurately the colour of surfaces appears
under different light sources. It is expressed by a colour rendering index (Ra) of up to 100. A
Ra of between 80-89 is considered very good, while one between 90-100 is regarded as
excellent. Colour temperature gives an indication of the appearance of the light. Lower colour
temperatures mean a ‘warmer’ appearance. Early fluorescent lamps had a high colour

temperature giving a very ‘cold’ appearance; but now a wide range of colour temperatures is
available, including some that are similar to incandescent lamps.
5.1 The three key energy efficient lighting one should keep in mind while selecting
High-efficacy luminaries: These lighting fixtures are designed and built to operate only
energy-efficient light sources, such as fluorescent T8 lamps, compact fluorescent lamps
(CFLs), and high intensity discharge (HID) lamps. Sensors: Occupancy sensors, vacancy
sensors, motion sensors, and daylight sensors are all devices that automatically turn off the
lights in response to conditions that they “sense” or “see.” Dimmers: Dimmers, which are
already common in many residential applications, allow the room occupants to lower the
room lighting (and thus the power used) as desired.
6. Role of architect in energy efficient lighting design
6.1 Lighting design
When considering alternative lighting arrangements or styles, it is important to recall the
basic principles of lighting design. Designers divide lighting into three types:
Such as a central hanging light.
Task lighting – for example, a desk or table lamp.
Atmospheric or ornamental – such as a spotlight on a picture.
The following guidelines can help in making the correct choices:
Decide what the lighting is really needed for; then design a scheme and choose the
position of the lights where they will be used. Include task lighting and provide sockets
for reading lights.
Direct light where it is required.
Use lamps appropriate for the fitting.
Use lighting to aid safety.
Use lighting for effect – reduced background
Lighting will create more contrast in a room as well as saving energy.
6.2 Lighting control
If each fitting has its own switch it can be switched on and off independently when
needed.
If switches are conveniently situated, occupants will be more inclined to switch lights off
when not required.
Dimmers can be used to vary lighting in an energy efficient way.
Use automatic controls where appropriate.

7. Prescribed type of energy efficient lights in a residential building
Hallways: A central fixture can provide a warm reception for visitors. Flush ceiling fittings
maximise headroom in this often small area. Fluorescent lamps are particularly suitable here
as their low running temperatures reduce potential heat build-up in flush fittings. Since
hallways are generally lit for long periods, the use of low energy lighting will maximise
savings. Living rooms: Living rooms need a relaxed atmosphere and some flexibility in
lighting provision: this requires a variety of light sources. Avoiding glare from the lamps is
also important and wall lights such as uplighters can meet this need. Central, flush ceiling
luminaries will also reduce glare by hiding the light source. There is a wide range of fittings
designed for use with CFLs. Dining rooms: Lighting can be used to create different ‘moods’.
A wash of light over one wall or the ceiling can provide a background level of lighting
against which a variety of lighting effects can be achieved using portable luminaires. The
wash can be created using tubular fluorescent lamps shielded in such a way that light is
directed down the wall or across the ceiling. Kitchens: The detailed tasks being carried out in
a kitchen require high levels of lighting, particularly since many of activities involve the use
of sharp tools. Fluorescent lighting under kitchen cabinets provides this and helps to reduce
risk to people who might otherwise be working in their own shadows in a centrally lit room.
Stairs and landings: As in the case of hallways, flush fittings maximise headroom in these
‘transit’ areas, but there are also other issues to consider. Stairs must have adequate lighting
and this will generally require luminaires either along them or above them – or in close
proximity on the landing. The risks of falls associated with replacing lamps can be reduced
considerably by using CFLs because they have a much longer service life than incandescent
lamps. Bedrooms: While providing good general light levels, bright central light sources can
create glare for occupants reclining in bed. This can be reduced by directing lighting onto
surfaces. Providing a separate circuit specifically for bedside lighting, with lighting socket
outlets and two-way switching will help to ensure that lights are not left on unnecessarily.
Bathrooms: Although bathrooms are not lit for long periods, the use of low energy lighting
with a long service life can be particularly appropriate for enclosed fittings where lamps may
be difficult to replace. Studies: Harsh lighting can create glare on computer screens and
paper-covered desks. This can be avoided by arranging a low level of background light: CFL
dedicated wall uplighters can be used to create a general wash of light. External lighting: The
selection of external lighting will largely depend upon its purpose and the way it is to be
used. Where lighting is only required for short periods – for example to light a path while it is
in use – then a standard incandescent lamp may be suitable, provided it has adequate controls.
These might include a photocell (to prevent the light being used in daylight) and a presence
detector.
8. Energy efficient techniques
Natural Day Lighting: North lighting by use if single-pitched truss of the saw-tooth type is a
common industrial practice; this design is suitable for latitudes north of 23 i.e. in North India.
In South India, north lighting may not be appropriate unless diffusing glasses are used to cut
out the direct sunlight. Innovative designs are possible which eliminates the glare of daylight
and blend well with the interiors. Glass strips, running continuously across the breadth of the
roof at regular intervals, can provide good, uniform lighting on industrial shop floors and
storage bays. A good design incorporating sky lights with FRP (fiber reinforced plastic)
material along with transparent or translucent false ceiling can provide good glare-free
lighting; the false ceiling will also cut out the heat that comes with natural light. Use of

atrium with FRP dome in the basic architecture can eliminate the use of electric lights in
passages of tall buildings. Natural light from windows should also be used. However, it
should be well designed to avoid glare. Light shelves can be used to provide natural light
without glare.
De-lamping to Reduce Excess Lighting: De-lamping is an effective method to reduce lighting
energy consumption. In some industries, reducing the mounting height of lamps, providing
efficient luminaires and then de-lamping has ensured that the illuminance is hardly affected.
De-lamping at empty spaces where active work is not being performed is also a useful
concept.
Task Lighting: Task lighting implies providing the required good illuminance only in the
actual small area where the task is being performed, while the general illuminance of the shop
floor or office is kept at a lower level; e.g. Machine mounted lamps or table lamps. Energy
saving takes place because good task lighting can be achieved with low wattage lamps. The
concept of task lighting if sensibly implemented, can reduce the number of general lighting
fixtures, reduce the wattage of lamps, save considerable energy and provide better
illuminance and also provide aesthetically pleasing ambience.
High Efficiency Lamps & Luminaries: Installation of metal halide lamps in place of mercury
/sodium vapor lamps. Metal halide lamps provide a high color rendering index when
compared with mercury & sodium vapour lamps. These lamps offer efficient white light.
Hence, metal halide is the choice for color critical applications where, higher illumination
levels are required. These lamps are highly suitable for applications such as assembly lines,
inspection areas, painting shops, etc. It is recommended to install metal halide lamps where
color rendering is more critical. Installation of high pressure sodium vapors (HPSV) lamps
for applications where color rendering is not critical. High pressure sodium vapour (HPSV)
lamps offer more efficacy. But the color rendering property of HPSV is very low. Hence, it is
recommended to install HPSV lamps for applications such street lighting, yard lighting, etc.
Panel indicator lamps are used widely in industries for monitoring, fault indication, signaling,
etc.
Low Loss Electromagnetic Ballasts for Tube Lights: The loss in standard electromagnetic
choke of a tube light is likely to be 10 to 15 Watts. Use of low loss electromagnetic chokes
can save about 8 to 10 Watts per tube light. The saving is due to the use of more copper and
low loss steel laminations in the choke, leading to lower losses.
Timers, Twilight Switches & Occupancy Sensors: Timers: Automatic control for switching
off unnecessary lights can lead to good energy savings. Twilight switches: can be used to
switch the lighting depending on the availability of daylight. Infrared and Ultrasonic
occupancy sensors can be used to control lighting in cabins as well as in large offices.
T5 Fluorescent Tube Light: The fluorescent tube lights in use presently in India are of the
T12 (40W) and T8 (36W). T12 implies that the tube diameter is 12/8” (33.8mm), T8 implies
diameter of 8/8” (26mm) and T5 implies diameter of 5/8” (16mm). This means that the T5
lamp is slimmer than the 36W slim tube light. These lamps are available abroad in ratings of
14W, 21W, 28W and 35W.
Lighting Maintenance: Maintenance is vital to lighting efficiency. Light levels decrease over
time because of aging lamps and dirt on fixtures, lamps and room surfaces. Together, these

factors can reduce total illumination by 50 percent or more, while lights continue drawing full
power. The following basic maintenance suggestions can help prevent this. Clean fixtures,
lamps and lenses every 6 to 24 months by wiping off the dust. Replace lenses if they appear
yellow. Clean or repaint small rooms every year and larger rooms every 2 to 3 years. Dirt
collects on surfaces, which reduces the amount of light they reflect.
9. Policy recommendations
Often in industrial plants, the use of efficient lighting is not considered important, as energy
consumption for lighting purposes generally forms only a small component of the total
energy consumed. Recognizing the importance and benefits of energy efficiency, the
Government of India enacted the Energy Conservation Act, 2001, which came into force on 1
March 2002. The following policy measures will help overcome the barriers stated earlier:
Prescribing energy conservation building codes for efficient use of energy and its
conservation in commercial buildings
Formulating energy conservation building codes to suit regional and local climatic
conditions.
Organizing training programmes for personnel and specialists in the techniques of
efficient energy use and conservation
Creating awareness and disseminating information
Promoting research and development
Promoting the use of energy-efficient products, fittings, devices, and systems (The cost of
energy-efficient equipment in India is higher compared to other developed countries.)
Encouraging the use of energy-efficient equipment by giving preferential treatment.
Awareness Generation: There has been continuous development in lighting technologies over
the past 60 years to produce the best lighting products and controls for creating higher
lighting quality with reduced energy consumption. However, the speed at which these
technological developments have taken place has not been complemented by a corresponding
pace in generating awareness about them and their availability to the end-users. Also, the
emergence of new secondary players has generated a lot of competition in the lighting
market. These market barriers should be addressed through aggressive customer-oriented
awareness programmes and demonstration projects.
10. Conclusion
In the Telecom Buildings in India, though the norms for lighting in switches have been
revised, resulting into substantial savings in energy consumptions due to lighting, yet, energy
efficient tubes , electronic chokes, sensors , dimmers etc. etc. have not been used. This is
mainly on account of barriers as indicated in the paper .Notwithstanding the barriers, it is
recommended that we may identify few Telecom Buildings in each state for taking up energy
efficient lighting installations using these energy saving devices and fixtures. This will
definitely help in increasing the awareness and energy conservation. Energy demand for
lighting can be reduced by: Using energy efficient lamps and luminaires (light fittings);
Directing light to where it is needed; controlling the use of lighting; Making the most of
daylight and using reflective room surfaces and the influencing user behaviour.

Lighting systems offer a powerful leverage on energy costs, if the measures are pursued in
proper sequence. The 21 st century is witnessing Urbanization and Industrialization at a very
fast rate in India. The rate of increase in generation of Electrical Energy has not been
sufficient enough to meet the growing demand. The gap between the demand and supply is
increasing with each passing day. Urgent measures need to be developing so that the gap
between demand and supply is reduced. The buildings consume significant energy and need
to be designed to reduce consumption and save energy.
References
1. CEA (Central Electricity Authority). 2004 Operation performance monitoring division
data, as on 4 June 2004 Available at , last
accessed on 1 June 2004
2. Energy efficiency in lighting: an overview
3. Climate Responsive architecture : Author Arvind Krishan
4. “Energy-Efficient Lighting, Naturally,” Popular Science, August 1990.
5. A vehicle to energy-efficient lighting, (a) Jan de Boer and Anna Staudt, (b) Fraunhofer
Institute of Building Physics, Germany.
6. ‘Residential lighting design guide’ best practices & lighting designs to help builder’s
company with California’s 2005 Title 24 energy code, developed by California lighting
technology centre.
7. Energy efficient lighting – guidance for installers & specifiers, by Energy saving trust.
8. Passive Design Features for Energy-Efficient Residential Buildings in Tropical Climates:
the context of Dhaka, Bangladesh by Tahmina Ahsan.
9. Energy efficiency in architecture: An overview of design concepts and architectural
interventions.

Solution of Integral Equation applying Finite Difference
Approach for Evaluating Visible Radiation Exchange including
Multiple Inter-Reflection in Building Enclosures
Abstract
Ms Chhavi
CSIR- Central Building Research Institute, Roorkee
Corresponding Author, Email:chhavi.cbri@gmail.com
Visible radiation exchange including multiple inter – reflection in enclosures makes
significant contribution toward overall radiant flux density e.g illuminance level, which is
important in lighting design for energy conservation in buildings. The exchange of visible
radiation between internal surfaces of room is represented by an integral equation of the
Poission Volttera Fredholm type which may be integrated only for idealized geometries and
typical radiation excitations. In this paper, finite difference approach has been applied to
solve the integral equation for evaluating visible radiation exchange involving multiple inter
– reflection in building enclosures. For this purpose a typical cubical enclosure ( room ) with
a north facing window has been considered and using IDMP daylight data as input data finite
difference approach has been applied for solution of integral equation. The result has been
compared with enclosures of assumed geometry as equivalent bi-hemispheres as well as a
single integrating sphere for the same surface area as that of actual room under consideration.
1. Introduction
Inter-reflected light in a building enclosure involves visible radiation exchange between
various surface elements. It depends upon initial excitation or initial luminous flux density at
each surface element, their reflectance (or interior finish), mutual geometrical configuration
(or shape factors) of different surface elements with respect to other surface elements with in
the enclosure. In case of day light initial excitation depend upon the out door day light
availability e.g sky luminance and luminance of external surfaces such as ground as well as
upon the size and location of the window aperture and characteristics of glazing material
(transmittance, reflectance and absorptance ). In view of complexity of the problem Arndt
attempted to arrive at an approximation solution through a simplifying assumption of treating
a building enclosure as an integrating sphere having same surface area as total area of all the
surfaces of the enclosure (room) and its reflectance equal to mean reflectance of all the
internal surfaces of the enclosure and initial excitation as proportional to luminous flux
entering the aperture. However, the actual exchange of visible radiation including multiple
inter-reflections in an enclosure is represented by an integral equation, which is amenable to
solution only for idealized conditions. In this paper finite difference approach has been
attempted for solution of integral equation. The out door day light data has been taken in
accordance with the published IDMP data. The ground reflectance and interior surface finish

of different surfaces of the enclosure viz. ceiling, floor, and walls has been varied. The result
has been compared with those obtained by the integrating sphere approach. As a variant of
the integrating sphere equivalent bi-hemispheres of same total equivalent surface area but of
different mean reflectance and initial luminance emittance corresponding to upper and lower
half of the building enclosure have also been considered for comparison.
2. Problem formulation
The luminous flux transfer in a room involves the coupling of excitation (or the initial
emittance distribution) and the final response (or the total luminous pattern).The luminous
flux transfer system or room which couples the excitation with response is characterized by
relative surface geometry and the surface reflectance distribution. The fundamental equation
of luminous flux transfer is obtained as follows from the principal of conservation of flux at a
surface element.
L(s) = Lo(s) + ds (1)
Where L(s) is the total luminous emittance (including multiple reflections) as function of
space coordinates.
Lo(s) the initial luminance emittance (excluding inter- reflection) as a function of space
coordinates.
R(s) the reflectance distribution function
X(s) the geometrical distribution function
This is an integral equation of Poisson Volttera Fredholm type and may be integrated directly
only for very idealized geometries and luminous excitation. Moon [1] has solved this
equation for a uniform sphere by direct integration. But for a slightly more complicated case
of a cylinder with symmetrical excitation and reflectance distribution, the kernel of integral
equation is not integrable in closed form without some approximations. Buckley [2], Hottel
[3] ,Moon [4] [6], Lijima [5] have employed approximate exponential kernel to solve several
idealized radiant and luminous transfer system.
Yamult [7] suggested to use finite difference equation for solving the problem of inter-
reflection for the luminous transfer system when assumed to have a constant reflectance and
uniform luminous emittance over some finite region of space coordinates. The function R(s)
and L(s) may be separated and the integral equation can be written as a set of finite difference
equations. If A1, A2 …….. An are assumed areas of constant diffuse reflectance R1, R2 ……..
Rn and uniform final total luminous emittance as L1, L2 …… Ln for initial emittance as Lo1,
Lo2, ……. Lon the set of finite difference equation can be expressed as follows.
L1 = Lo1 + R1 [ F1-2 L2 + F1-3 L3 + …………………………….. + F1-n Ln ]
L2 = Lo2 + R2 [ F2-1 L1 + F2-3 L3 + …………………………….. + F2-n Ln ]
……………………………………………………………………………………
Ln = Lon + Rn [ Fn-1 L1 + Fn-2 L2 + …………………………….. + Fn-(n-1) Ln-1 ] (2)

or
1/R1 -F1-2 -F1-3 ………………………… -F1-n L1 Lo1/R1
-F2-1 1/ R2 -F2-3 ………………………… -F2-n L2 Lo2/R2
……………………………………………………. … = … (3)
……………………………………………………. … ….
-Fn-1 -Fn-2 -Fn-3 ………………………… 1/Rn Ln Lon/Rn
Here F1-n is the shape factor of finite area An with respect to entire area A1 and is defined as
the ratio of the diffuse flux received by An to the total flux emitted by A1 ie
Fn-1 = 1/π A1
Where rn-1 is the distance between elemental area dA1 and dAn and Ø1 and Øn are the
angles of the normal to dA1 and dAn with the direction of rn-1 .
Shape factor between the variousaly oriented surfaces have reported by Hemilton and
Morgon[8], Gauffe [9], Biji [10], Oberien [11], Hottel [3], and Moon [1].
The finite difference method for the inter – reflection of light has been successfully applied
by Caracciolo [12], Dourgnon [13], Philips [14], Ingustin and Cenfeno [15], and Obrien and
Ross [16] and Oberin and Roward [17], mostly using a digital computer and solving the
equation either by iterative method or by transforming them to Kirochhoffs node equation
and using an analogue computer.
As simplifying assumption a room may be considered to be divided into two compartments
just above and below the mid level of the window through which light flux from the ground
and the sky may be assumed to be entering the upper and lower compartments respectively.
Fuether the two compartments of the system may be treated as bi-hemispheres of uniform
initial emittance for applying finite difference approach to radiation equilibrium between the
two hemispheres. Mean initial emittance may be computed by multiplying the flux above the
horizon by the mean reflectance of the upper compartment.
Suppose Ra and Rb are the respective mean reflectance of upper and lower compartments and
Loa and Lob the mean initial emittance factor of upper and lower compartments assumed to
be hemi – spheres, and then the final luminous emittances are given by the following finite
difference equation in the matrix form.
1/Ra -1 La Loa/Ra
-1 1/Rb Lb Lob/Rb
= (5)

So that
La = ( Loa + Ra Lob ) / ( 1- Ra Rb ) (6)
Lb = ( Lob + Rb Loa ) / ( 1- Ra Rb ) (7)
The internal reflected illuminance due to upper compartment on the horizontal plane
anywhere with in the upper compartment would be numerically equal to La on the horizontal
plane (facing the ceiling). For a plane located below the mid height of the window the inter –
reflected illuminance is contributed by a belt of the lower compartment above the reflectance
plane and also due to the whole of the upper compartment.
Arndt [18] applied Ulbricht theory of inter – reflection in an integrating sphere by making a
highly simplified assumption that room behaves as an integrating sphere of reflectance equal
to the mean diffuse reflectance of all the surfaces in a room. If F1 is the first reflected flux
and Rm the mean reflectance of the room surface and if F1 is assumed to be uniformly
distributed over the whole enclosure in the same way as in an integrating sphere of
reflectance Rm, then the total amount of the reflected and integrated flux Fr is given by
Fr = F1 + (F1 * Rm ) + (F2 * Rm ) Rm +………..
= F1 [ 1 Rm + Rm 2 +…………… ]
= F1 / ( 1- Rm ) (8)
Hence, the mean luminous emittance of the room surfaces and the average internal reflected
illuminance Er at any point inside the assumed uniform diffuser is given by
Er = F1 / A (1- Rm) (9)
Where A is the total area of all surfaces in the room and the first reflected flux F1 is obtained
by multiplying the total flux F entering the window with the mean reflectance of all the
surfaces in the room. In the finite difference approach for a six surfaces enclosure (1 ceiling,
2 floor, 3 east wall, 4 west wall, 5 south wall, and 6 north wall ), the matrix can be written as
follows.
1/R1 - F1-2 - F1-3 - F1-4 - F1-5 - F1-6 L1 Lo1/R1
- F2-1 1/R2 - F2-3 - F2-4 - F2-5 - F2-6 L2 Lo2/R2
- F3-1 - F3-2 -1/R3 F3-4 - F3-5 - F3-6 L3 = Lo3/R3 (10)
- F4-1 - F4-2 - F4-3 1/R4 - F4-5 - F4-6 L4 Lo4/R4
- F5-1 - F5-2 - F5-3 - F5-4 1/R5 - F5-6 L5 Lo5/R5
- F6-1 - F6-2 - F6-3 - F6-4 - F6-5 1/R6 L6 Lo6/R6

Figure1. Sketch of cubical building enclosure of size 3m*3m*3m provided with a
symmetrically located North facing window aperture covered with 3mm thick plain glass.
Figure 2. Bi- hemisphere of 4.16m diameter represented upper and lower halves of
the enclosure
Figure 3. Sphere of 4016m diameter and same mean reflectance and area as that
of the enclosure

Here, if the geometry of the enclosure is assumed as cubical, the shape factors between
parallel surfaces viz ceiling- floor, north – south walls, east – west walls are same ie.
F1-2 = F2-1 = F3-4 = F4-3 = F5-6 = F6-5 and have the value as 0.20 and rest all
others adjoining perpendicular surfaces have also same shape factor and have the value as
0.19 [22]. Here, the reflectance of the window wall has to be taken as area weighted
reflectance of glass and rest of the window wall which comes out to be 0.45.
3. Case study
For the study a cubical enclosure of diameter 3m*3m*3m has been chosen. The interior
finish of ceiling, walls, floor have been assumed as 0.7 (0.5), 0.5, 0.3 respectively
representing white ceiling, off white walls, and gray floor. The enclosure oriented with its
wall facing cardinal directions (viz. north, south, east, and west). A window having glass
reflectance of 0.15 and the dimension 1.5m*0.9m is supposed to be provided in the center of
the north facing wall at a sill height of 1.05m. It is also assumed there is no obstruction in
front of the window which implies that the light flux entering the glazed window is only from
the sky and ground.
If the cubical enclosure is divided into two equal parts from the mid level of the glass
window and these two upper and lower parts are assumed as hemispheres, the average
reflectance of the two upper and lower parts are Ra = 0.558, Rb = 0.425 and the matrix
equation for the assumed geometry of bi- hemispheres may be simplified as follows.
1/Ra -1 La Loa/Ra
-1 1/Rb Lb Lob/Rb
1/0.558 -1 La Loa/0.558
-1 1/0.425 Lb Lob/0.425
= (11)
= (12)
In the most simplifying approach of Arndt the shape of the cubical enclosure is assumed to be
a sphere such that its internal surface area is same as that of the cubical enclosure.
Such an equivalent sphere for the present case study has a radius of 2.08 m and average
reflectance as 0.49. Total internal surface area of the cubical enclosure as well as that of the
assumed equivalent sphere of radius 2.08 m is A = 54 m 2 .

4. Input data
North sky luminance (Ls) based on IDMP data taken as uniform luminance of 2545.5 Cd/ m 2
which produces window illuminance ( incident light flux on vertical window plane ) of pLs
/2 = 4000 lux (lm / m 2 ) .
Total outdoor horizontal illuminance from IDMP data has been taken as 16000 lux which for
ground reflectance of 0.2 result in ground luminance emittance of 16000* 0.2 or 3200 lm / m 2
(or equivalent luminance of 3200/p Cd / m 2 ). Assuming ground of infinite size the window
illuminance (incident light flux on vertical window plane) due to ground emittance of 3200*
lm / m 2 will be 3200*1/2 lux. Thus, the total window illuminance facing uniform north sky of
luminance 2545.5 Cd / m 2 and infinite uniform ground of luminous emittance of 3200 lm / m 2
respectively amounts to 2545.5 p/2( 4000) + 3200 *1/2 ie 5600 lux (lm / m 2 ). Similarly for
ground reflectance of 0.25 the window illuminance comes out to be 6000 lux. Accordingly,
for ground reflectance of 0.2 and0.25 the amount of flux entering the window of area 1.35 m 2
and glass transmittance as 0.85 are 6426 lm, 6885 lm respectively
The room surfaces viz. ceiling, floor, east wall, west wall, south wall, north wall each have
been divided into four equal parts. At the center of each of these surfaces elements sky
factors [20] have been determined for the north facing window of size 1.5 m* 0.9 m located
centrally in the wall at the sill height of 1.05 m. The reflectance of ceiling, walls, and floor
have been taken as 0.7 and 0.5 (white and off white finish ), and 0.3 (gray) respectively.
Table 1. Average Incident Flux Density in Lux (lm / m 2 ) at four points of each surfaces for
ground reflectance of 0.25
Ceiling Floor East/West Wall South Wall North Wall
142.1 283.6 90.3 125.1 0
142.1 283.6 180.3 125.1 0
75.1 150.3 41.6 250.9 0
75.1 150.3 83.6 250.9 0
180.6 216.9 98.1 187.6 0
Table 2. Average Incident Flux Density in Lux (lm / m 2 ) at four points of each surfaces for
ground reflectance of 0.2
Ceiling Floor East/West Wall South Wall North Wall
113.7 283.6 72.3 100.1 0
113.7 283.6 180.3 100.1 0
60.1 150.3 83.2 250.2 0
60.1 150.3 83.2 250.2 0
86.9 216.9 91.7 175.1 0

5. Result and discussion
For a cubical enclosure of size 3 m *3 m *3 m having symmetrically located north facing
window of size 1.5 m *0.9 m, incident flux density at four points on floor, ceiling and walls
have been computed from sky factor [20] and are given Table 1 and 2. The initial luminous
emittances are product of incident flux density and respective reflectance of each surface,
from which the final luminous emittances are obtained by solving the finite difference
equation in matrix form. The final luminous emittances of ceiling, floor and walls for ceiling
of 0.7 and 0.5 and ground reflectance of 0.25 and 0.2 are given in Table 3 &4. The
reflectances of walls, floor and glass have been taken as 0.5, 0.3, and 0.15 respectively. For
the purpose of bi- hemispheres approach the mean initial luminous emittances of upper half
and lower half of room enclosure have been estimated and final luminous of the upper and
lower halves approximated as bi – hemisphere have been determined from the corresponding
matrix equations. The mean initial and final emittances ob bi – hemisphere are given in Table
5. Finally the inter – reflected flux density (ie. Inter – reflected illuminance) has been
estimated at the center of the floor which are given Table 6.
Table 3. Initial and Final Luminous Emittance (lm / m 2 ) of Ceiling and Floor
Ceiling and Ground Ceiling Floor
Reflectance Initial Final Initial Final
Lo1 L1 Lo1 L1
Rc=0.7, Rg=0.25 76.0 145.7 65.1 97.8
Rc=0.5, Rg=0.25 54.3 101.0 65.1 93.5
Rc=0.7, Rg=0.2 60.8 125.6 65.1 94.7
Rc=0.5, Rg=0.2 43.5 87.1 65. 1 91.0
Table 4. Initial and Final Luminous Emittance (lm / m 2 ) of Walls
Ceiling and Ground East/West Wall South Wall North Wall
Reflectance Initial Final Initial Final Initial Final
Lo3/o4 L3/4 Lo5 L5 Lo6 L6
Rc=0.7, Rg=0.25 51.7 103.4 93.8 143.8 0 53.1
Rc=0.5, Rg=0.25 51.7 96.6 93.8 136.8 0 46.9
Rc=0.7, Rg=0.2 45.8 95.2 87.7 133.8 0 48.7
Rc=0.5, Rg=0.2 45.8 89.3 87.7 127.2 0 43.2
Table 5. Mean Initial and Final Luminous Emittance Upper and Lower Hemi-sphere
Ceiling and Ground Upper Hemi-sphere Lower Hemi-sphere
Reflectance Initial Final Initial Final
Loa La Lob Lb
Rc=0.7, Rg=0.25 46.7 109.6 66.0 112.6
Rc=0.5, Rg=0.25 39.5 100.0 66.0 108.7
Rc=0.7, Rg=0.2 37.2 97.0 66.0 107.3
Rc=0.5, Rg=0.2 31.4 86.4 66.0 104.0

Table 6. Inter – Reflected Flux Density in Lux (lm / m 2 ) at Centre of the Floor
Ceiling and Ground Finite Difference Bi-Hemispheres Integrating Sphere
Reflectance Approach
Rc=0.7, Rg=0.25 109.8 111.7 123.0
Rc=0.5, Rg=0.25 94.8 104.3 107.0
Rc=0.7, Rg=0.2 98.8 106.1 114.8
Rc=0.5, Rg=0.2 86.5 96.8 100.6
The integrating sphere results in higher values of inter-reflected illuminance which gives an
over estimate of about 13 to 15% from the measured values according to Narasimhan –
Sexena et al [21]. Also as seen from Table 6 the values computed from integrating sphere
approach are 12-16% higher than those obtained by finite difference approach. Accordingly,
it is inferred that the results obtained by finite difference approach closely conform with the
actual values. The values computed from bi-hemispheres approximation are slightly less than
those computed from integrated sphere formula but are upto 12% higher than precise values.
6. Conclusion
The finite difference approach to the solution of integral equation representing visible
radiation exchange and multiple reflection provides a precise method for computing interreflected
luminance in building enclosure. The effect of interior finish (surface reflectance )
on the inter- reflected illuminance, which make a significant contribution to the total
illuminance, can also be precisely evaluated by the proposed methodology.
The integrating sphere approach and bi-hemisphere approximation lead to an over estimate of
inter-reflected illuminance by 12 – 16% and upto 12% respectively and may be utilized for
the purpose of rough estimate only.
7. Acknowledgement
The author is grateful is grateful to Dr. P.K. Bhargava Chief Scientist and Coordinator
Efficiency of Building Division for constant encouragement and valuable guidance and Dr.
B. K. Saxena former Dy. Director CBRI and Coordinator International Daylight
Measurement Program (IDMP) for providing valuable suggestions and input data on outdoor
daylight levels. Thanks to Mr. Nagesh Babu for extending computer guidance and literature
support and to Dr. B. M. Suman for including the paper for presentation in conference. The
author is also thankful to CSIR for granting fellowship to pursue at CBRI Roorkee as well as
to the Director CBRI for providing all the necessary facilities and overall guidance.
References
1. Moon, P. (1961), The Scientific Basis of Illuminating Engineering, Dover Publication
Inc., New Yark.
2. Bukley, H..(1927), Philosophical Magazine London, volume 4, Pages 753-760.
3. Hottel, H.C., Keller, J.D.(1933), Transaction of the American Soc. of Mechanical
Engineers (Iron and Steel Div.), Volume 55-56, Pages 39-45.

4. Moon, p.(1941), J. Opt. Soc. America, Volume 31, Pages 375-380.
5. Lijima, T., (1949) The Japan Science Review, Volume 1, Pages 9-15
6. Moon, P., Spencer, D.B. (1948), Lighting Design, Addision Wrsky Press, Cambridge.
7. Yamutt, Z. (1926), ), J. Opt. Soc. America, Volume 16, pages 561-568
8. Hamilton, D.C., Morgan, W.R. (Dec. 1952), National Advisory Committee for
Aeronautics, Technical Note 2836.
9. Gauffe, A. (Sep. 1955), Cahieres du centre Scientifique et Technique du Bariment No. 27.
10. Ziji, R. (1951), Mannual of Illuminating Engineers on Large Sized Perfect Diffussers,
Philips Technical Publication, Eindhoven.
11. O’Brien,P.P.(1956), ), J. Opt. Soc. America, Volume 46, Pages 343-350.
12. Carracciolo, F.B.(1952), L” Ingegnere NO. 10, Italy.
13. Dourgnon, J.(Sep.1955), Cahieres du centre Scientifique etTechnique du Bariment No. 27
14. Philips, Ro., The Calculation of Inter-Reflected Illuminance and Lumiancesin room using
electronic computer, New Southwalves University of Technology, School of Architecture
(Sep. 1957).
15. Centeno, M, Zagustin, A. (1953), Inter- Refletance in two dimension Universal central
Venesuela Caracas.
16. O”Brien, P.P., Ross, D. B. (Jan. 1958), Luminous flux distribution with a cubical room,
University of California, Deptt. Of Ening., Los Angeles California.
17. O’ Brien, P.P., Howard, J. A.(1959) Illum. Enig., New Yark, Volume 54, P. 209-216.
18. Arndt, W. (1953), Proc. IB. Daylight Technical Committee France.
19. BIS, (1988), Handbook on Functional Requirement of Building (other than Industrial
Buildings), Parts 1-4, SP: 41, Bureau of Indian Standards Manak Bhavan, Bahadurshah
Zafar Marg, New Delhi.
20. Saxena, B.K. (1999), Daylight and IDMP data Directory of Lighting Industry in India,
Prakash 99, Published by ISLE (Indian Society of Lighting Engineers), Pages 75-90.
21. Narasimhan, V.., Saxena, B.K. , Majtreya, V.K. (1968), Inter- Reflected Component of
Daylight, Indian Journal of Pure and Applied Physics, Volume 6, No. 2, Pages 100-101.
22. Cengle, Y.A., (2007), Heat and Mass Transfer- A Practical Approach, Tata Mc Graw Hill
Compnies.

Solution of Integral Equation applying Finite Difference
Approach for Evaluating Visible Radiation Exchange including
Multiple Inter-Reflection in Building Enclosures
Abstract
Ms Chhavi
CSIR- Central Building Research Institute, Roorkee
Corresponding Author, Email:chhavi.cbri@gmail.com
Visible radiation exchange including multiple inter – reflection in enclosures makes
significant contribution toward overall radiant flux density e.g illuminance level, which is
important in lighting design for energy conservation in buildings. The exchange of visible
radiation between internal surfaces of room is represented by an integral equation of the
Poission Volttera Fredholm type which may be integrated only for idealized geometries and
typical radiation excitations. In this paper, finite difference approach has been applied to
solve the integral equation for evaluating visible radiation exchange involving multiple inter
– reflection in building enclosures. For this purpose a typical cubical enclosure ( room ) with
a north facing window has been considered and using IDMP daylight data as input data finite
difference approach has been applied for solution of integral equation. The result has been
compared with enclosures of assumed geometry as equivalent bi-hemispheres as well as a
single integrating sphere for the same surface area as that of actual room under consideration.
1. Introduction
Inter-reflected light in a building enclosure involves visible radiation exchange between
various surface elements. It depends upon initial excitation or initial luminous flux density at
each surface element, their reflectance (or interior finish), mutual geometrical configuration
(or shape factors) of different surface elements with respect to other surface elements with in
the enclosure. In case of day light initial excitation depend upon the out door day light
availability e.g sky luminance and luminance of external surfaces such as ground as well as
upon the size and location of the window aperture and characteristics of glazing material
(transmittance, reflectance and absorptance ). In view of complexity of the problem Arndt
attempted to arrive at an approximation solution through a simplifying assumption of treating
a building enclosure as an integrating sphere having same surface area as total area of all the
surfaces of the enclosure (room) and its reflectance equal to mean reflectance of all the
internal surfaces of the enclosure and initial excitation as proportional to luminous flux
entering the aperture. However, the actual exchange of visible radiation including multiple
inter-reflections in an enclosure is represented by an integral equation, which is amenable to
solution only for idealized conditions. In this paper finite difference approach has been
attempted for solution of integral equation. The out door day light data has been taken in
accordance with the published IDMP data. The ground reflectance and interior surface finish

of different surfaces of the enclosure viz. ceiling, floor, and walls has been varied. The result
has been compared with those obtained by the integrating sphere approach. As a variant of
the integrating sphere equivalent bi-hemispheres of same total equivalent surface area but of
different mean reflectance and initial luminance emittance corresponding to upper and lower
half of the building enclosure have also been considered for comparison.
2. Problem formulation
The luminous flux transfer in a room involves the coupling of excitation (or the initial
emittance distribution) and the final response (or the total luminous pattern).The luminous
flux transfer system or room which couples the excitation with response is characterized by
relative surface geometry and the surface reflectance distribution. The fundamental equation
of luminous flux transfer is obtained as follows from the principal of conservation of flux at a
surface element.
L(s) = Lo(s) + Rs Xs Ls
ds (1)
Where L(s) is the total luminous emittance (including multiple reflections) as function of
space coordinates.
Lo(s) the initial luminance emittance (excluding inter- reflection) as a function of space
coordinates.
R(s) the reflectance distribution function
X(s) the geometrical distribution function
This is an integral equation of Poisson Volttera Fredholm type and may be integrated directly
only for very idealized geometries and luminous excitation. Moon [1] has solved this
equation for a uniform sphere by direct integration. But for a slightly more complicated case
of a cylinder with symmetrical excitation and reflectance distribution, the kernel of integral
equation is not integrable in closed form without some approximations. Buckley [2], Hottel
[3] ,Moon [4] [6], Lijima [5] have employed approximate exponential kernel to solve several
idealized radiant and luminous transfer system.
Yamult [7] suggested to use finite difference equation for solving the problem of inter-
reflection for the luminous transfer system when assumed to have a constant reflectance and
uniform luminous emittance over some finite region of space coordinates. The function R(s)
and L(s) may be separated and the integral equation can be written as a set of finite difference
equations. If A1, A2 …….. An are assumed areas of constant diffuse reflectance R1, R2 ……..
Rn and uniform final total luminous emittance as L1, L2 …… Ln for initial emittance as Lo1,
Lo2, ……. Lon the set of finite difference equation can be expressed as follows.
L1 = Lo1 + R1 [ F1-2 L2 + F1-3 L3 + …………………………….. + F1-n Ln ]
L2 = Lo2 + R2 [ F2-1 L1 + F2-3 L3 + …………………………….. + F2-n Ln ]
……………………………………………………………………………………
Ln = Lon + Rn [ Fn-1 L1 + Fn-2 L2 + …………………………….. + Fn-(n-1) Ln-1 ] (2)

or
1/R1 -F1-2 -F1-3 ………………………… -F1-n L1 Lo1/R1
-F2-1 1/ R2 -F2-3 ………………………… -F2-n L2 Lo2/R2
……………………………………………………. … = … (3)
……………………………………………………. … ….
-Fn-1 -Fn-2 -Fn-3 ………………………… 1/Rn Ln Lon/Rn
Here F1-n is the shape factor of finite area An with respect to entire area A1 and is defined as
the ratio of the diffuse flux received by An to the total flux emitted by A1 ie
Fn-1 = 1/π A1 ∬ cosØ cosØ dAdA1/r n 1 4
Where rn-1 is the distance between elemental area dA1 and dAn and Ø1 and Øn are the
angles of the normal to dA1 and dAn with the direction of rn-1 .
Shape factor between the variousaly oriented surfaces have reported by Hemilton and
Morgon[8], Gauffe [9], Biji [10], Oberien [11], Hottel [3], and Moon [1].
The finite difference method for the inter – reflection of light has been successfully applied
by Caracciolo [12], Dourgnon [13], Philips [14], Ingustin and Cenfeno [15], and Obrien and
Ross [16] and Oberin and Roward [17], mostly using a digital computer and solving the
equation either by iterative method or by transforming them to Kirochhoffs node equation
and using an analogue computer.
As simplifying assumption a room may be considered to be divided into two compartments
just above and below the mid level of the window through which light flux from the ground
and the sky may be assumed to be entering the upper and lower compartments respectively.
Fuether the two compartments of the system may be treated as bi-hemispheres of uniform
initial emittance for applying finite difference approach to radiation equilibrium between the
two hemispheres. Mean initial emittance may be computed by multiplying the flux above the
horizon by the mean reflectance of the upper compartment.
Suppose Ra and Rb are the respective mean reflectance of upper and lower compartments and
Loa and Lob the mean initial emittance factor of upper and lower compartments assumed to
be hemi – spheres, and then the final luminous emittances are given by the following finite
difference equation in the matrix form.
1/Ra -1 La Loa/Ra
-1 1/Rb Lb Lob/Rb
= (5)

So that
La = ( Loa + Ra Lob ) / ( 1- Ra Rb ) (6)
Lb = ( Lob + Rb Loa ) / ( 1- Ra Rb ) (7)
The internal reflected illuminance due to upper compartment on the horizontal plane
anywhere with in the upper compartment would be numerically equal to La on the horizontal
plane (facing the ceiling). For a plane located below the mid height of the window the inter –
reflected illuminance is contributed by a belt of the lower compartment above the reflectance
plane and also due to the whole of the upper compartment.
Arndt [18] applied Ulbricht theory of inter – reflection in an integrating sphere by making a
highly simplified assumption that room behaves as an integrating sphere of reflectance equal
to the mean diffuse reflectance of all the surfaces in a room. If F1 is the first reflected flux
and Rm the mean reflectance of the room surface and if F1 is assumed to be uniformly
distributed over the whole enclosure in the same way as in an integrating sphere of
reflectance Rm, then the total amount of the reflected and integrated flux Fr is given by
Fr = F1 + (F1 * Rm ) + (F2 * Rm ) Rm +………..
= F1 [ 1 Rm + Rm 2 +…………… ]
= F1 / ( 1- Rm ) (8)
Hence, the mean luminous emittance of the room surfaces and the average internal reflected
illuminance Er at any point inside the assumed uniform diffuser is given by
Er = F1 / A (1- Rm) (9)
Where A is the total area of all surfaces in the room and the first reflected flux F1 is obtained
by multiplying the total flux F entering the window with the mean reflectance of all the
surfaces in the room. In the finite difference approach for a six surfaces enclosure (1 ceiling,
2 floor, 3 east wall, 4 west wall, 5 south wall, and 6 north wall ), the matrix can be written as
follows.
1/R1 - F1-2 - F1-3 - F1-4 - F1-5 - F1-6 L1 Lo1/R1
- F2-1 1/R2 - F2-3 - F2-4 - F2-5 - F2-6 L2 Lo2/R2
- F3-1 - F3-2 -1/R3 F3-4 - F3-5 - F3-6 L3 = Lo3/R3 (10)
- F4-1 - F4-2 - F4-3 1/R4 - F4-5 - F4-6 L4 Lo4/R4
- F5-1 - F5-2 - F5-3 - F5-4 1/R5 - F5-6 L5 Lo5/R5
- F6-1 - F6-2 - F6-3 - F6-4 - F6-5 1/R6 L6 Lo6/R6

Figure1. Sketch of cubical building enclosure of size 3m*3m*3m provided with a
symmetrically located North facing window aperture covered with 3mm thick plain glass.
Figure 2. Bi- hemisphere of 4.16m diameter represented upper and lower halves of
the enclosure
Figure 3. Sphere of 4016m diameter and same mean reflectance and area as that
of the enclosure

Here, if the geometry of the enclosure is assumed as cubical, the shape factors between
parallel surfaces viz ceiling- floor, north – south walls, east – west walls are same ie.
F1-2 = F2-1 = F3-4 = F4-3 = F5-6 = F6-5 and have the value as 0.20 and rest all
others adjoining perpendicular surfaces have also same shape factor and have the value as
0.19 [22]. Here, the reflectance of the window wall has to be taken as area weighted
reflectance of glass and rest of the window wall which comes out to be 0.45.
3. Case study
For the study a cubical enclosure of diameter 3m*3m*3m has been chosen. The interior
finish of ceiling, walls, floor have been assumed as 0.7 (0.5), 0.5, 0.3 respectively
representing white ceiling, off white walls, and gray floor. The enclosure oriented with its
wall facing cardinal directions (viz. north, south, east, and west). A window having glass
reflectance of 0.15 and the dimension 1.5m*0.9m is supposed to be provided in the center of
the north facing wall at a sill height of 1.05m. It is also assumed there is no obstruction in
front of the window which implies that the light flux entering the glazed window is only from
the sky and ground.
If the cubical enclosure is divided into two equal parts from the mid level of the glass
window and these two upper and lower parts are assumed as hemispheres, the average
reflectance of the two upper and lower parts are Ra = 0.558, Rb = 0.425 and the matrix
equation for the assumed geometry of bi- hemispheres may be simplified as follows.
1/Ra -1 La Loa/Ra
-1 1/Rb Lb Lob/Rb
1/0.558 -1 La Loa/0.558
-1 1/0.425 Lb Lob/0.425
= (11)
= (12)
In the most simplifying approach of Arndt the shape of the cubical enclosure is assumed to be
a sphere such that its internal surface area is same as that of the cubical enclosure.
Such an equivalent sphere for the present case study has a radius of 2.08 m and average
reflectance as 0.49. Total internal surface area of the cubical enclosure as well as that of the
assumed equivalent sphere of radius 2.08 m is A = 54 m 2 .

4. Input data
North sky luminance (Ls) based on IDMP data taken as uniform luminance of 2545.5 Cd/ m 2
which produces window illuminance ( incident light flux on vertical window plane ) of pLs
/2 = 4000 lux (lm / m 2 ) .
Total outdoor horizontal illuminance from IDMP data has been taken as 16000 lux which for
ground reflectance of 0.2 result in ground luminance emittance of 16000* 0.2 or 3200 lm / m 2
(or equivalent luminance of 3200/p Cd / m 2 ). Assuming ground of infinite size the window
illuminance (incident light flux on vertical window plane) due to ground emittance of 3200*
lm / m 2 will be 3200*1/2 lux. Thus, the total window illuminance facing uniform north sky of
luminance 2545.5 Cd / m 2 and infinite uniform ground of luminous emittance of 3200 lm / m 2
respectively amounts to 2545.5 p/2( 4000) + 3200 *1/2 ie 5600 lux (lm / m 2 ). Similarly for
ground reflectance of 0.25 the window illuminance comes out to be 6000 lux. Accordingly,
for ground reflectance of 0.2 and0.25 the amount of flux entering the window of area 1.35 m 2
and glass transmittance as 0.85 are 6426 lm, 6885 lm respectively
The room surfaces viz. ceiling, floor, east wall, west wall, south wall, north wall each have
been divided into four equal parts. At the center of each of these surfaces elements sky
factors [20] have been determined for the north facing window of size 1.5 m* 0.9 m located
centrally in the wall at the sill height of 1.05 m. The reflectance of ceiling, walls, and floor
have been taken as 0.7 and 0.5 (white and off white finish ), and 0.3 (gray) respectively.
Table 1. Average Incident Flux Density in Lux (lm / m 2 ) at four points of each surfaces for
ground reflectance of 0.25
Ceiling Floor East/West Wall South Wall North Wall
142.1 283.6 90.3 125.1 0
142.1 283.6 180.3 125.1 0
75.1 150.3 41.6 250.9 0
75.1 150.3 83.6 250.9 0
180.6 216.9 98.1 187.6 0
Table 2. Average Incident Flux Density in Lux (lm / m 2 ) at four points of each surfaces for
ground reflectance of 0.2
Ceiling Floor East/West Wall South Wall North Wall
113.7 283.6 72.3 100.1 0
113.7 283.6 180.3 100.1 0
60.1 150.3 83.2 250.2 0
60.1 150.3 83.2 250.2 0
86.9 216.9 91.7 175.1 0

5. Result and discussion
For a cubical enclosure of size 3 m *3 m *3 m having symmetrically located north facing
window of size 1.5 m *0.9 m, incident flux density at four points on floor, ceiling and walls
have been computed from sky factor [20] and are given Table 1 and 2. The initial luminous
emittances are product of incident flux density and respective reflectance of each surface,
from which the final luminous emittances are obtained by solving the finite difference
equation in matrix form. The final luminous emittances of ceiling, floor and walls for ceiling
of 0.7 and 0.5 and ground reflectance of 0.25 and 0.2 are given in Table 3 &4. The
reflectances of walls, floor and glass have been taken as 0.5, 0.3, and 0.15 respectively. For
the purpose of bi- hemispheres approach the mean initial luminous emittances of upper half
and lower half of room enclosure have been estimated and final luminous of the upper and
lower halves approximated as bi – hemisphere have been determined from the corresponding
matrix equations. The mean initial and final emittances ob bi – hemisphere are given in Table
5. Finally the inter – reflected flux density (ie. Inter – reflected illuminance) has been
estimated at the center of the floor which are given Table 6.
Table 3. Initial and Final Luminous Emittance (lm / m 2 ) of Ceiling and Floor
Ceiling and Ground Ceiling Floor
Reflectance Initial Final Initial Final
Lo1 L1 Lo1 L1
Rc=0.7, Rg=0.25 76.0 145.7 65.1 97.8
Rc=0.5, Rg=0.25 54.3 101.0 65.1 93.5
Rc=0.7, Rg=0.2 60.8 125.6 65.1 94.7
Rc=0.5, Rg=0.2 43.5 87.1 65. 1 91.0
Table 4. Initial and Final Luminous Emittance (lm / m 2 ) of Walls
Ceiling and Ground East/West Wall South Wall North Wall
Reflectance Initial Final Initial Final Initial Final
Lo3/o4 L3/4 Lo5 L5 Lo6 L6
Rc=0.7, Rg=0.25 51.7 103.4 93.8 143.8 0 53.1
Rc=0.5, Rg=0.25 51.7 96.6 93.8 136.8 0 46.9
Rc=0.7, Rg=0.2 45.8 95.2 87.7 133.8 0 48.7
Rc=0.5, Rg=0.2 45.8 89.3 87.7 127.2 0 43.2
Table 5. Mean Initial and Final Luminous Emittance Upper and Lower Hemi-sphere
Ceiling and Ground Upper Hemi-sphere Lower Hemi-sphere
Reflectance Initial Final Initial Final
Loa La Lob Lb
Rc=0.7, Rg=0.25 46.7 109.6 66.0 112.6
Rc=0.5, Rg=0.25 39.5 100.0 66.0 108.7
Rc=0.7, Rg=0.2 37.2 97.0 66.0 107.3
Rc=0.5, Rg=0.2 31.4 86.4 66.0 104.0

Table 6. Inter – Reflected Flux Density in Lux (lm / m 2 ) at Centre of the Floor
Ceiling and Ground Finite Difference Bi-Hemispheres Integrating Sphere
Reflectance Approach
Rc=0.7, Rg=0.25 109.8 111.7 123.0
Rc=0.5, Rg=0.25 94.8 104.3 107.0
Rc=0.7, Rg=0.2 98.8 106.1 114.8
Rc=0.5, Rg=0.2 86.5 96.8 100.6
The integrating sphere results in higher values of inter-reflected illuminance which gives an
over estimate of about 13 to 15% from the measured values according to Narasimhan –
Sexena et al [21]. Also as seen from Table 6 the values computed from integrating sphere
approach are 12-16% higher than those obtained by finite difference approach. Accordingly,
it is inferred that the results obtained by finite difference approach closely conform with the
actual values. The values computed from bi-hemispheres approximation are slightly less than
those computed from integrated sphere formula but are upto 12% higher than precise values.
6. Conclusion
The finite difference approach to the solution of integral equation representing visible
radiation exchange and multiple reflection provides a precise method for computing interreflected
luminance in building enclosure. The effect of interior finish (surface reflectance )
on the inter- reflected illuminance, which make a significant contribution to the total
illuminance, can also be precisely evaluated by the proposed methodology.
The integrating sphere approach and bi-hemisphere approximation lead to an over estimate of
inter-reflected illuminance by 12 – 16% and upto 12% respectively and may be utilized for
the purpose of rough estimate only.
7. Acknowledgement
The author is grateful is grateful to Dr. P.K. Bhargava Chief Scientist and Coordinator
Efficiency of Building Division for constant encouragement and valuable guidance and Dr.
B. K. Saxena former Dy. Director CBRI and Coordinator International Daylight
Measurement Program (IDMP) for providing valuable suggestions and input data on outdoor
daylight levels. Thanks to Mr. Nagesh Babu for extending computer guidance and literature
support and to Dr. B. M. Suman for including the paper for presentation in conference. The
author is also thankful to CSIR for granting fellowship to pursue at CBRI Roorkee as well as
to the Director CBRI for providing all the necessary facilities and overall guidance.
References
1. Moon, P. (1961), The Scientific Basis of Illuminating Engineering, Dover Publication
Inc., New Yark.
2. Bukley, H..(1927), Philosophical Magazine London, volume 4, Pages 753-760.
3. Hottel, H.C., Keller, J.D.(1933), Transaction of the American Soc. of Mechanical
Engineers (Iron and Steel Div.), Volume 55-56, Pages 39-45.

4. Moon, p.(1941), J. Opt. Soc. America, Volume 31, Pages 375-380.
5. Lijima, T., (1949) The Japan Science Review, Volume 1, Pages 9-15
6. Moon, P., Spencer, D.B. (1948), Lighting Design, Addision Wrsky Press, Cambridge.
7. Yamutt, Z. (1926), ), J. Opt. Soc. America, Volume 16, pages 561-568
8. Hamilton, D.C., Morgan, W.R. (Dec. 1952), National Advisory Committee for
Aeronautics, Technical Note 2836.
9. Gauffe, A. (Sep. 1955), Cahieres du centre Scientifique et Technique du Bariment No. 27.
10. Ziji, R. (1951), Mannual of Illuminating Engineers on Large Sized Perfect Diffussers,
Philips Technical Publication, Eindhoven.
11. O’Brien,P.P.(1956), ), J. Opt. Soc. America, Volume 46, Pages 343-350.
12. Carracciolo, F.B.(1952), L” Ingegnere NO. 10, Italy.
13. Dourgnon, J.(Sep.1955), Cahieres du centre Scientifique etTechnique du Bariment No. 27
14. Philips, Ro., The Calculation of Inter-Reflected Illuminance and Lumiancesin room using
electronic computer, New Southwalves University of Technology, School of Architecture
(Sep. 1957).
15. Centeno, M, Zagustin, A. (1953), Inter- Refletance in two dimension Universal central
Venesuela Caracas.
16. O”Brien, P.P., Ross, D. B. (Jan. 1958), Luminous flux distribution with a cubical room,
University of California, Deptt. Of Ening., Los Angeles California.
17. O’ Brien, P.P., Howard, J. A.(1959) Illum. Enig., New Yark, Volume 54, P. 209-216.
18. Arndt, W. (1953), Proc. IB. Daylight Technical Committee France.
19. BIS, (1988), Handbook on Functional Requirement of Building (other than Industrial
Buildings), Parts 1-4, SP: 41, Bureau of Indian Standards Manak Bhavan, Bahadurshah
Zafar Marg, New Delhi.
20. Saxena, B.K. (1999), Daylight and IDMP data Directory of Lighting Industry in India,
Prakash 99, Published by ISLE (Indian Society of Lighting Engineers), Pages 75-90.
21. Narasimhan, V.., Saxena, B.K. , Majtreya, V.K. (1968), Inter- Reflected Component of
Daylight, Indian Journal of Pure and Applied Physics, Volume 6, No. 2, Pages 100-101.
22. Cengle, Y.A., (2007), Heat and Mass Transfer- A Practical Approach, Tata Mc Graw Hill
Compnies.

A Study on Stack Ventilation System and Integrated Approaches
Abstract.
Shiv Lal * , S.C. Kaushik*and P.K. Bhargava**
*Centre for Energy Studies, Indian Institute of Technology, Delhi
**CSIR-Central Building Research Institute Roorkee
* Corresponding author, E-mail address: Shivlal1@gmail.com
The better life style of society evidently demands huge energy. The building, transportation
and industries are major energy demand sectors where 39% energy is consumed by building
sector [14]. The ventilation & HVAC load of building can be reduced by adopting the stack
ventilation systems and integration techniques. There is immense opportunity for R&D
particularly in the application for enhancement of ventilation and thermal conditioning. This
paper communicates the method of reducing ventilation and cooling load of building by
application of solar chimney and integrated approach in modern buildings.
Key words: Ventilation, Solar chimney, roof solar collector, Earth air tunnel etc.
1. Introduction
The largest energy consumed by commercial and residential building apart from 33%
industry and 28% transportation as shown in figure 1. The energy is consumed in lightning,
heating, cooling, cooking, ventilation, washing, computer, and refrigerator, etc. whereas
heating and lighting are the major energy contributors. The end use contribution by
ventilation equipments in USA is 12% [10] but in India it is approximate 6% [16]. The
ventilation energy consumption is not a less amount so small energy saving in this field will
reduce the building energy load and help to save environment.
Figure1. Energy demand scenario. [14]

It can be possible by build a solar chimney in south side of building. The cause of selection of
south direction is that the building situated in north hemisphere. If wind flow is negligible i.e.
in metropolitan cities due to cluster of buildings, window services are ineffective then
ventilation can be enhanced through applying solar chimney technology and produce better
environment conditions.
The better environmental condition means more satisfying work place and gives more
productive workforce. The evidence of this statement is not found but differences were
described by Paul and Taylor in 2008 [22]. They studied two different universities building
and found HVAC retrofitted building was more thermally comfort but natural ventilated
building was having better air quality. In this study thermally discomfort is the negative
aspect in normal building but when we provide natural cooling (through EATH, adsorption,
absorption and evaporative cooling) will give better satisfying condition.
The energy consumption is less in green buildings as compared to conventional buildings.
The reduction of energy demand in building sector is an important goal in current scenario
and will be reviewed the architectural design of building. It has been used in urban planning
from last few years. Okeil [2010] has given the more energy efficient building forms. He
studied the various parameters responsible for increasing the winter solar exposure, reducing
the urban heat mitigation by channel flow or through improved air flow for which promoting
the green roofs [20].
This paper deals with the enhancement techniques of natural ventilation and performance
improving integration techniques of solar chimney as RSC and ETHE integration.
2. Conventional solar chimney
In a building air flows through an opening is due to (i) wind forces and (ii) thermal forces.
When wind strikes on building it creates positive pressure on windward wall and negative
pressure on leeward wall. If we provide window on both walls, due to pressure difference or
so developed aero motive force, wind starts flowing from higher pressure region to lower
pressure region and the space get ventilated. The rate of air flow increases with increase in
window area and becomes optimum at 40% area of floor area. Further increase in window
area, the increase in wind flow is insignificant. When wind speed is not sufficient to induce
natural ventilation by wind forces, then wind flow may be induced by thermal forces based
on the principle of stack effect.
To counter this problem of ventilation due to thermal forces, solar chimney can be formulated
in building. The schematic view of a simple solar chimney is shown in figure 2. The solar
chimney is working on the principle of buoyancy or stack effect where air is heated by solar
insolation. The solar chimney design is based on the fact that hot air rises up creates suction
effect and that replaces room air by ambient air. The solar chimney mainly made of a black
hollow thermal mass with opening at the top for exit the hot air and at bottom for entering the
room air. The air is passed through the room and exit from the top of chimney. The chimney
enhances the ventilation and reduces the temperature inside the room when damper operates
at position (1). It can work as reverse for heating the room in cold region when damper
operates at position (2) where chimney hot air can be circulated in room. The merits of solar
chimneys are; there is no mechanical part, Low maintenance, No electrical power

Consumption, No global warming, No Pollution and can be used for both heating and
cooling. Only one drawback is to increases the cost of building.
Figure2. Solar chimney used in building ventilation.
The solar chimneys have attracted much interest in various investigations in past two
decades. Bansal et al. [1993] analytically studied a solar chimney-assisted wind tower for
natural ventilation in buildings. The expected effect of the solar chimney was shown to be
extensive in inducing natural ventilation for low wind speeds.
Gan and Riffat (1998) have investigated solar-assisted natural ventilation with heat-pipe heat
recovery in naturally ventilated buildings using a CFD technique.
The natural ventilation and space conditioning enhancement methods for buildings have been
proposed by Barrozi et al [3], Hirunlabh et al [9], Alfonso [1], Drori [5], Khedari et al [24],
Ong [18] etc. The solar chimney have used for centuries particularly in Europe by Romans as
well as Middle East and north east by Persians [8].
3. Solar chimney and roof solar collector integration
The roof integrator solar collector means solar collector would be situated at top of roof. It is
different from trombe wall. Zhai et al. [30] suggested single pass and double pass roof solar
collectors (RSC) for two modes operation as space heating and natural ventilation mode as
shown in figure 3 (i) & (ii).
As per the constructional feature of the single pass RSC is given by the numbering and detail
in figure 3(i) where 1 & are damper, 3-glass cover, 4-absorber plate, 5-insulation plate, 6-air
channel, 7&10-tuyere, 8-air duct and 9-fan. The damper 1 & 2 are used to operate the system
in two different modes. The double pass RSC found 10% higher efficiency than the single
pass RSC.

(a) (b)
Figure3. (i) Structure of single pass roof solar collector (a) Space heating mode. (b) Natural
ventilation mode. [Zhai et al. 2004]
(c) (d)
Figure3. (ii) Structure of double pass roof solar collector (a) Space heating mode. (b) Natural
ventilation mode. 1—damper,2—damper, 3—damper, 4—glass cover, 5—absorber plate, 6—
insulation plate, 7—damper, 8—tuyere, 9—tuyere, 10—fan, 11-tuyere, 12—air channel 1,
13—air channel 2, 14—air duct.[ Zhai et al. 2004].
The roof solar chimney incorporates the full collector area. RSC is insulated against the room
when it operates in summer. There are many advantages of RSC as follows [Harris and
Helwig 2007]
1. It is more aesthetical and pleasing than tower
2. Large collector area easily achieved
3. No additional tower needed
4. Less cost that tower
5. Easier to retrofit
Some of disadvantages of RSC are: it restricted the stack height, heat transfer between glass
cover and air is higher than tower, higher pressure loss due to additional bends and
incorporate of additional thermal mass is more difficult.
An integrated approach of trombe wall and RSC can be used to increase the performance of
solar chimney or to increase the ventilation of building in summer and heating in winter. This
approach is shown in figure 4, where damper position 1 and 2 are used for ventilation and

space heating. This configuration gives better result than individual approaches of RSC and
conventional solar chimney.
Figure4. RSC and conventional solar chimney
4. Solar chimney and earth tunnel heat exchanger Integration
The soil temperature at the depth of 2-3 meter found stable and constant throughout the year
and it is approximately equal to the average annual ambient air temperature. Sharan and
Jadhav [2002] studied the soil temperature regimes of Ahmedabad India. The result of their
work is that the depth below 3 meter is suitable for earth air tunnel or Earth tunnel heat
exchanger (ETHE). The ETHE can be used in buildings for heating in winter and cooling in
summer up to some extent that surely reduces the energy bill. A schematic diagram 5 is
shown the earth tunnel heat exchanger.
(a) (b)
Figure5. Earth tunnel heat exchanger for conditioning of buildings. [Sharan and Jadhav
2003]
The ETHE is made of low cost mild steel pipe of moderate conductivity (45-65 W/m 2 K) as
shown in table 1, where rate of mild steel pipe is also compared with other pipes as per Indian
market.
The sharan and Jadhav [2003] have experimentally analyzed the single pass ETHE system
and found 3.3 COP in cooling mode and 3.8 COP in heating mode. The temperature of indoor

air was reduced up to 14ºC from maximum hot temperature in May-June and warm up to
26ºC (annual average air temperature) in December-January. Sodha et al. [1985] have
designed ETHE for a hospital in Mathura India having cooling capacity 512kWh and heating
capacity 269 kWh at air velocity of 4.89m/s. The Singh [1994] optimized and analyzed the
ETHE and found various parameters and constant required to design the system.
Table 1. Thermal conductivity and cost of some important pipe materials
S.No. Material Thermal
Conductivit
y (W/m 2 k) #
Density
(kg/m 3 )
#
Size (outer
diameter
for 2.5mm
thickness)
Mass of
pipe
(kg/m)
Approximate
Cost per
meter @
Rs USD
1. Aluminum 235 2712 4 ’’ 5.3 1500 29.34
2. Copper 400 8940 4 ’’ 17.49 5000 97.83
3. Cast iron 80 7000 4 ’’ 13.69 1200 23.48
4. Mild steel 61 7850 4 ’’ 15.39 599 11.72
(black)
5. Stainless steel 14 8000 4 ’’ 15.65 2500 41.91
6. Wrought Iron 102 7850 4 ’’ 15.39 1400 27.39
* using conversion values of Indian Rupees to USD from Monday, April 09,
2012(http://www.x-rates.com) @Rates as per Indian market Feb. 2012 and #
http://www.engineeringtoolbox.com
Figure 6. ETHE and vertical solar chimney
Mathur and Bansal [2009] used evaporative cooling to enhance the performance of ETHE.
The main advantages of the ETHE system is to conserve 1/3 rd energy of conventional AC and
100% fresh air circulated in the building. The integrated approach of conventional solar
chimney and earth air tunnel heat exchanger is shown in figure 6, where suction effect is

generated by conventional solar chimney and the cooling effect generated by earth air tunnel
and it gives better indoor air quality.
5. Solar chimney, RSC and ETHE integration
The individual approaches are described in above literature where individual system gives
lower performance and air quality but integrated approach gives better air quality for
individual summer and winter season. Two different integrated approaches can be coupled
and the proposed system can run whole year which shown in figure 7.
6. Conclusions
Figure 7. RSC, ETHE and vertical solar chimney
The green buildings are naturally ventilated with good quality air, thermally comfort energy
efficient buildings. This review is presenting the major energy conservation criteria other
than HVCs in buildings. The study have presented that the better environmental condition can
be achieved by integrated approach of conventional solar chimney, RSC and ETHE. Present
scenario is demanding group housing and energy where all these aspects must be included in
design for better living standard via energy conservation. The government should make rule
for adoption this approach in star rating of buildings to reduce energy demand and carbon
emissions and it will be helpful for sustainable future.
7. Future Scope
There is need to research in the field given below to improve performance of buildings
towards the side of energy conservation and comfort living etc.

There is a need to study the solar chimney with new alternate materials for low cost
glazing, chimney structure and wall insulation for intended task.
There is so need to study of various thermal energy storage options so as to make solar
chimney work continuously rather than day time only.
There is need to study the material selection, and underground work place thermal data
collection for ETHE.
There is need to study on implementation of vastu in architectural design.
8. Acknowledgement
The author (Shiv Lal) gratefully acknowledges University College of Engineering, Rajasthan
Technical University, Kota, Rajasthan (India) and IIT Delhi (India), for sponsorship under
quality improvement program of government of India.
References
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Buildings, pages 71-79.
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ventilation”, Building and Environment, volume 28, issue 3, pages 373-377.
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Buildings, volume 36, issue 9, pages 881-890.
6. Gan, G. and Riffat S.B. (1998), “A numerical study of solar chimney for natural
ventilation of building with heat recovery”, Applied Thermal Engineering, volume 18,
pages 1171- 1187.
7. Harris D.J., Helwig N. (2007), “Solar chimney and building ventilation”, Applied energy,
volume 84, pages135-146.
8. Hien V.D., Chirarattananon S. (2007), “Daylighting through light pipe for deep interior
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Abstract
Passive Cooling of Buildings
H.K.Jain*, P.K.Bhargava* and Shiv lal**
*CSIR-Central Building Research Institute, Roorkee
**Centre of Energy Studies, Indian Institute of Technology, Delhi
Corresponding Author, Email: jainhk55@gmail.com
The external climate (temperature, radiation, humidity, and wind) determines the heating and
cooling requirements of a building. Increased cooling load due to solar gain is generally the
main problem being faced by designers, but this can usually be taken care of by good
innovative design. Besides shading of windows from direct sun, especially on the east and
west facades, protection from diffused sunlight and reflected sunlight is also important. Solar
heat ingress through walls and roof can be reduced by using white or light colours, selective
paints etc on the exterior and by providing appropriate insulation. Shading by vegetation is
particularly effective because it also reduces heat island effect and the surrounding air is
cooled by transpiration. Several natural systems of creating an indoor heat sink by cooling the
structure by night sky radiation or by evaporation of water can be used to cool buildings with
negligible energy consumption. These cooling systems will be briefly described in relation to
their applicability in different climates.
Paper describes a variety of natural cooling techniques and various options available for low
energy cooling of buildings like natural ventilation, evaporative cooling, thermal mass,
nocturnal ventilation, phase change materials, or mechanical air conditioning etc. Salient
features of various studies on passive cooling techniques are discussed in this paper.
Keywords: Temperature, humidity, comfort, cooling, evaporative cooling, passive features
1. Introduction
With growing appreciation of energy conservation, efforts are being made all over the world
to evolve techniques of designing more energy efficient buildings having an inherent healthy
and comfortable indoor environment. Reduction in energy consumption in buildings can be
achieved in two different ways;
(i) by alleviating wastage in energy by the traditional inefficient and improperly designed
heating, cooling, ventilating and lighting appliances and
(ii) by optimum utilization of non-conventional renewable sources of energy like solar and
wind energy and by the integration of passive devices in the design of buildings for
comfort conditioning’.
These two approaches jointly contribute towards the overall energy efficiency of buildings.

Appropriate architectural design such as orientation of buildings, the location of fenestrations
with appropriate shading devices, creating a green belt of trees and vegetation around the
buildings for reducing heat island effect and cooling of ambient air appreciably improves
thermal performance by reducing heat load. Massive walls and high ceiling were common
passive features used to reduce the swing in temperature. Such proven energy conservation
features have now been forgotten by the building designers.
In view of the fact that a large population in developing countries like India, living in hot-dry
and in hot-humid conditions suffers serious thermal discomfort for a considerable part of the
year. The condition is worsened by the already inadequate and depleting sources of
conventional energy leading to ever increasing emphasis on the search for effective solutions
for low-cost cooling targeting innovative S&T concepts, materials and designs.
2. Comfort conditioning - basic techniques
Air-conditioning is a system of conditioning air by reducing or increasing its temperature and
humidity but it does not deal with the effect of excessively hot or cold structure on human
comfort. Comfort conditioning deals with both the building envelop as well as the ambientb
air. Thermal comfort is directly related to the conditions under which human body can give
off surplus metabolic heat. Human body gives off this heat by evaporation of sweat, radiation
and convection. At air 23 o C temperature and structure also at 23 o C, the heat loss due to these
avenues is 17% by evaporation 13% by radiation to cool structure and 70% by convection[1].
With air temperature at about 30 o C and structure at 52 o C heat is lost by evaporation 78%,
radiation 0% and convection 22%. But when indoor air temperature reaches above 37 o C and
structure is at 50 o C (common condition in
Indian houses in peak summer) body can
lose heat only by evaporation, aided by fan
as long as humidity is low, and gains heat
both from hot air and hot structure.
This is a highly uncomfortable situation.
Now, as the humidity goes above 65%
sweat does not evaporate fully and flows on
body surface. Such running sweat does not
help in heat removal as such it becomes
almost impossible for the body to give off
heat. However, heat loss by radiation
towards a cool structure is not affected by
ambient air temperature. Under these
situations if the structure is cooled down to
wet bulb temperature (about 25 o Figure -1:
C) a large
amount of body heat is lost by radiation towards the cool structure. Thus cooling of structure
plays very important role both in hot dry and hot humid conditions in summer, even under
high humidity, while the heat loss by radiation remains unaffected.
Human body has 98% absorptivity and emissivity in the infrared long wave region.
Therefore, it has a tremendous potential of absorbing heat from hot walls and ceiling and also
of radiating heat to cool walls and ceiling.

Table1. Percentage of actual heat loss to the environment by various avenues
Air
Temperature
( o C)
17.1
16.0
22.8
29.4
35.4
Wall
Temperature
( o C)
19.1
49.1
22.8
52.4
36.6
Percentage Heat Loss due to
Evaporation Radiation Convection
10
21
17
78
100
Several natural processes or a combination thereof, can be used to provide thermal comfort
in buildings which may include cooling by long-wave radiation towards night sky or a heat
sink, slowing the rate of heat flow, exchanging unwanted heat of a building by induced
ventilation through stored ‘çoolth’ of mild climates, cool dry nights or underground earth or
water which maintains a constant temperature throughout the year. In hot humid climates
with uncomfortable warm / humid nights, such ventilation can be counterproductive, and
there some type of solar air conditioning may be more cost effective
Although there are many strategies of natural cooling of buildings, the primary cooling
systems in relation to their applicability in different climate types are briefly described.
2.1 Convective cooling
Convective cooling implies cooling the structural mass of the building by air at night and
utilizing the cooled mass during the following day as a sink, to absorb heat entering into a
building or generated inside the building. During the day, interior ventilation is deliberately
kept as low as possible to avoid bringing in hot daytime air. As a result, the indoor
temperatures remain lower than those in a similar building without such convective cooling.
Convective cooling is being applied successfully in many regions with suitable climate
conditions. It is a proven cooling technique, but it is essential that the required building
design characteristics are achieved.
2.2 Nocturnal ventilation
Theoretical as well as experimental studies on assessment of contribution of night ventilation
towards cooling of buildings during the following day have been carried out by several
investigators for different types of structures under different climatic conditions. In 1992
Givoni [2] derived relationships for estimating the reduction caused in indoor minimum
(eq.1) and maximum temperatures (eq.2) caused by the provision of night ventilation for
medium and high mass buildings with light external colour and fully shaded windows.
It is also reported that potential of night ventilation for lowering the day time temperature
indoors below the outdoor temperature is proportional to the ambient diurnal temperature
range. It was observed that night ventilation has only a very small effect on the indoor
maxima of the low-mass buildings. However, it is very effective in lowering the indoor
maximum temperature for high mass buildings below the outdoor maximum. In case of the
particular buildings covered in the above studies, the maximum temperature in the low mass
building was 2 0 C above the outdoor maxima whereas in a high mass building the maximum
40
13
50
79
70
22

temperature was 2 0 C below the corresponding outdoor maxima when there was no night
ventilation in the buildings. The provision of night ventilation in low mass buildings resulted
in indoor maximum temperature which was very close to the outdoor maxima. In case of high
mass building, the night ventilation at the rate of 45 ach lowered the indoor maximum
temperature by 3.5 0 C when outdoor maximum temperature was 38 0 C . Extensive studies on
the effect of these parameters on the availability of indoor air motion have been carried out in
CBRI.
This type of cooling is applicable in regions with
vapour pressure below approximately 17 mm HG
and a large diurnal temperature range (above
approximately 10° C), where the day-time
temperature is above the comfort limit and the
minimum temperature is below approximately 20°C.
Under these conditions, daytime ventilation is not
desired. In order to secure effective convective
cooling, the envelope of the building should be wellinsulated
(average U value below approximately 0.67
W/m 2 °C) and have sufficient thermal mass.
2.3 Radiant cooling
Building envelope which gets heated during sunshine hours emits long wave radiation to sky
during night due to the fact that the mean radiant temperature of the clear sky falls below the
ambient air temperature. Thus heat in the building's structure is discharged by long-wave
radiation to the night sky, as a result of this; exposed building surfaces lose heat which
ultimately causes cooling of building. Roof having maximum exposure to sky is the most
effective radiative cooling part of the building envelope.
There are two primary types of radiant cooling systems. The first type is delivers cooling
through the building structure, usually slabs, these systems are also named thermally
activated building systems (TABS). The second type is systems that deliver cooling through
specialized panels. Systems using concrete slabs are generally cheaper than panel systems
and offer the advantage of thermal mass while panel systems offer faster temperature control
and flexibility. Radiant cooling systems are usually hydronic, cooling using circulating water
running in pipes in thermal contact with the surface. Typically the circulating water only
needs to be 2-4°C below the desired indoor air temperature [3]. Once having been absorbed
by the actively cooled surface, heat is removed by water flowing through a hydronic circuit,
replacing the warmed water with cooler water. Underground water which remains at about
23 o C (Roorkee) throughout the year can be used as the coolant in summer and as source of
heat in winters.
Radiant nocturnal cooling of a massive roof can provide effective cooling in almost all
climates, except in humid cloudy regions. This system can be applied only to one-storey
buildings, with a roof of high mass and high conductivity.
2.4 Roof surface evaporative cooling
Figure2. Solar Chimney for improving
indoor ventilation
It is well established fact that 60% to 80% of incident heat on buildings enters through the
roofs and only 20% to 40% heat enters either through the fenestration on exposed walls of a

single story building. Cooling caused due to evaporation of water has been used in a number
of ways for cooling the interior of buildings. It was revealed that evaporative roof cooling
could reduce the cooling load by 40 per cent in hot dry climates. Results of computation of
the interior surface temperature of a typical concrete roof treated by a controlled water spray
and an untreated roof indicate significant decrease in ceiling temperature due to roof
spraying. Further, controlled spraying was found to be more effective as compared to the
continuous spraying.
Roof-Surface-Evaporative technology developed at CBRI Roorkee [4] has been observed to
possess the potential of complete neutralization of total incident heat on roofs and the roof so
cooled act as a heat sink to the heat that enters through fenestration /exposed walls.
Figure 3. Effect of RSEC on exposed RCC roof and reversal of temperature gradient by RSEC
The technology consists of laying a thin uniform organic material lining (double layered
empty jute cement bags or 6 mm thick Coir matting in its natural colour) on either especially
designed or treated roof terraces, in their close contact. The lining is constantly maintained in
a just moist condition by electronically controlled spray of water, day and night throughout
the hot dry/ hot humid periods for continuous and
quick evaporation of water from the roof surface by
absorbing solar radiation in the day time and by
sucking out heat from indoor air at night. Necessary
gadgets both for manual or automatic operations have
been developed to accomplish the above
requirements. The water trapped in the jute bags/Coir
matting evaporates continuously at all temperatures.
This water is evaporated by solar heat absorbed by
roof aided by summer air movements. The incident
heat due to Sun’s rays on roofs is also consumed from
the evaporation of the water present in wet mattings
and therefore, the same cannot add to the heat content
of roof. Higher the incident heat of the sun and wind
speed on roofs higher will be the quantity of water
evaporated and higher will be the cooling effect.
Figure 4. Effect of RSEC on indoor air
temperature
The process is ideal for all types of buildings viz low cost, multi-storied, industrial,
conditioned or thermally uncomfortable buildings to bring appreciable saving in energy,
running & Capital cost of air-conditioning and increase human welfare, efficiency &
productivity. Water requirement varies from buildings to building depending on the actual
heat content and also on the climate conditions. The average requirement for a normal single
story building is 6 to 9 lit of water per sq meter of roof area per day under hot humid to hot
dry climates. It has been calculated, based on experimental results, that 1000 gallons of water
can produce cooling equivalent to nearly 900 tons of refrigeration with the proper installation
& utilization of the technology.

A complete know-how of the above system has been developed after successfully
implementing the cooling technology in more than two hundred buildings
(Unconditioned/Conditioned) single and up to five storied, industrial sheds of AC/G.I. Sheet
roofing including folded plate roofs at different parts of the country under different water
supply conditions. Among the various installations, the one on the roofs of Solar Energy
Centre, is the largest for which advanced automatic spraying system was designed by CSIR-
CBRI.
2.5 Earth air tunnel cooling
Near constancy of temperature at a few metre depth inside the ground has been in use for
cooling of buildings in hot climates in different parts of the world for centuries. It is reported
that temperature at a depth of 4 metre below the surface of the earth remains nearly constant
round the year. In summer the outdoor air is at a temperature higher than the temperature
inside the ground. Hence the outdoor hot air during its passage through a tunnel constructed
at a depth of about 4 metre below the earth’s surface gets cooled. This cool air is passed
through the building and thus the indoor environment is cooled.
It is well established that the cooling efficiency of the
aforesaid system depends, interalia, upon the length, size
and material of the pipe and its depth below the ground
surface, local climatic conditions and the rate of air supply
through the pipe. A study on assessment of heating and
cooling performance of earth tube heat exchanger for
moderate climates was carried out by Trombe et al [5].
The heat exchanger consisted of a PVC tube with external
and internal diameter equal to 0.20 and 0.19 m
respectively. This was buried at an average depth of 2.5 m
below the earth’s surface. The air flow rate through the
pipe was varied from 306 to 405 m 3 / h. It was observed
that the temperature at the exit of the pipe was higher for
the higher flow rates. The increase was higher when the
air blower was run round the clock as compared to the
increase observed with intermittent running of the fan. Hence a proper management of
running the fan is necessary for adequate functioning of the system. It was found that air from
the unconditioned room is effectively cooled by 3 0 Hot air in
|Air pump
Cool air out
Ground level
Figure5. Earth air tunnel cooling
C as it passes through the earth coupled
heat exchanger tube.
3 Other passive cooling features
Louvers, overhangs or awnings provided on windows help control direct entry of sun into the
room especially during summer months. Shading a building from solar radiation can be
achieved in many ways. Buildings can be orientated to take advantage of winter sun (longer
in the East / West dimension), while shading walls and windows from direct hot summer sun.
This can be achieved by designing location-specific wide eaves or overhangs above the
Equator-side vertical windows (South side in the Northern hemisphere, North side in the
Southern hemisphere). The walls exposed to sun shaded by providing appropriate texture
thereon or by erecting some external screen in front of the wall are effective to prevent direct
sun entry into buildings. Shading of roof which receives the maximum solar radiation as

compared to walls oriented in different directions has been recognized as an important step in
achieving reduction of external heat entry in buildings. One of the very effective method of
lowering the external surface temperature of the roof is to paint it with a coating which has
minimum absorption for solar radiation and high emission for long wave radiations. Few
passive features are described below:
3.1 Shading of roof
Roof receives the maximum solar radiation as compared to walls oriented in different
directions. Therefore, shading of roof has been recognized as an important step in achieving
reduction of external heat entry in buildings. Several methods have been attempted to exploit
this aspect of passive cooling. Planting of deciduous plants or creepers atop the roof is the
simplest method for shading the roof and lowering its temperature. It has been shown that a
well-designed green roof with a covering of plants having thick foliage and horizontal leaf
distribution acts as a high quality insulation and reduces the heat entry through roof in
summer. Experimental observations indicated that surface temperature of roof top without
vegetation were more than 15 0 C higher than that of the roof covered with vegetation.
Computation of heat flux through the roof also revealed that heat flux of 200 W/ m 2 entered
the room through the uncovered roof whereas at the roof section covered with vegetation,
about 10 W / m 2 was transferred upward from inside of the room[6]. Roof shaded by Roof
Surface Evaporative Cooling (para 2.3) can reduce roof top temperature of RCC slabs from
60 o C to nearly 30 o C in hot dry summers. A study conducted by Gupta [7] in Jodhpur showed
that a layer of closely packed small inverted earthen pots is very effective in reducing the
heat transmission through the roof in hot-dry climate. Investigations carried out in CBRI [8]
on heat flow through roofs demonstrated through field measurements that removable
insulation which can be rolled during night also contributes significantly towards reduction in
heat flow through roofs.
3.2 Shading of walls
The walls exposed to sun are shaded by providing appropriate texture thereon or by erecting
some external screen in front of the wall.
These provisions cut the direct solar
radiation on the walls and may also add to
the aesthetics of the building. Experimental
study carried out revealed that shading of
houses by nearby trees reduces the cooling
load and causes about 30 per cent reduction
in seasonal cooling energy.
Hayano [9] also reported that heat gain
through a wall is reduced by 75 per cent
simply by growing a thick layer of wines on
the wall. A row of trees is reported to
produce 50 per cent reduction in heat gain
through an adjoining West facing wall.
Figure 6. Shading of walls with trees and louvers

3.3 Shading of windows
Fig 7:Shading of windows located in different directions. Only rain shade for North facing windows
Extensive studies on development of shading
devices for windows have been carried out in
CBRI. Based on these studies, simple method for
designing appropriate shading devices for
windows with different orientations have been
evolved. This data has been included in BIS code
and also published in the form of a Building
Digest [ 10 ]. With this information in hand, it is
possible to design vertical louver or horizontal
louver or their combination to achieve complete
shading of a window at any desired station in the
country. Apart from louvers mounted externally on
windows, venetian blinds mounted thereon or
deciduous trees may also be used to prevent the direct entry of sun through windows.
Optimum dimensions of the louver depend on the duration of sunshine on the window façade.
Windows of the same dimensions but oriented differently should have different dimensions
of louvers to be effective. A simple box type of louver may be suitable on an eastern façade,
a slightly more complicated vertical and horizontal louver system on the southern façade and
egg crate type on the western façade. The northern façade receives only very early morning
or late afternoon sunshine and hence no elaborate systems are needed and only rain shade is
sufficient. It is reported [11] that overhang with optimum dimensions can produce cooling
load reduction of 12.7 per cent in summer without causing any sufficient change in sunshine
hours received in winter. It is worth mentioning that an overshadowing of the windows must
be avoided as it reduces availability of daylight indoors, which in turn results in increased
consumption of energy for artificial lighting.
3.4 Shading from blinds and trees
West-facing rooms are especially prone to overheating because the low afternoon sun that
penetrates deeper into rooms during the hottest part of the day. Methods of shading against
low East and West sun are deciduous planting and vertical shutters or blinds. West-facing
windows should be minimized or eliminated in passive solar design. Methods of shading
against low East and West sun are deciduous planting and vertical shutters or blinds. Westfacing
windows should be minimized or eliminated in passive solar design.

3.5 Painting of roof
One of the very effective method of lowering the external surface temperature of the roof is
to paint it with a coating which has minimum absorption for solar radiation and high emission
for long wave radiations. Studies carried out in Delhi [12] also showed that depending on the
level of ventilation, air temperatures within the white coloured buildings were 4 0 to 8 0 C lower
than the dark buildings during mid summer conditions. Study at CSIR-CBRI of roofs treated
with white glazed tiles showed a reduction of roof surface temperature by 25 o C, due to their
high reflectivity of solar heat. Estimation of reduction in energy consumed for cooling is
also a basis to assess the thermal
performance of heat reflective coatings. A
series of tests
carried out by Parker et al [13] in occupied
houses in Florida revealed that the drop in
consumption in air conditioning energy after
the application of reflective roof coatings
was around 19 per cent of the pre treated
situation. In a similar study carried out by
Akbari et al [14], it was found that changing
the roof albedo from 0.18 to 0.73 would
save about 23 to 80 per cent of cooling
energy during the entire cooling season.
Studies carried out in CBRI [15] have also
demonstrated considerable reduction in
energy consumption in cold storage
buildings by treating the roof and walls with white glazed tiles and heat reflective coatings.
3.6 Proper insulation of roof & walls and use of Phase change materials
In a climate that is cool at night and hot in the day, phase change materials can be
strategically placed inside the building structure to absorb latent heat of phase change to
liquid in the day time and gradually give it off at night as the material changes its phase back
to solid and gives off its latent heat of condensation which may be removed by radiationto the
cool night sky if needed. The process thus acts as an insulation which slows the heating of the
building when the sun is hot. Phase change materials can be designed to extract unwanted
heat during the day, and release it at night.
4. Conclusion
Figure 8. Heat reflective white glazed tile treatment on
roof
In developing countries of the world situated in/near the tropical zone more than 80%
population is forced to live and work in horrible thermal conditions. Thermally
uncomfortable conditions are not only harmful to the physical and mental development but
are a main cause of lower work output. The limited financial and energy resources of such
countries cannot provide comfortable living and working environment to their people without
the use of passive cooling techniques. The techniques can be integrated in the design of
buildings in an effective and acceptable manner without hampering the aesthetics of the
buildings. Natural cooling and cooling-load avoidance will not only help to conserve energy
and help reduce the adverse environmental impacts of fossil-fuel use but also satisfy
bioclimatic comfort requirements within the buildings. To promote the use of these

technologies nationwide awareness, dissemination and training activities are required to be
organized on priority. Sets of minimal meteorological data as well as information on thermal
properties of indigenous building materials are required. The adaptation and improvement of
traditional passive cooling and storage systems may offer useful solutions if adequate
research and development effort is put into the study of the subject. In this scenario hybrid
passive system emerges a viable option that may provide greater reliability and attract wider
application of passive techniques in the design of buildings in hot climate.
5. Acknowledgement
The study forms a part of the research programme of Central Building Research Institute,
Roorkee and the paper is published with the kind permission of the Director.
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Abstract.
Energy Efficient Building Technologies
An Approach towards Sustainable Development
Yogesh P Kajale * , Jalaj Parashar ** and Ajay Chourasia**
* BG Shirke Construction Technology Pvt. Ltd., Pune
** CSIR-Central Building Research Institute, Roorkee
Corresponding Author, Email: jalajp@rediffmail.com
With rapid growth in urbanization, sustainable development and utilization of resources is of
paramount importance, which can be addressed by development of proven prefab system for
mass housing construction. The developed system shall have edge in regards to safety,
speed, serviceability. The paper attempts to highlight the features of one of the prefab
system notably 3-S prefab building system. The sustainability aspect of building construction
vis-à-vis the prefab system of industrialize housing construction is elaborated. The system
describes use of prefab elements to a maximum possible extent with connections facilitated
through certain level of cast-in-situ concrete at project sites. The building system has been
evolved and perfected to cater to the seismic requirements as well as typical conditions
prevailing in India.
Keywords: sustainable, mass housing, prefabrication, 3-S system, precast, reverse cyclic
load, performance evaluation, and autoclaved lightweight cellular concrete.
1. Introduction
Construction industry is one of the largest consumers of natural resources such as water,
sand, crushed rock, gravel, minerals, timber etc. The demand for housing units, energy, clean
water & air, safe & rapid transport etc. is also increasing with the growing development.
Construction Industry is primarily dependant on certain manufacturing industries such as
cement, steel and aluminum; which are amongst the most energy intensive apart from major
consumer of scares natural resources. This calls for adoption of energy efficient technologies
for sustainable development in the construction leading to ‘Green Future’. Sustainable
construction encompasses the process which caters needs of the present without
compromising the ability of future generations. The sustainable technology of construction
therefore requires maintaining the harmony of the earth’s eco-system. The concept of
sustainable building construction is to incorporate technologies that result in environment
protection, water conservation, energy efficiency, usages of recycled products and renewable
energy. Such technology ensures that waste is minimized at every stage during construction
and operation of the building, resulting in low costs.

The prerequisites for energy efficient sustainable construction are:
Judicial use of construction materials there by requiring lesser materials i.e. products that
conserve natural resources
Use of energy efficient building materials and products that save energy or water i.e. the
materials requiring low energy for their production as well as will consume lesser energy
during life cycle of building
Use of products that avoid toxic or other emissions
Reduction in wastage of materials during construction of buildings& utilizing wastes to
make construction materials
Use of recycled aggregates in construction
Reducing emissions during the production of construction materials
Using more durable materials in buildings thereby requiring lesser maintenance cost
Use of products that contribute to a safe, healthy built environment
Use of construction system minimizing air, water and noise pollution during construction,
at the same with higher level of safety and speed.
To meet out the prerequisites, Prefab building techniques with building components made-up
of energy efficient technologies viz. AAC blocks/slabs, are the best proposition for building
construction on mass scale. The paper attempts to illustrate the features of above technology
with reference to energy saving.
2. Prefab technology – energy efficient proposition
2.1 The System
3-S prefab (Fig.1) solution for the housing sector includes following elements:
1. Precast RCC dense cement concrete slabs or Autoclaved light-weight energy efficient
cellular reinforced cement concrete slabs for floor and roof
2. Autoclaved light-weight energy efficient cellular cement concrete building blocks
3. Precast reinforced dense cement concrete structural components e.g. columns,
beams,toilet slabs, stairs, etc.
4. Galvanised powder coated press metal frames and shutters for doors / windows.
Figure1 View of 3-S Prefabricated
Building System

The technology makes use of the construction materials mainly precast RCC columns,
beams, lightweight autoclaved cellular reinforced cement concrete slabs / precast RCC slabs,
lightweight autoclaved cellular un-reinforced masonry blocks and galvanised powder coated
press metal frames and shutters for doors / windows, thereby eliminating demand of timber
and agricultural soilin construction. Moreover, due to factory manufacturing, lesser quantity
of water consumption is reduced drastically since autoclaving is resorted for curing under
controlled condition. Further, the prefabrication process yields very high repetition of formwork
(i.e. steel moulds); thereby resulting into very minimal consumption of raw material for
false work. Similarly, the construction raw material requirement is much less due to
production of lesser density materials having high ratio of strength/weight i.e. having higher
strength for lesser weight. The building elements of the system have low energy cost since
these are concrete, cellular concrete, cement and steel. The energy consumed for various
construction materials[1] for the present system is presented at Fig.2.
Figure 2. Embodied energy for various construction materials
Figure 3. Embodied energy for various masonry units

The system utilizes autoclaved aerated concrete (AAC) material for walling and floor / roof
slabs; which has very low energy consumption in itsproduction [2] (Fig.3).
2.2 Indoor air quality
Due to high insulating properties of lightweight autoclaved cellular concrete masonry blocks
and roof slabs, the solar heat transfer within the building is much less thereby making the
inside spaces more comfortable [3] . Fig.4 shows the inside temperature for AAC construction.
Figure 4. Outside Vs Inside temperature for AAC construction.
It can be seen from the Table-1that thermal efficiency of 125mm thick light weight
autoclaved cellular ‘Siporex’ roof slab is three times more than that of conventional RCC cast
in-situ roof slabs. This enables the end user to restrict the use of air-conditioning / fans to the
minimum, thereby requiring lesser electrical energy. Similarly thermal efficiency of 150mm
thick light weight autoclaved cellular ‘Siporex’ block masonry is two to three times more
than that of conventional masonry units like bricks / concrete blocks. All building designs
which have to take account of energy conservation need to consider the effect of the thermal
capacity of the building cladding / roofing. Calculations which take into account only the
thermal insulation of the fabric assume steady-state conditions which do not occur in practice.
Autoclaved lightweight cellular concrete provides useful thermal capacity combined with
good thermal insulation properties. This combination reduces the extremes of temperature
experienced in the building, compared with buildings made of lighter structures (e.g. metalframed
which have minimum thermal capacity) or heavier structures (e.g. solid brickwork /
concrete block work which provides less thermal insulation). During the warm season the
thermal capacity of an autoclaved lightweight cellular concrete roof of normal thickness
works in such a way that inside the building the rise of temperature due to solar radiation is
delayed by approximately 5-6 hours, counted from the time of day when the effect of solar
radiation is at its maximum. After this period, the effect of radiation decreases considerably.
The roof then emits its accumulated heat during the cooler part of the day. This reduction in

heating and cooling load requires less capacity from the heating or cooling equipment,
wherever used. Thus, by use of autoclaved cellular concrete slabs and masonry blocks the airconditioning
load is reduced substantially thereby reducing the capital investment towards
AC installation. The recurring cost of electricity bills are also considerably reduced for the
buildings constructed using ‘3-S’ system.
Table 1. Thermal efficiency for roofs with different construction material [5]
THERMAL TRANSMITTANCE (U) in W/(m 2 K) FOR
ROOF
Formfinish
RCC
roof
slab
RCC roof
slab with
ceiling
plaster
AACRoof
slab
Thickness of slab in mm 115 115 125
Thermal conductivity of slab material in W/(mK) 1.58 1.58 0.188
Internal surface resistance
{Considering inside film coefficient at still air = 9.36
W/(m 2 K)}
Outside surface resistance
{Considering outside film coefficient at an air velocity of
8.0km/h as 19.86W/(m 2 K)}
Internal ceiling plaster resistance
{Considering thermal conductivity of
0.721W/(mK)}
Brick bat coba resistance
{Considering thermal conductivity of
0.793W/(mK)}
External CM treatment resistance
{Considering thermal conductivity of
0.721W/(mK)}
RCC screed resistance
{Considering thermal conductivity of
1.58W/(mK)}
Thk. in
mm
0.107 0.107 0.107
0.050 0.050 0.050
0 10 0
Resistance 0.000 0.014 0.000
Thk. in
mm
75 75 75
Resistance 0.095 0.095 0.095
Thk. in
mm
25 25 25
Resistance 0.035 0.035 0.035
Thk. in
mm
0 0 30
Resistance 0.000 0.000 0.019
Slab material resistance Resistance 0.073 0.073 0.665
Total resistance 0.359 0.373 0.970
Thermal transmittance (U) in W/(m 2 K) 2.78 2.68 1.03
Maximum permitted value of Thermal transmittance
(As per IS: 3792)
Thermal efficiency
(Considering 100% for thermal transmittance of 2.33)
2.33 for 'Hot Dry', 'Hot Humid'
and 'Warm Humid' zones
84% 87% 226%

Table 2. Thermal efficiency for walls with different construction material [5]
THERMAL TRANSMITTANCE (U) in
W/(m 2 K) FOR EXTERNAL WALL
Burnt brick
wall
Solid
concrete
block wall
Autoclaved
cellular
concrete
block wall
Thickness of walling unit in mm 150 230 150 200 150 200
Thermal conductivity of walling material in
W/(mK)
Internal surface resistance {Considering
inside film coefficient at still air = 9.36
W/(m 2 K)}
Outside surface resistance {Considering
outside film coefficient at an air velocity of
8.0km/h as 19.86W/(m 2 K)}
Internal plaster resistance
{Considering thermal
conductivity of
0.721W/(mK)}
External plaster resistance
{Considering thermal
conductivity of
0.721W/(mK)}
Thk. in
mm
0.811 0.811 1.155 1.155 0.188 0.188
0.107 0.107 0.107 0.107 0.107 0.107
0.050 0.050 0.050 0.050 0.050 0.050
12 12 12 12 12 12
Resistance 0.017 0.017 0.017 0.017 0.017 0.017
Thk. in
mm
22 22 22 22 22 22
Resistance 0.031 0.031 0.031 0.031 0.031 0.031
Walling material resistance Resistance 0.185 0.284 0.130 0.173 0.798 1.064
Total resistance 0.389 0.488 0.334 0.378 1.002 1.268
Thermal transmittance (U) in W/(m 2 K) 2.57 2.05 2.99 2.65 1.00 0.79
Maximum permitted value of Thermal
transmittance (As per IS: 3792)
Thermal efficiency for 'Hot Dry' & 'Hot
Humid' zones (Considering 100% for
thermal transmittance of 2.56)
Thermal efficiency for 'Warm Humid'
zones (Considering 100% for thermal
transmittance of 2.91)
3. Energy consumption scenario for construction
2.56 for 'Hot Dry', 'Hot Humid' zones and 2.91 for
'Warm Humid' zone
100% 125% 86% 97% 257% 325%
113% 142% 97% 110% 292% 369%
The statistical study on energy consumption, projected demand and energy in transportation
of few construction materials in India is highlighted at Table-3, 4 and 5 respectively.

Table 3. Volume and energy consumption of building materials in India (2003) [6]
Material Production volume per annum
(2000)
Thermal Energy
(MJ per kg)
Total Energy
(GJ)
Bricks 150 x 10 9 Nos 1.40 630 x 10 6
Cement 96 x 10 6 tonnes 4.20 403 x 10 6
Aluminium 0.8 x 10 6 Nos 236.8 189 x 10 6
Structural steel 11 x 10 6 Nos 42.0 462 x 10 6
Table 4. Projected demand for building Table 5. Energy in transportation of building
Material[13] material [6]
Material 2020 Material Energy (MJ) for
100km transport
Bricks (Nos) 246 x 10 9
Bricks (Cum) 200
Cement (Tonne) 255 x 10 6
Structural steel (Tonne) 30 x 10 6
Rebars (Tonne) 15.3 x 10 9
3.1 Need for switchover to sustainable alternatives
Sand (Cum) 175
Cement (Tonne) 100
Structural steel (Tonne) 100
Steel, cement, glass, aluminium, plastics, bricks, etc. are energy-intensive materials,
commonly used for building construction. Generally these materials are transported over
great distances. Extensive use of these materials can drain the energy resources and adversely
affect the environment. It is therefore essential to adopt energy efficient innovative materials
and prefab technology to meet the ever-growing demand for buildings. There is an immediate
need for optimum utilization of available energy resources and raw materials to produce
simple, energy efficient, environment friendly and sustainable building alternatives and
techniques to satisfy the increasing demand for buildings.
Some of the guiding principles in adopting the sustainable alternative building technologies
can be summarized as follows: Energy conservation; Minimize the use of high energy
materials; Concern for environment, environment-friendly technologies; Minimize
transportation; Decentralized production and maximum use of local skills; Utilization of
industrial and mine wastes for the production of building materials; Recycling of building
wastes, and Use of renewable energy sources. Time-tested prefab building technologies like
3-S, meeting these principles could only be sustainable and will facilitate sharing the
resources especially energy resources more efficiently, causing minimum damage to the
environment.

3.2 Energy efficient: thermal mass benefits
High thermal mass of precast concrete enables it to absorb, store and later radiate heat. Also,
using precast concrete in passive solar designs allows natural heating in winter and cooling in
summer, thereby reducing the need to rely on artificial heating and cooling.
3.3 Improved internal building amenity
Use of precast concrete can even out internal diurnal building temperatures.3-S Prefab
technology having light-weight cellular concrete elements for slabs and walling can improve
indoor air quality, providing comfortable temperature inside the home.
3.4 Acoustic performance
The high thermal mass of precast concrete assists with sound insulation to reduce noise and
absorb noise impact.
3.5 Environmental sustainability of Prefab
High thermal insulation results in achieving energy efficiency resulting in safe & durable
Green building Construction
4. Conclusion
The ‘Prefab technology for sustainable building’ movement is advancing at a rapid pace in
other parts of the world and is yet to take accelerating mode in India. Considering the
tremendous technological, energy efficiency and ecological benefits such prefab buildings
systems can result a milestone for sustainable development. By adopting prefab building
technology, using light weight building materials such as AAC to the extent possible, cement
replacement materials such as fly ash in concrete, designing for durability as well as
undertaking life cycle analysis of construction projects, it is possible to direct the construction
industry, a more sustainable path with higher energy efficiency.
5. Acknowledgment
The authors are grateful to Director, CBRI for granting permission to publish the paper.
References
1. Atlas Environment du Monde Diplomatique (2007); Federation of Natural Stone
Industries (SN Roc); CTBA, L, Essentielsur le bois (2001)
2. W. Marmé and J. Seeberger; AAC data from Dr. Briesemann und Dr. Frey (1997)
3. CEB (1987), “Autoclaved Aerated Concrete”, CEB Manual of Design and Technology,
The Construction Press, Lancaster
4. IS: 3792, “Guide for Heat Insulation of Non-Industrial Buildings”, BIS, New Delhi

5. Jain R.K., Asthana K.K., Gupta Manorama (1989), “Evaluation of Anticorrosive
Treatment on Steel Reinforcement in SIPOREX Concrete” Central Building Research
Institute, Roorkee AND Sharma T.P., Lal B.B. (1997), “Fire Performance Evaluation and
Upgradation of SIPOREX Slabs, Blocks and Panels” Central Building Research Institute,
Roorkee
6. Reddy Venkatarama B.V. (2004), “Sustainable building technologies” Current Science,
Vol. 87, NO. 7
7. National Buildings Organization (1990), “The Handbook of Housing Statistics Part – 1”,
New Delhi, India

Abstract
Considerations for an Energy Efficient Building Design
Karamjit Singh Chahal
Guru Nanak Dev University, Amritsar, India
Corresponding Author, Email: kschahal@rediffmail.com
Energy efficiency and sustainable design features has become extremely important in
buildings because of the growing demand for energy and a wide gap between demand and
supply Buildings account for 40% of energy consumption in most countries and their
potential for energy efficiency is huge. Efficient use of energy is important since global
energy resources are finite and power generation using fossil fuels (such as coal and oil) has
adverse environmental effects. The huge potential of energy efficiency in buildings has been
recognised. By using well-proven energy efficiency measures, 70 to 90 % of a building’s
energy need for heating or cooling can be cut. Energy efficient building design is locationdependent.
The local climate must be considered when selecting appropriate design
strategies. characteristics of an energy-efficient building includes: well-insulated walls, a
ventilated roof with a thick layer of insulation over the ceiling, quality windows with low-
Emission glass, and a high-efficiency heating and cooling system. This paper is an attempt to
summarise various passive cooling techniques for the practicing architects and students of
architecture to promote the awareness of the subject and present methods for incorporating
these measures into their designs.
Key words: passive cooling technique; stack effect; Energy efficiency; energy efficient;
earth tunnels
1. Introduction
In traditional building construction methods energy
conservation measures were often ingenious and simplistic;
these were also healthy and effective as they required
minimal human intervention, involving zero energy use e.g.
ventilation, stacks. Architects are today faced with a greater
challenge. Energy demand is ever on the increase. Energy
conservation is however not merely about reducing energy
demands from the national infrastructure or energy bills,
but it is more about preserving the environment for our
coming generations. Energy conservation and the
environment protection are key issues
Figure 1. Fuel share of Energy
Consumption in India,) Source:
Energy Information Administration

facing the building professions worldwide. There has
been a steady increase in the use of energy in India and
energy conservation is of crucial both economically and
environmentally. Presently, construction industry is
developing at a rapid pace. With the increase in
population, improved living standard, the energy
consumption in buildings is increasing day by day [1].
Almost 29% of the electricity generated is consumed in
the building sector in India and the consumption rate is
increasing at rapid pace 9 . Buildings are one of the biggest
energy consumers in the world, accounting for one-third of
all energy use and a similar amount of greenhouse gas Figure 2. Energy Consumption by
emissions. Passive design methods contain optimising solar Various Sectors in India, Source:
orientation, heat insulation, shape, structure, shading and Central electricity authority, 2009
natural ventilating of buildings, etc. and minimise use of
conventional energy to create comfortable living environment. Passive cooling strategies can
take on the heat and humidity load of the building partly [1].
2. A Growing demand for energy
India is one of the fastest growing economies in the world, with this development the energy
requirements are also growing at a rapid pace. India currently ranks sixth in the world in
terms of primary energy demand. As per the Planning Commission’s integrated energy policy
report (Planning Commission 2006), if India maintains economic growth rate of 8% of GDP
per annum through 2031-32, its primary energy supply will grow by 3 to 4 times, and
electricity generation capacity by 5 to 6 times compared to 2003-04. It is estimated that by
2031-32, the country’s power generation capacity would be 800,000 MW from a current level
of 160,000 MW. Central Electricity Authority (CEA) has estimated that the country is
currently facing electricity shortage of 9.9% and peak demand shortage of 16.6% (CEA
2009). While it is essential to add new power generation capacity to meet the nation’s
growing energy requirements, it is equally important to look out for options which would
help in reducing energy demand for various end-use sectors. The energy efficient building
design is the need of the hour as there are serious economic and social costs for letting the
energy shortage go unaddressed. Since buildings account for approximately 33% of
electricity consumption and is the fastest growing sector, it is critical that policy interventions
are put in place to improve energy efficiency in both new construction as well as existing
buildings [2].
3. What makes buildings energy efficient?
The basic principle of building energy efficiency is to use less energy for heating, cooling,
and lighting, without affecting the comfort of the occupants. High-performance buildings not
only save energy costs and natural resources, but also provide a better indoor environment.
The benefits of building energy efficiency include:
Reduced resource consumption: Improving building energy efficiency significantly reduces
demand for electricity.
Minimized Life-cycle Costs: Improving building energy efficiency reduces the amount of
energy required to operate a building and also reduces costs for building occupants.

Reduced Environmental Impact: Improving building energy efficiency reduces the need for
fossil fuels and reduces greenhouse gas emissions [3].
Passive systems provide thermal and visual comfort by using natural energy sources and
sinks e.g. solar radiation, outside air, sky, wet surfaces, vegetation, internal gains etc. Energy
flows in these systems are by natural means such as by radiation, conduction, convection with
minimal or no use of mechanical means. The solar passive systems thus, vary from one
climate to the other e.g. in a hot climate the primary aim would be to reduce solar gains,
maximise natural ventilation, but in a cold climate an architects’ aim would be design a
building in such a way that solar gains are maximised, and so on. The two broad categories of
Passive concepts are as follow
a) Passive cooling concepts (evaporative cooling, ventilation, wind tower, earth-air tunnel,
etc.).
b) Passive heating concepts (direct gain system, indirect gain system, sunspaces, etc.)[4]
4. Fundamental planning decisions
The comfortable living conditions in a building can be provided by active systems and/or
passive systems. The active systems generally consist of electricity powered equipments
which consumes significant energy. It is not always
necessary to install active system to provide
acceptable thermal condition indoors. Good thermal
insulation, low proportion of glazing, outdoor solar
shading, the use of thermal mass, night ventilation
and alternate cooling/heating technologies can
sometimes jointly minimise the need for active
system. These forms of passive climate controls need
less energy, for cooling as well as heating, and make
the indoor environment more stable.
Even in combination with an active climate control
system, good passive design can make the
environmental conditions more comfortable. Passive
cooling works on two basic concepts [5]:
Minimizing heat gain and
Rejecting unwanted heat
Protection from sun
Figure 3. A reduction of the summer
cooling load may be obtained, in the
planning stage, by having recourse to
bioclimatic strategies.
Heat-gain control is simple and effective strategy. It involves intervening the external setting
by means of reducing the impact of solar radiation and internal heat gains. The simplest and
most effective passive cooling techniques include:
Protection from the sun for windows, walls and surface covers, by using artificial or
natural screening devices;
Provision of adequate ventilation.
Reduction of outside temperature by intervening on the external setting in close proximity to
the building by means of:
Increase of relative air humidity by means of ponds, fountains and vegetation.

Shading through planting schemes (trees, pergolas, etc.).
reduction of external sun-glare (creation of green areas).
Choice of light-coloured scheme for exterior walls[6].
5. Passive cooling features
Architects can achieve energy
efficiency in the buildings by studying
the macro and micro climate of the
site, applying bioclimatic architectural
principles to combat the adverse
conditions, and taking advantage of
the desirable conditions. Passive
cooling systems rely on natural heatsinks
to remove heat from the
building. They derive cooling directly
from evaporation, convection and
radiation without using any Figure 4. Passive cooling techniques
intermediate electrical devices. All
passive cooling strategies rely on daily changes in temperature and relative humidity. The
applicability of each system depends on the climatic conditions. Design elements that directly
or indirectly affect thermal comfort conditions and thereby the energy consumption in
building are
Site Selection
Landscaping
Shading
Orientation
Building Form
5.1 Site selection
Evaporative cooling
Building finishes
Ventilation
FenestrationMaterials
A large amount of energy is spent on transportation of people from work place to home, by
locating residential areas near to workplaces, schools, public transport routes, etc. transport
energy consumption can be reduced. The selection of a site which is north south facing is
better for passive solar cooling. In rural areas there may be potential for renewable energy
sources other than solar, for example the use of biogas[7].
5.2 Landscaping
Landscaping is an important element in changing the microclimate. Landscaping design can
reduce direct and indirect heating up of building surfaces. Landscaping also creates different
airflow patterns and can be used to direct or divert the wind advantageously by causing a
pressure difference. Additionally, the shade created by trees and the effect of grass and shrubs
reduce air temperatures adjoining the building and provide evaporative cooling. Terrace
gardens can help to reduce heat loads in a building. The ambient air under a tree adjacent to
the wall is about 2 °C to 2.5 °C lower than that for unshaded areas, which reduces heat gain
by conduction [4].

5.3 Shading
When landscaping is impractical on a given site, combinations of
overhangs, awnings, exterior shades, venetian blinds, curtains and drapers
can be used effectively for shading. The effectiveness of sun shades is not
uniform on all directions and therefore glazed areas should be provided
only in those positions where effective protection against the sun can be
ensured. To reduce heat gain through glazed areas these should be kept to
the optimum for good day light.
Shading against direct radiation is easiest to provide on the south
wall. A horizontal projection of at least half the window height
will exclude the summer sun while still permitting sun light in
the building in winter.
Mitigation of heat through roof and the east/west walls requires a different approach.
Since the sun is low in the horizon during sunrise and sunset, overhangs are not effective
and vertical louvers, or a movable screen is a better option. Vegetation is perhaps the
most effective way of keeping the intense morning and afternoon sun off the east and
west walls and windows, but care must be taken to avoid blockage of night time summer
breezes that can be part of the diurnal cooling strategy.
The north wall can be protected by vertical louvers.
The roof can be shaded only by a horizontal cover extending over the whole roof and
projecting beyond it on the east, west and south sides [5].
5.4 Orientation
Winter Spring Summer Autumn
Figure 6. Natural protection from the sun ensured by means of suitable
Figure 5. Shading of
wall
Building orientation is a significant design consideration, mainly with regard to solar
radiation and wind. In predominantly hot regions, buildings should be oriented to minimize
solar gain and to keep out the sun's heat from entering the building; the reverse is advisable
for cold regions. The fact that the sun is lower in the sky in winter than in summer allows
architects to design and construct buildings that capture heat in winter and reject it in
summer. The orientation of the building plays an important part; the ideal orientation for hot
and dry climates should be to keep long axis of the building North-South. This will reduce
the heat gain. Conversely, buildings with their long axis running East-West will have higher
heat gain and will require obviously high energy costs for cooling 5 . In regions where seasonal
changes are very pronounced, both the situations may arise periodically. Similarly, wind can
be desirable or undesirable. Quite often, a compromise is required between sun and wind
orientations. With careful design, shading and deflecting devices can be incorporated to
exclude the sun or redirect it into the building [4].

5.5 Building form
A compact building form with minimum surface to volume ratio is best for reducing heat
gain/loss and affects the thermal performance of the building. Surface-to-volume ratio is
determined by the building form. For any given building volume the more compact the form,
the less wasteful it is in gaining/losing heat. Hence, buildings compact in form with a low
S/V ratio reduce heat gain and losses respectively. However, a rectangular building with one
of the longer facades facing north allows enhanced passive solar cooling, day-lighting and
natural ventilation[7]. The building form determines the airflow pattern around the building,
directly affecting its ventilation. The depth of a building also determines the requirements for
artificial lighting, greater the depth, higher the need for artificial lighting.
5.6 Evaporative cooling
Water is a very good changer of microclimate. It takes up a large amount of heat in
evaporation and causes significant cooling especially in a hot and dry climate. Evaporative
cooling lowers indoor air temperature by evaporating water. It is effective in hot-dry climate
where the atmospheric humidity is low. In evaporative cooling, the sensible heat of air is used
to evaporate water, thereby cooling the air, which in turn cools the building interiors. Increase
in contact between water and air increases rate of evaporation. The presence of a water body
such as a pond, lake, sea etc. near the building or a fountain in a courtyard can provide a
cooling effect[7]. Water has been used very effectively as a modifier of microclimate in many
buildings in India e.g. Lake palace Udaipur
5.7 Building finishes
Light-colour paints and finishes on the roof and the walls
have low absorption coefficient. This has an important
advantage of reflecting more heat than darker materials do.
A white roof may absorb only 25 percent of solar heat, far
less than the 90 percent absorbed by a black one. This
greatly reduces the amount of heat getting into the building.
Whitewash with lower reflectivity will stay cooler when
exposed to solar radiation because of its very high
emissivity. Roof surfaces, which are exposed to solar
radiation for long hours in summer, should be painted
white[5].
5.8 Ventilation
Figure 7. Light coloured Dark Surface
Surface
Adequate ventilation is essential to provide fresh air and to Figure 8. Natural ventilation
remove moisture, odours and pollutants. A constant supply of
fresh outdoor air can provide a good indoor air quality and improved comfort. Outdoor
breezes create air movement through the house interior by the ‘push-pull’ effect of positive
air pressure on the windward side and negative pressure (suction) on the leeward side. Good
natural ventilation requires locating openings in opposite pressure zones. Stack effect can be
used to enhance natural ventilation. With openings near the top of stacks, warm air can
escape whereas cooler air enters the building from openings near the ground[4].

5.9 Fenestration
Fenestration design is primarily governed by requirements of heat gain and loss, ventilation
and day lighting. The important components of a window that govern these are the glazing
systems and shading devices. Windows and other glazed areas are most vulnerable to heat
gain or losses. Proper location, sizing, and detailing of windows and shading form an
important part of design as they help to keep the sun and wind out of a building or allow them
when needed. The location of openings for ventilation is determined by prevalent wind
direction. Openings at higher levels naturally aid in venting out hot air. Size, shape and
orientation of openings moderate air velocity and flow in the room; a small inlet and large
outlet increase velocity and distribution of airflow through the room. When possible, the
house should be so positioned on the site that takes it advantage of prevailing winds. There
should be sufficient air motion in hot humid and warm humid climate. In such areas, fans are
essential to provide comfortable air motion indoors. Fenestrations having 15 to 20% of floor
area are found adequate for both ventilation and daylighting in hot and dry, and hot and
humid regions[4].
5.10 Materials
Choice of building materials is very important in reducing the energy contents of buildings.
Reducing the strain on conventional energy can be achieved by low-energy buildings with
low-energy materials. The embodied energy of a product is the energy used to produce it, and
includes energy used in extracting raw materials, processing and transport, e.g. Indian timber
will incur lower transport energy use than timber imported from overseas. Building
components should be designed for long life and durability, and ideally should be recyclable
at the end of their operating lives 7 . Use of materials with low embodied energy also form a
major component in energy-efficient building design.
6. Construction techniques
An energy efficient building balances all aspects of energy use in a building: lighting, space
conditioning and ventilation, by providing an optimised mix of passive solar design
strategies, energy efficient equipments, renewable sources
of energy and construction techniques. Reduction of heat
transmission in the building can be achieved by
construction techniques like [4]
Thermal Insulation
Cavity Walls
Wind Tower
Courtyard Effects
Roof Sprinkling
Earth Air Tunnels
Passive downdraught cooling
6.1 Thermal insulation
Figure 9. Thermal Insulation of terrace
Insulation is of great value when a building requires mechanical heating or cooling and helps
reducing the space-conditioning loads. Location of insulation and its optimum thickness are
very important. In hot climates, insulation is placed on the exterior face of the wall so that
thermal mass of the wall is weakly coupled with the external source.

6.1.1 Roof
The roof receives significant solar radiation and plays an important role in heat gain/losses.
Depending on the climatic needs proper roof treatment is very essential. In a hot region, the
roof should have enough insulating properties to minimize heat gains. Some roof protection
methods are as follows
A cover of deciduous plants or creepers can be provided. Evaporation from leaf surfaces
will keep the rooms cool.
The entire roof surface can be covered with inverted earthen pots. It is also an insulating
cover of still air over the roof.
Roof should be painted white to minimize the radiation absorbed by the roof and
consequent conductive heat gain through it.
6.1.2 Walls
Walls are a major part of the building envelope and receive large amounts of solar radiation.
The heat storage capacity and heat conduction property of walls are key to meeting desired
thermal comfort conditions. The wall thickness, material, and finishes can be chosen based on
the heating and cooling needs of the building. Appropriate thermal insulation and air cavities
in walls reduce heat transmission into the building, which is the primary aim in a hot region.
6.2 Cavity walls
Air cavities within walls or in the roof ceiling combination reduce the solar heat gain factor,
thereby reducing space-conditioning loads. The performance improves if the void is
ventilated. Heat is transmitted through the air cavity by convection and radiation.
6.3 Wind tower
In a wind tower, the hot ambient air enters the tower
through the openings in the tower, gets cooled, and thus
becomes heavier and sinks down. The inlet and outlet of
rooms induce cool air movement. The tower walls absorb
heat during the daytime and release it at night, warming the
cool night air in the tower. Warm air moves up, creating an
upward draft, and draws cool night air through the doors
and windows into the building. The system works
effectively in hot and dry climates where diurnal
variations are high.
6.4 Courtyard effects
Due to incident solar radiation in a
courtyard, the air gets warmer and
rises. Cool air from the ground
level flows through the openings
of rooms surrounding a courtyard,
thus producing air flow. At night,
the warm roof surfaces get
cooled by convection and
Figure 10. Building-integrated chimney in
Sudha & Atam Kumar’s residence in New Delhi
Figure 11.Courtyard as a moderator of internal climate

adiation. However, care should be taken that the courtyard does not receive intense solar
radiation, which would lead to conduction and radiation heat gains into the building.
6.5 Roof sprinkling
In many buildings particularly with flat roofs; a main part of the external heat gains comes
from the roof. Roof sprinkling is based on evaporation of a water mist layer created by
misting spray heads on roof of the building; when the water evaporates, it absorbs large
amounts of heat[5].
6.6 Underground earth tunnels
Ground cooling system involves the concept of
routing air through underground metal or plastic
tubes or chambers. The idea is that as the air travels
through the pipes, it gives up some of its heat to the
surrounding soil, and thus entering the space as
cooler air. The surrounding earth insulates them,
which helps in maintaining a more or less constant
temperature. Temperatures at roughly 4 metres
below the surface are stable and reflect the average
annual temperature of a place. However the tunnels
cannot remove the excess humidity from the air
during the monsoon and hence its efficiency drops
in the humid summer and monsoon period[10]. Tubes made of aluminium, plastic, and other
materials are being used. The choice of material has little influence on thermal performance.
Optimum tube diameter varies widely with tube length, tube costs, flow velocity, and flow
volumes. The various installations use tubes anywhere from 4 to 18 inches. There is no
simple formula for determining the proper tube length in relation to the amount of cooling
desired. Local soil conditions, soil moisture, tube depth, and other site-specific factors should
be considered to determine the proper length. The longer you make the earth tube, the closer
the air flowing through the tube and finally gets to the earth temperature, length of around 75
to 100 ft is considered to be optimum. The temperature change in the tube air after 150 ft
length appears to be small. Pipes must be laid at a depth of at least 6 ft; for best possible heat
transfer, pipe should be laid in solid ground (not laid in sand). Make sure the ground is well
compressed around the pipes and the pipes are to be laid at least 3 ft from the building and
from each other with approx 2 % gradient.
6.7 Passive downdraught cooling
It is an evaporative cooling that has
been used for centuries in many parts of
the world, e.g. Iran, India and Turkey. In
this system, wind catchers guide outside
air over water-filled pots, inducing
evaporation and causing a significant
drop in temperature before the air
enters the interior. Such wind catchers
Figure 12. Passive Space Conditioning
Using Earth Air Tunnel System
Figure 13. Torrent Research Centre Schematic Section
in Ahmedabad,
become primary elements of the architectural form also. Passive downdraught evaporative

cooling is particularly effective in hot dry climates. Ahmedabad based architects Parul Zaveri
and Nimish Patel (Abhikram Architects) known for green buildings and sustainability
designed the Torrent Research Centre in Ahmedabad in 2000, a project is hailed as one of the
successful experiments of passage cooling in India. A successful case study for green
projects, it is estimated that the additional expenditure for sustainable design elements has
been recovered in less than one year, the successful returns can be proven from the fact that
from the savings of the electrical costs,; the cost of all the buildings will be recovered in 13
years and the entire investment in the research activities will get recovered in 39 years[11].
7. Design Energy-Efficient Lighting and HVAC System
When the passive architectural concepts are applied in a building, the load on conventional
systems (HVAC and lighting) is reduced. Further, energy conservation is possible by
judicious design of the artificial lighting and HVAC system using energy efficient
equipments, controls and operation strategies. Energy-efficient lamps and fittings should be
used in areas where lights are likely to be switched on for long periods. All electronic and
electrical appliances are now required by law to display Energy Labels indicating their
energy efficiency. These labels can assist the purchaser in selecting an energy efficient
model.
8. Performance Parameters of conventional and energy efficient buildings
The Table 1 compares the design features, lighting system, Air conditioning and energy performance
of conventional and energy efficient buildings, The Energy Performance Index (kWh/m2) of energy
efficient buildings is very low as compared to the conventional buildings. The features that contribute
to low energy consumption are as follows:
North–south orientation
Shading of the west façade
Shading of roof
Large window openings on north–south façade
Least exposure and windows on east–west façade
Natural ventilation for circulation areas
9. Conclusion
Every project today has energy efficiency as a major consideration. For an energy efficient
building, efficient use of energy design is not an afterthought; it is a major design
consideration that impacts design decisions at every stage from conception to completion.
The Incorporation of simple energy efficient measures in buildings can reduce a significant
amount of energy consumption. We can improve effectively the indoor thermal environment,
meet the ventilation requirement and create comfort conditions through passive cooling
strategies. For the passive cooling strategies, the regional climate analysis is very important.
Both the effective application of passive cooling methods and the reasonable application
methods of equipments cool are helpful for the improvement of the indoor thermal
environment and the comfort in summer and reduce the energy consumption. The concept of
thermal mass in buildings had been used by our ancestors today it is thought of as a means of
conserving energy. Energy efficiency is one of the simplest, quickest, cheapest, cleanest ways
to address energy and environmental challenges. It is economical to save electricity used in

uildings by adopting energy efficient techniques rather than increasing generation capacity.
Building bye-laws needs to be changed in accordance with guidelines for energy efficiency in
buildings. There is a need to incorporate these concepts in the syllabus architecture schools in India.
Table 1 Performance Parameters of conventional and energy efficient buildings [8]
S.No Parameter Conventional Buildings Energy Efficient Buildings
1. Design Feature Long facades east-west Long facades north south
No Shading Shading of east west facade
Single glazed windows Mix of Single and double glazed
windows
2. Lighting System No daylight integration Daylight
integration
and artificial lighting
No lighting control Occupancy
controls
sensors and dimming
Lighting power density is in the range
of 15-20 W/m 3
Lighting power density is less than 15-20
W/m 3
3. Air conditioning No use of passive cooling techniques Circulation areas are naturally ventilated
Chiller coefficient of performance on Chiller coefficient of performance on the
the lower side
higher side
Sqmt/TR (tonne of refrigeration) lies
in the rage 9-15
Sqmt/TR lies in the rage 32-42
4. Energy Lighting performance index lies in the
Performance range 37-60 KWh 2 Lighting performance index lies in the
/yr
range 21-28 KWh 2 /yr
Air conditioning performance index Air conditioning performance index for
for different climate zones are: different climate zones are:
Warm and Humid: 263KWh/m2 Warm and Humid: 195KWh/m2
per year (10 hours operation)
per year (24 hours operation)
Moderate: 259KWh/m2 per year Moderate: 105KWh/m2 per year
(10 hours operation)
(10 hours operation)
Composite: 183KWh/m2 per year Composite: 144KWh/m2 per year
(10 hours operation)
(10 hours operation)
Cold: 251KWh/m2 per year (24 Cold: 41KWh/m2 per year (10
hours operation)
hours operation)
References
1. Junli Zhou, Jiasheng Wu, Guoqiang Zhang, Yan Xu, Development of the Passive Cooling
Technique in China1 Proceedings of the Sixth International Conference for Enhanced Building
Operations, Shenzhen, China, Nov 6 - 9,
2. Satish Kumar, Ravi Kapoor, Rajan Rawal, Sanjay Seth, Archana Walia, Mission Developing an
Energy Conservation Building Code Implementation Strategy in India, May, 2010
3. Wen Hong, Madelaine Steller Chiang, Ruth A. Shapiro, Mark L. Clifford Ed Why Green
Buildings Are Key to Asia’s Future, the Asia Business Council, 2007,
4. http://bookstore.teriin.org/docs/ books/Introduction-%20energy%20eff%20biuldings.pdf
5. Inc. 9 Greyridge Farm Court Stony Point, NY 10980
6. www.raee.org/.../doc/technical_overview_of_active _techniques.pdf
7. www.sei.ie
8. www.teriin.org
9. PLEA 2008 – 25th Conference on Passive and Low Energy Architecture, Dublin, October 2008
10. http://www.teriin.org/index.php?option=com_content&task=view&id=32
11. http://www.nbmcw.com/articles/green-construction/25585-the-cost-of-going-green.html

Passive Design Features for Energy Conservation in Residential
Buildings
Abstract.
P.K.Bhargava, Nagesh Babu Balam and A.K.Roy
CSIR- Central Building Research Institute, Roorkee
Corresponding Author, bhargavapk@rediffmail.com
Energy consumed in controlling environment in respect of temperature, air movement,
humidity and hygienic condition inside buildings contributes a significant proportion towards
the total energy consumed in the building sector. An increasing demand of electricity during
the summer period due to extensive use of air-conditioning systems has necessitated
evolution and incorporation of various passive techniques in design of buildings which can
save a considerable part of conventional energy consumed in buildings for cooling and
lighting. The three main aspects involved in the development of a passive system are (i)
determination of the design climatic parameters at the building site (ii) knowledge of the
desired environmental conditions indoors and (iii) application of basic principles of heat
transfer in the evolution of appropriate passive system which on incorporation in the design
of buildings may lead to the desired thermal environment indoors. Various investigations
carried out at CSIR-CBRI covering these aspects to make residential buildings energy
efficient have been reviewed. It is observed that passive cooling techniques have not yet
reached the stage of established practice and constant efforts are being made world over to
make advancement in the existing knowledge in this field.
Keywords: Passive feature, climatic zones, thermal comfort, ventilation, energy efficiency
and residential building.
1. Introduction
Comfort within buildings is primarily controlled by four major factors: air temperature, mean
radiant temperature, humidity and air flow [1]. Lot of electrical energy is consumed in
buildings to control these dominant factors. Natural renewable energies as substitute for
conventional energies had been used earlier and many examples of ancient architecture have
special design features to achieve comfortable indoor environment without the use of
conventional energy. Present energy crisis and growing degradation in environment have
again developed interest in design of modern buildings using passive cooling techniques.
Passive cooling techniques means that enable the indoor temperatures of buildings to be
lowered through the use of natural energy sources. The term passive does not exclude the use
of mechanical devices such as fan and other electrical gadgets which may also be used
together to enhance the performance further. A systematic approach is taken in the design of
such buildings by the leading architect and few energy efficient buildings with passive

features have come up. These techniques provide comfortable indoor environment mainly by
natural means and minimizing consumption of conventional exhaustible energy sources.
Here, it would not be out of place to mention that the Bureau of Energy Efficiency
constituted by the Govt. of India has launched in February 2009 a star rating programme that
rates commercial buildings on the actual energy consumption in terms of kWh/sqm/ year.
ECBC Codes launched in 2007 also sets minimum energy efficiency standards for new
commercial buildings. The focus of these areas is directed towards improving energy
efficiency in existing buildings and development of codes so that new buildings be designed
and built with energy efficiency considerations having been incorporated right from the
planning stage. Extensive studies covering the afore-said aspects have been carried out at
Central Building Research Institute, Roorkee and elsewhere also. A few salient features of
these studies are described in the present paper.
2. Climatic classification
Classification of climate in respect of building design means zoning the country into regions
in such a way that the differences of climate from region to region are reflected in the
building design, warranting some special provision for each region. Based on the following
criteria, the country has been divided [2] into five major climatic zones, via, (i) Hot –Dry (ii)
Warm –Humid (iii) Cold (iv) Temperate and (v) Composite as depicted in Table 1.
Table 1. Criteria for classification of climatic zone
Climatic Zone Mean monthly maximum
Temperature O C
Hot-Dry
Warm-Humid
Temperate
Cold
Composite
above 30
above 30
above 25
between 25-30
below 25
Criteria explained in the
Mean monthly relative
Humidity %
below 55
above 55
above 75
below 75
all values
following paragraph
A given station is categorized under a particular zone if its climate conforms to that zone for
six or more months, otherwise it falls under the composite zone. A map of India depicting
various climatic zones is shown in figure1.
3. Thermal comfort
The amount of fresh air needed to maintain Carbon dioxide concentration of air within safe
limits is only 6.3m 3 / h / person whereas 2.2m 3 / h /person is sufficient to provide necessary
Oxygen for breathing. Comfort conditions depend upon air temperature, relative humidity,
wind speed, as well as on clothing, acclimatization, age, sex, and type of activity of the
people. Air motion has important influence on man’s thermal sensation as it can spell comfort
or discomfort depending upon the climatic conditions. Air movement influences bodily heat

alance by affecting the rate of convective heat transfer between skin and air, and the rate of
bodily cooling through evaporation of skin moisture. Necessity of high rates of air motion for
thermal comfort in tropics is an established fact. Studies on thermal comfort carried out in
Figure 1. Climatic Map of India
this institute [3] yielded a Comfort Index, known as Tropical Summer Index (T.S.I). The TSI
is defined as the temperature of calm air, at 50% relative humidity which imparts the some
thermal sensation as the given environment. This index has been used for determining the
minimum desirable wind speeds for thermal comfort under different conditions of
temperature and humidity. These wind speeds may be calculated by the equation:
TSI a
w
0. 745t
0.
308t
2 v
0.
841
Where ta = dry bulb (globe) temperature, O C.
tw = wet bulb temperature O C
v = air speed in m/sec

The thermal comfort of people lies between TSI values of 25 O C and 30 O C with maximum
per cent of people being comfortable at 27.5 O C.
Table 2. Desirable minimum wind speed (m/sec.) For thermal comfort
Dry Bulb Relative Humidity (Percentage)
Temperature
o C 30 40 50 60 70 80 90
30 * * * 0.06 0.24 0.53 0.85
31 * 0.06 0.24 0.53 1.04 1.47 2.10
32 0.20 0.46 0.94 1.59 2.26 3.04 +
33 0.77 1.36 2.12 3.00 + + +
34 1.85 2.72 + + + + +
35 3.20 + + + + + +
* None, + Higher than those acceptable in practice
4. Design considerations for energy efficiency in buildings
Energy efficiency in buildings broadly implies three aspects; (i) obviating wastage in energy
due to unwanted and non judicious use of electrically operated gadgets (ii) development of
energy efficient appliances and (iii) optimum utilization of non conventional sources of
energy through judicious planning and design of buildings. The aspects (i) and (ii) concern
with the design, installation and operation of electrical appliances; whereas aspect (iii) is
related to incorporation of appropriate passive features at the initial design stage of the
buildings. Several theoretical and experimental studies [4] have demonstrated the usefulness
of these techniques in respect of ameliorating thermal environment indoors. In context with
cooling of buildings in hot dry and warm humid climates, the passive techniques mainly aim
towards reduction in heat penetration through building envelope and provision of fenestration
for inducing desired natural ventilation indoors. Few of these features are discussed below;
4.1 Site planning and landscaping
Sites in which the slope, elevation, orientation, vegetation and wind pattern act to increase
summer cooling by wind and decrease radiation effects by shading should be used. Locations
near large bodies of water may be preferable if cooling breezes can be directed into the
building(s).
4.2 Building space & orientation
Buildings must be spaced to allow winds to reach the ventilation openings. In general, it is
not desirable to site buildings within the wake of surrounding structures or landscaping. The
terrain, surrounding vegetation and plans and layout of buildings may be used to "channelize
the air flow” into the building. Buildings constructed on earth mounds or sloping sites of hills
gets advantage of enhanced wind speeds. Air motion in a shielded building is less than that
in an unobstructed building. To minimise shielding effect, the distance between the two

ows should be about 8H for semidetached houses and 10H for a long rows houses.
However, the shielding effect is diminished by raising the height of the shielded
building.Orientation of a building plays an important role in governing the total amount of
solar radiation incident on the building envelope. It is well known [5] that the amount of daily
solar radiation incident per unit area on N and S facing walls is much less as compared to that
on the walls facing other directions. Hence, for minimum solar heat gain by the building
envelope, it is desired that the longer axis of building should lie along East-West direction.
Further, the effect of orientation of a building on heat penetration through envelope also
depends on the aspect ratio (length/breadth) of the building. For a building with square plan
(aspect ratio 1:1) and glass area equally distributed on all the four walls, the effect of
orientation is nil, while for a rectangular building with aspect ratio 2:1, the fabric load is
reduced by 30 per cent due to change in orientation from worst to best. Data on the amount of
solar radiation received by walls oriented in different directions at different latitudes are
readily available in the Climatic Data Hand-Book [2]. Using these data, an optimum
orientation that corresponds to the minimum value of total solar radiation can be easily
worked out.
4.3 Landscaping
Plantation of trees can result in energy saving, reduction of noise and pollution, modification
of temperatures and relative humidity and psychological benefits on humans. Hedges and
shrubs deflect the air away from the inlet openings and cause a reduction in air motion
indoors. These elements should not be planted at a distance of about 8 metre from the
building because the induced air motion is reduced to minimum in that case. However, air
motion in the leeward part of the building can be enhanced by planting a low hedge at a
distance of 2 metre from the building. Trees with large foliage mass having trunk bare of
branches up to the top level of window, deflect the outdoor wind downward and promote air
motion in the occupancy zone inside the buildings. Trees can act complementary to window
overhangs, as they are better for blocking low morning and afternoon sun, while overhangs
are better barriers for high noon sunshine The cooling loads of a house can be reduced by
10%- 40% by appropriate tree plantation.
5. Building design for natural ventilation
The primary comfort requirements for buildings using natural ventilation are to protect
occupants from the sun and rain without obstructing the airflow that cools both the occupants
and the building structure. Minimizing heat gain and promoting maximum ventilation are of
primary requirement for design of energy efficient buildings. Natural ventilation in buildings
is produced by pressure differences between the inside and the outside of the building. The
magnitude of the pressure difference and the resistance to flow across the openings in the
envelope will determine the rate of airflow through the openings. The two main forces
producing pressure differences are the wind force and the thermal force or stack effect.
5.1 Ventilation due to thermal forces
When a temperature difference exists between the outside and inside air of a building, a
pressure gradient is developed along the vertical direction over the walls of the building. If
the inside temperature is higher than that outside, the upper parts of the building will have
excess pressure while the lower parts will have under pressure. When openings are

provided in these regions, air enters through the lower openings and escapes through
the upper. In case the indoor air temperature is lower than outside, the air flow will be
reversed. This is exactly what happens when a building is ventilated by thermal forces, a
process often referred to as the "Stack Effect". The rate of air flow induced by thermal
forces is given by the equation,
where
Q 7A h.
Q = Volume of air flow in m 3 /min.
A = Free area of inlet opening in m 2
h = Vertical distance between inlet and outlet in m
= Difference in temperature of indoor and outdoor air.
In buildings employing natural ventilation, the temperature difference between indoor
and outdoor air is only a few degree Centigrade (say 2 o C). Furthermore, the height between
inlet and outlet openings in single storey houses with 3 m ceiling height is restricted to a
maximum of , say , about 1.5 metre. Therefore, the maximum contribution of thermal force to
ventilation will be given by
5 . 0
1.
5 2
Q 7 1
= 12 m 3 / min. / m 2 of top or bottom openings.
This rate of air flow is too small to meet the requirements of comfort ventilation.
5.2 Ventilation due to wind force
When wind strikes a building , a region of excess pressure is created on windward wall ,
while the sides , leeward wall and roof are all subjected to reduced pressure . A pressure
gradient is thereby created across the building in the direction of the incident wind. This
pressure gradient causes the air to flow through the building from openings in the region
of higher pressure to openings located in lower pressure zones . In the simple case of an
isolated enclosure in which openings are provided in each of the two opposite walls,
required area of ventilation openings may be calculated by the equation
Q
A
KV
where
A = Area of each opening in m 2
Q = Desired rate of air flow m 3 / hr
V = Outside wind speed m / hr
K = Coefficient of effectiveness
( 0.6 for normally incident wind and 0.3 for obliquely incident wind )
In case the inlet and outlet openings are of different sizes, say A1 and A2, then the value of A
can be worked out using the equation
2 1 1
2
A A A
2
1
2
2

5.3 Nocturnal ventilation
Theoretical as well as experimental studies on assessment of contribution of night ventilation
towards cooling of buildings during the following day have been carried out by several
investigators for different types of structures under different climatic conditions. In 1992
Givoni [6] derived following relationships for estimating the reduction caused in indoor
minimum (eq.1) and maximum temperatures (eq.2) caused by the provision of night
ventilation for medium and high mass buildings with light external colour and fully shaded
windows,
Tmin unvent - Tmin vent = 0.5 ( Tmin unvent - Tmin out side ) (1)
Tmax unvent - T max vent = 0.25 ( Tmax out side - T max unvent ) (2)
It is also reported that potential of night ventilation for lowering the day time temperature
indoors below the outdoor temperature is proportional to the ambient diurnal temperature
range. It was observed that night ventilation has only a very small effect on the indoor
maxima of the low-mass buildings. However, it is very effective in lowering the indoor
maximum temperature for high mass buildings below the outdoor maximum. In case of high
mass building, the night ventilation at the rate of 45 ach lowered the indoor maximum
temperature by 3.5 0 C when outdoor maximum temperature was 38 0 C Extensive studies on
the effect of these parameters on the availability of indoor air motion have been carried out in
CBRI. Based on the findings of these studies simple design guidelines for design of airy
buildings [7] have been prepared and included in BIS codes.
5.4 Non-conventional system of ventilation
A non-conventional system of ventilation, commonly called as wind tower, help induce air
motion in rooms devoid of windows on two exposed walls. The wind tower broadly consists
of a vertical wind carrying shaft with a wind scooping attachment atop thereof. On its vertical
sides, the shaft is provided with several openings, which connect the tower to the
different rooms intended to be ventilated. Openings in rooms are also provided on walls
other than the one facing the tower. Such an arrangement of openings facilitates cross
ventilation in the rooms. The impingement of wind on the face of the tower causes
development of positive pressure thereon.
As the wind flows around the building,
separation of flow takes place at the
windward edges and negative pressure is
created over all the leeward faces of the
building.
Thus a pressure difference exists between
the tower inlet and openings located on
leeward sides of the rooms. Consequently
flow of wind occurs from tower inlet to the
room openings. In this process the wind
entering through the wind tower sweeps
room area and finally exits through the
room opening. Thus the room gets
ventilated with the help of the tower.
Figure.2 Model of Wind Tower placed at top
of roof

6. Energy saving in buildings due to various passive systems
The studies carried out at CSIR-CBRI and other R&D organisations on different passive
features incorporated in buildings revealed that considerable amount of energy may be saved.
Few examples are reported in table given below.
Table3. Energy saving due to implementation of various passive features
Proper orientation (change) in longer axis
from N-S to E-W)
30 per cent reduction in solar radiation
incident on walls.
Proper shading of windows Over 10 per cent reduction in cooling load.
Painting of external surfaces of walls with
minimum absorption of solar radiation and
high emission in longer wave region
40 to 50 per cent saving in electrical energy.
Application of high albedo coating on roofs. 10 to 43 per cent saving in energy used to
cool the buildings
Change in roof albedo from 0.18 to .81 69 per cent saving in cooling energy.
Shading of houses by nearby trees 30per cent reduction in heat
Shading of walls by a row of trees. 50 per cent reduction in heat-gain through
the wall.
Growing a thick layer of vines on wall 75 per cent reduction in heat gain through
the wall
Covering the roof top with deciduous plants
or creepers
Roof top temperature is reduced by 15°c.
Heat flow of 200w/m 2 enters through un-
covered roof whereas 10w/m 2 is transferred
upward from inside the room.
Evaporative cooling of roof. Cooling load is reduced by 40 per cent
Replacement of air within glazing by argon,
krypton or xenon
U-value is reduced to 1.3w/m 2 k and 1w/m 2 k
respectively.
Provision of cross ventilation Contributes significantly towards
ameliorating thermal environment indoors.
Saving in energy varies from case to case.
Nocturnal ventilation
Radiative cooling using metallic nocturnal
radiator
In low mass building indoor maxima is very
close to outdoor maxima, but in high mass
building the indoor maxima is reduced by
3.5°c.
The indoor air temperature is reduced by 4 to
6 °c

Earth air tunnel
Use of renewable energy sources such as
wind, solar etc.
The air is effectively cooled by 3°c as it
passes through the earth coupled heat
exchanger tube.
Saving in energy varies from case to case.
Use of hollow clay tiles for roofs Saving of 18% - 30% of cooling energy
7. Barriers in adopting energy efficiency in residential buildings
(i) Architects are neither fully aware of the energy situation of the country nor wellinformed
about energy efficient design features. They need more information and
technical skills to design energy efficient buildings [8].
(ii) The interior designers too are not aware of the energy efficient design features that the
architect may have designed. They should be involved at initial stage of design.
(iii) The different energy efficient features can only be implemented if the clients are
prepared to pay the extra costs and compromise with reduced floor area. Residents need
to be explained about the necessity of energy efficient buildings.
(iv) The lifestyle of the higher income groups contradicts with the notion of energy
efficiency. For example, using air conditioners in each and every room, latest and
biggest appliances irrespective of their energy use and plenty of trendy lights such as
spotlights, chandeliers in an interior decorated house is a matter of status symbol for the
upper income groups.
(v) Flat owners do not always reside in the flats they buy. They rent the flats to tenants. The
owners are therefore not interested in energy efficient design features as they are not the
end users and would not bear the energy costs.
8. Conclusion
Design techniques for cooling of buildings have been described. It has been established that
adoption of some simple passive features results in significant saving in the energy consumed
in creating comfortable environment indoors. It is also observed that despite clinching
shortage of conventional energy and well known benefits of use of non- conventional
energies like solar and wind energy, the concept of passive systems could not find wide
application in design of buildings. Further, the basic principles of various passive systems are
well defined, but the technology of passive cooling is yet to reach the level of an established
practice. Response of users of buildings provided with passive cooling systems to the private
queries about the viability of the system also lacks consistency. More over efforts are
continuously being made world over to make further advancement in knowledge in area of
passive design of buildings. In this scenario hybrid passive system emerges a viable option
that may provide greater reliability and attract wider application of passive techniques in the
design of buildings in hot climate. Hence hybrid passive cooling is an important R & D area
for functional and energy efficient design of buildings.

9. Acknowledgement
The study forms a part of the research programme of Central Building Research Institute,
Roorkee and the paper is published with the kind permission of the Director.
References
1. Sodha, M.S. et. al, (1986) “Solar passive buildings”, Pergamon Press page. 126.
2. Chand, Ishwar and Bhargava, P.K. (1999), “The climatic data hand book, Tata McGraw
Hill, New Delhi
3. Sharma, M.R. and Ali, S. (1986) , “Tropical Summer Index- a study of thermal comfort
of Indian Subjects”, Building and Environment, Vol.21.
4. Kumar, Shree and Bhargava, P.K. (2009), “Studies on Thermal Environment in Enclosure
Exposed on Single Side: A Case Study in Northern India, Architectural Science Review,
Volume 52.1, pages 40-47.
5. CBRI, Roorkee (1963), “Orientation of Buildings”, Building Digest no.74.
6. Givoni, B. (1992) “Comfort, climate analysis and building design guidelines”, Energy
and Buildings, 18, 11.
7. CBRI, Roorkee (1976), “Guidelines for designing airy buildings”, Building Digest
no.121.
8. Department of Defence, United States of America (2004), “Cooling Buildings by Natural
ventilation”, report No. ufc 3-440-06n.

Abstract.
A Process of Heat- Reflective Insulation for Roof
K.L.Chhabra and Rajeev
CSIR- Central Building Research Institute, Roorkee
Corresponding Author, Email: kl_chhabra@yahoo.co.in,
In plain regions of our country, specially areas having hot-dry summers, generally two types
of treatments viz Lime Concrete Terracing or Mud Phuska with Brick Tiles are being used
on common flat pakka roofs for thermal comfort. Although these treatments provide thermal
comfort to some extent in day time in summers but due to large mass and thick layers of the
treatments, indoor heat is hardly removed through the roof upto late evening hours. Besides
the higher cost of the treatments, due to the above mentioned disadvantages, occupants or
users do not feel sufficient thermal comfort in hot dry areas. On the other side the application
of cost effective thin layer of white glazed china clay tile pieces provides better thermal
comfort. The benefits and effectiveness of the application of white glazed china clay tile
pieces, its comparison with mud phuska and lime concrete terracing and laying system have
been described shortly in the paper.
This treatment may be applied on old roofs having lime concrete layer or simple rendering
with mortar as well as on new roofs. More than one lakh square feet area of terraces have
been covered with this system by many govt. and Pvt. Organizations and individuals. Some
practical implementations which have been made in and around Roorkee and metropolitan
cities have also been briefed in the paper. Feed back studies about treatment on various
buildings , show its energy saving efficacy and good thermal comfort performance.
Keywords: Thermal Insulation, Heat Reflection, Water Proofing, Roof Repairing
1. Introduction
We are aware, most of the heat enters buildings through roofs, as these are exposed to sun
through out the day. Many attempts have been made to reduce the ingress of heat by various
methods like, by increasing thickness of roofs and providing different types of insulation
layers for minimizing the ingress of heat.
2. Heat insulation to roofs by using principles of heat-reflection and low heat conduction
Many problems are associated with common conventional heat insulation cum water resisting
materials and treatments like degradation of traditional roof surfaces and their finish, leakage
through cracks developed in the applied treatment’s layers due to the weathering actions i.e.
mainly by constant heating and cooling of roofs / thermal movements, attack of U.V.

adiations and rains etc. The existing traditional heat insulating materials commonly used in
most of plain areas of our country are very bulky and heavy i.e. upto 250 kg/sqm., resulting
in increase of considerable dead loads on buildings which in turn requires additional concrete
(15 to 20%) , reinforcement (20 to 30%) and heavier or more durable foundation. Too much
load on roof also causes for creation of extra momentum during the earthquake.
If we apply the simple white washing treatment on roofs which is a common practice to
reflect incident heat, then of course heat to the roof is reflected to some extent but there are
many practical difficulties in maintaining it over roof surfaces. Also existing roofs can be
seen to be highly absorptive to incident heat due to their reddish/grayish or algae blackish
colour surface. Such roofs besides causing discomfort to the occupants by additional heat
gains , affect also the human efficiency and productivity. It also adds up to the cooling loads
on conditioned buildings to affect the overall cost of air conditioning.
In view of the fact that roof receives the greatest proportion of incident heat during day and
also looses the greatest amount of stored heat during night, but the thick layers of treatment
act as insulating layers and do not allow heat to escape at night. The above problem is solved
by the thin and more conductive, heat reflective treatment using a kind of waste and cheaper-
easily available material. By its application in proper suggested way user can draw optimum
benefits to meet the various actual functional requirements of roofs in tropics.
4. Suggestive approach
In place of heavy lime-concrete and mud phuska with clay tiles and white washing treatment,
a light weight concrete (1500-1800 kg/ Cum) of cement and cinder or brick aggregate could
be employed in lean mix in 4c.m. (average) thickness preferably in alternate square or
rectangular panels (not more than 1.5 sqm.in area). After just laying the concrete a layer of
white glossy/glazed china broken tile pieces is laid with 1:2 cement-sand mortar (1cement : 2
fine sand). Such thin layer of light weight medium type of inorganic insulating material,
(i) Reduces appreciable dead loads on roofs
(ii) Increases Heat - Flow through roofs
An easy application procedure has been developed by Central Building Research Institute,
Roorkee. By following the same a gang of two masons and two beldars may apply the
treatment on 5 Sq.m. area of the roof in one day work.
Table (2) shows the relative thermal performance of conventional vs described treatment.
Apparently the roof surface and ceiling temperatures could be reduced by 16.5 degree C and
12.5 degree C respectively with the said treatment on 10.0 cm R.C.C. panel. When similar
roofs of two identical full size test room (11.4 cm RCC and 23 cm solid brick walls) i.e. one
treated and the other was kept untreated, the difference in roofs, ceiling and indoor air
temperatures could be reduced by 18 degree C, 13 degree C and 4 degree C respectively
under the same hot weather periods. The enhanced difference is due to the enclosure effect.
Therefore the thermal performance of this treatment is remarkable. Apart from the thermal
comfort , the said treatment could provide a glossy/ glazed white , smooth and weather
resistant, durable rock type, toping surface to roofs, which has been found to work as the first
line of defense from the adverse effects of sun’s radiation and rains. Relative difference in
dead-loads and life expectancy is described in table (1).

Some examples of its applications are
1. Solar Energy Centre building at Gawal – Pahari under MNES New Delhi
2. Modi Continental Tyre Factory, Modipuram, UP
3. CBRI Director’s Bungalow in CBRI Colony
4. CDIL ( Air- Conditioned Building at New Delhi)
5. Mughal Shereton Hotel ( A five star hotel at Agra)
6. Knowledge Resource Centre ,Welhem Boys School, Dehradun
7. Terrace of four storeyed lift building at CBRI premises
8. Roof of a store having L-Panel roofing system at CBRI
9. Terrace of Management Department, IIT, Roorkee
10. ONGC Staff quarter at Ankleshwar, Gujarat
Sl.
No.
Table 1. Relative difference in dead-loads and life expectancy
Specification of heat-insulating
treatment over 10 cm RCC
Total
thickn
ess
(cms)
Bulk
Density
(Kg/Cu
m)
Dead loads
on
buildings
(kg/Sq.m
Estimate
d cost*
per sqm
Rs.
Life
Expect
ancy in
years
1. 10 cm lime concrete 20.0 2400 240 520/- 10
15
to
2. 10 cm mud phuska with 5.0cm
brick tiles
25.0 1900 285 460/- 5 to 10
3. 0.4 cm glazed china ceramic 11.5 2200 30 340/- 20 or
tile pieces embedded in 1.0 cm
thick cement mortar
more
4. 0.4 cm glazed china ceramic 15.5 1400 60 520/- 20 or
tile pieces embedded in 1.0 cm
thick cement mortar over a
layer of 4cm thick (average)
light weight lean concrete
more
5 0.4 cm glazed china ceramic 14.5 2200 60 540/- 20 or
tile pieces embedded in 1.0 cm
thick cement mortar over a
layer of 30 mm thick (average)
ferro cement lair
more
Table (2) shows the result of relative heat reflection of conventional vs. newly designed heat
reflective PANELS (60cmx60cm) specially designed thermal chambers to study PANEL
effect under highly controlled conditions (uniformity in materials, mix, supervision ,
workman ship in the construction of panels) and under periodic heat flow condition on a hot
clear, sunny & calm day under actual field conditions.
Thermal performance of different roof sections in unconditioned building with same
construction materials and similar conditions have been shown in Table (3). It has been
observed that thermal performance of roof with a layer of white glazed china ceramic tile
pieces is most appreciable and acceptable.

Sl.
No.
5. Benefits
Table 2. Relative heat reflection from various roof surfaces
Roof Specifications Measured Max. Surface
Temps. on a hot summer day
(degree C)
Exposed roof Ceiling
1. 10.0 cm RCC 58.0 52.7
2. 10.0 cm lime-conc. over 10 cm RCC 53.0 38.8
3. 0.4 cm white glazed china ceramic tile pieces on
10.0 cm RCC
4. 0.4 cm white glazed china ceramic tile pieces on
a layer of 4cm thick (average) light weight
concrete over 10.0 cm RCC
Table 3. Thermal performance of different roof sections
Basic Element Treatment U-Value Kcal/m 2 hr o C
10 cm RCC Tar felt 3.143
“ Average 9.0cm lime conc.+
white wash
“ 5cm brick tile + 10cm mud
phuska.+ white wash
“ Glazed china ceramic tile
pieces embedded in 1.0 cm
thick cement mortar over a
layer of 4cm thick
(average) light weight lean
concrete
41.5 40.2
43.6 38.4
2.221
1.695
1.500
Application of tile pieces requires utmost precautions by skilled persons so as to become an
integral part of roof construction.
Some benefits are as
Lime-concrete and mud phuska cum / brick tile treatment can be replaced by simple
lightweight white china mosaic treatment so as to work as heat-reflective insulation and
water-proofing of roofs in general.
Large savings of materials and energy in the construction of unconditioned and
conditioned buildings.
Gaining substantial thermal comfort indoors both during day and night hours in ordinary -
unconditioned buildings.

Reduction in dead and heat loads on buildings leading to the construction of cost effective
thermally efficient design of buildings.
Good-life expectancy and strong/durable roofs to cause zero maintenance cost and no
inconvenience to the occupants.
Resistant to algae growth.
Provides optimum design specifications of roofs to meet all the functional aspects of roof
within the minimum possible roof thickness.
Persistent neatness of roof for aesthetic considerations
The roof remains fully useable
Higher reflection of solar heat compared to other white coatings
Saving in steel and concrete may be achieved due to reduced dead load on roof
Old roofs having deteriorated lime concrete surface or other rendered surface can be
improved and life is increased to some extent with out enhancing too much dead weight
over the poor roof to be treated.
Provides new life with new values to old RBC /RCC leaky roofs having deteriorated
exposed surface along with foot traffic resistance and impact loading characteristics with
out enhancing too much dead weight over the poor roof to be treated.
Roof surface temperature range is appreciably minimized to reduce thermal movements
in roof surface.
Provides good water resistance
6. Application procedure in brief
6.1 On newly constructed RCC / RBC roof slabs
Employment of glazed china tile pieces of 3 sq cm and above in their minimum and equal
thickness (3mm) demands certain precautions so that the treatment really forms an integral
part of the roof. In order to avoid accumulation of water on roofs which causes erosion of
cement matrix between joints of tile pieces, roofs should be provided with proper slope/
gradient as per Indian Standards / CPWD specifications. For surface preparation it is
necessary to do its tucking before brushing (with hard brush) to remove dust etc. Tile pieces
should be dipped into water for minimum two hours so that when embedded into mortar on
roof , may not suck-up water from the mortar to make it dry. About 1 cm thick layer of
cement mortar of 1:2 ratio (1cement: 2 fine sand) is laid in small patches (say about
50x50cm which is within the easy approach of mason) . An integral water proofing
compound should also be mixed in proper appropriate quantity in cement mortar. Thereafter
the tile pieces be laid on the mortar layer just by putting it very near to its final embedding
position on the laid cement mortar and then slipped it over to its right position. Finally there
should be minimum distance between the tile pieces. After embedding the tiles in bed mortar-
these are pressed uniformly and gently with wooden strips so as to keep the surface in
uniform level. Later concentrated cement slurry in water is poured over the embedded tile
portion. This slurry is filled into the spaces between the tile pieces and in this way all the tile
pieces are perfectly bonded with each other at the surface. For removing the surplus slurry- a
mixture of 1:2 dry cement-sand is spread over the treated part which is finally wiped-off with
a piece of cloth. Curing of the joints is done by sprinkling the water upto minimum seven
days. For continuously wetting the surface it is advisable to first spread the fine sand over the
surface in thin layer and then cover the surface by wet empty gunny bags. After proper curing

when gunny bags and sand is removed and the surface is cleaned, a ROCK type ceramic
glossy white inherited roof surface is obtained.
6.2 On existing lime-concrete or old rendered surface
For laying the glazed tile pieces on existing lime concrete surface – Firstly the top thin layer
of lime- concrete is scrapped off . After removing all dust and brooming and washing the
surface, concentrated cement slurry ( at least 5 kg per 10 sqm.) is spread over the surface and
then 25 mm thick 1:2:4 cement concrete (1 cement: 2 coarse sand and 4 stone aggregate – 10
mm and down guage) is laid approximately in alternate squared panels having area not more
than 1.5 sqm. in perfect leveling. The top of concrete panels is kept rough to receive further
treatment. Now, the tile pieces are employed in the same manner as described earlier.
The tile pieces are also laid at the bottom of gola existing all along the parapets upto a
minimum depth of 1 cm inside. It is preferable that the laying of tile pieces is extended on
parapet walls upto a height of nearly 15 cm. In case the existing slopes on lime concrete is
less than the value given in IS Code , this must be increased / corrected with the provision of
appropriate thickness of cement concrete laid in panels.
7. Results
Author itself has acted as instrumental in get applying the said treatment on thousands sq.ft.
roof area of several residential and office buildings in and out side Roorkee. According to
feed back collected, all treated surfaces have been working satisfactorily even after fifteen
years or so. The treated surfaces were found water resistant apart from their heat reflective
quality.
8. Conclusion
The mentioned approach has been observed to provide a low-cost, energy & material
efficient, almost maintenance free design of roofs also leading to improved indoor thermal
comfort and water proofing qualities. Finally an optimum design of roof, with minimum
possible materials could be constructed as per the said approach to meet the various
functional requirements of roofs in practice, which may be recommended for hot-dry regions
as well as in high rain fall areas also.
References
1. Technical paper of Mr. Jain S.P., former scientist, CSIR-CBRI published in the
proceeding of National Seminar on “Planning of Cities of Uttaranchal in Relation to
Vernacular Architecture, held at Roorkee on 16-17 March, 2002.
2. BHAWNIKA, a quarterly news letter (Samachar Patrak) published by Central Building
Research Institute, Roorkee for the period: January- March, 1991.
3. Schedule of Rates of Maharashtra PWD

Comparative Influence of Building Envelope Criteria on Energy
Efficiency of the Building Envelope
Abstract
Seema Devgan* and B. Bhattacharjee **
* Univ. School of Arch. & Plan. G G S Indraprastha University, Delhi
** Indian Institute of Technology, New Delhi
Corresponding author, E-mail: bishwa@civil.iitd.ac.in
Various limiting criteria for the building envelope such as U-value of the walls, solar
absorptance of the wall, U- value of the window glass and shading coefficient of the window
glass have been incorporated in the Building Energy Codes as limiting criteria in order to
achieve the energy efficiency of the building envelope. However, whether good correlation
exists between these envelope criteria and annual energy use for space cooling and heating is
not widely discussed in literature. In this paper, the building simulation results using building
energy simulation tool eQuest v3.6, for four case study buildings for various parametric
studies have been used to qualitatively and quantitatively compare the energy efficiency
performance of the various envelope criteria. It has been found that shading coefficient of
window glass has the largest magnitude of influence on the energy efficiency of the building
envelope. Shading coefficient of window glass and wall solar transmittance (Uw*) have the
best correlation with annual energy use for space cooling and heating and Uw*has second
largest influence on annual energy use amongst envelope parameters. U-value of the wall and
U-value of the window have very less influence on annual energy and poor correlation of
these parameters with energy use and a large component of constant in the correlation
equation also implies that factors other than these have a much higher influence on the energy
performance of the building envelope.
Keywords: Annual energy use for space cooling and heating, U-value of wall, Solar
absorptance of wall, U-value of window, Shading Coefficient of window glass.
1. Introduction
Building Energy Codes (BECs) have an important role in promoting energy efficient design
of buildings. Building envelope is a major contributor of the cooling and heating load and
hence building envelope criteria in BECs are aimed at reducing heat gains/losses through the
envelope and thereby reducing the energy used for space cooling and heating. For a given
internal loads and mechanical devices, the annual space cooling and heating energy
consumption in an air-conditioned building depends on the conduction heat gains through the
walls, windows (and roof), direct radiation gain through the window glass and secondary
conduction gain due to the solar radiation impinging on the opaque walls. Therefore, the
annual space cooling and heating energy of the air-conditioned building would be influenced

y a number of building envelope properties like U-value of the opaque wall (Uw), U-value of
the window glass (Uf), solar absorptance of the opaque wall () and shading coefficient of the
window glass (SC). Besides these envelope properties, energy use in space cooling and
heating is also dependent on the size, shape and areas of the building envelope facing
different orientations.
Various Building Energy Codes (BECs) of different countries stipulate prescriptive and
performance criteria for the building envelope or its individual properties. While countries
like Hong Kong and Singapore have adopted the Overall Thermal Transfer Value (OTTV)
approach[1], the BEC in India, Energy Conservation Building Code (ECBC)[2], adopts the
‘component approach’ that limits the U-value of the opaque wall and roof and the U-value of
the window glass, shading coefficient (SC) of the window glass and the window to wall area
ratio (WWR). Amongst the component characteristics of the building envelope, solar
absorptance of the opaque wall (), which influences the conduction heat flow through the
opaque walls due to impinging solar radiation has not been included in ECBC of India.
One of the roles of any BEC is to raise concern and awareness amongst architects, builders
and building professionals about energy efficiency of buildings. By listing the above limiting
criteria for the various components of the building envelope it does not become apparent how
and how much energy would be saved by complying with each of these criteria. Also, the
importance of shading and orientation of building envelope surfaces has not been highlighted
in the presriptive criteria of BECs. The correlation between the various envelope parameters
such as U-value of the opaque wall (Uw), U-value of the window glass (Uf), solar absorptance
of the opaque wall () and shading coefficient of the window glass (SC) with annual energy
use has not been widely reported for tropical climates.
Hence, there is a need to examine these correlations and make a qualitative and quantitative
comparison of these envelope parameters based on their role in making the building envelope
energy efficient. In this paper, possible correlations between annual energy consumption and
above factors are investigated and the results are reported.
2. Method
The parametric study results of eQuest v.3.6 building simulation for the four case study
buildings (93 and 97 parametric case of window constructions and opaque wall constructions
respectively) in three tropical climates- Composite, Hot- Dry and Warm- Humid, have been
used to obtain correlation between envelope parameters and simulated annual energy use of
space cooling and heating.
All the four case study buildings were modelled as individual projects using eQuest v.3.6.
After the modelling of the four case study building in eQuest v.3.6 with the available climate
data, the parametric runs (for varying wall and window constructions) were set up for all four
case study buildings. While performing the window parametric runs the window glass
properties of shading coefficient and U- value are changed in each successive run, while the
U-value of the opaque wall and solar absorptance remains unchanged. Similarly, in the wall
paramteric runs, the U- value of the wall and solar absorptance () is changed in each
successive run while the shading coefficient of window glass and U- value of the window
glass is kept constant. Thus, large amount of simulation data is obtained for annual energy
use for space cooling and heating for four case study buildings for various envelope
parameters in all three climates.

2.1 Case study buildings
Of the four case study buildings selected two were mid- rise and the other two were high-
rise. Figure 1 shows the actual photos of the four case study buildings. While all four
buildings are located in the same climate, after modelling in eQuest v.3.6 all four buildings
were simulated for the three tropical climates- Composite, Hot- Dry and Warm- Humid.
Figure 2 shows the eQuest v.3.6 models for the four buildings. It can be seen that the case
study buildings have been modelled with accuracies of their envelope details of opaque walls
and windows in various orientations. Elaborate details of these case study buiildings is
available in [3].
Table 1 gives a summary of the data of the buildings A, B, C and D. Table 2 gives the range
of envelope properties varied in the 97 parametric runs of the opaque walls. Similarly, the 93
types of window constructions are varied in a range of parameters described in Table 3. The
results of annual energy use was compiled for both space cooling and heating. Only in the
Warm- Humid climate, there was no heating energy use due to the absence of any cold
season requiring heating requirement.
Building A Building B
Building C Building D

Figure 1. Actual Photos of the Buildings A, B, C and D
Building A Building B
Building C Building D
Figure 2. eQuest v.3.6 models of the Buildings A, B, C and D
Table1. Summary of data for the four Case Study Buildings
Buildings A B C D
Number of Storey 6 6 15 15
Total floor area (m 2 ) 30658 30250 20199 33740
Envelope area (m 2 ) 10587 9459 8112 15633
WWR 0.28 0.45 0.47 0.41
Table2. Ranges of Properties of 97 Opaque Wall Constructions used in Parametric Studies
Thermal Property Units Ranges
Thermal Transmissivity or U-
value of Opaque Wall (Uw)
W/m 2 -°C 0.23 - 2.87
Solar Absorptance () - 0.25 - 0.85
Table3. Ranges of Glass Properties in 93 Window Constructions used in Parametric Studies
Thermal Property
Thermal Transmissivity or U-
Units Ranges
value of Window Glass (Uf) W/m 2 -°C 0.66 - 6.31
Shading Coefficient (SC) - 0.15 - 1

3. Results
For the cases of all four buildings in three climates (all parametric window and wall runs) the
correlation was obtained between individual envelope parameters- U- value of opaque wall,
solar transmittance of opaque wall (Uw*), shading coefficient of window glass (SC) and U-
value of window glass with annual space cooling and heating energy. Figure 3 shows this
correlation for Building ‘B’ in Composite climate. The linear regression equations for the
four envelope parameters and annual energy use for space cooling and heating (E) is
presented as Equation 1-4.
E= 13.9* SC + 25.9 ………..Eq. 1 (R=0.98)
E= 1.08* Uf + 29.8 ………..Eq. 2 (R=0.42)
E= 2.39* Uw* + 32 ………..Eq.3 (R=0.95)
E= 1.03* Uw+ 32.2 ……….. Eq.4 (R= 0.71)
Annual Energy for Cooling & Heating
(kWh/m 2 )
43
41
39
37
35
33
31
29
27
25
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
U-value of wall, U-value of window, Shading coefficient of window glass, U w*
U-wall
U*a
U-window
SCwindow
Figure3. Correlation of U-value of wall, U-value of window, Shading coefficient of window
glass, Uw* with Annual space cooling and Heating Enegy - Building ‘B’- Composite
Climate
The slope, intercept and coefficient of correlation (R) for various correlations are tabulated in
tables 4, 5, 6 and 7 for buildings A, B, C and D respectively for all three tropical climates. It
can be inferred from these tables that:

The shading coefficient of window glass has the highest magnitude of influence on
annual energy use for space cooling and heating.
The shading coefficient of window glass and solar transmittance of opaque wall (Uw*)
have the best correlation with annual energy use for space heating and cooling. (R= 0.94-
0.99 and R= 0.91-0.99 respectively).
U-value of window has the lowest impact on the annual energy use for space heating and
cooling (R= 0.37- 0.57, m= 0.69-2.89).
U-value of wall also has relatively lower impact on annual energy use for space heating
and cooling (m= 0.37-1.8).
The high values of c (in tables 4-7) in case of envelope parameters such as U-value of
window and U-value of glass also indicates that the annual space cooling and heating
energy depends largely on factors other than these variables.
Table 1. Correlation between Envelope parameters and Annual Space Cooling and Heating
Energy- Building A- All Climates.
window
parametric
runs
Constant:
Uw= 2.5,
=0.6
wall
parametric
runs
Constant:
SC= 0.27, Uwin=
2.95
Dependent
variable Climate
SC
U-window
Uw*
U-wall
Building A (WWR= 0.28) mid-rise
Slope
(m)
Intercept
(c)
Coefficient
of
Correlation
(R)
Composite 7.17 28.2 0.94
Hot- Dry 10.5 34.1 0.97
Warm Humid 11.7 37.5 0.98
Composite 0.69 29.8 0.52
Hot- Dry 0.94 36.8 0.49
Warm Humid 0.88 40.9 0.41
Composite 3.96 25.5 0.95
Hot- Dry 4.44 32.3 0.91
Warm Humid 3.8 36.2 0.92
Composite 1.55 25.8 0.73
Hot- Dry 1.8 32.5 0.66
Warm Humid 1.47 36.5 0.64

Table2. Correlation between Envelope parameters and Annual Space Cooling and Heating
Energy- Building B- All Climates
window
parametric
runs
Constant:
Uw= 1.514,
=0.6
wall
parametric
runs
Constant:
SC= 0.17,
U-win=
2.79
Building B (WWR= 0.45) mid-rise
Dependent
Slope Intercept
Coefficient
of
Correlation
variable Climate (m) (c) (R)
Composite 13.9 25.9 0.98
SC Hot- Dry 16.8 32 0.98
Warm Humid 17.3 36.8 0.99
Composite 1.08 29.8 0.42
U-window Hot- Dry 1.35 36.7 0.44
Warm Humid 1.17 42.2 0.37
Composite 2.39 32 0.95
Uw* Hot- Dry 3 31.9 0.96
Warm Humid 3.08 36.8 0.97
Composite 1.03 32.2 0.71
U-wall Hot- Dry 1.23 32.1 0.69
Warm Humid 1.43 36.97 0.75
Table3. Correlation between Envelope parameters and Annual Space Cooling and Heating
Energy- Building C- All Climates.
window
parametric
runs
Constant:
Uw= 2.59,
=0.84
wall
parametric
runs
Constant:
SC= 0.27,
U-win= 2.5
Building C (WWR= 0.47) high-rise
Dependent
Slope Intercept
Coefficient
of
Correlation
variable Climate (m) (c) (R)
Composite 19.35 22.94 0.98
SC Hot- Dry 22.7 28.3 0.98
Warm Humid 25.3 30.7 0.99
Composite 2.42 26.54 0.57
U-window Hot- Dry 2.7 32.6 0.56
Warm Humid 2.89 36 0.53
Composite 1.54 28.46 0.91
Uw*
Hot- Dry 1.79 32.2 0.97
Warm Humid 1.96 35.07 0.93
U-wall
Composite 0.86 28.35 0.91
Hot- Dry 0.92 32.15 0.87
Warm Humid 1.08 34.9 0.92

4. Conclusion
Table4. Correlation between Envelope parameters and Annual Space Cooling and
Heating Energy- Building D- All Climates.
The U- value of opaque wall and U- value of the window glass are building envelope
parameters which show poor correlation with annual space cooling and heating energy.
Therefore, Building Energy Codes which specify limiting criteria based on these parameters
of the building envelope can be reevaluated based on objective of achieving energy
efficiency. The envelope parameters such as shading coefficient of window glass and wall
solar transmittance have good correlation with annual space cooling and heating energy and
also shading coefficient has significantly high magnitude of influence. Hence, the orientation
and shading characteristics of the building envelope are crucial to the energy performance of
the building envelope and require emphasis in envelope criteria in building energy codes.
References
window
parametric
runs Constant:
Uw= 1.74,
=0.6
wall
parametric
runs Constant:
SC= 0.26, Uwin=
4.99
Building D (WWR= 0.41) high-rise
Dependent
Slope Intercept
Coefficient
of
Correlation
variable Climate (m) (c) (R)
Composite 9.68 19.4 0.97
SC Hot- Dry 11.4 23.1 0.98
Warm Humid 12 25.1 0.99
Composite 0.72 22.34 0.40
U-window Hot- Dry 0.79 26.6 0.39
Warm Humid 0.78 29 0.37
Composite 0.82 20.29 0.95
Uw* Hot- Dry 0.9 24 0.99
Warm Humid 0.96 26.7 0.97
Composite 0.37 20.32 0.77
U-wall Hot- Dry 0.36 24.11 0.67
Warm Humid 0.42 26.77 0.76
1. Devgan, S., Jain, A. K. and Bhattacharjee, B. (2010). “Predetermined overall
thermal transfer value coefficients for Composite, Hot- Dry and Warm- Humid
climates”. Energy and Buildings, Vol. 42, pages 1841-1861.
2. BEE. (2007). “Energy Conservation Building Code”. Bureau of Energy
Efficiency, Ministry of Power, Government of India. www.bee-india.nic.in.
3. Devgan, S. (2009). “Development of OTTV based approach for three tropical
climates as an alternative to prescriptive approach in building energy codes”.
Unpublished PhD thesis, Indian Institute of Technology, Delhi, India.

Abstract
The Concept and Need of Zero-energy Buildings in India
Present Scenario and Future Prospects
Rashmi Kumari and V. Devadas
Indian Institute of Technology, Roorkee
Corresponding Author, Email: rashidap@iitr.ernet.in
Besides serving the need for human habitat, buildings contribute to serious environmental
problems due to un-restrained consumption of energy & other natural resources during the
construction, maintenance and operation of the buildings. In a developing country like India,
rising population; increasing GDP & significantly increasing standards of living; and rapid
urbanization results in an increase in the building construction activities and the use of energy
to make them more comfortable and liveable. According to the ‘International Energy
Agency’ (IEA), the buildings sector accounted for the largest share, 47 percent of India's final
energy use. Air conditioning and lighting are the top two energy end users within the
buildings sector as most regions of India comes under the hot climatic condition. As most of
the required energy is currently derived from burning fossil fuels, the building sector has
emerged as a major factor impacting on the environment. In this scenario, the introduction of
energy-efficient building design concept has become critical for achieving the collective
objectives of energy security and environmental protection, which in turn can ensure
economic and social development. To achieve the collective objectives of energy security and
environmental protection, 'zero-energy building' should be considered and designed.
Key words: Zero-energy building; energy efficiency; energy conservation; global warming;
and HVAC.
1 Introduction
The global energy consumption has undergone a drastic increase in the last two decades. It is
estimated that almost 31 percent of the global energy demand is due to buildings and is
expected to grow by an additional 45 percent by 2025. In India, estimates suggest that about
20 to 25 percent of the total energy demand is due to manufacturing materials required in the
building sector, while another 15 percent goes into the running needs of the building. In a
developing country like India, rising population, increasing standards of living and rapid
urbanization result in an increase in building construction activities. This will demand a
larger share of the energy available in an already strained energy supply scenario. According
to the International Energy Agency, India’s carbon emission is expected to nearly triple
between 2007 and 2030, growing from 4.4 percent of the world’s emissions to 8.5 percent
over the next two decades. Commercial and residential buildings account for more than 30
percent of the electricity consumption in India. Air conditioning and lighting is the top two
energy end users within the building sector as most of the regions of India come under the hot

climatic condition. We add more than 40 million sq. m of commercial and residential space
annually which results in the additional burden of energy consumption. As most of the
required energy is currently derived from burning fossil fuels, the building sector has
emerged as a major factor impacting on the environment. Energy availability is scarce and
people have to protect themselves from these extremities of the climate in a natural way. One
of the best ways to achieve the collective objectives of energy conservation and
environmental protection is the introduction of energy efficient building design concept,
which in turn can ensure economic and social development.
To achieve energy efficiency and environmental protection, ‘zero-energy building’ that
consumes about 60 percent less energy and the remaining 40 percent is fully powered by
renewable energy, must be considered and designed. In general, energy efficiency in new
buildings can be achieved through: Bioclimatic architectural principles; Load minimization
by the incorporation of solar passive techniques in building design; Design of energy efficient
lighting and HVAC systems; Use of renewable energy systems to meet a part of the building
load; Use of low energy materials and energy efficient methods of construction; and
promoting implementation of program results in building energy codes, standards, and
practices.
The present paper deals with the present scenario and future prospects of the energy
consumption in buildings in India for acquiring substantial knowledge and understanding the
concept and the need of zero-energy buildings and their impact, to evolve plausible and fiscal
policies guidelines for the sustainable development of the study area (India).
2 Methodology
The study area of India has been selected for the present research. Data have been collected
from Secondary sources including books, government documents, journals, case studies etc.
The data collected from various sources have been analyzed to obtain the co-relation,
inferences and do the forecast. Statistical techniques have been employed to analyze the data
and draw the findings.
3 Energy consumption scenario in India
India, the seventh largest country and fifth largest energy consumer in the world, is a leading
economy and home to over one billion people living in various climatic zones. With 15
percent of the world’s population and an economic growth rate that increases the aspiration of
its people to a better quality of life, India has a voracious appetite for energy. But the country
lacks sufficient domestic energy resources, particularly of petroleum and natural gas, and
must import much of its growing requirements. According to the census of India, the
population of India (2011) is 1,210,193,422. India has total G.D.P. (2011) of 1848 billion $
(52.2 trillion Rs). According to a report published by the World Bank, the GDP value of India
is roughly equivalent to 2.79 percent of the world economy. Total energy consumption in
India (2010-11) was estimated 759 Mtoe (8827.17 billion kWh) which made it third largest
energy consumer in the world. However, India was third largest energy consumer on the
whole; the per capita energy consumption in India (2010-11) was 7294.02 kWh, one of the
lowest (109 th ) in the world (Table 2). Due to the large population India’s total energy
requirement is much more than that of other developed countries (Table 1). Even though,

most part of the population is facing the problem of energy scarcity due to lack of energy
supply means and infrastructure, the total energy consumption is higher than many developed
nations. The trends show, with growth in population and GDP, the building floor space;
energy consumption in general and in buildings; increases significantly (Table2, Figure 2).
As per Census of India 2011, only 67.3 percent of the total households have electricity
connection in India. It suggests that the need is to increase the capacity of renewable energy
supply to every household and to spread awareness about the need for energy conservation.
Table 1. Comparative data about Population, GDP and Energy Consumption of three
countries (India, China and USA).
Country Population
(2011)
RANK
in
world
GDP
(2011)
billion
US
dollars
RANK
in
world
Total energy
consumption
(2011)
Mtoe RANK
in
world
Energy
consumption
per capita
(2008)
KWh RANK
in
world
INDIA 1,21,01,93,422 2 1,676 11 759 3 6,280 109
CHINA 1,34,73,50,000 1 7,298 2 2648 1 18,608 73
USA 31,39,98,000 3 15,094 1 2225 2 87,216 10
Source: CIA World Factbook. World Bank Report, International monitory fund.
IEA/OECD, Population OECD/World Bank.
Figure 1. Energy Consumption Pattern in Residential and Commercial Buildings in India.
In 2005, building sector consumed 169 million toe (Mtoe), or 47 percent of the total final
energy use. Residential buildings accounted for the lion’s share (93 percent) of the total
building energy use the same year (IEA, 2007). Air conditioning and lighting are the top two
energy end users within the building sector. It is estimated that on an average in a typical
commercial building in India, around 60 percent of the total electricity is consumed for
lighting, 32 percent for space conditioning, and less than 8 percent for refrigeration. In a
typical residential building, around 28 percent of the total electricity is consumed for lighting,
45 percent for space conditioning, 13 percent for refrigeration, 4 percent for televisions and
10 percent for other appliances in the urban sector (Figure 1). Studies have indicated that
energy efficient lighting, air conditioning and electrical systems could save about 20 percent
of the energy used in existing buildings. In addition, some simulation studies also indicate
that new buildings can save up to 40 percent of energy with design interventions and stronger
building energy standards (BEE, 2007).

Table 2. Trend of energy consumption, population, GDP and per capita energy consumption
in India (1970 to 2011).
Year Energy
consumption in
billion KWH
Mid-year
population in
'000 numbers
GDP (Rs
crore) (1999-
2000 prices)
1970-71 663.99 551311 517148 1204.39
1975-76 840.53 617248 596428 1361.74
1980-81 1012.58 688320 695361 1471.09
1985-86 1477.5 766135 894041 1928.51
1990-91 1902.75 852297 1193650 2232.5
1995-96 2436.77 939540 1529453 2597.58
2000-01 3154.28 1034931 2030710 3047.81
2005-06 6686.17 1117734 2844942 5981.9
2010-11 8827.17 1210193 4464081 7294.02
Per capita energy
consumption
(KWH)
According to the U.S. Census Bureau the projected population of India (2030) is
1460743000. The projected GDP of India (2030-31) is 23752749.46 according to the ‘annual
table of socio-economic national statistics in its pocket world in Figures’ published by ‘The
Economists’.
3.1 Calculation
Regression analysis
Figure 2. Building Energy Consumption Framework.
Co-relation coefficient between population and energy consumption =0.900023
Co-relation coefficient between GDP and energy consumption =0.985582
Table 3. Result of Regression Analysis.
a= Intercept 319.1474899
b= X Variable 1 0.001218203
X= GDP (2030-31) 23752749
y= Energy consumption (2030-31) a+bX 29254.80741

It is clear that the Population, GDP and Energy consumption are closely related. Thus, the
future projections about the real energy consumption and required energy consumption have
been made accordingly (Table 3, Figure 3). The projected energy consumption in India
(2030-31) is 29254.81 billion KWH (Table 4). With the help of these projections the gap in
energy consumption in 2030 has been calculated. According to the present trend, the energy
consumption in buildings in India will increase from 4148.77 billion kWh in 2011 to
13829.23 in 2031 billion kWh (Table 5, Figure 4), thus, interventions are required.
Table 4. Present and Projected Energy Consumption and Required Energy Demand in India
for the year 2011 and 2030 respectively.
Total
energy
consumpt
ion (2011)
Ideal
energy
consumpt
ion per
capita
Required
Energy
consumpti
on in India
(2011)
Gap in
energy
consu
mptio
n
(2011)
Projected
Population
(2030)
Projected
Total
energy
consumpt
ion (2030)
Required
Energy
consumptio
n in India
(2030)
Gap in
energy
consump
tion
(2030)
Million KWh Million Million Million Million Million kWh Million
kWh
kWh MWh
MWh
kWh
8827170 87,216 105548229 96721 1461 29255 127400161 98145354
Figure 3. Energy Consumption Gap in 2011 and 2030 Figure 4. Energy Consumption in Buildings
in India. in India.
Table 5. Energy Consumption in Buildings in India.
Year Energy consumption in Total energy consumption
Buildings (billion KWH) (billion KWH)
2010-11 4148.77 8827.17
2030-31 13829.23 29254.81
Net increase in Energy
Consumption
9680.46 20427.64

4. ‘Zero-Energy Building’ concept
A simple definition of ‘Zero-Energy Building’ (ZEB) is a facility which produces at least as
much energy as it consumes, enabling buildings to be energy self-sufficient. A good ZEB
should first encourage energy efficiency by incorporating ‘climate responsive designs’ and ‘solar
passive designs’, and then use renewable energy sources available on site. The ZEBs consumes
about 60 percent less energy and the remaining 40 percent is fully powered by renewable
energy. Currently, the construction cost of Zero Energy Concept Building in the private
sector is within reach. The goal of zero energy building will become more broadly attainable
as advances in energy efficiency and renewable energy technologies improve system
performance and reduce cost.
The most cost-effective step toward the reduction in a building's energy consumption usually
occurs during the design process. To achieve efficient energy use, zero energy design departs
significantly from conventional construction practice. Successful zero energy building
designers typically combine time tested passive solar, or natural ‘Heating Ventilation & Airconditioning’
(HVAC) principles that work with the on-site assets. Sunlight and solar heat;
prevailing breezes; and the cool of the earth below a building, can provide day-lighting and
stable indoor temperatures with minimum mechanical means (Table 6). In addition, energy
can be saved by using fluorescent and LED lighting for night time illumination as they use
one-third or less power than incandescent lights, without adding unwanted heat. Other
techniques to reach net zero are Earth sheltered building principles, super insulation walls
using straw-bale construction, pre-fabricated building panels and roof elements plus exterior
landscaping for seasonal shading. Zero-energy buildings make use of heat energy that
conventional buildings may exhaust outside. They may use heat recovery ventilation, hot
water heat recycling, combined heat and power, and absorption chillers. In short, ZEB’s use
the concept of ‘Reduce, Recycle & Reuse’ for energy conservation and sustainable
development.
Table 6. Basic Energy Sources in an Eco-Friendly Building Complex.
Sun Earth Water Air
Heating
Electricity
Generation
Day Lighting
Greenhouse Effect
Solar Chimneys
Earth Tunnels
(for cooling)
Earth Berms (for
insulation)
Roof Gardens
Geothermal
Roof Ponds
Fountains for
Humidification
Rainwater harvesting
Hydro and Tidal Energy
(for electricity generation)
Ventilation
Heat sink
Wind tunnels
Stack effect
Wind energy (for
electricity)
All the technologies needed to create zero energy buildings are available today. Sophisticated
computer simulation tools are available to model how a building will perform with a range of
design variables such as building orientation (relative to the position of the sun; and the
direction of wind-flow); window and door type and placement, overhang depth, insulation
type, air tightness, the efficiency of heating, cooling, lighting and other equipment, microclimate
etc. These simulations help the designers predict how the building will perform
before it is built, and enable them to model the economic and financial implications on
building; cost-benefit analysis; or even more appropriate life cycle assessment.
3.2 Advantages of ZEB
a) Building owners of ZEBs are isolated from future energy price increases;

) The comfort level is much more due to more-uniform interior temperatures;
c) Total cost of ownership is reduced due to improved energy efficiency (Figure 5);
d) Reduced total net monthly cost of living;
e) Pollution reduction and eco-friendly environment;
f) More reliable building components- photovoltaic systems are available with 25-year
warranties, seldom fail during weather problems. The 1982 photovoltaic systems on the
Walt Disney World EPCOT Energy Pavilion are the examples of reliability as are still
working fine today even after going through 3 recent hurricanes;
g) Higher resale value as potential owners demand more ZEBs than available supply;
h) The cost of construction of a ZEB relative to similar conventional building is anticipated
to decrease with time due to the introduction of new technologies in this field through
research and development (Figure 5); and
i) Future legislative restrictions and carbon emission taxes/penalties may force expensive
retrofits to inefficient buildings.
3.3 Disadvantages of ZEB
Figure 5. ZEB’s Advantage over the Lifecycle.
a) Initial costs can be higher (Figure 5), subsidies on ZEB components are required;
b) Very few designers or builders have the necessary skills or experience to build ZEBs;
c) Possible declines in future utility company renewable energy costs may lessen the value
of capital invested in energy efficiency. New photovoltaic solar cells equipment
technology price has been falling at roughly 17% per year.
d) Challenge to recover higher initial costs on resale of the building.
e) Without an optimised thermal envelope the embodied energy, heating and cooling energy
and resource usage is higher than needed. ZEB by definition do not mandate a minimum
heating and cooling performance level thus allowing oversized renewable energy systems
to fill the energy gap.
4 Case Study: ZEB at BCA Academy, Singapore
The Zero Energy Building (ZEB), located within the BCA Academy, Singapore in South-east
Asia is retrofitted from an existing building. It is converted from a three-storey former
workshop to ZEB houses, offices, classrooms and a resource centre (Figure 6). The ZEB is a
zero energy building because the building produces enough energy to run itself. In all, the
building saves about $84,000 a year in energy cost compared to typical office in Singapore.

Figure 6. ZEB at BCA Academy, Singapore.
The cost of construction of this ZEB was $162 per sq.ft. The building achieves energy self
sufficiency through the combination of green building technology, smart building design that
takes advantages of natural ventilation and lighting (passive design strategies), and the
harnessing of solar energy (Figure 8). To be super energy efficient, the office of the future
adopts an integrated design approach that encompasses general principles to reduce energy
consumption (Figure 7)
1. Passive Design – Light Pipes and Light Shelves
2. Active Solutions – Personalized Ventilation, Displacement Cooling etc.
3. Active Controls – Motion sensors, CO2 sensors etc.
Figure 7. Natural Day-lighting and Ventilation Systems in the Office Building
The shading devices discover how strategically placed shading contraptions can shield the
building from the direct heat of sun while bouncing natural lighting into the interiors of the
building. The light pipes set on the top of the roof of the building collect sunrays and, through
reflection via highly reflective mirrors positioned at proper angles in the ducts (mirror ducts),

throw this harvested daylight into the room below. This collected sunlight is spread evenly
throughout the room by the diffusers. There is more natural lighting because the light shelves,
positioned outside the windows of this office, reflect sunlight deep into the room. The high
performance solar systems generate about 207,000 kWh of electricity a year which is enough
electricity in a year to power 45 four-room HDB flats. This energy is used to run the
building’s artificial lights, office equipments and air-conditioning. The solar chimneys are
also provided which are specially developed for the tropical climate, made of metal that
absorb solar radiation, are placed on the top of the roof or up high in a non air-conditioned
room, suck out warm air from the room. Through convection, cool air then rushes into the
room. The displacement cooling technique is utilized in which cool air is supplied from the
floor level at low velocity and warm air rises towards the ceiling where it is extracted. The
temperature of the top floor of the building is reduced by shading the roof from sun with the
rooftop gardens. Plants are planted vertically on the walls of the building which shade the
walls (Living walls) from the sun and lower indoor temperature (Figure 8). Another section
of the ZEB, ‘Office of the Future’ is an actual working office where personalized ventilation
system delivers fresh air directly to each occupant’s desk through pipes attached to the desk.
The Sophisticated Building Management System automatically controls the various systems
in the building to balance comfort and energy efficiency. The facility of automatic light level
adjustment is being provided in this office using sensors which measure the light intensity
within the office space. When light levels are sufficiently provided by natural light, the
artificial light is switched off. The presence of occupants is detected by sensors and the
cooling required is supplied accordingly.
Figure 8. Different Building Technologies used in ZEB at BCA Academy, Singapore.
Thus the ZEB at BCA Academy has a very important role to play in accelerating the greening
of Singapore’s built environment. The building demonstrates how an existing building can be
retrofitted with green building technologies to achieve energy efficiency and sustainability in
the tropical climatic condition. The building is also a test-bedding centre for exciting new

innovations in green building technology before they are promoted for adoption by the
building industry. These concepts of ZEB can easily be adopted in the study area to get the
similar upbeat results in the field of cost effective, energy efficient building construction as
the climatic conditions are similar in both the areas.
5 Result and conclusion
To achieve the collective objectives of energy security and environmental protection, ‘zeroenergy
building’ should be considered and designed. Due to lack of energy, most of the
people are forced to live without lighting and air conditioning facilities in India. The practice
of ZEBs, will not only save about 9680.46 billion kWh energy per year in 2030 but also able
to fulfil the energy requirements of each and every household (Table 5). The energy
efficiency and sustainability in the buildings can be achieved, through incorporating green
building technologies in the new buildings, as well as retrofitting existing buildings into
ZEBs. Thus, the study concluded with plausible recommendations for constructing costeffective
and energy efficient zero-energy buildings in the study area. It is anticipated that, if
the proposed model is implemented successfully in the study area, it will ensure sustainable
development definitely.
References
1. BEE, 2007. Annual Report 2006-07. Bureau of Energy Efficiency.
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Publishers Pvt. Ltd.
3. BAKER, N. and YANNAS, S. (1999) Climate Responsive Architecture. New Delhi: Tata
McGraw-Hill.
4. MAJUMDAR, M. (2009) Energy efficient buildings in India. New Delhi: TERI Press.
5. MAJID, M. A. (1991) Application of Energy Efficiency and Renewable Energy in
Buildings. New Delhi: Concept Publishing Company.
6. Confederation of Indian Industry, 2008. LEED-India Green Building Rating Program
(Green Habitat March 2008), www.igbc.in/site/igbc/publication.jsp, January 2011,
(Accessed).
7. EIA, 2008. World Carbon Dioxide Emissions from the Consumption and Flaring of Fossil
Fuels, www.eia.doe.gov/emeu/international/carbondioxide.html, January 2011,
(Accessed).
8. Hong, W., Chiang, M.S. and Shapiro, R.A., Clifford, M.L., 2007. Building Energy
Efficiency: Why Green Buildings Are Key to Asia's Future. Asia Business Council, Hong
Kong.
9. IGBC, 2008. LEED-India Green Building Rating Program,
www.igbc.in/site/mmbase/attachments/48240/GH_Mar_2008.pdf, December 2008,
(Accessed).
10. IMF, 2008. World Economic Outlook Databases, www.imf.org/external/ns/cs.aspx?id=2,
January 2009, (Accessed).
11. Mathur, A., 2006. Current Status of Energy Efficiency Building Codes in India,
www.iea.org/textbase/work/2006/buildings/mathur.pdf, January 2009, (Accessed).
12. HDB, Government of Singapore. A Tour of Singapore’s Greenest Building,
www.bcaa.edu.sg/zero_energy_building.aspx, June 2012, (Accessed).

Abstract
Dhajji Wall Construction
Md.Danish
Birla Institute of Technology, Mesra (Patna Campus)
E-mail: md7781@gmail.com
“Dhajji” is a Persian word meaning Patchwork quilts in ancient language of carpet weavers.
Because of its visual similarity to the type of patchwork construction in Kashmir, this term is
applied to this type of construction. This type of construction is quite prevalent in the
earthquake prone areas of Jammu & Kashmir. Availability of timber in abundance, local
expertise in construction supported by affordability has made this technology of construction
very popular. During 2005 Earthquake in Jammu & Kashmir, houses made up of Dhajji
technology proved to be more resilient and suffered minimal damage compared to modern
buildings made up of reinforced concrete. In the cool climate, the main function of the shelter
should be to provide thermal comfort to the occupants by reducing heat loss from the
buildings. Apart from pine needle and straw, other materials which can be added in the infills
for Dhajji wall construction are rice, wheat, maize, wool, cotton etc. which has a high
insulation value.
Keywords: Dhajji, Dewari, Insulation, Seismic, Mud-mortar, Dasa, Straw, Joints, Panels.
1. Dhajji wall: An Introduction
Dhajji dewari (Persian for “patch quilt wall”) is a traditional building type found in the
Himalayan belt of Pakistan and Jammu and Kashmir (Fig.1). Due to its resemblance in the
appearance to quilt patchwork of Persian weavers it is called as “Dhajji”. It is quite prevalent
in the earthquake prone areas of Jammu and Kashmir. Compared to conventional reinforced
construction,”Dhajji” construction is more popular. It is quite prevalent in the earthquake
prone areas of Jammu and Kashmir. Compared to conventional reinforced
construction,”Dhajji” construction is more popular. It is also referred to as Brick nogged
timber construction.
It mainly consists of a braced timber frame where the spaces between the bracings and frames
are filled up with stone and brick masonry laid in mud mortar.
These are generally laid on shallow foundation with stone masonry. Dhajji buildings are
typically 1-4 storeys tall and the roof may be a flat timber and mud roof, or a
pitched roof with timber/metal sheeting.

2. Seismic attributes
Figure 1. Patchwork quilt: "Dhajji" in Persian
A typical “Dhajji” House is composed of small panels of timber and stone which resembles a
patchwork (Fig.2). Compared to conventional House of Concrete, Dhajji house is more
earthquakes resilient.
Figure 2. Composition of Stone and Timber Infills
When an earthquake occurs in a conventional house,it usually makes one big
crack,another crack and then the wall get collapsed as the energy is concentrated at a point. In
case of a Dhajji House,there are many small cracks and these small cracks fall out,but the
wall remains as the small panels distribute the energy evenly (Fig.3). When we hit the
stone,either stone breaks or the person get injured,but if a heap of sand is pressed,no harm is
occurred and the grains move away,since the friction breaks down the energy (Fig.3).
Figure 3. Comparison of Seismic forces in Conventional V/S Dhajji House

Dhajji wall remains strong,only if all the joints are well executed,infills are done properly
and it is well protected from rain water (Fig.4).Small panels distribute the earthquake energy
evenly and the friction between all the panels and the infills break down the energy evenly.
Figure 4. Protective Features of Dhajji Wall
Figure 5. New Houses being Constructed under Dhajji Dewari technique after 2005 earthquake in
Jammu and Kashmir.
3. Components of Dhajji wall
Various components of Dhajji Wall are as follows:
3.1. Foundations.
3.2. Plinth Beams (Dasa).
3.3. Frame Structures.
3.4. Joints.
3.5. Roof Truss.
3.6. Walls and Bracings.
3.7. Windows and Doors.
3.8. Infills and Plaster.

3.1.Foundations
A good foundation is prepared with stone and cement mortar.To hold the mortar with stone
properly,anchor bolts made up of plate and hook are placed in the lower parts of the
foundation. Diameter of anchor bolts is ½ inch which is kept 6 feet apart from each other
(Fig.6). Foundations shouldn’t come out of ground much and be kept at a height of 1 foot
only.
Figure 6. Diagrammatic representation of Anchor bolts placed inside stone foundation
3.2.Plinth beams (Dasa)
Main objective while constructing plinth beams is to protect the foundation from rain and
insects and it should be anchored properly with the foundation.Minimum size of Dasa is kept
4”x4” and it is made up of good quality timber. Anchoring is done best by using bolts and
rebars (Figure 7).
3.3. Framed structure
A well proportioned framed
structure is very essential for the
Dhajji Wall. Main posts of sizes
4”x4” should be 4 feet-6 feet apart.
Panels to receive should be small
with the distance between vertical
posts be not exceeding 2 feet.
Figure 7. Dasa fixed with solid
washer(top),anchoring with bolts
and straps(bottom left),
Shade provision for rain water
protection(bottom right).

3.4. Joints
Figure 8. Intermediary gaps shown in Dhajji framed structure
Figure 9. Detailed out Dhajji framed structure
Dhajji framed structure consist of
following types of joints:Dasa extension
joints,Wall joints and Corner joints.
Dasa extension joints
For making the Dasa longer, scarf joints
or lap joints are used as shown in the Figure 10.
Figure 10. Dasa Extension Joints
using Scarf or Lap Joints

Wall joints
To join the posts with the dasa,tenon and mortise
joints are used.Posts can be joined with the dasa with
the help of nails or straps as shown in the Figure 11.
Figure 12. Wall Joints using Tenon and Mortise
Joints
Corner Joints: To make the Corner joints,quarter tenon and half tenon joints are used as
shown in the Fig.12.
3.5.Roof truss
Figure 13. Corner Joints using quarter tenon and half tenon joints
Dhajji House consists of two types of roof truss
system. They are “onto” and “against”. When
rafters are placed onto the tie beam,it is referred
as “onto” and when the rafters are placed
against the tie beam,it is called as “against” roof
truss system (Fig.13).
Figure 14. “Onto” and “Against” Roof Truss
System

3.6. Walls and bracings
Walls have to be filled up with the diagonal pieces of wood of thickness 1”-2” and it can be
subdivided into small panels in many ways as shown in Fig.14. Good Dhajji wall has small
panels while the wall gets weaker by big panels,strong diagonals with absence of plinth
beams as shown in Fig.15.
Figure 15. Different Styles of Dhajji Walls and Bracings
Figure 16. Good Examples of Dhajji Wall (Left) and Poor Examples of Dhajji Wall(Right)
3.7.Windows and doors
It is not advisable to place too many openings in the wall as it makes the structure
weak.Windows and doors should be 2 feet away from the corners and it should be placed
at least 2 feet apart as shown in Fig.16.

3.8. Infills and plaster
Figure 17. Correct Way (Left) and Incorrect Way (Right)
Cement-Sand infills makes the wall too rigid,due to which the small panels cannot move
individually and absorb the energy.Mud mortar is more effective,which can be made
more elastic by adding pine needles and straw.Mortar must be same throughout the
building. Infills are filled with stone and mud mortar.Stones used should not be too large
and use of small and irregular stones is preferred (Fig.17).
Figure 18. Correct Way (Left) and Incorrect Way (Right)
4. Dhajji wall: An alternative to thermal insulation
In cold places, a house must insulate its inhabitants from the outside temperature. This is
achieved by creating walls that are made from materials that insulate well, often requiring
layers of different materials.A typical “Dhajji House” is composed of small panels composed
of stone masonry and timber of thickness 45-60 cm which have a time lag of 8-9 hours which
keeps the houses warm in winter and cool in summer for maximum part of the year. Apart
from pine needle and straw, other materials which can be added in the infills for Dhajji wall
construction are rice, wheat, maize, wool, cotton etc. which has a high insulation value.

Roofing of Dhajji House is composed of twigs or reeds of sizes 6” to 8” which when covered
by topping of mud or earth leads to thermal insulation providing comfort to the inhabitants.
Apart from the resources available, passive solar heating can be applied by orienting and
clustering the livable spaces towards the sun for solar heat gain. At the ground floor, cattle are
kept to keep the house warm and the livable spaces are at the first floor as shown in the
Fig.18.
Figure 19. Plans,Elevation and Section of a typical Dhajji House
along with the photograph (at top).
Dhajji” House has straw, of K (Thermal Conductivity) Value of 0.09. Straw bale construction
takes space in walls normally reserved for sprayed insulation, rolled batts or rigid insulating
boards filled with stacked straw bales. Straw bales provide far superior insulation to
engineered products and are a recyclable material. It has been proved by laboratory testing
about the earthquake resistant properties of straw bale construction. PAKSAB (Pakistan
Straw bale and appropriate building) is a project undertaken to provide straw bale homes for
the local villagers.
4.References
1. Schacher,Tom and Ali,Dr. Qaisar: Dhajji_English.pdf, DHAJJI CONSTRUCTION For
one and two storey earthquake resistant houses,A guidebook for technicians and artisans.
2. Langenbach,Randolph: LANGENBACH_KEYNOTE-BNCA-HealthyCities.pdf, Keynote
Address Back to the Future:Lessons from the Past for a more Earthquake-Resistant City,
Conservationtech Consulting, Oakland, California, USA.
3. Schacher,Tom: Schacher-DhajjiLesson(8.3.07)(s).pdf, Basic Training on Dhajji
Construction (Power point Lesson),Version 13.12.06.
4. Sarkar,Ar.Amitava: v60-105.pdf,Adaptive Climate Responsive Vernacular Construction
in High Altitude, World Academy of Science, Engineering and Technology 60, 2011.
5. Kubilây Hiçyılmaz, Jitendra Bothara, Maggie Stephenson: wh100164.pdf,World Housing
Encyclopedia,Housing Report on Dhajji Dewari, an initiative of Earthquake Engineering
Research Institute (EERI) and International Association for Earthquake Engineering
(IAEE).
6. Green Home Guide.com
7. Wikipedia.org.
8. Paksab.org.
9. Webberenergyblog.com.

Pollution Free Design Patterns for Ecotourism: Innovative Ideas
from Traditional Settlements at ‘Nilgiris Biosphere Reserve’
Kala Choyimanikandiyil
Manipal School of Architecture and Planning, Manipal University, Manipal, Karnataka
Corresponding Author, E-mail: kala.cmk@manipal.edu
Abstract.
Most of the tribal settlements contain temporary and flimsy huts indicative of their living
habits which blend with nature. The modern generation has forgotten the fact that these
dwelling units are best adapted to the microclimate of the region. These indigenous
construction practices are now gradually ebbing away due to the public unawareness of their
good functional performance. The motivation required to be instilled in the present scenario
of research field is that these types of construction techniques have to be examined to bring
out design patterns applicable for ecotourism. The paper explains two case studies of
traditional tribal settlements of ‘Kurichiya’ community and that of ‘Toda’ community at
‘Nilgiris Biosphere Reserve’. The components of the settlements are designed for the benefit
of inhabitants’ daily activities and main occupation in life. Each and every element of their
housing settlements is ecologically sustainable. Both the settlements are made out of locally
available materials which still exist with no much maintenance and repair. The architecture
of these settlements are documented and better design patterns are formulated which can be
used for ecotourism. Development programs are suggested where tribal communities,
majority of which fall under poverty line, have to be trained to set up self-sufficient units for
ecotourism. It is suggested that these units can be created and maintained by themselves in
self- help process. These will provide them with all kinds of employment. The design and
architecture used for these centers should be entirely tribal in nature. This definitely will
attract a great number of tourists. According to the survey of Ministry of Tourism many of
the Indian and foreign travellers are aiming for holidays that can be spent inside villages.
Tourists like to interact with the villagers by being and living with them. A great number of
foreign tourists find joy in learning about the culture and activities of tribal society.
Keywords: Green Design Methods, Sustainable Architecture, Environment friendly
Materials, Traditional Tribal Settlements, Climate-responsive Architecture, Functional
Architecture for Ecotourism, Innovative Ideas for ecotourism.
1. Introduction
According to the Annual Report 2011-2012 of Ministry of Tourism, Government of India,
during the year 2011, the number of Foreign Tourist Arrivals in India reached the level of
6.29 million and the Foreign Exchange Earnings from tourism in India during 2011 were
$16.56 billion. Meanwhile 2.5% of Ministry’s total plan outlay for 2011-2012 has been
earmarked for development of tourism in tribal areas. The Approach Paper of the 12 th Five

Year Plan prepared by the Planning Commission highlights the need to adopt “pro-poor
tourism” for increasing net benefits to the poor and ensuring that tourism growth contributes
to poverty reduction. The Planning Commission has identified tourism as the second largest
sector in the country in providing employment opportunities for low-skilled workers [1].
The growing tourism is exerting pressure on our sensitive environment. India has nearly 1/6 th
of the world population, but amazingly only 2.2% of earth’s landmass. Considering the
importance of developing tourism in ecologically sustainable manner, the Ministry of
Tourism has been laying stress on maintenance of environmental integrity. The latest Annual
Report of Ministry of Tourism, Government of India states ecotourism as responsible travel
to fragile, pristine, and usually protected areas that strives to be low impact and often small
scale. It also directly benefit the economic development and political empowerment of local
communities, and foster respect for different cultures and human rights.
Scheduled Tribes are those which are notified as such by the President of India under Article
342 of the Constitution in 1950. As per the records of Ministry of Tribal Affairs, 82% of
total Scheduled Tribe workers are either cultivators or agricultural labourers. And most
notable thing is that 50% of the ST population are below poverty line in 2004- 2005 [2].
Every traditional tribal hamlet teaches us an age old green building technique which
completely merges with the nature in terms of climate and aesthetics. It took thousands of
years for our ancestors to make these dwellings of naturally available materials into a water
resistant, termite resistant and earth quake resistant one. To quote architect Laurie Baker it
would be absurd to leave aside what our ancestors have invented for us, instead the research
has to be continued.
Through two case studies on traditional tribal settlements the author tries to bring out the very
essence of the set-up which are directly linked with the occupants’ day-to-day activities that
can be used for the uplift of ecotourism field and make it more lively. Architectural
alterations required for the present generation of tourists have been identified to give a better
design patterns for Homestays. Meanwhile attempts like this will be promoting a new trend
in the field of ecotourism that is derived out of the old which is gold.
2. Background of the Study
2.1. National Policy on Tribals
After the country became independent, the Government of India proposed the formulation of
a National Policy on Scheduled Tribes. According to this, it says clearly under the title of
‘Traditional Wisdom’:- Dwelling amidst hills, forests, coastal areas, deserts etc. tribals over
the centuries have gained precious and vast experience in combating environmental hardships
and leading sustainable livelihoods. Their wisdom is reflected in their water harvesting
techniques, indigenously developed irrigation channels, construction of cane bridges in hills,
adaptation to desert life, meteorological assessment, utilization of forest species like herbs,
shrubs for medicinal purposes etc.
Five principles spelt out in 1952, known as Nehruvian Panchsheel had been guiding the
administration of tribal affairs. These principles are such as tribals should be allowed to
develop according to their own genius; tribals’ rights in land and forest should be respected;

tribal teams should be trained to undertake administration and development without too many
outsiders being inducted; tribal development should be undertaken without disturbing tribal
social and cultural institutions; and the index of tribal development should be quality of their
life and not the money spent. Every movement on tribal development was later based on this.
2.2. Census Data
According to the latest census, India has a population of 121 crore. And there are a total of
33.1 crore houses in the country. It is also listed that 3.3 crore household in rural India live in
houses with Grass/ Thatch/Bamboo/Wood/Mud as roof. Household listing for Scheduled
Tribes in the country as well as in the states of the study are as in following tables [3].
Table 1. Scheduled Tribe households by condition of census houses occupied by them
According to Census of India 2001, around 8% of the total population (84,326,240) of the
country was Scheduled Tribe, out of which 5.5% are living in the above mentioned three
South Indian states.
Table 2. Scheduled Tribe Households by Predominant Material of Roof of census houses
Total No. Of
households
Grass/Thatch/Bam
boo/Wood/Mud
India Karnataka Kerala TamilNadu
Total 2,33,29,105 9,36,995 1,36,006 3,84,713
Rural 2,01,42,434 7,11,110 1,15,630 2,40,002
Urban 31,86,671 2,25,885 20,376 1,44,711
India Karnataka Kerala TamilNadu
2,33,29,105 9,36,995 1,36,006 3,84,713
42,93,207 1,58,768 13,640 98,874
Table 3. Scheduled Tribe Households by Predominant Material of Floor of census houses
occupied by them
Total No. Of
households
Mud as material of
Floor
India Karnataka Kerala TamilNadu
2,33,29,105 9,36,995 1,36,006 3,84,713
1,71,18,810 3,33,637 59,985 1,20,481

Table 4. Scheduled Tribe Households by Predominant Material of Wall of census houses
occupied by them
From the above tables one can assume that Scheduled tribe households in the country made
of local materials are definitely over 1.7 crores. The latest web portal of Census of India
displays that in rural India proportions of households using materials like grass, thatch,
bamboo, wood, mud etc. are reduced to 20% from 27.7%. Meanwhile this paper highlights
the sustainable aspects of these very materials in the context.
2.3. Ecotourism
India Karnataka Kerala TamilNadu
Total No. Of households 2,33,29,105 9,36,995 1,36,006 3,84,713
Grass/Thatch/Bamboo
Mud/Burnt Brick
Wood
36,60,012
1,08,35,925
6,05,939
65,424
2,37,745
7,349
11,137
25,218
1,075
24,702
1,14,090
1,436
Tourism is primarily a consumptive activity based on presence of people. This sets the
picture upside down and questions the very basis of PAs (protected areas) which excludes a
sparsely numbered indigenous community living with no or minimum infrastructure, in the
name of conservation [4].
Tourism is one of the strongest drivers of world trade and prosperity. Poverty alleviation is
one of the greatest global challenges. Despite turbulent times for the world economy, these
basic facts are unlikely to change. Focusing the wealth creating power on tourism on people
remains an immense task [5]. According to the World Tourism Organization, the United
Nations agency responsible for the promotion of responsible, sustainable and universally
acceptable tourism; ecotourism means tourism that involves travelling to relatively
undisturbed natural areas with the objective of studying, admiring and enjoying the scenery
as well as any cultural aspects found in the areas. An optimum number of environment
friendly visitor activities, which do not have any serious impact on the ecosystem and the
local community in maintaining the ecological balance are some of the key elements.
As stated in the Annual Report 2011-2012 of Ministry of Tourism, Government of India,
ecotourism is held as important by those who participate in it so that future generations may
experience aspects of the environment relatively untouched by human intervention. The
Ministry recognizes many cardinal principles for ecotourism like involvement of the local
community and for overall economic development of the area; promoting the livelihood of
local inhabitants; keeping the scale of ecotourism development which should be compatible
with the environment and socio-cultural characteristics of the local community etc.
The scheme of Rural Tourism was started by the Ministry in 2002-03 with the objective of
showcasing rural life, art, culture and heritage at rural locations and in villages, which have

core competence in art & craft, handloom, and textiles as also an asset base in the natural
environment. The intention is to benefit the local community economically and socially as
well as enable interaction with the tourists for a mutually enriching experience. The
promotion of village tourism is also aimed at generating revenue for the rural communities
through tourist visitations, thereby checking migration from rural to urban areas [1].
3. Nilgiris biosphere reserve (NBR)
3.1. Geographical information about Nilgiris biosphere reserve
As a follow up of UNESCO’s Man and Biosphere Programme, in August 1986, Nilgiris
Biosphere Reserve was formed which extends across 11 0 36' to 12 0 00' N and 76 0 00' to 77 0 15'
E and the altitude of which ranges from 300m to 2,670m above sea level [6]. The purpose of
its formation includes conservation of biodiversity, involvement of local inhabitants for
effective management, integration of scientific research with traditional knowledge of
conservation etc. The total area of NBR is 5520 Sq.Km. which includes 2537.6 Sq.Km. in
Tamil Nadu, 1527 Sq. Km. in Karnataka and 1455.4 Sq. Km. in Kerala. The same is divided
into Core Zone (1240.3 Sq.Km.), Forestry Zone (3238.7 Sq. Km.), Tourism Zone (335.0
Sq.km.) and Restoration Zone (706.4 Sq.Km.). The annual rainfall ranges from 500 mm to
7000mm with temperature from 0 0 C in winter to 41 0 C in summer.
3.2. Scope of Ecotourism in NBR using traditional tribal settings
Tribal groups like the Todas, Kottas, Irulas, Kurumbas, Paniyas, Adiyans, EdanadanChettis,
Kurichiyas, Cholanaikkens etc. are native to this reserve. Indigenous people have a very
good understanding about their natural environment and know that destruction of nature will
result in their own doom. Perhaps so, they created forms of economic activities and life style
which is ideally suited to the existence of their habitat. Earlier their main occupations were
agriculture, food gathering, hunting, fishing, fire walking etc. To quote PriyaDavidaret. al.,
sustainable extraction can be achieved only under particular conditions of low population
density, simple technology, localized resources and limited possibilities of expansion[7].
The number of tourists visiting places to enjoy the scenery and surroundings and to see wild
animals is increasing rapidly. The present District Forest Officer, the Nilgiris South, Mr.
Anurag Misra supported the Avalanchi Eco Development Committee to ensure tourists’
safety as well as protect environment by making a new arrangement to control the vehicular
traffic[8]. Majority of the tourists are coming from metros. They would prefer to spend
holidays in a novel way by experiencing the divinity of nature by being a part of the tribal
culture and staying at their settlements.
Traditional employment like dairy farming, honey bee raising etc. have to be geared up along
with the uplift of traditional handicrafts, cultivation of crops and afforestation programs; all
of which knowledge could be imparted to the tourists by making them part of the daily
schedule (karmayoga). The intimacy of the whole program can be attained by the tourists if
and only if the architectural set up is also tribal in every sense. In this context, what the
author tries to emphasize is the need of scientific and architectural up gradation required for
the constructional methods of tribal architecture without losing its pristine beauty and grace.

4. Case Studies of traditional tribal settlements at NBR
4.1. Case study I: Tribal Settlement of Kurichiya at Wayanad, Kerala
The hamlet taken for study is situated in Pakkam village at Wayanad. There are 22 huts, all
arranged in a haphazard manner. But their active social life is reflected here from the
minimum distance given between the huts as well as their verandahs of huts overlooking the
same courtyards. The wide overhang of the roofs, the low eaves and the high plinth of the
verandahs provide a shaded seating for the people to sit and chat across facing the
neighboring hut (Fig 1).
Figure 1. Typical Kurichiya Huts at Pakkam, Wayanad
The area of any of these traditional huts does not exceed more than 4.0 m x 3.5 m. including
the two sided verandah. Most of these huts have only a single room, though a few have an
additional room either meant for storage of firewood or bed. But nobody has tried to include
a toilet! The distance between the plinths of two huts are sometimes as small as 1 m. The
open outer courtyard either forms a cooking area, drying area for grains or to plant Tulsi on
raised platform. This Tulsitara must be an addition that happened in the recent past.
Some of the huts have wattle and daub wall (bamboo slats and mud plaster on either side) or
adobe wall construction (Fig 1). The whole structure stands on a high earthen plinth at least
60-75 cms. The verandah is normally 90cm wide and either two sided or three sided. If
present on the rear side, occupants use it for cooking with firewood, having a raised platform
to place grinding stone etc. (Fig 2).
Figure 2. Rear side of a Tribal Hut
Most of the huts have their kitchen and sleeping area in the dark single room they have
inside(Fig 3). The horizontal bamboo poles loosely placed across the ridges of the walls form
a small attic where they keep things (Fig 4). The headroom below this attic is hardly 2 m.
The roofing materials used are either Lemon grass, Darbha grass or paddy straw.

Figure 3. Inner side of a hut.
Figure 4. Attic extended on top of verandah
For openings mostly woven bamboo slats for doors fixed inside a frame of around 70 cm x
200 cm., hinged to another wooden post attached on the walls; and small series of parallel
slits for windows of around 10 cm x 30 cm are given an the wall. The room is totally dark
even during shining sunny days (Fig. 5). This dark interior facilitates exercise of the iris.
Figure 5. Door and Window Openings
Flooring is these days done with black oxide or red oxide instead of the antique practice of
smearing cow dung. And every where a pattern is given which you can see in all the tribal
huts in the region (Fig 6).
Figure 6. Typical tribal pattern given on the plinth in black oxide and red oxide
4.2. Case Study II: Tribal Settlement of Toda at Ooty, Tamilnadu
The Toda settlements or villages are known as ‘munds’. These are located invariably near
forests, streams or pasture lands in a picturesque landscape. These originally consisted of
three to four barrel huts (‘arsh’), open cattle shed for big buffaloes (‘thoovarsh’), cattle sheds
in rectangular shape with sloping roof for calves (‘kodarsh’) and temples either like ‘arsh’
(‘paluvarsh’) or single circular, conical shaped (‘poovarsh’). Examples are shown in Fig. 7.

Figure 7. Different units of a ‘mund’ (Toda village)
There are 14 head villages and 60 villages for Todas. There exist around 1800 Toda people
in Nilgiris. Their main occupation originally is dairy farming. But these days Toda women
also prepare a special red and black embroidery on off-white cloth for shawls, table cloths,
mufflers etc. which is called ‘putkuli’. They also make walking sticks and butter churning
paddle out of bamboo by treating it for more than seven months (fig.8).
Figure 8. ‘Putkuli’ designed shawls and other bamboo equipments
The huts or ‘arsh’ have the curved shape which resembles the back of an elephant. The total
width of the structure extends upto 4.5 m., height upto 3.3 m. and the length around 4.5 m.
The arch shape is maintained by the two opposite walls on either side with wooden planks in
mud mortar (fig.7). On top of these, right in the centre there will be a strong pole of around
12cm dia. running along the depth of the structure. Thinner and strong poles of wood goes
parallel to it at intervals; eleven numbers on either side of the arch. The air gap is filled with
mud plaster. On top of this wooden poles, bunches of thin bamboos which are tied together in
a circular manner are placed in arcuated shape at around 30cm interval; meeting at top from
either side which on the other end is inserted one foot deep inside the ground. On top of this
ribcage, thin round wooden poles are tied close to each other which extends across the roof.
For tying Todas use only spiral of cane or bamboo splits. The roof projection on either side
from the wall is 60 cm. At the extreme edges, the members forming the ribcage is tied
around with grass called ‘ovul’ (Eriochrysis Genus) using bamboo splits very tighly. This
gives an elegant look. The last part is the roofing with the same grass. These grass is cut in
30 cm. length and tied in bunches which is ultimately tied to thin bamboo poles which again
is running across the depth. These bamboo poles containing grass on it are tied starting from
below by overlapping at least half length of grass underneath it. Details are shown in Fig. 9.
Figure 9: Details showing the roofing pattern

These dwelling units have a raised platform 45 cm high on right side for sleeping as you enter
by creeping through the small door, 60 cm x 75 cm. The door might have made this tiny in
order to give protection from weather as well as sudden attack of wild animals. Apart from
this there are two tiny holes either circular or rectangular in shape on top of the door for
ventilation which often has shutters.
Centuries ago it used to snow in Nilgiris. But these days, to adapt with the present climate,
modifications have to be given for ventilation. At the other end of the door is the cooking
area where fuel used is firewood. There is no separate chimney for the outlet of smoke.
Flooring is usually smoothened mud mortar. The floor level is just raised some 15-20 cm
from ground.
The temples called ‘paluvarsh’ have the same shape; the only difference is that there are two
rooms separated by similar arch shaped wall. These structures have stone walls instead of
wooden planks. Also the stones on the front façade are decorated with dark engravings of
stars, moons, buffalo head, flowers etc. One more difference here is that the door is still
smaller (45 cm x 60 cm). Only one priest enters here. The other type of temple called
‘poovarsh’ are cylindrical with a conical shape. The diameter of the structure is less than 3m.
and height almost 10 m.
The buffaloes sleep in the circular open ground fenced off with stone retaining walls and
calves have separate sheds. Case studies were carried out at Thalpatherimund, Munjkalmund
and Cogeremund.
5. Conclusion
5.1. Tourism centre following settlement pattern I
The overall scale of the hutments are very much in proportion to the density of tribals as
well as human scale. This scale has to be always maintained. No huts should be more
than 4 m x 3m.
Overall height of the hut including the plinth should not be more than 4.5m. The slope of
the roof can be either 30 0 or 45 0 depending on the span of the structure. Only the
restaurant can have height more than 4.5 m.
The very same building materials and construction technique has to be followed for the
overall tourism unit. Even the color of set up which contains only grey, black and
terracotta has to be maintained as not to deviate from the aesthetical factor.
Every hut should be designed only for sleeping and relaxing purpose with two sided
verandah of 1.2 m. width. Even the windows should be the same old slit holes on the
walls used without any change.
The plastering should be made in lime plaster. The flooring, skirting etc. should be
treated with black oxide with the typical tribal pattern of lines.
Separate structure should be made for toilets, one toilet block for 4 huts; and for overall
colony one big semi open restaurant with the same local building materials. Tourists can
sit on the floor and can have the traditional food sitting on the floor.
At least at some part of the structure should have a minimum distance of 1 m. with
neighboring hut; also having an overlooking courtyard of minimum 6m. x 8m.
Tourists should take part in agriculture, honey bee raising, cooking and construction
activities for maintenance, along with the tribals as a part of leisure.

Semi open prayer court should be given near any big tree where a small altar can be set
up. Tribal art forms like thira etc. can be performed here.
5.2. Tourism centre following settlement pattern II
Every tourism centre should be ideally located to have grazing gorund for the buffaloes in
the premises. Main temple which is cylindrical in shape should be the focal point in
design where the ceremonial functions take place.
The landscaping should be decorated with the typical traditional stone fencing, stone
chairs and oil lamps.
The door ways can be made of the same size for ‘arsh’ but kept at height of 45cms. on the
wall, from floor level so that one can enter turning sideways and meanwhile the air
movement will take place in the living zone inside. The same size of opening should be
given on the opposite wall.
These dwelling units should be used only for sleeping and separate similar structure
should be added for toilets. Additional structure deep in dimension by extending the
length of the poles of the roof should be given for cooking and eating.
Tourists can take part in taking care of the buffaloes, agriculture, handicrafts and in all the
other things that Todas do.
Acknowledgements
Special gratitude goes to Ms. Nadja Helen Haeussler and Mr. ChristophScheffel,
International students from Germany at MIT, Manipal University for helping me in carrying
out case study at Nilgiris, Tamilnadu.
References
1. Ministry of Tourism, Government of India, Annual Report 2011- 2012, Section 1, 3 &4.
2. Statistical Profile of Scheduled Tribes in India 2010, Ministry of Tribal Affairs,
Government of India.
3. Houselisting and Housing Census Data 2011 as in www.censusofindia.gov.in retrieved on
28th August 2012
4. EQUATIONS TEAM, Bangalore, “Nilgiris Biosphere Reseve, Fading Glory”, Page 13.
5. “Tourism and Poverty Alleviation”, as in www2.unwto.org retrieved on 4th September
2012.
6. Web Portal of Tamil Nadu Forest Department: www.forests.tn.nic.in retrieved on 4th
September 2012.
7. Davidar Priya et. al.,2007, “Forest Degardation in the Western Ghats Biodiversity
Hotspot: Resource Collection, Livelihood Concerns and Sustainability”, Journal of
Current Science, Volume 93, Issue 11, page 1573.
8. “Tourism to be streamlined in Nilgiris South Division”, as in www.thehindu.com/todayspaper/tp-national/tp-tamilnadu/article3382513.ece,
Udhagamandalam, May 4, 2012,
retrieved on 20th August 2012.

Abstract
Low Energy Residential Building Design
for Hot Arid Climate – A Review
Tejwant Singh Brar* and Pinto Emerson **
* Sushant School of Art & Architecture, Ansals University, Gurgaon
**Nanak Dev University, Amritsar
Corresponding Author, Email: brartejwant@yahoo.com
There are, presently, two schools of thought when it comes to designing buildings that promote
sustainable development. One school emphasizes materials use and ‘‘green’’ buildings, while the
other emphasizes energy use and low energy buildings. The promoters of ‘‘green’’ buildings
often claim that the reduced energy use during operation of the low energy and solar buildings is
counteracted by the increased embodied energy in these buildings.
This paper gives categorical analysis of the technologies available for Low energy and green
architecture and emphasizes the need to integrate both in residential buildings to of lower the
energy use in operation during the lifetime in a residential building in hot arid climate. The
results also show that there should be little difference between the approaches of the two schools
of thought. The best buildings will generally be those that are both low energy, and ‘‘green’’.
This paper also gives policy guidelines to integrate them in the building bye-laws for hot arid
climate.
Key words: Green Architecture, Green Buildings, Solar Architecture, Hot Arid Climate
Urbanization and Integrated Water Supply, Sewerage and Drainage Plan.
1. Introduction
In order to produce buildings that promote sustainable development, several problems have to be
addressed. One of the major problems is energy use in these buildings. Other problems, for
instance material use, involving issues such as recyclability, waste minimization, and the impact
on indoor air quality, are also important, but energy is the single most important factor. The
reasons for this are:
Energy is one of the most important resources used in buildings (both in the production of the
building and during its operation), and
Energy use often has serious environmental impacts, both locally and globally.
The total amount of energy used in buildings during operation constitutes a significant part of the
total amount of energy used in a country (Winther B.N.and Hestnes A. G., 1999). Housing forms

y far the most common building type through out the world. Over 15% of all savings in
developing countries is invested in residential construction. The buildings use 1/3 rd of all energy
consumed in India and 2/3 rd of all electricity.
The term ‘Green Architecture’ is used for the integration of construction of all separate
technologies disciplines involved in the research and promotion of sustainable solutions. It aims
at creating environment friendly and energy efficient buildings. This entails active harnessing
‘Solar Energy’ and using materials which do the least damage to air, water and ground. The Idea
is to first reduce the light and energy demands through architecture and space designing and then
meet those demands by using energy.
This paper gives categorical analysis of the technologies available for solar and green
architecture and emphasizes the need to integrate the solar and green architecture in residential
buildings to of lower the energy use in operation during the lifetime in a residential building in
hot arid climate.
2. Nature of hot arid climate
Hot arid climate normally occurs between latitudes 15º and 35º (Fig: 1)north and south of
equator. The sun is almost overhead at noon in the hottest months but in the winter months it has
an altitude of approx. 45º (Fig: 1) at noon and in this climate hot dry winds increase the
discomfort. Another climatic feature which often occurs in hot dry climates is the temperature
inversion with large variation between day and night temperatures. Mean maximum air
temperature for summer months is between 43 to 48º C and minimum is between 27 to 30º C
While in winters Mean maximum air temperature is between 24 to 30º C and minimum is
between 17 to 22º C. The Precipitation is slightly variable throughout the year from 300 to 600
mm per annum with maximum during the monsoon months. The sky conditions are normally
clear with few clouds. The sky is usually sky blue with a luminance of 1700 to 2500 cd/m 2 . Solar
radiation is direct and strong during the day, but the absence of clouds permit easy release of heat
stored during the day time in the form of long wave radiation towards the night sky. Winds are
usually local often caused by temperature inversion due to hot ground and cooler upper air
resulting in local whirlwinds. Vegetation is sparse and difficult to maintain because of the lack of
rain and low humidity. The factors which affect the design of a residential building in Hot Arid
climate are Topography, Water, Ground surface, Vegetation, Windbreaks & Orientation. The
design features in hot arid climate include features like compact form, use of materials with
absorptive, insulation, and high thermal capacity, evaporative cooling, use of internal courtyards,
use of reflective surfaces and brise-soleils or sun breakers,
3. Solar and Green architecture
Green buildings are buildings in which all of the materials and systems are designed with an
emphasis on their integration into a whole for minimizing the impact on the globe and on the
occupants. While Green Architecture is recognizes that buildings play a role in the
environment and tries to optimize the performance of the building, to conserve important
resources like water land and energy (http;//www.athena.org).

For this Energy intensiveness of materials is taken into consideration while selecting the
building materials (Table 1).
Hot Arid Climatic Zone
Table1. Energy Intensiveness of Materials
S. No. Material Energy Content KWH/Kg
1 Sand 0.01
2 Wood 0.1
3 Concrete 0.2
4 Sand Lime Concrete 0.4
5 Light Weight Concrete 0.5
6 Plaster Board 1.0
7 Brick Work 1.2
8 Cement 2.2
9 Glass 6.0
10 Plastics 10
11 Steel 10
12 Copper 16
13 Aluminum 56

Physiological uncomfortable conditions in arid climates are mainly caused by the extreme heat
and dryness and to a lesser extent by sand and dust storms. Human thermal comfort is usually
found when the mean skin temperature is maintained by various means below 33.9º C and above
31.1º C (Koenigsberger 1973). In a building the heat loss from the body to the surroundings
mainly related to the air temperature, humidity and air movement. The inter relationship of the
various factors is complex and to a degree affects the other. Movement of air for instance,
reduces the effect of the humidity and radiation may increase the temperature. To control the
climate conditions with energy conservation in mind methods for climate control can be divided
into Passive and Active methods (Vale B. and Vale R. , 1991).
Passive energy conserving climate control is the use of the building itself to provide warmth in
winter and comfortable temperatures in the summers. This can be achieved with insulation,
window shading, and placement of the building to admit the breeze or keep it away as required
i.e Thermal conductivity and form of the building (Table 3 & 4). While Active energy
conserving climate control usually starts with an energy distribution system very much like
conventional one to heat and cool the building. The energy required to produce the heat or cold
and to operate the required pumps and fans is taken, as much as possible from sources other than
fossil fuels. The most promising untapped source of energy for this purpose is solar energy.
Light colors tend to reduce building heat gain in summer. Accordingly the light colored walls
with high mass will have lowest Equilent temperature differential values (Table 2).
Table 2. Effect of Color
S no. Material % Total Incident Heat Reflected
1 Tar and Gravel 7
2 Slate 15
3 Grass 30
4 Copper foil:
Tarnished
36
New
75
5 Paints:
Light Gray
25
Red
26
Aluminum
46
Light Green
50
Light Cream
65
White
75
6 White wash 80
7 Aluminum foil 95

Brick
Concrete
Table4. Time Lag Values Of different Materials
Material Thickness U-Values Time Lag (Hours)
Insulating Fiber Board
Wood
Table 3. Requirement for building form in relation to climate
Climate Element and requirement Purpose
Hot Arid Climate
Minimize South Walls and West Walls To Reduce Heat Gain
Minimize Surface Area To Reduce Heat Gain and Loss
Maximize Building depth To increase thermal capacity
Minimize window wall
4
8
12
4
8
12
2
4
½
1
2
To control ventilation heat gain and
light
0.61
0.41
0.31
0.85
0.67
0.55
0.61
0.09
0.68
0.47
0.30
2 - 21/2
5 - 21/2
8 - 21/2
2 - 21/2
5
8
Hence the buildings with large thermal mass with light coloured walls and reflective surfaces are
suitable for climates which require heating in winter and cooling in summer and can reduce the
energy needed considerably, Other than these passive cooling devices are also used to reduce the
internal temperatures these are mainly of two types – Radiation cooling and cooling by
evaporation. Active climate control using solar energy in building is by use of Air conditioners,
Water heaters, Solar Collectors and Lighting powered by solar power by using Photovoltaic
cells. These can be integrated in the building design on the roof and south and west walls and can
reduce the energy demand by 2/3 rd in a residential building in hot arid climate (Krishan A.,
2001).
0.7
0.3
0.2
0.4
1

Recommendations
Energy consumption can be reduced by adopting energy conservation techniques which
begins at planning stage like – Orientation, Use of Common walls, Zoning of spaces, Use of
low energy intensive materials,
Building Forms Should be compact and low rise, using small courtyards to provide light and
air. With inward looking form of residential buildings and windowless boundary walls, the
building sheltering the next
Massive buildings with high volume to surface ratio are advantageous since this will reduce
the high external temperature
Medium rise apartment blocks are suitable to provide a dense and continuous urban form and
to avoid exposure to west sun.
Pale surfaces, Double roofs, Reflective foil ins roof and walls is necessary
Small North facing windows, and no windows on eastern or western side of the house
shading of any south facing opening if house site is north of 23.5º S.
Southerly Orientation calls for the combinative shadow mask
Westerly Orientation will receive solar radiation when air temperatures are high from high
altitude and low angle of sun, hence windows are to be avoided.
For north westerly orientation vertical devices would serve well having radial mask when
inclined toward north they give more protection from southern positions of sun.
East facing windows will receive morning sun at low angle when it is warm but it could be
comfortable in winters.
Vegetation and Verandahs around the house to provide shade.
This is perfect climate for Solar Power.
Evaporative coolers work well in this climate along with cooling effect of plants.
Considerable heat storage capacity with low energy intensive materials like – Bricks, Stones,
Concrete to keep day time temperatures low.
So by incorporating these changes in design and use of green materials for construction will
result in residential buildings with low energy consumption. This indicates that best buildings are
those that combine both solar, low energy and green.
References
Central Building Research Institute, (1991) Building Research Notes: Thermal Performance
of Building Sections in Different Climate Zones UDC: 699.-38, SBF: ab-8. CBRI, Roorkee.
Central Building Research Institute, (1991) Building Research Notes: Integrated
Environment Design (Hot and Dry climates), UDC: 725-23, SBF: (92)
http;//www.athena.org
Koenigsberger ( 1973) Manual of Tropical Housing and Building Design. Orient Longman
Krishan A., (2001) Climate Responsive Architecture: A design handbook for energy efficient
building. Tata McGraw Hill
Vale B. and Vale R. , (1991) Design for a Sustainable Future. Thames and Hudson.
Winther B.N.and Hestnes A. G., (1999) Solar Versus Green: The Analysis Of Norwegian
Row House. Solar Energy Vol. 66, pages 387 – 393.

Modeling and Simulation of Composite Steel-Concrete Columns
for High-Rise Buildings
Abstract.
Ziyad A. Khaudhair, P. K. Gupta and A. K. Ahuja
Indian Institute of Technology Roorkee
Corresponding Author, Email: ziyaddce@iite.ernet.in
In this paper an effort has been put to provide an alternative to experiments through Finite
Element simulations. Axially loaded concrete filled steel tube (CFST) columns have been
simulated using Finite Element commercial code ANSYS. Three dimensional nonlinear
(geometric nonlinearity and materials nonlinearity) Finite Element model has been
developed and proposed to model axial compression process of concrete filled tubular
columns. The proposed model has been verified with selected experimental results available
in literature. It has been concluded that the proposed model is capable to predict the
behavior and axial load carrying capacity of concrete filled steel tube columns with different
geometries and filled with different grades of concrete.
1. Introduction
Simulation works are the most used and useful techniques of researchers and industrial
engineers. Due to the huge increase in cost of materials and experimentation, to understand
the actual behaviors of engineering systems simulation remained only alternative. In
simulation work the engineering concepts of analysis and design are modeled to obtain the
out similar to experimental output.
Due to the growing requirements to increase the flexibility of the floor space of buildings
and increase the load carrying capacity with seismic resistance, composite columns came
into the picture. Two common types of composite columns have been used in the structural
systems: composite columns in which the steel sections encased in concrete and steel tubes
columns filled with concrete. Concrete filled steel tubular columns have been used more due
to the confinement of concrete core which gives columns with reduced cross sections and
more ductility to resist the earthquake loading. However, for high rise buildings it is often
required to use high strength concrete to permit more useable floor area. To prevent the
expected brittle failure of high strength reinforced concrete columns, columns concrete
filled steel tube columns (CFST) may be a better alternative. Use of CFST columns in
structural buildings has increased in many countries in last two decades: Japan, USA and
China especially in zones of high seismic activities (Shams & Saadeghvaziri, 1999). Due the
advantages of CFST columns like high load carrying capacity, high ductility, high shear
resistance their behaviour was investigated experimentally by many researchers. However,
the structural behaviour of CFST columns is affected by many factors, such as the geometry

of steel section, column slenderness and member material properties (Gupta, Khaudhair, &
Ahuja, 2012). Gardner and Jacobson tested twenty two circular CFST columns with D/t
(outer diameter to wall thickness of steel tube) ratios between 30 and 40. In their results they
suggested that experimentally measured failure loads were significantly more than the
calculated failure loads (sum of the failure loads of steel and concrete acting alone).
Knowles and Park (Knowles & Park, 1969) studied twelve circular and seven square
columns with D/t ratios of 15, 22, and 59, and L/D (length (L) / outer diameter (D)) ratios
ranging from 2 to 21. They found that the short column with L/D (Length to outer diameter)
less than 11 were giving experimental results more than the calculated. It is also recognized
by many researchers (Ellobody, Young, & Lam, 2006) (Gupta, Sarda, & Kumar, 2007)
(Huang, et al., 2002) (Johansson M. , 2002) (Sakino, Nakahara, Morino, & Nishiyama,
2004) that the experimental results for CFST with circular cross section and axially loaded
were more than the calculated load which is, basically, sum of the failure load of concrete
and steel independently. Analytical studies have been carried out by researchers to estimate
this increase. Sakino et al. (Sakino, Nakahara, Morino, & Nishiyama, 2004) proposed
analytical model to calculate the ultimate load of CFST columns with circular and square
cross sections. Other models were also proposed to predict the ultimate load (Johansson &
Gylltoft, 2002) (Liang & Fragomeni, 2009) (Susanatha, GE, & Usami, 2001) (O'shea &
Bridge, 2000). Schneider (Schneider, 1998) developed a computational model using finite
element code ABAQUS to simulate the axially loaded CFST columns with circular cross
sections. His model gave good agreement with the experimental results. Other
computational models were also developed using ABAQUS by researchers (Ellobody,
Young, & Lam, 2006) (Hu, Huang, & Chen, 2005) (Johansson & Gylltoft, 2002) (Liang &
Fragomeni, 2009) (Shams & Saadeghvaziri, 1999) (Susanatha, GE, & Usami, 2001). Two
dimensional computational models have been developed using finite elements software
ANSYS by Gupta et al. (Gupta, Sarda, & Kumar, 2007) to simulate the behaviour of axially
loaded CFST columns. The developed model was verified with the experimental results and
good agreement was concluded. ABAQUS has been employed by many researchers to
develop computational model but ANSYS Code is used by only a few researchers.
Therefore, in the present study, a three dimensional nonlinear model has been developed to
simulate the behaviour of CFST circular columns with axial loading using finite element
commercial software ANSYS. The developed model has been verified with selected
experimental results available in literature.
2. Computational model
2.1 General characteristics
The aim of the proposed model is to investigate, with better understanding, the actual
behavior of axially loaded concrete filled steel tube columns. To simulate the CFST
columns, the proposed model should be able to simulate the actual loading conditions and
expected deformed shape. Hence, a three-dimensional nonlinear (geometric nonlinearity and
material nonlinearity) Finite Element model was developed. ANSYS 12.0 general finite
element code was used for all nonlinear analytical modeling. To simulate the physical model
in the laboratory, the components of the composite column (steel tube, concrete core and the
loading plates) have modeled in separate fashion from each other, and then contacts have
been modeled among them.

3. Modeling of steel tube
When a concrete filled steel tube column axially loaded in compression, the expected
deformation in the concrete core is translation in compression without rotation, so elements
with translations degree of freedom will be good sufficient to simulate this behavior. In spite
of steel tube section thickness is relatively small compared to other dimensions (diameter
and length), using solid elements will makes the hollow section mesh follows the contacting
surface reasonably, increases the total number of elements (i.e. finer mesh which means
more accuracy) and also reflects the deformation features of the hollow section. For these
two reasons, it has been decided to model the steel tube using SOLID45 element. The
element is defined by eight nodes having three degrees of freedom at each node: translations
in the nodal x, y, and z directions. The element has plasticity, large deflection, and large
strain capabilities (ANSYS Inc.). Geometric of SOLID45 element is shown in Figure 1
while Figure 2 shows the SOLID45 element in the proposed model after meshing.
Figure 1. Geometry of SOLID45 element
(ANSYS Inc., User Guides, Release 12)
Elastic-Perfectly-Plastic model with Mises plasticity has been used to simulate the material
behavior of steel tube in the proposed model with initial Young’s modulus of 200 GPa and
Poisson’s ratio of 0.3.
4. Modeling of concrete core
Figure 2. SOLID45 elements for steel
tube elements in the proposed model
SOLID65 element (3-D Reinforced Concrete Solid) is adopted to simulate the concrete core
elements. SOLID65 is a three-dimensional element which is defined by eight nodes having
three translational degrees of freedom at each node. This solid element is also capable of
cracking in tension and crushing in compression, plastic deformation and creep. This
element can predict the brittle failure behavior of concrete through concrete material model
which is available from ANSYS with SOLID65 element. Geometry of SOLID65 element is
shown in Figure 3. Figure 4 shows the elements of SOLID65 after meshing.
Figure3. Geometry of SOLID65 element
(ANSYS Inc., User Guides, Release 12)
Figure 4. SOLID65 elements for concrete core
elements in the proposed model

Due to the interaction between the steel tube and the concrete core in circular CFST
columns, a triaxial stress state is developed in concrete core which corresponding to
confinement of concrete (Johansson M. , 2002). The confined concrete can sustain large
deformations without substantial reduction of the load carrying capacity and fails gradually
in a ductile way (Hatzigeorgiou, 2008). Hence, confined concrete model should be adopted
to simulate the actual behavior of the concrete core. Confined concrete model proposed by
Hu et al. (Hu, Huang, & Wu, 2003) to compute the uniaxial strength of concrete confined
with circular steel tube has been adopted to simulate the confining pressure of concrete core.
The adopted model formulas are given by:
(1)
(2)
Where, = the outer diameter of the tube section; t = the tube wall thickness; is the yield
strength of the tube section and = Lateral confining pressure. The confined compressive
strength and corresponding strain is calculated based on the equations proposed by Mander
et al. (Mander, Priestley, & Park, 1988)
(3)
Where, = uniaxial compressive strength of confined concrete, = concrete strain
corresponding to stress, = concrete strain corresponding to stress, considered as
0.003 as per ACI code, (ACI 318 Committee, 2008), and may be defined as confining
factors, considered as 4.1 and 20.5 (5 as recommended by Richart et al. (Ellobody,
Young, & Lam, 2006). To simulate the stress-strain relationship of concrete core, the
equivalent uniaxial stress strain curve for confined concrete identified by Ellobody et al.
(Ellobody, Young, & Lam, 2006) has been adopted in this study. The stress-strain
relationship of confined concrete is shown in Figure 5 which is also clearly explains the
difference between the stress-strain relationship of confined and unconfined concrete. The
stress-strain relationship has been considered as three different parts. The first part defines
the elastic behavior of the confined concrete (from zero stress strain point till the
proportional level) and the proportional limit stress has been assumed to be with
initial confined concrete modulus of elasticity as per the formula given in ACI
Figure 5. Equivalent stress-strain curve for confined
and unconfined concrete (Ellobody, Young, & Lam,
(4)

code and described as , in MPa. The second part of the stress-strain
curve describes the nonlinear behavior of the confined concrete, before reaching the
maximum strength of concrete. Hence this part starts from the proportional limit
stress, , to the maximum strength of the confined concrete, . The stress-strain
relationship proposed by Saenz (Saenz, 1964) has been adopted to represent this part of
confined concrete; this relationship may be given as:
Where,
.
The third part of the curve of confined concrete starts from the maximum confined concrete
compressive strength, and ends at ultimate strength of confined concrete, which
represents the post peak behaviour of concrete (descending part), with the corresponding
strain, . Hu et al. (Hu, Huang, & Chen, 2005) proposed a formula to calculate
the ultimate strength of concrete core confined with circular steel tubes as ,
Where, may be defined as material degradation parameter and it is given by two
empirical equations as:
Ellobody et al. (Ellobody, Young, & Lam, 2006) modified the formula which has been
proposed by Hu et al. (Hu, Huang, & Wu, 2003) to calculate the value of for same
corresponding strain, , as: , Where r is a parameter can be taken as parameter r
can be taken as 1.0 for concrete with cube strength of 30 MPa and 0.5 for concrete with
cube strength of 100 MPa, respectively and linear interpolation may be used for concrete
with cube strength between 30 and 100 MPa.
5. Modeling of steel-concrete interaction
Surface to surface contact element with low order has been used (CONTA173). CONTA173
element is used to represent contact and sliding between 3-D “target” surfaces (TARGE170)
and a deformable surface defined by this element. This element is applicable to three
dimensional field contact analyses and it’s located on the surfaces of 3-D solid or shell
elements without midside nodes (like SOLID65 & SOLID45).
Two rigid loading plates were used at the column ends as shown in Figure 4 therefore; those
plates have been simulated as rigid blocks. Direct contact existed between the end plates and
the end surfaces of the column, therefore; surface to surface contact (CONTACT173) has
been used to simulate the contact between the rigid plate and the column end surfaces.
Different friction factors were tried for the contact behavior it was found that, when friction
factor is less a relative sliding between the column end and rigid plate occurred, as it’s also
observed by Ellobody and Lam (Ellobody, Young, & Lam, 2006), therefore; friction factors
(6)
(7)
(5)

have been adopted as 0.2-0.3 for top and bottom ends. The top and bottom end surfaces of
the specimen were fixed against all degrees of freedom except for the displacement at the
loaded end (top end) in the direction of applied load.
6. Verification of the proposed model
The proposed model has been verified with selected experimental results available in
literature. The experimental works have been simulated and the results have been compared
with the numerical results of the proposed model. The details of the simulated samples are
listed in Table 1. The experimental results and the results of the proposed model have been
compared in Figures 6–9. It has been concluded that the proposed model is giving numerical
results with good agreement with the experimental results as shown in figures.
Figure 6. Experimental results and numerical results of the proposed model
for samples of Johansson (Johansson M. , 2002)
Figure 7. Experimental results and numerical results of the proposed model for
samples of Giakoumelis and Lam (Giakoumelis & Lam, 2004)
Figure 8 Experimental results and numerical results of the proposed model
for samples of Gupta et al. (Gupta, Sarda, & Kumar, 2007)
Figure 9. Experimental results and numerical results of the proposed model for
samples of Oliveira et al. (Oliveira W. , Nardin, El Debs, & El Debs, 2009)

Conclusion
In the present study, the Finite Elements Code ANSYS has been used to simulate the axially
loaded concrete filled steel tube (CFST) columns. In this paper details of the simulation
process are presented. Three-dimensional model has been developed with confined concrete
stress-strain model available in the literature and elastic- perfectly-plastic model for
simulation of steel tubes. The proposed ANSYS model has been verified with some of
experimental results available in the literature. It is observed that the proposed ANSYS
model combined with adopted stress-strain model could be used to predict the axial load
capacity and behavior of concrete filled steel tubes filled with different grades of concrete.
Thus, simulation study can be replaced the expensive experimental investigations.
References
Sample
ID
Outer
Dia.(mm)
Table 1. Details of simulated samples
Wall
Thick.(mm)
Length
(mm)
Comp. St.
of Con.
Cyl. (MPa)
Yield
Str. of
Steel
(MPa)
Johansson (Johansson M. , 2002)
SFE1 159 4.8 650 64.5 433
SFE8 159 6.8 650 93.8 402
Giakoumelis and Lam (Giakoumelis & Lam, 2004)
C7 114.88 4.91 300.5 34.7 365
C8 115.04 4.92 300 104.9 365
Gupta et al. (Gupta, Sard, & Kumar, 2007)
D3M4 89.32 2.74 340 37.6 360
D4M3 112.56 2.89 340 25.15 360
Oliveira et al. (Oliveira W. , Nardin, El Debs, & El Debs, 2009)
C30L5D 114.3 3.35 571.5 32.7 287.33
C60L7D 114.3 3.35 800.1 58.7 287.33
1. Abedi, K., Ferdousi, A., & Afshin, H. (2008). A novel steel section for concrete-filled
tubular columns. Thin Walled Structures, 46, 310-319.
2. ACI 318 Committee. (2008). Building Code REquirements for structural Concrete (ACI
318M-08) and Commentry. American Concrete Institute.
3. ANSYS Inc. User Guides, Release 12.
4. Dai, X., & Lam, D. (2010). Numerical modelling of the axial compressive behaviour of
short concrete-filled elliptical steel columns. Jounal of Constructional Steel Research,
66, 931-942.
5. Ellobody, E., Young, B., & Lam, D. (2006). Behaviour of normal and high strength
concrete-filled compact steel tube circular stub columns. Journal of Constructional Steel
Research, 62, 706-715.

6. Giakoumelis, G., & Lam, D. (2004). Axial capacity of circular concrete-filled tube
columns. Journal of Constructional Steel Research, 60, 1049-1068.
7. Gupta, P. K., Khaudhair, Ziyad. A., & Ahuja, A. K. (2012). A study on load carrying
capacity and behaviour of concrete filled steel tubular members subjected to axial
compression. the 11th International Conference on Concrete Engineering and
Technology 2012 (pp. 337-342). Putrajaya, Malaysia: CONCET 2012.
8. Gupta, P. K., Sarda, S., & Kumar, M. (2007). Experimental and computational study of
concrete filled steel tubular columns under axial loads. Journal of Constructional Steel
Research, 63, 182–193.
9. Hu, H.-T., Huang, C.-S., & Wu, M.-H. (2003). Nonlinear Analysis of Axially loaded
Concrete-Filled Tube Columns with Confinement Effect. Journal of Structural
Engineering, 129(10), 1322-1329.
10. Huang, C., Yeh, Y., Liu, G., Hu, H. T., Tsai, K., Weng, Y., et al. (2002). Axial Load
Behavior of Stiffened Concrete-Filled Steel Columns. Journal of Structural
Engineering,ASCE, Vol. 128, No. 9, 1222-1230.
11. Johansson, M. ( 2002). The efficiency of passive confinement in CFT columns. Steel
and Composite Structures, vol. 2, No. 5, 379-369.
12. Johansson, M., & Gylltoft, K. (2002, August,1). Mechanical Behavior of Circular Steel–
Concrete Composite Stub Columns. Journal of Structural Engineering, 128(8), 1073–
1081.
13. Knowles , R. B., & Park, R. (1969). Strength of concrete filled steel tubular columns.
Journal of the structural division, Proceedings of the American Society of Civil
Engineering, 95((ST12)), 2565-2587.
14. Liang, Q.Q., & Fragomeni, S. (2009). Nonlinear analysis of circular concrete-filled steel
tubular columns under axial loading. J. of Constructional steel Research, 65, 2186-2196.
15. Mander, J. B., Priestley, M. J., & Park, R. (1988). Theoritical Stress-Strain model of
confined concrete. Journal of Structural Engineering, 114(8), 1804-1826.
16. Oliveira, W. L., Nardin, S. D., El Debs, A. L., & El Debs, M. K. (2010). Evaluation of
passive confinement in CFT columns. 66, 487-495.
17. Oliveira, W., Nardin, S., El Debs, A., & El Debs, M. (2009). Influence of concrete
strength and length/diameter on the axial capacity of CFT columns. Journal of
Constructional Steel Research, 65, 2103-2110.
18. O'shea, M. D., & Bridge, R. Q. (2000). Design of Circular Thin-Walled Concrete Filled
Steel Tubes. Journal of Structural Engineering, 126, 1295-1303.
19. Saenz, L. P. (1964). Discussion of ‘Equation for the stress-strain curve of concrete’ by
P. Desayi, and S. Krishnan. ACI Journal, 61, 1229–1235.
20. Sakino, K., Nakahara, H., Morino, S., & Nishiyama, I. (2004). Behavior of Centrally
Loaded Concrete-Filled Steel-Tube Short Columns. Jouranl of Structural Engineering,
ASCE, Vol. 130, No. 2, 180-188.
21. Schneider, S. (1998). Axially Loaded Concrete-Filled Steel Tubes. Journal of Structural
Engineeing, ASCE, Vol. 124, No. 10, 1125-1138.
22. Shams, M., & Saadeghvaziri, M. (1997). State of the Art of Concrete-Filled Steel
Tubular Columns. ACI Structural Journal, Title No. 94-S51, 558-569.
23. Shams, M., & Saadeghvaziri, M. A. (1999). Nonlinear Response of Concrete-Filled
Steel Tubular Columns under Axial Loading. ACI Structural J., 96-S112, 1009-1018.
24. Susanatha, K. A., Ge, H., & Usami, T. (2001). A capacity prediction procedures for
concrete-filled steel columns. Journal of Earth Quick Engineering, 5(4), 483-520.
25. Susanatha, K. A., Ge, H., & Usami, T. (2001). Uniaxial stress-strain relatioship of
concrete confined by varioys shaped steel tubes. Engineering Structures, 23, 1331-1347.

Energy Simulation for Sustainable Building with Application of
Roof and Wall Insulation
Abstract
B. M. Suman
CSIR- Central Building Research Institute Roorkee (India)
Corresponding Author, Email: bs_ashishh@rediffmail.com
The simulation study has been carried out for evaluation and performance of roof and wall
insulation to be applied in building to assess its energy saving potential in air conditioned
building and reduction in indoor air temperature to be achieved in unconditioned building
during summer season. Heat conduction transfer functions or response factor methodology to
predict the thermal history of multi layer slabs in the software TRNSYS [1], developed by
Mitalas, Stephenson and Arseneault have been used for the calculation of transient heat
transfer through walls and roof of building. The study has been undertaken for a period of
one year for a single zone building in composite climate of India. Result of the study states
that more than 29 % energy can be saved by treating a building with good insulation system.
1. Introduction
Modern buildings in India consume about 25 to 30 percent of total energy generated.
Although the present energy consumption per capita in India is a fraction of that of most
developed nations, but with its projected growth, unless enough measures are taken, it may
lead to acceleration of destruction of environment, leading to further global warming and
climate change. Sustainable building may contribute towards cutting down energy
consumption. The approach of developed nation to sustainability concentrates on energy
conservation through high technology innovations, use of products and materials with lower
embodied energy and green rating based on intent, which implies expert inputs and
simulation. Indian construction industry will do better using quality thermal insulation apart
from applying low cost technology innovations, using recycled materials and recognizing
performance through easily measurable parameters.
In this study a computer model TRNSYS; version 16, very versatile software has been used
for thermal simulation study of the building. The study on thermal behavior has been
undertaken for the building located at New Delhi which falls in the composite climatic zone
of India. The solar radiation and climatic data of this station is available in the desired format
i.e. TMY2 (New Typical Meteorological Year) as required in TRNSYS Software. The
important data elements which are being used as input in the software are hourly values of
about 20 parameters. These parameters are, Extraterrestrial Horizontal Radiation,
Extraterrestrial Direct Normal Radiation, Global Horizontal Radiation, Direct Normal
Radiation, Diffuse Horizontal Radiation, Global Horizontal Illuminance, Direct Normal

Illuminance, Diffuse Horizontal Illuminance, Zenith Luminance, Total Sky Cover, Opaque
Sky Cover, Dry Bulb Temperature, Dew Point Temperature, Relative Humidity,
Atmospheric Pressure, Wind Direction, Wind Speed, Horizontal Visibility, Precipitable
Water and Aerosol Optical Depth.
2. Objective
The objective of this study is to estimate the building energy consumption and evaluation of
indoor air temperature for using different type of thermal insulation on roof, wall, and roof
and wall both. Energy simulation of eleven cases of building specifications has been carried
out for hourly basis far all 8,760 hours in the year. The evaluation has been made in the form
of hourly indoor temperature profile for non air condition building and for air conditioned
building, space air conditioners of cooling capacity of 60kJ/hour has been considered for
untreated case and cooling capacity of 40kJ/hour has been considered for treated cases. In
this study no adjacent or internal wall is considered as all the four walls are external wall
each made of non negligible mass. In the untreated case basic conventional construction
material has been used. The walls are 0.230m thick brick plastered on both side with cement
mortar of 0.013m thickness. The total thickness of each of four walls is 0.256m and its Uvalue
is 2.376w/m 2 K. The solar absorption co-efficient of the walls is 0.6 on the front side
and 0.6 on the back side. The convective heat transfer coefficient of wall are 11 kJ/hm 2 K on
the front side (inside surface) hi and 64 kJ/hm 2 K on the back side (outside surface) ho. Roof
is 0.150m thick heavy reinforced concrete slab plastered inside with thickness of 0.013m.
The total thickness of each of roof is 0.163m and its U-value is 4.023w/m 2 K. The solar
absorption co-efficient of the roof is 0.6 on the front side and 0.6 on the back side. The floor
of the building is made of marble stone of 0.025m thick laid over heavy concrete of 0.100m,
and clay-soil of at least 0.100m thickness. The total thickness of the floor is 0.255m and its
U-value is 3.290w/m 2 K. The treatment such as application of various layers of insulation
material on roof using different insulation materials have been considered in various treated
case. Applications of wall insulation along with roof insulation have also been considered.
3. Methodology
A holistic approach to building design requires a methodology to estimate the performance of
the proposed design and material in advance and in such a way that the interactions between
different technical domains may be judiciously incorporated. Performance of different
building and insulating materials are needed to be evaluated quantitatively for their thermal
behaviors as if they are applied to actual building for a whole of the year covering most of
the weather conditions that may the building will face. Building performance [2] analysis is
essential at the design stage in order to prevent the delivery of building with unacceptable
performance characteristics. Based on the literature survey and our experience in the research
and development in this area, some of the approaches for evaluation of performance of a
design of building and building materials are tabulated below. The advantage and
disadvantage of different methodologies are given in Table 1. Currently 16 th version of
TRNSYS is available at CBRI Roorkee. TRNSYS version 16 is capable of predicting hourly
indoor temperature profile and also cooling/heating loads. This software is also capable of
carrying thermal simulation of multi-zone building. Thence this software has been used for
the evaluation of indoor air temperature and cooling load of a typical building with a view to
evaluate the performance of difference type of roof and wall insulation.

Table 1. Comparison of merit and demerit of different methodologies
________________________________________________________________________
Approach Type Advantage Disadvantages
________________________________________________________________________
Experimental Small scale Reproductive experiment Scale effects
model study) low cost modeling error
Full scale Complex phenomenon Time consuming
global analysis expensive
Analytical Easy to use Large errors due
to Mathematical
simplification
Numerical Complex model Validation, model
(computer fast calculation might be complex,
simulation) compare different model
variants approximately/error
________________________________________________________________________
Currently 16 th version of TRNSYS is available at CBRI Roorkee. TRNSYS version 16 is
capable of predicting hourly indoor temperature profile and also cooling/heating loads. This
software is also capable of carrying thermal simulation of multi-zone building. Thence this
software has been used for the evaluation of indoor air temperature and cooling load of a
typical building with a view to evaluate the performance of difference type of roof and wall
insulation.
This software has in-built weather file containing detailed climatic data of many stations
covering all over the world. The climatic data of more than 70 stations of India are also
included in it. In this software heat conduction transfer functions or response factor
methodology to predict the thermal history of multi layer slabs, developed by Mitalas,
Stephenson and Arseneault have been used for the calculation of transient heat transfer
through walls and roof of building. The long wave radiation exchange between the surfaces
with in the zone and the convective heat flux from the inside surfaces to the one air are
approximated using the star network proposed by Seem. A2- Band- Solar-Radiation-
Window-Model and Window 4.1 program developed at LBL USA have been used for taking
into account the effect of the heat transmission through windows.
4. Basic considerations
The indoor thermal environment depends on many factors such as outdoor climatic
conditions, thermo- physical properties of materials used in the construction of building
envelope. The building envelope consists of opaque roof and walls, transparent or translucent
glazing and projections such as overhang and wing walls for shading of windows. The
overall heat transmittance (U-value) of wall, roof and other component of building envelope
is the most important parameter, which affects heat transmittance of any building interior
from thermal viewpoint. The overall heat transmittance of any building element such as roof
or wall is a function of thermal conductivity (k-value), thickness of different layers of
material of which it is composed of, and convective heat transfer coefficient of inside and

outside surface i.e. hi and ho. The external surface characteristics such as solar absorption,
reflectance, emissivity of walls and roof, and transmittance of window elements determine
the influence of the exposure of the building envelope to the building depends upon the
orientation and form of the envelope whether it is square, rectangular or cylindrical.
The case under consideration is a single storey residential building having a big hall room.
The dimension of the room selected is such that it is rectangular in shape with aspect ratio of
the order of 3:2 and it is 15m long and 10m wide and 4m height located on ground floor with
all the four vertical walls facing cardinal directions (North, East, South and West) and flat
horizontal roof exposed to external environment. Each wall has window of 1.2 m height at a
sill level of 0.9m above floor; the area of each window is 15% of the corresponding wall
area. Windows have horizontal overhangs of 0.45m wide on their top. A suitable orientation
helps in achieving better conditions indoors through reduction of solar heat ingress and
enhancement of natural ventilation. Long axis of the building along East-West with windows
of larger sizes facing north and south provides advantage of solar heat in winter minimizing
it in summer.
Generally in a thermal zone of building walls are classified into four types viz.
1. External: The wall separating the zone from external ambient environment.
2. Adjacent: Wall separating different thermal zones.
3. Internal: Wall within a thermal zone under consideration.
4. Boundary: Wall within having known external boundary conditions.
Walls are generally made up of layers of various thicknesses of different materials.
There are three types of layers that may be defined
Layers having non-negligible mass (massive layers)
Layers to be treated as pure resistances
Active layers
Table 2. Thermo-Physical properties of insulation product
Product Average Density
(kg/m 3 Average K-value Average K-value
)
(W/mK)
(kJ/hmK)
Elastopor board 44.32 0.0248 0.1040
Peripor board 32.60 0.0322 0.1350
Neopor board 17.50 0.0318 0.1340
Elastospray 43.80 0.0229 0.0962
Styropor 19.23 0.0346 0.1450
Thermocrete 752.0 0.2300 0.9660
The most important factor for thermal simulation study of the building design will be the
climatic condition outdoor. It is proposed to study the thermal behavior of the building as if it
is located at New Delhi which falls in the composite climatic zone of India as per new

climatic zone 2 . The solar radiation and climatic data of this station is available in the desired
format i.e. TMY2 (New Typical Meteorological Year) as required in TRYNSIS Software.
The important data elements which are being used as input in the software are hourly values
of about 20 parameters listed below.
Extraterrestrial Horizontal Radiation, Extraterrestrial Direct Normal Radiation, Global
Horizontal Radiation, Direct Normal Radiation, Diffuse Horizontal Radiation, Global
Horizontal Illuminance, Direct Normal Illuminance, Diffuse Horizontal Illuminance, Zenith
Luminance, Total Sky Cover, Opaque Sky Cover, Dry Bulb Temperature, Dew Point
Temperature, Relative Humidity, Atmospheric Pressure, Wind Direction, Wind Speed,
Horizontal Visibility, Precipitable Water and Aerosol Optical Depth etc.
4.1 Common optical and thermal characteristics of single glazed window
Overall heat transfer coefficient U= 5.8W/m 2 K
Solar transmittance g = 0.855
Frame area is 15% of total window area.
Frame U-value = 2.27 W/m 2 K
Tilt of window from horizontal = 90.0 Deg (Vertical)
Total height = 1219.2mm
Total width = 914.4mm
Glass height = 1079.5mm
Glass width = 774.7mm
5. Simulation study
The simulation program is a computer based program for the analysis of energy consumption
in buildings. In the case under study no adjacent or internal wall is considered as all the four
walls are external wall each made of non negligible mass. The untreated base case has
conventional construction material used. The walls are 0.230m thick brick wall plastered on
both side with cement mortar of 0.013m thickness. The solar absorption coefficients of the
walls are 0.6 on the front side and 0.6 on the back side. The convective heat transfer
coefficient hi, on the front side (inside surface) is 11 kJ/hm 2 K and ho on back side (outside
surface) is 64 kJ/hm 2 K for both roof and wall.
Roof consists of 0.150m thick heavy reinforced concrete slab plastered inside with thickness
of 0.013m. The total thickness of each of roof is 0.163m and its U-value is 4.023w/m 2 K. The
solar absorptances of the roof are 0.6 on the front side and 0.6 on the back side. The floor of
the building is made of marble stone of 0.025m thick laid over heavy concrete of 0.100m,
and clay-soil of at least 0.100m thickness. The total thickness of the floor is 0.255m and its
U-value is 3.290w/m 2 K. The solar absorption coefficient of front side as well as back side is
0.6 and the convective heat transfer coefficients of floor for front side surface and back side
are 11 kJ/hm 2 K. The treatment such as application of various layers of insulation material on
roof as per recommended practice in India using different insulation materials have been
considered in various treated case. Applications of wall insulation along with roof insulation
have also been considered. All thermo-physical and construction parameters for different
cases are tabulated below.

Category A. Conventional Construction (untreated)
Layers Thickness
L (m)
Case 1. Wall specification
Thermal
conductivity
K (W/mK)
Thermal
capacity
C (KJ/KgK)
Cement Plaster 0.013 1.07 0.84 2000
Density
ρ (Kg/m 3 )
Brick 0.230 0.85 0.84 1750
Cement Plaster 0.013 1.07 0.84 2000
Total thickness = 0.256 m, U-Value = 2.376 W/m 2 K
Layers Thickness
L (m)
Roof specification
Thermal
conductivity
K (W/mK)
Thermal
capacity
C (KJ/KgK)
Density
ρ (Kg/m 3 )
Cement plaster 0.013 1.07 0.84 2000
Heavy reinforced concrete 0.150 1.89 0.84 2400
Total thickness = 0.163 m, U-Value = 4.023 W/m 2 K
Layers Thickness
L(m)
Floor specification
Thermal
conductivity
K (W/mK)
Thermal
capacity
C (KJ/Kg K)
Density
Ρ (Kg/m 3 )
Marble 0.025 2.52 0.84 2550
Heavy Concrete 0.100 1.46 0.84 2200
Soil 0.100 1.29 1.80 1500
Total thickness = 0.225 m, U-Value = 3.290 W/m 2 K
Category B. Wall and Floor Specification: Same as Case1
Layers Thickness
L (m)
Case 2. Roof treated with Elastopor insulation
Roof specification
Thermal
conductivity
K (W/mK)
Thermal
capacity
C (KJ/KgK)
Density
ρ
(Kg/m 3 )
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Elastopor 0.050 0.0249 0.84 44.32
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.425 W/m 2 K

Layers Thickness
L (m)
Case 3. Roof treated with Peripor insulation
Roof specification
Thermal
conductivity
K (W/mK)
Thermal
capacity
C (KJ/KgK)
Density
ρ (Kg/m 3 )
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Peripor 0.050 0.0324 0.84 32.60
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.511 W/m 2 K
Case 4. Roof treated with Neopor insulation
Roof specification
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Neopor 0.050 0.0319 0.84 17.50
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.508 W/m 2 K
Case 5. Roof treated with Elastospray insulation
Roof specification
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Elastospray 0.050 0.0231 0.84 43.8
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.401 W/m 2 K
Case 6. Roof treated with Styropor insulation
Roof specification
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Styropor 0.050 0.0345 0.84 19.23
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.536 W/m 2 K

Category C. Floor Specification same as case 1
Wall treatment by applying EPS insulation inside of the room Wall specification
Layers Thickness
L (m)
Thermal
conductivity
K (W/mK)
Thermal
capacity
C (KJ/KgK)
Density
ρ (Kg/m 3 )
EPS 0.050 0.032 0.84 21.68
Cement Plaster 0.013 1.07 0.84 2000
Brick 0.230 0.85 0.84 1750
Cement Plaster 0.013 1.07 0.84 2000
Total thickness = 0.306 m, U-Value = 0.545 W/m 2 K
Case 7. Roof treated with Elastopor insulation
Roof specification
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Elastopor 0.050 0.0249 0.84 44.32
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.425 W/m 2 K
Case 8. Roof treated with Peripor insulation
Roof specification
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Peripor 0.050 0.0324 0.84 32.60
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.511 W/m 2 K
Case 9. Roof treated with Neopor insulation
Roof specification
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Neopor 0.050 0.0319 0.84 17.50
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.508 W/m 2 K

Case 10. Roof treated with Elastospray insulation
Roof specification
Layers Thickness
L (m)
Thermal
conductivity
K (W/mK)
Thermal
capacity
C (KJ/KgK)
Density
ρ (Kg/m 3 )
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Elastospray 0.050 0.0231 0.84 43.8
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.401 W/m 2 K
Case 11. Roof treated with Styropor insulation
Roof specification
Cement Plaster 0.013 1.070 0.84 2000
Heavy Reinforced Concrete 0.150 1.890 0.84 2400
Styropor 0.050 0.0345 0.84 19.23
Thermocrete 0.100 0.230 0.84 752
China Mosaic 0.003 1.030 1.00 2000
Total thickness = 0.316 m, U-Value = 0.536 W/m 2 K
In all eleven cases has been considered for simulation. The first case deals with untreated
conventional construction, in second to sixth case roof is treated with Elastopor insulation,
Peripor insulation, Neopor insulation, Elastospray and Styropor insulation respectively with
no wall treatment. The remaining cases from seventh to eleventh, the roof were treated with
respective thermal insulation with wall treated by EPS insulation from inside of the room.
The outputs are in the form of hourly indoor temperature profile after running the simulation
for whole of the year covering all the seasons. For air conditioned space air conditioners of
cooling capacity of 60kJ/hour has been considered for untreated case and cooling capacity of
40kJ/hour has been considered for treated cases.
6. Conclusion
From the study made above, following conclusion may be drawn.
The performance of a building when both roof and wall is treated gives better result than the
treatment made only on roof of the building. The best result is obtained when a building roof
is treated by Elastospray insulation and walls are treated with Expanded Polystyrene thermal
insulation as the lowest minimum and maximum indoor air temperature are recorded in
compare to other thermal insulation. The performance of a building is found same for roof
treated by Elastopor insulation or by roof gravel and the walls treated by EPS. Similarly the
behavior of the building is approximately the same if the roof is treated by either by Styropor
or Pavor elastopor thermal insulation.

The study show that cooling load consumption in a building can be reduced by over 30
percent when the roof treated with Elastospray and wall treated with EPS thermal insulation.
7. Acknowledgement
The study forms part of regular R & D work done at Central Building Research Institute
(CBRI), Roorkee. The paper is sent for publication with permission of the Director, CBRI
Roorkee.
Reference
Figure1.Outdoor air temperature and indoor air temperature of all the cases (11)
for whole of the year (8760 hours).
1 TRNSYS version 16.00 Transient system simulation program developed by solar Energy
Laboratory, University of Wisconsin- Madison, USA TRANS Solar Energietechnik
GmbH and Centre Scientifique du Batiment and Thermal Energy System specialists,
LLC, 2002-2005.
2 National Building Code of India 2005,Group 4 , Bureau of Indian Standards, Second
revision, pages 8-9.

Abstract.
CFD Modelling of Wind Flow around Buildings
for Wind Energy Conversion
A.K. Roy and P.K. Bhargava
CSIR-Central Building Research Institute, Roorkee 247667, India
Corresponding author; Email: amritworld@gmail.com
Wind energy conversion through wind turbine is so far well-established concept and very
popular out of all available renewable energy sources. Research works are going on to
optimize the efficiency of the energy extraction process by inventing advanced wind turbine
replacing the old one. Wind speeds of more than 18 km/hr measured at a height of 10 mare
sufficient enough for the functioning of wind turbine system. So the wind velocity at the sites
is an important parameter for the development. Finding out wind velocities around closely
spaced buildings with the help of codes is not possible. It requires extensive wind tunnel
testing which is very expensive and time consuming. In this research work, CFD simulation
of atmospheric boundary layer wind flow around high-rise urban buildings with different
arrangements and wind incidence angles was carried out to observe the variation of wind
velocity potential surrounding the buildings. It has been observed that on the leeward side
formation of wake zone due to obstructing the flow results in low wind speeds which could
be the reasons of poor efficiency of the installed wind turbine. The results are presented in the
form of velocity magnitude and velocity vector around the buildings. It has also been
observed that significant enhancement of velocity occurred at the roof top of the buildings.
Although too many investigations are still required, here only a study has been carried out to
explore some possibilities of enhancing the efficiency of wind energy conversion in high-rise
urban buildings.
Keywords: Wind energy, velocity potential, wind turbine, CFD simulation, wind tunnel,
1. Introduction
The main source of energy production i.e. oil, coal and gas are being used to a great extent
with the advancement of the civilization and about to be finished in the next 30 years.
Renewable energy sources i.e. hydro power, solar energy, geo thermal and wind energy are
the next best choice for the survival of the civilization. Total wind energy available (1700
TW) all around the world is the second highest after solar energy (Solar PV 6500TW and
Concentrated Solar Power 4600TW). It’s the current trend followed in developed countries to
utilize the huge wind power with the help of building mounted wind turbine and fulfill the
increased power demand. Wind energy conversion has reached a significant milestone with
success of providing support to our increased electricity demand of our major cities around
1

the world. Yet there are so many technology and invention left in this area so that this
abundant source of wind energy can be utilized to produce electric energy.
In an urban area buildings are oriented haphazardly which influence the wind flow and wind
velocity varies place to place around building. This variation can be observed by wind tunnel
tests with the help of Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry
(PIV) or numerical calculations using CFD codes.
In recent years, there are significant progress in the application of CFD to evaluate wind
loads on buildings and structures (e.g. [1-4]and others). Architectural Institute of Japan (AIJ)
[5-6] and the European cooperation in the field of scientific and technical (COST) research[7]
have established working groups to investigate the practical applicability of CFD and to
develop recommendations for their use for wind resistant design of actual buildings and for
assessing pedestrian level winds. AIJ has also provided methods for predicting wind loading
on buildings by the Reynolds Averaged Navier Stokes equations (RANS) and LES.
Pedestrian level wind evaluation carried out by numbers of researchers, where only the mean
wind speeds are required for evaluating pedestrian comfort. Computational studies on tall
Buildings have been conducted by [3],[8] and others. The flow pattern and mean and rms
pressure coefficient of the aerodynamics of Commonwealth Advisory Aeronautical Council
(CAARC) building model is investigated by [9] and others. CAARC tall building is
considered as one of the most extensively and systematically studied building model and
popular in wind tunnel researcher community [10].
In this research work the main concerned area selected just to find out the velocity potential
around the building so that wind turbine installation can be optimized to get the maximum
power conversion. CFD simulation of the wind flow around tall building has been done to
observe the variation of velocity potential. Wind tunnel experimental data has been used to
validate the CFD results.
2. Numerical simulation of wind flow on high-rise building
In the present study measurements of wind tunnel experiments on tall building [8] conducted
at IIT Roorkee, India have been used. The wind tunnel experimental velocity profile and the
turbulence intensity are considered here to simulate the boundary layer wind. This wind
tunnel is an open circuit type boundary layer wind tunnel with no thermal stratification. It has
a test section of 2.1m x 2m cross-section with 15m length. The present study assumes that the
power law expression is valid for representing the wind velocity variation in the atmospheric
boundary layer and a power law exponent (n) equal to 0.15 is used which corresponds to the
open terrain category mentioned as category No.2 in the Indian Standard for wind loads [11].
Other wind standards [12-14] have also been used to validate the simulation study.
2.1 Details of models used for the CFD simulation
The present research work aims at studying the effect of neighbouring buildings on mean
wind velocity magnitude observed around the building. In selecting the model scale it is
important to avoid the influence of the wind tunnel walls and an excessive blockage of the
test section. Corrections are generally applied if the blockage by the model of the building
and its immediate surroundings exceeds about 5% to 10%.Typical geometrical scales used in
2

studies of wind flow on large buildings are about 1:300 to 1:600, and while for models of
small buildings larger scales in the range of 1:100 may be used.
In the current study two setups of building models have been considered. The test setup 1 was
the isolated building without any interfering building (Figure 1). Test Setup 2 and 3are two
building model with 50 mm and 100mm (2×B) spacing respectively. Size of object building
and interfering building was kept same with dimensions L × B × H = 50×50×400mm 3 . Wind
incidence angle (β) has been varied from 0° to 180° with increment of 30° in anticlockwise
direction as shown in Fig. 1.
Figure 1.Test setup of buildings with wind direction angles considered for the study.
2.2 Domains and meshes
Grid generation is one of the very important considerations during the pre-processing stage,
the type of mesh chosen for a given flow problem can determine the success or failure in
attainment of computational solution. The mesh should be sufficiently fine to provide an
adequate resolution of the important flow features and geometrical structures. Generally for
flow with bounded walls steep flow gradients within the viscous boundary layers are properly
resolved through locally refining the mesh in the vicinity of wall boundaries. Accurate
simulation of ABL flow in the computational domain is essential to obtain accurate and
reliable predictions of the related atmospheric processes. To have the geometric similarity
cross section of computational domain and model dimension was kept same as that of the
wind tunnel study and the upstream/downstream length was kept as per the requirement
[15-16]. The geometric scale of model of a building is chosen to maintain the equality of
ratios of overall building dimensions to the inherent lengths of the generated model. The
dimensions of the computational domain are i.e. LD × BD × HD = 2.55 × 2.65 × 2 m 3 as shown
schematically in Fig. 2, which shows the coordinate system used.
3
Wind Incident Angles

Figure 2. Computational domain of the isolated building model used for CFD simulation.
The surface mesh close to the foot of the building shows the growth of the cells in the
boundary layer next to the building. Clearly the aspect ratios of these boundary layer cells are
very large, but as [17] indicates, there is no formal restriction on the size of cells in the wallparallel
direction in RANS simulations. However, Spalart (2000) is discussing streamlined
bodies, not the complex detached flows seen with the bluff body under discussion here. At
the leeward side of the building the mesh was more refined in the wake region relative to the
more distant regions of the domain.
(a)
26B
20B
26B
Fig. 3Surface meshes on the domain showing (a) isolated building model and (b) the two
building model used for CFD simulation.
4
5H
30B
(b)

2.3 Turbulence model
Researchers have already examined different turbulent models for their relative suitability for
the atmospheric boundary layer airflow ([15] and [18]). It has been observed that for this kind
of problem the realizable k-ε model [19] is most suitable. The commercial CFD code Ansys
Fluent 13.0.0 [20] is used to solve the 3D Reynolds-averaged Navier–Stokes equations and
the continuity equation using the control volume method. Closure is obtained using the
realizable k-ε model (Shih). Pressure–velocity coupling is taken care of by the SIMPLE
algorithm. Pressure interpolation is second order. Second-order discretization schemes are
used for both the convection terms and the viscous terms of the governing equations.
2.4 Boundary condition
For real physical representation of the fluid flow suitable boundary condition that actually
simulate the real flow is required, there is always great difficulty in defining in detail the
boundary conditions at the inlet and outlet of the flow domain that is required for accurate
solution. At the upwind boundary, a velocity inlet was used with the following
expressions for the along wind component of velocity, U which is similar to the
experimental study.
Standard representation of the velocity profile in the ABL is as shown below.
In the present work the values are of the parameters m and m/s.
The measured longitudinal turbulence intensity ( ) is converted to turbulent kinetic energy
as input for the simulations using Eq. (10), assuming that and . It is
observed that with a higher , a small discrepancy in the results in the order of a few
percentages (

modelled as slip walls (zero normal velocity and zero normal gradients of all variables). At
the outlet, zero static pressure is specified. The standard coefficients of the realizable k-ε
model were used. The Reynolds number for the flow is 2.65 × 10 6 , using the building height,
, and the velocity at as reference values. At the downwind boundary, a pressure
outlet was used, with the relative pressure specified at and backflow conditions for
and set to those of the inlet. In the domains, however, backflow was not observed because
the downwind boundary was sufficiently far from the building.
On the bottom wall of the domain, a rough wall was specified to model the effect of the
ground roughness. The values of and are needed as input. According to Blocken et al.
(2007a), the roughness constant ( ) in the law of the wall was specified as below
with taking its default value of 0.5. The walls of the building were specified as smooth.
Eqs. (10) to (11) were used to specify the field variables throughout the domain as initial
conditions at the start of the steady-state simulation.
The standard wall functions modified for roughness are employed. As already specified that
for the chosen simulation scale (1/300) the value for and the reference wind speed
taken from the wind tunnel experiments yields a suitable value of y+ for the use of wall
functions (between 30 and 300). for the bottom of the computational domain (
representing the wind tunnel floor downstream of the roughness elements, including the
turntable) is taken 3.33×10 -7 m (simulation scale) or 0.0001m (full scale), which is an estimate
of the equivalent sand-grain roughness of the smooth floor. This value is smaller than (=
0.004 m, simulation scale) as required.
2.5 Solver settings
Ansys Fluent uses the finite-volume method to solve underlying governing equations and
associated problem-specific boundary conditions. A fundamental premise of using finite
element procedure is that the body is sub divided into small discrete regions known as finite
elements. These elements defined by nodes and interpolation functions. Governing equations
are written for each element & these elements are assembled into a global matrix.
As mentioned in earlier the solutions were steady-state. Second-order differencing was used
for the pressure, momentum and turbulence equations and the “coupled” pressure-velocity
coupling approach due to its robustness for steady-state, single-phase flow problems.
The residuals fell below the commonly applied criteria of falling to 10 -4 of their initial
values after several hundred iterations. However, this was not the only test for convergence
- the drag, lift and side forces and the moments acting on the building were monitored during
the simulation and only when they achieved stationary values were the simulations deemed to
6

have converged. Although the simulations were steady-state, there was some variation (< 1%)
in the “steady” values of the various monitoring values.
3. Numerical simulation and validation
The velocity profile obtained by fluent was compared with the velocity profile of the wind
tunnel experimental study as shown in Fig. 4. It is observed that by incorporating all the
consideration and boundary condition the inlet velocity profile are very much similar as it
was in the experimental study.
Figure 4. comparison of velocity profiles of wind tunnel experimental study and CFD
simulation.
Results obtained through CFD simulation are fairly good and compared with experimental
results [8] and wind standards available of different countries. Pressure coefficient for all
four faces of isolated building (Setup-1) at 0° wind incidence angle (Fig. 5) is presented in
tabular form as given in Table 1.
Table 1.Comparison of results obtained by CFD simulation with experimental results and
wind standards of different countries for all four faces of object building (Setup-1) at 0° wind
incidence angle
FACE
CFD
results
Wind
Tunnel
Exp.
Average Face Pressure Coefficient (Cp)
BS 6399-
2:1997
7
IS-875 Part-
ASCE 7-02 AS/NZ 1170.2
3
Face A 0.906 0.83 0.85 0.80 0.80 0.95
Face B -0.827 -0.84 -0.80 -0.70 -0.65 -0.70
Face C -0.508 -0.71 -0.50 -0.50 -0.50 -1.25

Face D -0.827 -0.85 -0.80 -0.70 -0.65 -0.70
4. Wind flow pattern for different combination of building model
CFD simulation of wind tunnel experiment was carried out to observe the variation of wind
velocities around tall buildings with different arrangement and wind incidence angles. Few of
the results are presented in the form of velocity magnitude around the buildings and mean
pressure coefficients for different faces of buildings. It has been observed that the significant
enhancement of velocity and pressure occurred in some case studies considered. With the
help of these observations some possibilities have been explored to install domestic wind
turbine in and around buildings to fulfil its electricity requirement along with the available
power supply.
4.1 Setup-1 (Isolated building)
In this setup (Fig. 1) isolated building model has been considered and observed velocity
potential around the building at different wind incidence angle i.e. 0° to 90° with an
increment of 15° in anticlockwise direction.
The value of velocity magnitude varies significantly around the building for this wind
incidence as shown in Fig. 5. In this case maximum wind velocity is observed near around
the roof top corner of the building and a wake zone formed at the rare face of the building
towards leeward side.
8

Figure 5. Velocity potential and vectors at vertical plane around the isolated model through
CFD simulation
9

4.2 Setup-2 and 3 (Two building with 50mm and 100 mm spacing)
In this case two building models with a spacing of 50mm and 100mm (Fig. 1) are considered.
It is observed that interfering building provide sheltering effect to the object building at 0°
wind incidence angle and as the angle increases this sheltering effect vanishes. In figure 6
different cut planes has been shown where the velocity potential is measured to observe the
variation of the flow field. The intensity of the wind flow i.e. the velocity varies significantly
around the building and considerable wake zone with lesser velocity potential can be seen
which is larger than it is for isolated building.
Setup 2: Spacing = 50mm, wind 0° Setup 3: Spacing = 100mm, wind 0°
Setup 2: Spacing = 50mm, wind 40° Spacing = 50mm, wind 60°
Figure 6. Variation of velocity potential around the two building model through CFD simulation
5. Conclusion/Remark/ Discussion
The use of wind energy for domestic purpose there are numbers of possibilities that the
performance and efficiency may get reduced due to the complex wind flow which is the
consequence of having a haphazard building orientation in our urban areas. To find the
solution of this complex flow field it is necessary to look into the wind flow pattern around
building.CFD simulation and the experimental results are very much similar to the
experimental study. The accuracy of results depend also on exactly the modeling according to
the scale, proper meshing of the model geometry and defining the physical property values
exactly as the realistic environment conditions.
Wind flow filed has been seen influenced significantly in presence of the building structure in
a various pattern and extent which is responsible for increasing or decreasing the
performance of the wind turbine installed in these areas.Wind incidence angle in all cases has
shown a tremendous effect on wind flow around the buildings.In case of group of building
extensive wind tunnel testing considering wind interference effect is required to accurately
estimate before installing and designing the domestic wind turbine.Many complicated and
complex model can be examined with the help of CFD analysis and the designing criteria of
the wind turbine system at any flow field can be standardized. Apart from wind tunnel study,
10

full scale model of physical problem need to be modelled and analyzed with this numerical
simulation for better understanding of the wind flow field.
11

Reference
1. Murakami, S. (1998), “Overview of turbulence models applied in CWE”, Jnl. of Wind
Eng. Ind. Aerodyn. 74-76, 1-24.
2. Stathopoulos, T. Wu, H. (2004), “Using Computational Fluid Dynamics (CFD) for
pedestrian winds”, Proceedings of the 2004 Structures Congress, Nashville, TN.
3. Tominaga, Y., Mochida, A., Murakami, S., and Sawaki, S. (2008a), “Comparison of
various revised k–ε models and LES applied to flow around a high-rise building model
with 1:1:2 shape placed within the surface boundary layer”, Jnl. of Wind Eng. Ind.
Aerod., 96(4), 389-411.
4. Costola, D., Blocken, B. and Hensen, J.L.M. (2009), “Overview of pressure coefficient
data in building energy simulation and airflow network programs”, Building and
Environment, 44 (10), 2027–2036.
5. Tamura, T., Nozawa, K., and Kondo, K. (2008), “AIJ guide for numerical prediction of
wind loads on buildings”, Jnl. of Wind Eng. Ind. Aerod., 96, 1974–1984.
6. Tominaga, Y., Mochida, A., Yoshiec, R., Kataokad, H., Nozu,T., Masaru, Yoshikawa,
M., Shirasawa, T. (2008b), “AIJ guidelines for practical applications of CFD to
pedestrian wind environment around buildings”, Jnl. of Wind Eng. Ind. Aerod., 96.1.
7. Franke, J., Hirsch, C., Jensen, A., Krus, H, Schatzmann, M., Westbury, P., Miles, S.,
Wisse, J. and Wright, N.G. (2004), Recommendations on the Use of CFD in Wind
Engineering, In: van Beeck JPAJ (Ed.), COST Action C14, Impact of Wind and Storm
on City Life and Built Environment, Saint-Genesius-Rode, Belgium, 5-7 May 2004.
8. VermaSK,(2009)Wind effect on structurally coupled tall buildings. PhDthesis,IIT Roorkee.
9. Braun, A.L. (2009), “Aerodynamicand aeroelastic analysesonthe CAARC standard
tallbuilding model usingnumericalsimulation”, Computerand Structures87. 564-581.
10. Wardlaw, R.L., Moss, G.F.(1970), “A standard tallbuilding modelforthecomparison
ofsimulated naturalwindsin wind tunnels”,CAARC, C.C.662mTech;25January.
11. IS: 875 (Part 3) – 1987, Code of practice for design loads (Other than earthquake for
buildings and structures), Part 3- wind loads, BIS, New Delhi (India).
12. AS/NZS 1170.2:2002, Australian/New Zeeland Standard - Structural Design Action, Part
2: Wind Action, Standards Australia International Ltd, Sydney.
13. ASCE7-05, 2005, Minimizing design loads for building and other structures, Published
by Structural Engineering Institute, Reston, VA.
14. BSI BS 6399, 1997, Loadings for Buildings-Part2; Code of Practice for wind loads,
British Standard Institution.
15. Blocken, B., Carmeliet, J., Stathopoulos, T. (2007a), "CFD evaluation of wind speed
conditions in passages between parallel buildings – effect of wall-function roughness
modifications for the atmospheric boundary layer flow", Journal of Wind Engineering
and Industrial Aerodynamics, Volume 95, Issues 9–11, Pages 941-962.
16. Revuz J., Hargreaves D.M. and Owen J.S. (2012), "On the domain size for the steadystate
CFD modelling of a tall building", Wind and Structures, 15(4), 313-329.
17. Spalart, P.R. (2000), “Strategies for turbulence modelling and simulations”,
International Journal of Heat and Fluid Flow, Volume 21, Issue 3, Pages 252-263.
18. Blocken, B., Stathopoulos, T., Carmeliet, J. (2007b), “CFD simulation of the atmospheric
boundary layer: wall function problems”, Atmos. Environ., 41, 238–252.
19. Shih, T.H. et al. 1995. A new k- eddy-viscosity model for high Reynolds number
turbulent flows—model development and validation. Comput. Fluids 24 (3), 227–238.
20. ANSYS Ltd., 2010. Ansys Fluent solver, Release 13.0.0: Theory. Canonsburg.
21. Richards, P.J., Hoxey, R.P. (1993), Appropriate boundary conditions for computational
wind engineering models using the k-ε turbulence model, 46–47, Pages 145-153.
12

Abstract.
CFD Modelling of Wind Flow around Buildings
for Wind Energy Conversion
A.K. Roy and P.K. Bhargava
CSIR-Central Building Research Institute, Roorkee 247667, India
Corresponding author; Email: amritworld@gmail.com
Wind energy conversion through wind turbine is so far well-established concept and very
popular out of all available renewable energy sources. Research works are going on to
optimize the efficiency of the energy extraction process by inventing advanced wind turbine
replacing the old one. Wind speeds of more than 18 km/hr measured at a height of 10 mare
sufficient enough for the functioning of wind turbine system. So the wind velocity at the sites
is an important parameter for the development. Finding out wind velocities around closely
spaced buildings with the help of codes is not possible. It requires extensive wind tunnel
testing which is very expensive and time consuming. In this research work, CFD simulation
of atmospheric boundary layer wind flow around high-rise urban buildings with different
arrangements and wind incidence angles was carried out to observe the variation of wind
velocity potential surrounding the buildings. It has been observed that on the leeward side
formation of wake zone due to obstructing the flow results in low wind speeds which could
be the reasons of poor efficiency of the installed wind turbine. The results are presented in the
form of velocity magnitude and velocity vector around the buildings. It has also been
observed that significant enhancement of velocity occurred at the roof top of the buildings.
Although too many investigations are still required, here only a study has been carried out to
explore some possibilities of enhancing the efficiency of wind energy conversion in high-rise
urban buildings.
Keywords: Wind energy, velocity potential, wind turbine, CFD simulation, wind tunnel,
1. Introduction
The main source of energy production i.e. oil, coal and gas are being used to a great extent
with the advancement of the civilization and about to be finished in the next 30 years.
Renewable energy sources i.e. hydro power, solar energy, geo thermal and wind energy are
the next best choice for the survival of the civilization. Total wind energy available (1700
TW) all around the world is the second highest after solar energy (Solar PV 6500TW and
Concentrated Solar Power 4600TW). It’s the current trend followed in developed countries to
utilize the huge wind power with the help of building mounted wind turbine and fulfill the
increased power demand. Wind energy conversion has reached a significant milestone with
success of providing support to our increased electricity demand of our major cities around
1

the world. Yet there are so many technology and invention left in this area so that this
abundant source of wind energy can be utilized to produce electric energy.
In an urban area buildings are oriented haphazardly which influence the wind flow and wind
velocity varies place to place around building. This variation can be observed by wind tunnel
tests with the help of Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry
(PIV) or numerical calculations using CFD codes.
In recent years, there are significant progress in the application of CFD to evaluate wind
loads on buildings and structures (e.g. [1-4]and others). Architectural Institute of Japan (AIJ)
[5-6] and the European cooperation in the field of scientific and technical (COST) research[7]
have established working groups to investigate the practical applicability of CFD and to
develop recommendations for their use for wind resistant design of actual buildings and for
assessing pedestrian level winds. AIJ has also provided methods for predicting wind loading
on buildings by the Reynolds Averaged Navier Stokes equations (RANS) and LES.
Pedestrian level wind evaluation carried out by numbers of researchers, where only the mean
wind speeds are required for evaluating pedestrian comfort. Computational studies on tall
Buildings have been conducted by [3],[8] and others. The flow pattern and mean and rms
pressure coefficient of the aerodynamics of Commonwealth Advisory Aeronautical Council
(CAARC) building model is investigated by [9] and others. CAARC tall building is
considered as one of the most extensively and systematically studied building model and
popular in wind tunnel researcher community [10].
In this research work the main concerned area selected just to find out the velocity potential
around the building so that wind turbine installation can be optimized to get the maximum
power conversion. CFD simulation of the wind flow around tall building has been done to
observe the variation of velocity potential. Wind tunnel experimental data has been used to
validate the CFD results.
2. Numerical simulation of wind flow on high-rise building
In the present study measurements of wind tunnel experiments on tall building [8] conducted
at IIT Roorkee, India have been used. The wind tunnel experimental velocity profile and the
turbulence intensity are considered here to simulate the boundary layer wind. This wind
tunnel is an open circuit type boundary layer wind tunnel with no thermal stratification. It has
a test section of 2.1m x 2m cross-section with 15m length. The present study assumes that the
power law expression is valid for representing the wind velocity variation in the atmospheric
boundary layer and a power law exponent (n) equal to 0.15 is used which corresponds to the
open terrain category mentioned as category No.2 in the Indian Standard for wind loads [11].
Other wind standards [12-14] have also been used to validate the simulation study.
2.1 Details of models used for the CFD simulation
The present research work aims at studying the effect of neighbouring buildings on mean
wind velocity magnitude observed around the building. In selecting the model scale it is
important to avoid the influence of the wind tunnel walls and an excessive blockage of the
test section. Corrections are generally applied if the blockage by the model of the building
and its immediate surroundings exceeds about 5% to 10%.Typical geometrical scales used in
2

studies of wind flow on large buildings are about 1:300 to 1:600, and while for models of
small buildings larger scales in the range of 1:100 may be used.
In the current study two setups of building models have been considered. The test setup 1 was
the isolated building without any interfering building (Figure 1). Test Setup 2 and 3are two
building model with 50 mm and 100mm (2×B) spacing respectively. Size of object building
and interfering building was kept same with dimensions L × B × H = 50×50×400mm 3 . Wind
incidence angle (β) has been varied from 0° to 180° with increment of 30° in anticlockwise
direction as shown in Fig. 1.
Figure 1.Test setup of buildings with wind direction angles considered for the study.
2.2 Domains and meshes
Grid generation is one of the very important considerations during the pre-processing stage,
the type of mesh chosen for a given flow problem can determine the success or failure in
attainment of computational solution. The mesh should be sufficiently fine to provide an
adequate resolution of the important flow features and geometrical structures. Generally for
flow with bounded walls steep flow gradients within the viscous boundary layers are properly
resolved through locally refining the mesh in the vicinity of wall boundaries. Accurate
simulation of ABL flow in the computational domain is essential to obtain accurate and
reliable predictions of the related atmospheric processes. To have the geometric similarity
cross section of computational domain and model dimension was kept same as that of the
wind tunnel study and the upstream/downstream length was kept as per the requirement
[15-16]. The geometric scale of model of a building is chosen to maintain the equality of
ratios of overall building dimensions to the inherent lengths of the generated model. The
dimensions of the computational domain are i.e. LD × BD × HD = 2.55 × 2.65 × 2 m 3 as shown
schematically in Fig. 2, which shows the coordinate system used.
3
Wind Incident Angles

Figure 2. Computational domain of the isolated building model used for CFD simulation.
The surface mesh close to the foot of the building shows the growth of the cells in the
boundary layer next to the building. Clearly the aspect ratios of these boundary layer cells are
very large, but as [17] indicates, there is no formal restriction on the size of cells in the wallparallel
direction in RANS simulations. However, Spalart (2000) is discussing streamlined
bodies, not the complex detached flows seen with the bluff body under discussion here. At
the leeward side of the building the mesh was more refined in the wake region relative to the
more distant regions of the domain.
(a)
26B
20B
26B
Fig. 3Surface meshes on the domain showing (a) isolated building model and (b) the two
building model used for CFD simulation.
4
5H
30B
(b)

2.3 Turbulence model
Researchers have already examined different turbulent models for their relative suitability for
the atmospheric boundary layer airflow ([15] and [18]). It has been observed that for this kind
of problem the realizable k-ε model [19] is most suitable. The commercial CFD code Ansys
Fluent 13.0.0 [20] is used to solve the 3D Reynolds-averaged Navier–Stokes equations and
the continuity equation using the control volume method. Closure is obtained using the
realizable k-ε model (Shih). Pressure–velocity coupling is taken care of by the SIMPLE
algorithm. Pressure interpolation is second order. Second-order discretization schemes are
used for both the convection terms and the viscous terms of the governing equations.
2.4 Boundary condition
For real physical representation of the fluid flow suitable boundary condition that actually
simulate the real flow is required, there is always great difficulty in defining in detail the
boundary conditions at the inlet and outlet of the flow domain that is required for accurate
solution. At the upwind boundary, a velocity inlet was used with the following
expressions for the along wind component of velocity, U which is similar to the
experimental study.
Uz 1.8715logz 16.94 8
Standard representation of the velocity profile in the ABL is as shown below.
Uz u∗ κ ln zz
9
z
In the present work the values are of the parameters z 0.0001 m and u ∗ 0.11m/s.
The measured longitudinal turbulence intensity () is converted to turbulent kinetic energy
as input for the simulations using Eq. (10), assuming that and . It is
observed that with a higher, a small discrepancy in the results in the order of a few
percentages (

static pressure is specified. The standard coefficients of the realizable k-ε model were used.
The Reynolds number for the flow is 2.65 × 10 6 , using the building height, , and the
velocity at as reference values. At the downwind boundary, a pressure outlet was
used, with the relative pressure specified at 0 and backflow conditions for and set to
those of the inlet. In the domains, however, backflow was not observed because the
downwind boundary was sufficiently far from the building.
On the bottom wall of the domain, a rough wall was specified to model the effect of the
ground roughness. The values of and are needed as input. According to Blocken et al.
(2007a), the roughness constant (k ) in the law of the wall was specified as below
k 9.793
z 1.9610
C 12
with taking its default value of 0.5. The walls of the building were specified as smooth.
Eqs. (10) to (11) were used to specify the field variables throughout the domain as initial
conditions at the start of the steady-state simulation.
The standard wall functions modified for roughness are employed. As already specified that
for the chosen simulation scale (1/300) the value for and the reference wind speed
taken from the wind tunnel experiments yields a suitable value of y+ for the use of wall
functions (between 30 and 300). for the bottom of the computational domain (
representing the wind tunnel floor downstream of the roughness elements, including the
turntable) is taken 3.33×10 -7 m (simulation scale) or 0.0001m (full scale), which is an estimate
of the equivalent sand-grain roughness of the smooth floor. This value is smaller than (=
0.004 m, simulation scale) as required.
2.5 Solver settings
Ansys Fluent uses the finite-volume method to solve underlying governing equations and
associated problem-specific boundary conditions. A fundamental premise of using finite
element procedure is that the body is sub divided into small discrete regions known as finite
elements. These elements defined by nodes and interpolation functions. Governing equations
are written for each element & these elements are assembled into a global matrix.
As mentioned in earlier the solutions were steady-state. Second-order differencing was used
for the pressure, momentum and turbulence equations and the “coupled” pressure-velocity
coupling approach due to its robustness for steady-state, single-phase flow problems.
The residuals fell below the commonly applied criteria of falling to 10 -4 of their initial
values after several hundred iterations. However, this was not the only test for convergence
- the drag, lift and side forces and the moments acting on the building were monitored during
the simulation and only when they achieved stationary values were the simulations deemed to
have converged. Although the simulations were steady-state, there was some variation (< 1%)
in the “steady” values of the various monitoring values.
6

3. Numerical simulation and validation
The velocity profile obtained by fluent was compared with the velocity profile of the wind
tunnel experimental study as shown in Fig. 4. It is observed that by incorporating all the
consideration and boundary condition the inlet velocity profile are very much similar as it
was in the experimental study.
Figure 4. comparison of velocity profiles of wind tunnel experimental study and CFD
simulation.
Results obtained through CFD simulation are fairly good and compared with experimental
results [8] and wind standards available of different countries. Pressure coefficient for all
four faces of isolated building (Setup-1) at 0° wind incidence angle (Fig. 5) is presented in
tabular form as given in Table 1.
Table 1.Comparison of results obtained by CFD simulation with experimental results and
wind standards of different countries for all four faces of object building (Setup-1) at 0° wind
incidence angle
FACE
CFD
results
Wind
Tunnel
Exp.
Average Face Pressure Coefficient (Cp)
BS 6399-
2:1997
7
IS-875 Part-
ASCE 7-02 AS/NZ 1170.2
3
Face A 0.906 0.83 0.85 0.80 0.80 0.95
Face B -0.827 -0.84 -0.80 -0.70 -0.65 -0.70
Face C -0.508 -0.71 -0.50 -0.50 -0.50 -1.25
Face D -0.827 -0.85 -0.80 -0.70 -0.65 -0.70

4. Wind flow pattern for different combination of building model
CFD simulation of wind tunnel experiment was carried out to observe the variation of wind
velocities around tall buildings with different arrangement and wind incidence angles. Few of
the results are presented in the form of velocity magnitude around the buildings and mean
pressure coefficients for different faces of buildings. It has been observed that the significant
enhancement of velocity and pressure occurred in some case studies considered. With the
help of these observations some possibilities have been explored to install domestic wind
turbine in and around buildings to fulfil its electricity requirement along with the available
power supply.
4.1 Setup-1 (Isolated building)
In this setup (Fig. 1) isolated building model has been considered and observed velocity
potential around the building at different wind incidence angle i.e. 0° to 90° with an
increment of 15° in anticlockwise direction.
The value of velocity magnitude varies significantly around the building for this wind
incidence as shown in Fig. 5. In this case maximum wind velocity is observed near around
the roof top corner of the building and a wake zone formed at the rare face of the building
towards leeward side.
Figure 5. Velocity potential and vectors at vertical plane around the isolated model through
CFD simulation
8

4.2 Setup-2 and 3 (Two building with 50mm and 100 mm spacing)
In this case two building models with a spacing of 50mm and 100mm (Fig. 1) are considered.
It is observed that interfering building provide sheltering effect to the object building at 0°
wind incidence angle and as the angle increases this sheltering effect vanishes. In figure 6
different cut planes has been shown where the velocity potential is measured to observe the
variation of the flow field. The intensity of the wind flow i.e. the velocity varies significantly
around the building and considerable wake zone with lesser velocity potential can be seen
which is larger than it is for isolated building.
Setup 2: Spacing = 50mm, wind 0° Setup 3: Spacing = 100mm, wind 0°
Setup 2: Spacing = 50mm, wind 40° Spacing = 50mm, wind 60°
Figure 6. Variation of velocity potential around the two building model through CFD simulation
5. Conclusion/Remark/ Discussion
The use of wind energy for domestic purpose there are numbers of possibilities that the
performance and efficiency may get reduced due to the complex wind flow which is the
consequence of having a haphazard building orientation in our urban areas. To find the
solution of this complex flow field it is necessary to look into the wind flow pattern around
building.CFD simulation and the experimental results are very much similar to the
experimental study. The accuracy of results depend also on exactly the modeling according to
the scale, proper meshing of the model geometry and defining the physical property values
exactly as the realistic environment conditions.
Wind flow filed has been seen influenced significantly in presence of the building structure in
a various pattern and extent which is responsible for increasing or decreasing the
performance of the wind turbine installed in these areas.Wind incidence angle in all cases has
shown a tremendous effect on wind flow around the buildings.In case of group of building
extensive wind tunnel testing considering wind interference effect is required to accurately
estimate before installing and designing the domestic wind turbine.Many complicated and
complex model can be examined with the help of CFD analysis and the designing criteria of
the wind turbine system at any flow field can be standardized. Apart from wind tunnel study,
full scale model of physical problem need to be modelled and analyzed with this numerical
simulation for better understanding of the wind flow field.
9

Reference
1. Murakami, S. (1998), “Overview of turbulence models applied in CWE”, Jnl. of Wind
Eng. Ind. Aerodyn. 74-76, 1-24.
2. Stathopoulos, T. Wu, H. (2004), “Using Computational Fluid Dynamics (CFD) for
pedestrian winds”, Proceedings of the 2004 Structures Congress, Nashville, TN.
3. Tominaga, Y., Mochida, A., Murakami, S., and Sawaki, S. (2008a), “Comparison of
various revised k–ε models and LES applied to flow around a high-rise building model
with 1:1:2 shape placed within the surface boundary layer”, Jnl. of Wind Eng. Ind.
Aerod., 96(4), 389-411.
4. Costola, D., Blocken, B. and Hensen, J.L.M. (2009), “Overview of pressure coefficient
data in building energy simulation and airflow network programs”, Building and
Environment, 44 (10), 2027–2036.
5. Tamura, T., Nozawa, K., and Kondo, K. (2008), “AIJ guide for numerical prediction of
wind loads on buildings”, Jnl. of Wind Eng. Ind. Aerod., 96, 1974–1984.
6. Tominaga, Y., Mochida, A., Yoshiec, R., Kataokad, H., Nozu,T., Masaru, Yoshikawa,
M., Shirasawa, T. (2008b), “AIJ guidelines for practical applications of CFD to
pedestrian wind environment around buildings”, Jnl. of Wind Eng. Ind. Aerod., 96.1.
7. Franke, J., Hirsch, C., Jensen, A., Krus, H, Schatzmann, M., Westbury, P., Miles, S.,
Wisse, J. and Wright, N.G. (2004), Recommendations on the Use of CFD in Wind
Engineering, In: van Beeck JPAJ (Ed.), COST Action C14, Impact of Wind and Storm
on City Life and Built Environment, Saint-Genesius-Rode, Belgium, 5-7 May 2004.
8. VermaSK,(2009)Wind effect on structurally coupled tall buildings. PhDthesis,IIT Roorkee.
9. Braun, A.L. (2009), “Aerodynamicand aeroelastic analysesonthe CAARC standard
tallbuilding model usingnumericalsimulation”, Computerand Structures87. 564-581.
10. Wardlaw, R.L., Moss, G.F.(1970), “A standard tallbuilding modelforthecomparison
ofsimulated naturalwindsin wind tunnels”,CAARC, C.C.662mTech;25January.
11. IS: 875 (Part 3) – 1987, Code of practice for design loads (Other than earthquake for
buildings and structures), Part 3- wind loads, BIS, New Delhi (India).
12. AS/NZS 1170.2:2002, Australian/New Zeeland Standard - Structural Design Action, Part
2: Wind Action, Standards Australia International Ltd, Sydney.
13. ASCE7-05, 2005, Minimizing design loads for building and other structures, Published
by Structural Engineering Institute, Reston, VA.
14. BSI BS 6399, 1997, Loadings for Buildings-Part2; Code of Practice for wind loads,
British Standard Institution.
15. Blocken, B., Carmeliet, J., Stathopoulos, T. (2007a), "CFD evaluation of wind speed
conditions in passages between parallel buildings – effect of wall-function roughness
modifications for the atmospheric boundary layer flow", Journal of Wind Engineering
and Industrial Aerodynamics, Volume 95, Issues 9–11, Pages 941-962.
16. Revuz J., Hargreaves D.M. and Owen J.S. (2012), "On the domain size for the steadystate
CFD modelling of a tall building", Wind and Structures, 15(4), 313-329.
17. Spalart, P.R. (2000), “Strategies for turbulence modelling and simulations”,
International Journal of Heat and Fluid Flow, Volume 21, Issue 3, Pages 252-263.
18. Blocken, B., Stathopoulos, T., Carmeliet, J. (2007b), “CFD simulation of the atmospheric
boundary layer: wall function problems”, Atmos. Environ., 41, 238–252.
19. Shih, T.H. et al. 1995. A new k- eddy-viscosity model for high Reynolds number
turbulent flows—model development and validation. Comput. Fluids 24 (3), 227–238.
20. ANSYS Ltd., 2010. Ansys Fluent solver, Release 13.0.0: Theory. Canonsburg.
21. Richards, P.J., Hoxey, R.P. (1993), Appropriate boundary conditions for computational
wind engineering models using the k-ε turbulence model, 46–47, Pages 145-153.
10

Prediction of Indoor Thermal Comfort Level Using Fuzzy Logic
Abstract.
P.K. Yadav and B.M. Suman
CSIR- Central Building Research Institute, Roorkee
Corresponding author, E-mail: prd_yadav@rediffmail.com
Prediction of Indoor Thermal Comfort Level (TCL) is a complex phenomenon to understand.
Accordingly, TCL is very difficult to present mathematically since the real process has the
involvement of human beings. For analytical purposes, it can be considered that the human is
a “black box” which receives inputs as environmental conditions and individual variables,
whereas output is the subjective perception of TCL. Indoor comfort condition of a building
depends upon exterior climate and thermo-physical properties of the materials used in
building. The outside climatological parameters can be combined as a single parameter
known as Sol Air Temperature (SAT). Likewise, thermal properties of the materials used in
building, in-door and out-door surface heat transfer coefficients are combined in a single
factor, known as Overall Thermal Transmittance (OTT). In this paper, a fuzzy logic approach
is used to predict an appropriate TCL considering the SAT and OTT as input parameters. The
complexities of the human cognitive process and the imprecision of linguistic expressions are
taken into consideration. A detailed exposition of the application combining linguistic
approach to the optimization under multiple thermal conditions’ criteria is presented in this
study.
Keywords: Sol Air Temperature, Overall Thermal Transmittance, Thermal Comfort Level,
Fuzzy Logic
1. Introduction
Energy efficiency in building an engaging theme nowadays as it contributes simultaneously
to the reduction of conventional fuels consumption, energy cost cut for building owners and
decrease in global warming gas released in the environment. In either case, energy efficiency
must never compromise indoor TCL for building users [4]. TCL is defined as the state of
human mind that expresses satisfaction with the surrounding environment (ANSI/ASHRAE
Standard 55) [1]. The important goal of HVAC (heating, ventilation, and air conditioning) for
design engineers is to maintain the standard of thermal comfort for occupants in the buildings
or other enclosures. There are several factors which affect the TCL by heat conduction,
convection, radiation, and evaporative heat loss. These parameters provide some information
about the optimum conditions and what can be done locally to improve comfort levels in

elatively warm or cool indoor areas. Thermal comfort is maintained when the heat generated
by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the
surroundings. It has been long recognized that the sensation of feeling hot or cold is not just
dependent on air temperature alone.
Generally human concerns about indoor thermal comfort occur in areas that are poorly
ventilated and/or inadequately shaded from sunlight. Individual thermal comfort can also be
affected by physical exertion, crowded working areas and some medical conditions.
Thermal comfort is a subjective judgment, and even in optimal conditions some individuals
may experience discomfort. Therefore, maintaining a climate to the level of TCL is important
for the health and comfort of human.
TCL is very difficult to present mathematically since the real process has the involvement of
human awareness. It can be considered that the human is a “black box” which receives
environmental conditions and personal variables as input, whereas output is the subjective
perception of TCL. Figure 1 shows the Black Box process of human perception [2].
Figure 1. Black Box Process of Human Process
Comfort is a fuzzy concept, different for different people. A design of fuzzy system for living
space thermal-comfort regulation has been discussed by Dounis A.I. et al [3]. Design and
evaluation for buildings’ occupants’ thermal-visual comfort and indoor air quality
satisfaction have been studied by Kolokotsa D et al [4]. The advanced fuzzy logic controllers
like fuzzy PID, fuzzy PD and adaptive fuzzy PD control is used while designing the thermalvisual
comfort and indoor air quality satisfaction. Recently Singh et al. [5] has designed a
fuzzy controller for cabin to control the cabin temperature and introduced a concept of fuzzy
controller system to control thermal comfort of vehicle passengers.
A new systematic approach to process control is described with special emphasis on the
human factor, by using the measurement metric, which is a constituent part of the feedback
loop by Zoran L. Baus et al [6]. For the conventional thermal comfort maintenance process
control, a correction is provided in accordance with personal experience, while retaining
reference values within margins permissible by the applicable standard. The fuzzy sequence
control is studied incorporating the personal feeling of comfort. A comfort monitoring
system and hazard detection unit using fuzzy logic is described by Tennakoon et al [7]. The
idea behind the Comfort Monitoring System is to assist the user to get an idea how different
factors such as room temperature, humidity, airflow and clothing affect human comfort. In
this paper, a fuzzy logic approach is used to predict an appropriate TCL considering the SAT
and OTT as Input parameters. A detailed exposition of the application combining linguistic

approach to the optimization under multiple thermal condition criteria is presented in this
study.
2 Fuzzy Logic Modelling
Fuzzy modeling involves following three steps
I. Fuzzification
II. Fuzzy Rule Inference
III. Defuzzification
2.1 Fuzzification
The fuzzification comprises the process of transforming crisp values into grades of
membership for linguistic terms of fuzzy sets. The Membership Function (MF) is used to
associate a grade to each linguistic term. The terminology of linguistic variable was
introduced by Zadeh [8] as an approach to capture natural experience commonly used by
human black box.
2.2 Fuzzy rule inference
Fuzzy rule inference method is used to define some sets of fuzzy logic operators along with
production rules. The most common rule is called IF-THEN Rule, which can be used to
formulate the conditional statements that comprise fuzzy logic.
2.3 Defuzzification
In Defuzzification, Fuzzy sets act as the input in the process and output is the single number.
The aggregate of fuzzy set encompasses a range of output values and so must be defuzzified
in order to get the single output value from the set. A Conceptual Fuzzy Logic Modeling
Approach has been depicted in Figure 2.
Figure 2. Conceptual Fuzzy Logic Modeling

3. Fuzzy inference engine (FIE)
Fuzzy logic [9], [10] is an extension of conventional Boolean logic and extends it to deal
with new aspects such as partial truth and uncertainty. Fuzzy inference is the process of
formulating the mapping from a given input set to an output using fuzzy logic. The basic
elements of fuzzy logic are linguistic variables, fuzzy sets, and fuzzy rules [11]. In everyday
life, human beings always deal with linguistic variable to reflect their perception on certain
phenomena; e.g. to reflect their perception about the thermal comfort level of room they
answer in the terms like ‘Poor’, ‘Good’, ‘Excellent’, etc. A Fuzzy set is used to interpret that
linguistic value to make things discrete and it is assumed that each opinion or each
perception is rated by a number in a set of ‘A’. The fuzzy set “A” may be defined within a
finite interval called universe of discourse Z as follows:
A = {(x, fA (x)), fA (x): Z → [0,1]}
Z is the complete input range allowed for a given fuzzy linguistic variable. All fuzzy sets
related to a given variable make up the term set, the set of labels within the linguistic variable
described, or, more properly, granulated.
The degree to which crisp value belongs to a given fuzzy set is denoted by a function which
is known as Membership Function (MF). MF is a curve that defines how each point in the
input space is mapped to a degree of membership between 0 and 1. Different types of MF
curves such as triangular, trapezoidal, Gaussian distribution curve etc are used. It is essential
to choose a proper MF function for appropriate prediction of TCL.
A concept of approximation reasoning was introduced by Zadeh in 1975. This concept
provides a powerful framework for reasoning in the face of imprecise and uncertain
information. The implementation of the fuzzy IF-THEN rule is the basis of this theory, which
is a mathematical interpretation of the linguistic IF-THEN rule. A linguistic IF-THEN rule is
a linguistic sentence that is written in simple form such as:
If “X” is A and “Y” is B then “Z” is C
Here X, Y, Z, are variables, and A, B, and C are the corresponding linguistic values. The
rules identify the names of the variables X, Y, and Z with the universes in which the fuzzy
values A, B, and C live. There are two types of fuzzy inference models:
1. MAMDANI [12],
2. TSK OR SUGENO [13].
Interpreting an IF-THEN rule involves two distinct parts: first evaluating the antecedent and
then applying results to the consequent (known as implication). In the case of two-valued or
binary logic, if-then rules do not present much difficulty. If the premise is true, then the
conclusion is true, whereas with fuzzy approach, if the antecedent is true to some degree of
membership, then the consequent is also true to some degree.

Mamdani-type [12] inference expects the output membership functions to be fuzzy sets.
After the aggregation process, there is a fuzzy set for each output variable that needs
defuzzification. It is possible, and in many cases much more efficient, to use a single spike as
the output’s membership function rather than a distributed fuzzy set. This is sometimes
known as a singleton output membership function, and it can be thought of as a predefuzzified
fuzzy set. It enhances the efficiency of the defuzzification process because it
greatly simplifies the computation required by the more general Mamdani method, which
finds the centroid of a two-dimensional function. Rather than integrating across the twodimensional
function to find the centroid, Sugeno-type systems use weighted sum of a few
data points. In general, Sugeno-type systems can be used to model any inference system in
which the output membership functions are either linear or constant.
4. Proposed model
As shown in Fig. 3, the two major factors SAT and OTT are considered for the prediction of
TCL. The two input variable SAT and OTT which are considered to have profound effect on
TCL prediction are used to facilitate the optimal Temperature Difference which then will be
considered as the level of Thermal Comfort.
Figure 3. Inference system Block Diagram
In the present study membership function for SAT and OTT are taken to show the level of
thermal comfort and the output of the inference engine may be used to control the thermal
temperature inside a place.
4.1 Sol-Air temperature (SAT)
SAT is the temperature under conditions of no direct solar radiation and no air motion, which
would cause the same heat transfer into a house as that caused by the interplay of all existing
atmospheric conditions. It can be computed by the following expression,
--- --- ---- (1)
Where,
α - Absorptivity
ToA - Outside air temperature
ho - Outside film heat transfer coefficient
I - Solar radiation, and EIL represents long wave solar radiation.

4.2 Overall Thermal Transmittance (OTT)
OTT (also known as the U factor) is the rate of heat flow per unit square area of unit
thickness, when temperature difference of 1 0 C is maintained between the surroundings
separated by the slab. It includes thermal properties of the materials used in building, in-door
and out-door surface heat transfer. In numerical terms, the U-factor is the reciprocal value of
the total resistance (1/ΣR). The U-factor is only an indication of the conduction rate of heat
transfer; it is a quantitative measurement of how well heat conducts through a roof or wall for
a given temperature difference.
U = (hi -1 + (∑ ( L/K)I ) + ho -1 ) -1 --- --- ---- (2)
Where, hi and ho are inside and outside film heat transfer coefficient respectively.
L and K are thickness and thermal conductivity of the material of different layers.
4.3 Membership functions
For the fA(x) as the Membership Function (MF), a large class of functions can be taken viz.
triangular, trapezoidal, Gaussian and bell functions. However we have selected triangular for
its ease of use in fuzzy dedicated hardware. MFs considered for for SAT and OTT are “Very
Low”, “Low”, “Medium”, “High” and “Very High” represented by 5 Triangular curves for
this model illustrated in Fig. 4 and 5 and TCL is Taken as 5 curves of Gaussian MF “Cold”,
“Slightly Cold”, “Comfort” “Slightly Hot”, and “Hot” are shown in figure 6. We define the
levels of SAT and OTT in terms of temperature and U- value respectively for their levels as
given below in table 1.
Table 1. Levels of SAT and OTT in terms of temperature and U- value respectively
Level Sol Air Temperature ( o C) Overall Thermal Transmittance(W/m 2 K)
Very Low ≤ 20 ≤ 0.5
Low 20- 30 0.5- 1.75
Medium 30- 40 1.75- 3.0
High 40- 50 3.0- 3.75
Very High ≥50 ≥ 3.75
Figure 4. Membership Function of SAT

Figure 5. Membership Function of OTT
Figure 6. Membership Function of TCL
When multiple input combinations are to get executed, the basic concept of switching and
time slices comes into picture.
In our proposed algorithm as shown under, a newly SAT ( o C) and OTT (W/m 2 k) value, will
be added to the input queue. This queue consists of the remaining input values from last
cycle that has not yet been executed.
Loop
For each state of the temperature, do the following
1. For each value of comfort condition, feed its sol air temperature (SAT) and overall
thermal transmittance (OTT) into the inference engine. Consider the output of inference
module as thermal comfort level.
2. Store the values of thermal comfort level in an array (TCL).
3. Execute the corresponding (TCL)value of highest magnitude until a scheduling event
occurs.
4. Update the system states.
End Loop
5. Results and discussion
The number of rules in fuzzy inference engine has a direct effect on its time complexity
therefore having fewer rules may result in better system performance. Fuzzy rules try to

combine these parameters as they are connected in real worlds. Some of these rules are
mentioned here.
If SAT is very High and OTT is very high then TCL is Hot
If SAT is very High and OTT is very Low then TCL is Comfort
If SAT is Medium and OTT is very Low then TCL is Comfort
If SAT is Medium and OTT is High then TCL is Slightly Hot
Once all the variables of OTT and SAT get executed by the FIE, a decision surface can
generate showing the value of the output variable TCL. The decisions surface is the dynamic
combination of SAT and OTT affecting TCL. Figure 7 present a three-dimensional curve
representing the mapping from SAT and OTT as inputs (axis X and Y) and TCL as an output
(axis Z). The temperature, induced inside any of the place due to heat produced caused by the
thermal properties of the materials used in building, human metabolism, indoor and outdoor
surface heat transfer coefficients. In varying conditions of SAT and OTT parameters, the
maximum value of thermal comfort likely to be changes accordingly that depends on the
inference engine mechanism.
Figure 7: Decision Surface
According to the fuzzy inference rule, TCL is an output of the corresponding values of SAT
and OTT and shown in Figure 8 and fig. 9 showing the strong relationship between the SAT,
OTT and TCL. The nature of curves is show when SAT or OTT are increasing the TCL is
also increasing and shows that the comfort level is not suitable.
6. F
ut
Figure 8: Relation between SAT and TCL Figure 9: Relation between OTT and TCL

7. Future scope of work
In this paper we have developed a fuzzy logic approach to predict an appropriate TCL
considering the SAT and OTT as Input parameters. The model will be validated in future
through developing the fuzzy simulator for real environment.
8. Acknowledgement
Authors are grateful to acknowledge the patronage of The Director, CSIR-Central Building
Research Institute, Roorkee, for permitting to publish this paper.
References
1. ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy
2. Henry Feriadi, and Wong Nyuk Hien,(2003) “Modelling Thermal Comfort for Tropics
using Fuzzy Logic”, 8 th International IBPSA Conference, Netherlands, during Aug 11-14,
2003, pages 323-330.
3. Dounis A.I., and Manolakis D.E., (2000) “Design of fuzzy system for living space
thermal-comfort regulation”, Applied Energy, 69(2001), pages 119-144.
4. Kolokotsa D.,Tsiavos D., Stavrakakis G.S., Kalaitzakis K, and Antonidakis E., (2001)
“Advanced fyzzy logic controllers design and evaluation for buildings’ occupants
thermal-visual comfort and indoor air quality satisfaction” , Energy and Buildings
33(2001), pages 531-543
5. Singh Alok, and Kumar Sandeep, [2012] “ Controlling Thermal Comfort Of
Passenger Vehicle Using Fuzzy Controller “ International Journal of Engineering
Research and Applications (IJERA),Vol. 2(4), pages.640-644.
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for thermal comfort Maintenance using fuzzy logic”, Journal of electrical engineering,
Vol. 59(1), pages 34–39.
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system and hazard detection unit using fuzzy logic”, International society for
environmental Information sciences, Environmental Informatics Archives, Vol.5,
pages 621-630
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1980
10. L. A. Zadeh, "Fuzzy logic, neural networks, and soft computing," Commun. ACM, vol.
37, pp. 77-84, March 1994.
11. W. Pedrycz and F. Gomide, An introduction to fuzzy sets: analysis and design: The MIT
Press, 1998.
12. E. H. Mamdani, "Application of fuzzy algorithms for the control of a dynamic plant,"
Proc. IEE, vol. 121, pages 1585-1588, Dec 1974.
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modeling and control," IEEE Trans. Syst., Man, Cybern., vol. 15, pages 116-132, 1985.
14. Said Nawaf H and Wong J.T., “Effect of periodic variation of sol air temperature on the
performance of integrated solar collector storage system” J of Engg. (2010) Vol.2, pages
832 -840.

Test of Airflow in a Mono-Directional Wind-catcher for Various
Wind Conditions using Computational Fluid Dynamics
Abstract
Soumitree Devadutt* and Riyan Habeeb **
* The Energy and Resources Institute, New Delhi
** Engineers India Limited, New Delhi,
Corresponding author, E-mail: soumitree.devadutt@teri.res.in
Wind-catchers are one of the most extensively used passive technologies in history of arid
climatic regions, engaged to supplement airflow and maintain indoor comfort ventilation. It
was meant to catch the air flow high above the ground, which is greater in speed compared to
the flow at lower levels due to ground conditions. This study aims to analyse wind-catchers
with respect to different speeds and its orientation to prevailing winds for effective airflow. A
simple test case is considered where the geometry and physical parameters of the wind
catcher are fixed while wind speed and its incident angle are varied. Also the atmospheric
boundary layer is considered for terrain roughness in the analysis. CFD (3D) analysis was
carried out to find the efficiency of the wind catcher in terms of velocity at the outlet,
pressure differential between inlet and outlet and mass flow rate at the outlet. The test site is
chosen in a typical urban topography considering the atmospheric boundary layer and its
roughness height which impedes the airflow near the ground region and modifies the airflow
pattern in a power law profile. Multiple parametric analyses of the aforesaid parameters, i.e.,
flow speed and different orientation were carried out. The analysis shows that, in general the
air speed near the inlet of wind catcher is greatly reduced (almost by half in magnitude) due
to the terrain roughness. The air speed at the outlet increases with the increase in outdoor air
speed and is optimum when the incident angle of later is normal or up to an angle of 30 0 to
the surface of the inlet area of wind catcher.
Keywords: Wind catcher, Atmospheric Boundary Layer, CFD
1. Introduction
Wind catchers have been found in hot arid and hot humid coastal regions since ancient times.
Different designs are found in regions from North Africa (known as ‘malkaf’), Persia (known
as ‘badgir’), and Middle East to Sindh in Pakistan. “Wind catcher consists of an open vent,
raised above the roof level of the building, facing either into or away from the prevailing
wind. This vent is connected either by a vertical shaft or a direct opening in the roof and
ceiling, to the rooms below. The wind catcher acts as a high level indirect view-less window
through which air is introduced into or expelled from the room. Thus it enables air movement
through the room while minimizing the introduction of solar radiation and air borne debris
into it.” [1]. It may be a narrow mono directional vertical shaft built into a parapet to a multi
directional elaborate wind tower rising high above the roof, ventilating and cooling a two

story house [2] [11] [12]. With the advent of civilizations growing consent towards renewable
energy resources, wind catchers have a significant role to play in terms of minimizing carbon
footprints for buildings while
Figure 1. Four-sided wind tower of Isa bin
Ali House in Muharraq, Bahrain. [21]
Figure 2. Cross-section Section through the
Qa of Muhib Ad-Din Ash-Shf'i Al-Muwaqqi,
showing how the mulqaf and wind-escape
produce internal air movement [16]
maintaining comfort levels inside the building. A wind tower operates as a result of the
combination of three types of mechanism to induce ventilation in the interior a) Downdraft,
b) Wind effect and c) Stack effect [17]. Downdraft principle works when the cooled air which
is denser than the warmer air inside sinks down through the tower. The air is cooled either by
the tower walls (having enough thermal inertia) or by introducing moisture into the air
through evaporation of water. Wind effect occurs due to the pressure differential between the
inlet (positive) and outlet (negative) the air moves through the tower to the interior space.
Stack effect reverses the flow; the warm air inside the room creates an air density differential
and a reduced pressure zone at inlet of the tower, which causes an updraught.
2. Literature Review
Compared to multi-directional wind-catchers, mono-directional wind-catcher have greater
applicability on dense cities in hot and warm-humid climates (where it faces the prevailing
wind) as the thermal comfort depends upon effectiveness of air movement and urban density
reduces the wind speed at street level. As it is positioned at greater height above the street
level, it fetches the cool air from the top. Being smaller and higher than the building façade
offers less resistance/ screen to other buildings on the downwind. Moreover, it is useful in
reducing the wind-borne dust since the wind captured above buildings contains less solid
materials than the wind at lower heights [17]. However, despite all advantages, it has been
limited in use in modern buildings. Some researchers have argued on the utilization of windcatcher.
Being a passive device, the control of flow rate is almost zero and also it is less
efficient to areas of low wind speed [4]. Unsuccessful designs have also been reported where
careful considerations are not given to the site conditions, topography, wind conditions and
other architectural parameters, etc. On recent past, one such example is the large multidirectional
wind-catchers at the University of Qatar, Doha [20], where now it has been
converted into light towers to allow daylight instead of air. In this regard it is necessary to
study the importance of different factors that contribute in operation of this device.Several
studies were conducted in the past to investigate the influence of geometry and other design
conditions on aerodynamic performance of wind-catchers. [5] have investigated the

hydrodynamic effect on number of oppenings on a multi-directional wind-catcher using wind
tunnel and CFD experiments. In another study, they [6] evaluated the performance of monodirectional
wind-catchers for a given airflow rate again by both wind tunnel and CFD
analyses. Their work investigated principaly on the location and height of the wind-catcher.
[7] studied the the effect of wind speed and direction on four and six-sided wind-catcher in
wind tunnel analysis. They concluded that in variable wind conditions, multi-directional
wind-catchers have more reliable performance. [8] compared various cross sections of the
wind tower (multi-directional) using wind tunnel and later validated with CFD analysis. Their
study concluded that a square one has greater efficiency than the circular one in similar wind
conditions. Also they reported that the ventilation rate decreases with change in wind
direction from 0 0 to 45 measured from the normal of the inlet face. [9] have conducted a
study on performance of a louvered wind-catcher for different wind speeds and orientations
on using CFD and found their results quite in sync with the results of the earlier experiments
carried by Awbi and Elmualim. So far, studies have been conducted majorly for the multidirectional
wind-catchers, a very few studies are there on mono-directional wind-catchers in
terms of wind speed and orienation. Though there are certain studies conducted on monodirectional
wind-catchers along with cooling effects through evaporation of water droplets
[10], effect of heat source inside rooms on wind-catchers [11], etc, but no studies were found
(to the best of the authors’ knowledge) on the effects of wind conditions on a monodirectional
windcatcher’s performance.
3. Problem setup
3.1. Theory
The wind tower can be split into three major components in terms of airflow. i.e., a) wind
catcher for catchment of the prevailing wind, b) wind tower/shaft, which carries the air to the
interior space, and finally c) the exhaust system, which is responsible for the distribution of
Figure 3. Domain with Macro-climate including Meteorological terrain topography and
Micro-climate including the experiment site topography and building for CFD simulation of
Atmospheric Boundary Layer (ABL) flow- definition of approach flow, incident flow and
ABL thicknesses.

air in the space and determines the flow condition in terms of pressure differentials between
the inlet (wind catcher) and outlet (exhaust). For our study, we shall be more interested in the
wind catcher component only. Air flow efficiency is estimated by outlet velocity, pressure
differential, mass flow rate and coefficient of pressure at inlet surface. Two very essential
parameters needs to be considered in the analysis of airflow in the wind catcher are a) Air
Velocity and frequency, and b) terrain roughness/ Site obstruction. Air velocity (Umet) for a
given region which is available in standard meteorological data is generally measured in a
flat, open terrain at a reference height (Hmet) of 10 m. The data is usually specified in average
hourly or 10 minutes interval. The shortest time period considered being a “steady-state”
condition when considering atmospheric winds is 10 minutes interval period [22]. In a steady
state condition the time averaged properties such as flow velocities and turbulent fluctuations
are independent of time i.e., they are considered steady in the mean. Also, “In ventilation
design, the prime interest usually lies in time-averaged values of quantities, partly because
human beings and buildings respond slowly, compared to the timescales of turbulence
associated with the wind and with internal air motion.” [18]. Thus the frequency of
occurrence (unsteady flow) is neglected. The average wind velocity can be used to predict the
surface averaged pressures (Ps) which is proportional to the wind velocity pressure (Pv) [22].
= (1)
And is determined by Bernoulli’s equation given as:
Where
Wind velocity pressure
Surface averaged pressure
Coefficient of pressure, which is a dimensionless number
Ambient (outside) air density
Approach wind speed at upwind wall height
Generally to evaluate the airflow in the wind catcher, the pressure coefficients are required at
the inlet surface which can be calculated from equation 1 and 2. Also it is necessary to
consider the direction of the wind, as the pressure coefficients are not direction independent.
But it is difficult to specify values of wind speed and direction (Umet) that correspond to the
values used to define pressure coefficient as these are generally given at a meteorological
station (Macro climate), which may be far removed from the site in question [18]. The
topography of the earth’s surface can greatly influence the microclimate, altering direction
and speed of the wind. The topography can be represented by an aerodynamic length due to
surface roughness or terrain type i.e., open, urban areas or large city centre, which develops
an atmospheric boundary layer upto a height of 270-1500 metres depending on the terrain
type).
(2)

Due to this thickness the wind speed is distributed in a power law profile from the ground
surface in the vertical direction. So it is necessary to represent the microclimate wind
condition which can be interpolated from the reference meteorological wind data by the
following equation [22].
Where,
Approach wind speed at upwind wall height H
Hourly wind speed from a nearby meteorological station
Atmospheric boundary layer thickness at meteorological station
Height at which the anemometer that measures (generally 10 m)
Atmospheric boundary layer exponent at meteorological station
Wall height at which approach wind (upwind) speed is required
Atmospheric boundary layer thickness at approach wind speed terrain
Category.
However, the above equation gives the flow speed only, for estimation of the direction,
explicit modelling can be included or implicit methods can be applied in the domain upwind
region representing the site obstruction, which will then create an internal boundary layer and
produce the flow speed and direction.
Finally the distribution of over the surface will be based on values of wind in close
proximity (micro climate) to the wind catcher (which shall be generated with CFD)
considering equations 3, 2 and 1 respectively.
3.2. Analysis Plan
This study aims at testing air flow in a wind catcher and at the same time gain better
understanding how to integrate the real site boundary conditions in CFD. Hughes et al., [12]
in their paper has described the major design criteria for a wind catcher which are based on, “
Topography, climatic conditions, personal experience of architects, social positions of the
occupants and variation in height, cross-section of air channel, number of openings, size and
positioning of opening, form construction materials, and placement of the tower with respect
to the building.”
Montezeri et al., [13] also emphasized that, the key working condition as the pressure
differential between the air inlet and exhaust of the device. So the ambient air flow
characteristics, i.e., the speed, direction and frequency of occurrence will determine the
physical/architectural parameters of the wind tower and its openings to maximize the pressure
differential.
For mono-directional device, the direction of wind is most important to keep it functioning.
When incident wind blows from other than its design range, the wind catcher will function as
a solar chimney and flow will be reversed [12].
(3)

Keeping these in mind, a mono directional wind catcher in which air (prevailing wind) enters
only from one side travels down the shaft and exits at the outlet, is simulated for finding the
design range. The most common cross section of a traditional wind tower i.e. a square cross
section is studied (refer figure 4).
a a
3.3. Computational Settings
Figure 4. Wind catcher prototype for study
Steady state numerical simulations for the study are conducted by Finite Volume Method
using ANSYS Fluent 12 CFD code. For turbulence modeling Standard k-ε model is selected
as per the industry standard [3]. SIMPLE scheme is chosen for pressure velocity coupling and
spatial discretization first order upwind is used. The analysis is conducted without solving the
energy equation (only continuity and momentum term of the basic Navier Stokes equation
which are nonlinear partial differential equations are solved). The convergence criteria for
continuity and velocity residual errors are taken as low as10 -3 . If q is considered as any
general flow variable e.g., velocity component, then the Navier Stokes equation can be
written as:
Rate of
Change of
quantity inside
control volume
3.3.1. Domain
b
d
c
Advection
across surface
boundary
Inlet area
Shaft
Roof level
Oulet area
Diffusion
across
boundary
+ + =
a = 1.2 m
b = 2.7
m
c = 5.2 m
d = 1.8
m
Source
generation
inside
The domain shall be large enough to represent the flow scenario without any significant
blockage through the boundary walls (unbounded flow is required). Therefore based on the
(4)

guidelines provided by [3], initially three domains of various size were considered, out of
which the right domain (Domain a) is selected comparing the flow velocity along an
imaginary line (ss’) passing through the shaft center from domain top to bottom.
Wind
catcher
Inl
et
g
ss
’
Figure 5. The distances g, h, i and j are
varied and flow velocity is compared along
line ss’ to get the right domain size.
3.3.2. Boundary conditions
i
Rotating
disk
i
h
Outl
et
j
Table1. Domain size dimensions (m)
Distance Domain Domain Domain
a b c
g 8.5 8.5 8.5
h 27.2 33.5 23.5
i 6 7.5 4.5
j 13.5 15 9
Figure 6. Velocity magnitude along the line
ss’ for varying domain sizes.
To represent the influence of the topography and wind conditions, appropriate boundary
conditions are specified. The major challenge is to apply the atmospheric boundary layer in
the upstream region developed by the terrain roughness. In ANSYS Fluent 12, this roughness
(wall function) is specified by equivalent sand grain thickness (KS) which is quite inadequate
(very smaller) to provide the ABL thickness (δ) [14] for horizontal homogeneous flow in the
domain. So for ground boundary layer this type of roughness specification is not considered
(KS = 0).Instead, the approach flow velocity is programmed (in C+ programming
language) as a power law profile (refer figure 3) in the vertical component to approximately
simulate the urban terrain using equation 3.Two pressure outlets (gauge pressure = 0) are
considered, one at shaft bottom and another at opposite of inlet surface (refer figure 5).
However, at shaft outlet this assumption is not suitable (usually it opens in the interior of

oom which may be at different pressure level), but for our study it is considered as same as
the atmospheric domain outlet.
3.3.3. Mesh independency
In finite volume method, the computational domain is spatially and computationally discretized to
solve the governing partial differential equations. The spatial discretization divides the entire domain
into a number of small/control volumes (cells) for which the continuity and momentum terms of
Navier Stokes equation are solved. The number of cells and their spatial arrangement in terms of
distribution among the domain and regions of important flow field decides the accuracy of the
calculation. The higher (numbers) and denser the mesh, the accurate the solution is. However, we
have to restrict the number of mesh (without sacrificing the resolution) in order to reduce the
simulation time for a limited computing resources (Dual core with 4GB Memory and approximate
simulation time per run was 2 hours). Based on the guidelines developed by Franke et al [3], an
appropriate mesh (Medium mesh) arrangement is selected out of three initial mesh distribution types
considering the cell metric quality (skewness shall not be greater than 0.95 [19] ). A virtual rotating
disk (refer figure 5) has been integrated in which the wind catcher is embedded, so that when
simulations are carried in varying orientation, the original mesh distribution and density is retained. In
all the cases unstructured tetrahedral mesh has been used and the selected case consists of 240977
cells and maximum skewness is 0.84. Fine and course mesh consists of 544158 and 163712 cells
respectively.
Figure 7. Unstructured tetrahedral meshing of the
domain.
From figure 6, it can be observed that velocity magnitude along the line ss’ coincides with
each other, in other terms the result is grid independent and maintains a sufficient level of
accuracy for analysis.
4. Results and discussions
Figure 8. Grid sensitivity test,
Velocity magnitude along the line
ss’ for varying Meshing.
Common intuition says that the best orientation is to face the wind normally and with higher
wind speed the flow will be more; simulations were carried to check this. Various cases were
run with varying wind direction and speed with power law profile at the approach flow. For
wind direction (Ψ), a total of 10 cases were simulated for each 10 0 increment between
approach flow and inlet surface normal starting from 0 0 upto 90 0 with constant wind speed of
5 m/s. For wind speed (ν) a total of 5 cases were simulated with 1 m/s increment starting
from 3 m/s to 7 m/s with Ψ = 0 0 . The performance criteria as set in previous section are

esultant velocity along the vertical center line of shaft, velocity at the inlet and outlet,
pressure at wind-catcher inlet and total massflow rate at the shaft outlet.
4.1. Performance of wind-catchers with varying wind directions
From figure 9 it is observed that the resultant velocity in general decreases from inlet to outlet
apart from the initial reduction (in the centre region) upto an interval of 1/3 rd distance from
the inlet. This is due to the flow separation by sharp edges at the inlet surface. Also it can be
observed that the velocity is higher in cases Ψ = 0 0 to 40 0 . The velocity contours at the midplane
of the domain shows the effect of atmospheric boundary layer at the approach flow (left
side of the domain) resulting higher velocities in the top of the domain. This in general
confirms the higher positioning of the wind-catcher relative to the ground surface for better
catchment of the prevailing wind.
Figure 9. Air velocity magnitude along central axis of the height of wind catcher plotted for
10 angles (from Ψ = 0 0 to 90 0 ).
Ψ = 0 0
Ψ = 10 0
Figure 10a. Contours of air velocity at midplane vertical cross-section of windcatcher.
The speed increases from darker to lighter colour in five ranges starting from 1= 0 m/s to
5 = 4 m/s.

Ψ = 20 0
Ψ = 40 0
Ψ = 60 0
Ψ = 80 0
Ψ = 30 0
Ψ = 50 0
Ψ = 70 0
Ψ = 90 0
Figure 10b. Contours of air velocity at midplane vertical cross-section of windcatcher. The
speed increases from darker to lighter colour in five ranges starting from 1= 0 m/s to 5 = 4
m/s.

From figure 11a, 11b, and 11c, it is observed there is a gradual reduction of velocity in cases
(Ψ = 0 0 to 40 0 ) and the reduction amplified in cases (Ψ = 50 0 onwards). This can be explained
by the fact that the outlet pressure decreases with increase in Ψ ((becomes negative after Ψ =
50 0 )). Also as consequence massflow rate is negative (reverse flow) beyond Ψ = 50 0 .
Overall it can be concluded that the airflow is maximum when Ψ = 0 0 to 40 0 , after which it
decreases, and the design range is between 0 0 to 30 0 for a prevailing wind condition.
However, care must be taken when the ambient wind flows oblique to the inlet surface than Ψ
> 40 0 to check the reverse flow. Then the wind-catcher will act as an outflow device. This is
preferable in the night condition when it is required to vent the warm air accumulated during
daytime from the interior space (and normally in hot arid climate the prevailing wind is
inversed during night time).
(a)
(c) (d)
Min
Ave
Max
Figure 11. Bar charts showing velocity magnitudes at both inlet (a) and outlet (b), pressure at inlet (c)
and mass flow rate at outlet (d).
4.2. Performance of wind-catchers with varying wind speed
From figure 12, it is observed that the velocity in the wind catcher increases proportionally
with increase in approach wind speed. This is evident in the pressure contour plots (refer
figure 13). For higher speeds the positive pressure zone in shaft upper region increases and is
maximum at 7 m/s.
Figure 12. Air velocity magnitude along central axis of the height of wind catcher plotted for
5 wind speeds (from ν = 3 m/s to 7 m/s).
(b)

5. Conclusion
The primary parameters which may have the largest influence on the airflow performance of
wind catcher are varied. The two parameters tested are orientation of wind catcher inlet to the
prevailing wind and its speed. Orientation results shows that, the wind catcher performs well
in the range of ± 30 0 from the normal of the inlet surface to the approach wind. There after
flow through it falls and at about 60 0 onwards flow reversal is observed. The average velocity
(both at inlet and outlet) and pressure at inlet shows a polynomial trend of 3 rd and 2 nd order
respectively with increase in angle between inlet surface normal and prevailing wind. The
other parameter being varied is wind speed. It is observed that both velocity and pressure
satifies a linear growth with increase in speed of the approach flow. However, these trends
can diverge, as the experiments for each parameter are conducted in isolation and therefore
the combined effect both speed and direction may produce a different trend.
References
ν = 3 m/s
ν = 4m/s
ν = 5 m/s
ν = 6 m/s ν = 7m/s
Figure 13. Contours of air pressure at mid-plane vertical cross-section of wind catcher. The pressure
increases from darker to lighter color in eight ranges starting from 1= -5 Pa to 15 = 10 Pa
Figure 14. Bar charts showing velocity magnitudes at both inlet (a) and outlet (b), pressure at inlet
(c) and mass flow rate at outlet (d).
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