02020311 - Cafet Innova

International Journal of Earth Sciences and Engineering 

ISSN 0974-5904, Vol. 02, No. 03, July 2009, pp. 264-271 

264 

The passive environment control system of Kerala 

vernacular residential architecture: 

An experimental investigation on wind flow and 

thermal comfort 

DILI A. S.*, NASEER M. A. ** and ZACHARIA VARGHESE T. * 

* Department of Civil Engineering, National Institute of Technology Calicut, Kerala, India 

** Department of Architecture, National Institute of Technology Calicut, Kerala, India 

Email: dili@nitc.ac.in, naseer@nitc.ac.in, zacharia@nitc.ac.in 

Abstract: A building envelope is not only designed to house its occupants for various 

functional requirements but also for a comfortable indoor environment that is essential 

to perform various activities efficiently. The vernacular architecture at any place is 

evolved through ages by consistent and continuous effort for more efficient and perfect 

solutions. The vernacular architecture of Kerala is known for its use of natural and 

passive methods for a comfortable indoor environment. The orientation of building, 

internal arrangement of spaces, the presence of internal court-yard, use of locally 

available materials and special methods of construction etc. have together created the 

indoor environment. The authors have conducted a detailed investigation of the passive 

environment control system of vernacular architecture of Kerala by continuously 

monitoring the indoor comfort conditions in residential buildings of more than 250 years 

old. This investigation proves that the passive environment control system of Kerala 

vernacular architecture is very effective. 

Key words: Kerala, passive environment control system, vernacular architecture, wind 

velocity, thermal comfort 

Introduction 

One of the basic functions of a building is 

to provide its occupants, not only safety 

and shelter, but also protection from 

adverse natural elements like sun, rain 

and wind. In order to ensure that the 

occupants are comfortable physiologically 

and psychologically, it is important that 

the indoors are kept at optimum comfort 

conditions. The climatic elements –solar 

radiation, air temperature, relative 

humidity and air movement – play a vital 

role in conditioning the indoor 

environment. 

Climate of a region has a direct influence 

on the settlement pattern and in its built 

form. Any good building should relate and 

respond to the climate it is situated in. A 

built form is designed for the beneficial 

aspect of the climate and to reduce the 

impact of unfavorable conditions. The 

layout, orientation and scale of buildings 

and settlements should therefore be 

controlled in relation to the climatic zones 

(Krishnan A., et. al., 2001). The influence 

of climate in the evolution of vernacular 

architecture is evident from various forms 

that exist in many parts of the globe. 

Kerala has a characteristic Warm-Humid 

climate because of its geographic settings. 

The presence of high amount of moisture 

in the atmosphere for major part of the 

year causes thermal discomfort as there is 

less evaporation, resulting in sweating. 

This becomes more acute in summer when 

the air temperature is higher than the 

body temperature. Prolonged exposure to 

thermal discomfort conditions can create 

adverse effects including extensive loss of 

efficiency in work along with physical 

strain (Lekha S Hegde and K S 

Ananthakrishna, 2008). 

The principles of vernacular architecture of 

Kerala are based on empirical observations 

and experimental wisdoms acquired 

through generations (A. Achyuthan and 

Balagopal T S Prabhu, 1998). The strength 

of vernacular architecture is that it makes 

#02020311 Copyright © 2009 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.

265 

The passive environment control system of Kerala vernacular 

residential architecture: An experimental investigation on 

wind flow and thermal comfort 

buildings that are in natural harmony with 

climate, built form and people. The use of 

natural and passive methods in the 

vernacular Kerala architecture is found to 

be highly effective in providing thermal 

comfort – cool indoor climate during 

summer and warmth in winter. 

The modern practice in architecture lacks 

conscious effort in using passive methods 

of controlling the indoor environment 

(Sunil Edward and Dona Kurian, 2008). 

Excessive use of modern materials 

irrespective of their efficiency in regulating 

the indoor environment has often resulted 

in high energy consumption, leading to 

many environmental problems. There is a 

close connection between energy use in 

buildings and the resulted environmental 

damage. This is because of energy 

intensive solutions that are required in 

buildings to attain comfort conditions in 

terms of cooling, ventilation and lighting. 

This has caused severe depletion of nonrenewable 

energy resources and 

environmental degradation. 

Investigations on natural and passive 

methods of ventilation in buildings are 

underway in the form of continuous 

evaluation of thermal comfort parameters 

of traditional buildings, in various countries 

(Kyung-Hoi Lee et. al., 1996, Lin Borong, 

et. al., 2004, Do-Kyoung Kim, 2005. 

Youngryel Ryu et. al., 2008). Although 

there have been attempts for qualitative 

analysis of the traditional buildings of 

Kerala, a comprehensive and quantitative 

study of the efficiency of these buildings is 

so far absent. No detailed investigations in 

this area have been published, especially 

in the form of technical papers in referred 

journals so far. Thus, there is a need for a 

quantitative analysis of the passive design 

of traditional residential buildings of Kerala 

using a real-time evaluation method. This 

would help the present day architects and 

engineers to adopt suitable techniques to 

make their design energy efficient and 

sustainable. 

Climate of Kerala 

According to Bureau of Indian Standards, 

India has been divided into five different 

regions with distinct climates in which 

Kerala comes under the warm – humid 

region. The climate of Kerala is 

characterized by heavy rainfall and high 

relative humidity, and relatively moderate 

temperature. In effect, Kerala has only two 

predominant seasons- rainy and dry 

seasons. The rainy season lasts for about 

half of the year, which has greatly 

determined the character of built form with 

its characteristic sloping roof. Summer 

comes under the dry season with hot and 

humid days and nights and intense solar 

radiation during the day time. 

Wind speed and direction is determined by 

the season and the temperature 

differences between land and sea. 

Predominant wind direction during 

monsoon period, i.e., June to September is 

west to South west and the effect of land 

breeze is not dominant during this period. 

During October – November, wind 

direction changes from South - West to 

North - East. Though predominantly south 

west, the wind is influenced by the 

presence of other topographical features 

including the presence of large water 

bodies. 

Vernacular Architecture of Kerala 

Kerala vernacular buildings are built 

according to the principles of 

Vaastushastra, the Indian discipline on 

architecture (A. Achyuthan and Balagopal 

T S Prabhu, 1998). The basic house 

module of a vernacular Kerala house is 

nalukettu with four blocks built around an 

open courtyard. The blocks are topped 

with a sloping roof on four sides. They are 

generally rectangular or square in plan and 

the courtyard is open to sky for letting air 

and light inside. 

The enclosed courtyard is usually sunken 

such that cooler air settles down. The eves 

of the roof of the main blocks extends 

beyond the outer walls, covering another 

verandah at the front of the building (Fig 

1). 

The roofs have high pitch up to 45 degrees 

to help the rain water drainage easier. The 

gables (mughappu) provided at the ends 

of roof helps to enhance ventilation and to 

allow the warm air to escape. Further, 


ISSN 0974-5904, Vol. 02, No. 03, July 2009, pp. 264-271

DILI A. S, NASEER M. A, and ZACHARIA VARGHESE. T 

266 

ventilators are provided for attic 

ventilation when wooden false ceiling is 

incorporated for the room spaces. The 

roofs thus enclose a large insulated air 

space thus, keeping the lower areas 

cooler. 

and used as building blocks. Laterite 

blocks are mainly bonded in lime mortar, 

the classic binding material, in traditional 

buildings. It is strong and durable with 

exposure to atmospheric air. 

Wood is the major building material, used 

for construction, in Kerala. The skilful 

selection of wood, perfect joinery, artful 

assembly and subtle carving for columns, 

walls and roof frames are the unique 

characteristics of Kerala residential 

architecture. Mud is also used in many 

forms in traditional buildings which include 

mud walling, bricks, clay tiles (both roofing 

and flooring), mud mortar for laterite 

masonry and as filler for timber floors. 

Passive Environment Control System 

Fig. 1: Plan and Longitudinal Section of a 

typical vernacular Kerala house with two 

courtyards of different sizes 

A typical Kerala traditional house consists 

of two major living areas - inner one 

forming the core of the house and the 

outer verandahs forming the periphery. 

The house form offer flexibility and it helps 

the inhabitants to shift their activities from 

one place to another in different climatic 

conditions. An important aspect of the 

Kerala traditional architecture is the usage 

of courtyards. In dry season the inner 

courtyards are used for drying, cleaning 

and preparing cereals, food etc (D. Vyas, 

2005). The courtyard also functions as a 

major functional element in the house with 

most of the internal movement and 

circulation of people defined by the 

verandahs around the courtyard, as the 

major rooms are entered from this 

verandah. 

The commonly used building materials for 

vernacular construction in Kerala are mud, 

laterite, granite stone, lime mortar, wood, 

bamboo, clay tile roofing and coconut palm 

leaves. Laterite, seen in shallow depth, is 

the building material available in plenty in 

Kerala, which can be easily cut, dressed 

The traditional houses of Kerala are 

designed for the major problems faced due 

to excess 

of moisture in 

the atmosphere, heavy rainfall, intense 

solar radiation and effect of high 

temperature. Kerala vernacular buildings, 

square or rectangle in plan, are oriented 

strictly to the cardinal directions. This 

makes the spatial planning more perfect to 

control its environment with maximum 

comfort in all distinct seasons. 

The courtyard is commonly referred to as 

microclimate modifiers. They enjoy better 

microclimatic conditions than the 

surrounding open areas; have a positive 

effect on the indoor comfort conditions of 

the enclosing building volume (Krishnan 

A., et. al., 2001). 

Buildings usually have large number of 

openings, windows and ventilators. 

Provision of open or semi enclosed spaces 

also give comfort condition to the interiors. 

The buildings have verandahs located 

either on its two sides or on all four sides. 

Another remarkable feature in the Kerala 

vernacular architecture is the provision of 

open gables (mughappu) in the roof and 

the provision of wooden jalli (azhi) in the 

external walls at appropriate positions. The 

open gables (mughappu) seen mostly in 

southern part of Kerala, provides an 

opening in the roof for internal hot air to 

escape where false ceiling is not provided. 

The wooden jalli (azhi) in the external 

walls in appropriate positions helps to 



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draw external air with the effect of 

courtyards. 

The thermal insulation in buildings is 

achieved by the effective use of materials 

and the construction techniques used in 

building walls and roof. The external walls 

of vernacular buildings are usually very 

thick up to a maximum of 750 mm with 

double layer of laterite masonry with a gap 

in between that is filled with fine sand. 

This makes the external wall highly 

insulative. The roofs are sloping and in 

some cases at two levels - one provided 

over the verandah and other covering the 

rest of the rooms. 

Inorder to achieve thermal insulation, 

wooden ceiling (tattu) is also provided 

beneath the roof. This provides a large air 

space, which acts as an insulation layer 

against the conduction of external heat 

through the roof. The air space above the 

wooden false ceiling is well ventilated with 

openings (jalli) on both sides to permit 

maximum cross ventilation. The breathing 

space between the clay tiles that is used 

for roofing further helps in ventilating the 

under side of the roof reducing the 

temperature. 

Penetration of water to the interiors 

through the roof due to rain is prevented 

by pitched roofs protected with impervious 

materials like burnt roofing tiles, thatch 

etc. Dampness is eliminated by building on 

elevated lands with high plinths. 

sensors, data logger, memory module and 

computer interface (Figures 2, 3, 4, 5) was 

used to record the field data. Temperature 

sensors were located outside the building, 

in the courtyard, in the semi open space 

around the courtyard and in a bedroom 

adjacent to the courtyard. Indoor and 

outdoor wind velocities were also recorded 

simultaneously. A humidity sensor was 

fixed in the semi open space around the 

courtyard to record the indoor relative 

humidity. Continuous data were recorded 

for a period of 45 days at an interval of 15 

minutes. The windows were kept open 

throughout the investigation for 

unobstructed wind flow inside the building. 

Fig. 2: Data logger and memory module of 

the AES installed in the traditional house 

Experimental Investigation 

An investigation using quantitative 

recording of climatic parameters was 

carried out in a traditional residential 

building (around 250 years of old) at 

Nilambur in the Malappuram district of the 

northern part of Kerala. The courtyard of 

the building has an inward looking 

verandah of 1m width. The two sides of 

the courtyard are semi open spaces used 

for living and prayer. The other two sides 

are adjoined with rooms having windows 

opening to the courtyard. 

A custom made instrumentation set up 

called Architectural Evaluation System 

(AES), which is a combination of electronic 

Fig. 3: Indoor wind velocity sensor 

(bottom), Temperature and Humidity 

sensors (top) 




268 

Fig. 5: Outdoor wind velocity sensor 

Results 

Fig. 4: Outdoor temperature sensor 

While a diurnal variation of 17 o C (18 o C to 

35 o C) was observed in the outdoor 

temperature, a diurnal variation of just 

about 4 o C (24 o C to 28 o C) was observed 

in the simultaneous indoor temperature 

(Fig. 6). The temperature recorded inside 

the room is found to be lower than that of 

semi open space around the courtyard. It 

is observed that the indoor air 

temperature is maintained around 24 o C 

during night even when the outdoor 

temperature is as low as 18 o C. From the 

figure 6 it is evident that there is no time 

lag between the temperature outdoor and 

indoor. The indoor relative humidity varies 

from 45% to 90% and it is inversely 

proportional to the air temperature. 

The wind flow through the courtyard is 

almost continuous and consistent 

irrespective of the outside wind velocity. 

The figures 7 and 8 show the indoor and 

outdoor wind velocity when the outside 

wind velocity is very high and low. 



269 




Fig. 6: Air Temperature and Relative Humidity vs. Time 

Fig. 7: Wind Velocity vs. Time (when outdoor wind velocity is high) 

Discussion 

Fig. 8: Wind Velocity vs. Time (when outdoor wind velocity is low) 

The low diurnal variation of the indoor 

temperature proves the high thermal 

insulation property of the building 

envelope. The absence of time lag 

between outdoor and indoor temperatures 

is mainly due to the continuous air flow 

through the building. The air flow inside 

the building is maintained throughout 

(figures 7 and 8). This allows a convective 

heat exchange from outdoor to indoor. 

That is, when outdoor is very hot, those 

heat scalars are only transmitted into 

indoor by wind, which reduces the 

intensity of heat. 




270 

Figure 6 shows that during day time when 

the indoor temperature is high up to 28 o C, 

the humidity is as low as 45%. This falls 

well within the comfort zone of the 

bioclimatic chart (fig. 9) constructed by V. 

Olgyay (Koenigsberger, et al, 1975). This 

provides a very comfortable indoor 

environment. During night, since 

temperature becomes low up to 24 o C, the 

increase in humidity (up to 88%) does not 

really affect the indoor comfort condition. 

There is a very common saying that the 

main reason for the traditional buildings to 

keep cool when outside is hot is due to the 

maximum ventilation. In fact, maximum 

ventilation may bring more heat into the 

room and destroys the indoor thermal 

environment (Lin Borong, et. al., 2004). 

From the figures 7 and 8 it is evident that 

the passive environment control system of 

Kerala vernacular architecture really 

control and reduces the wind velocity 

inside the building in order to maintain its 

comfort level better. 

architecture. The presence of highly 

insulative building envelop for thermal 

protection, provision of verandahs for 

protection of external walls from solar 

radiation and the pitched roof for 

protection from heavy rain together are 

highly effective for a passive environment 

control system in Kerala vernacular 

residential architecture. The setting of 

building in the open land with judicious 

arrangement of living spaces around a 

courtyard with optimum size window 

openings is according to the requirement 

of wind for giving comfort in the humid 

climate. 

Conclusion 

Control of the indoor environment is 

always an important aspect of vernacular 

Fig. 9: Bioclimatic Chart (Koenigsberger, et al, 1975) 



271 




Acknowledgements 

The authors extend sincere gratitude to 

Mr. Ravi Varma of Nilamboor Kovilakam 

for his kind co operation for the conduct of 

the investigation. The authors also extend 

sincere gratitude to Dr. Ziaudeen, 

Principal, TKM College of Engineering for 

providing the equipment for this research. 

Mr. Sreejith T. S., Production Executive of 

EMCON, is also acknowledged by the 

authors for the supply and service of the 

equipment “Architectural Evaluation 

System”. 

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