(JBED) - Summer 2006 - The Whole Building Design Guide

JBED 

Summer 2006 

Journal of Building Enclosure Design 

An official publication of the Building Enclosure Technology and Environment 

Council (BETEC) of the National Institute of Building Sciences (NIBS) 

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2006 Matrix Group Publishing. All rights 

reserved. Contents may not be reproduced by 

any means, in whole or in part, without the 

prior written permission of the publisher. The 

opinions expressed in JBED are not necessarily 

those of Matrix Group Publishing. 

Features: 

10 

19 

26 

32 

37 

39 

Dynamic, Integrated Façade 

Systems for Energy Efficiency 

and Comfort 

All That Glass 

Architectural Glazing for Sound 

Isolation (an Acoustician’s 

Perspective) 

Occupant Thermal Comfort 

and Curtain Wall Selection 

Window Comfort & Energy 

Codes 

Messages: 

06 

08 

From NIBS President, David A. Harris 

From BETEC Chairman, Wagdy Anis 

Industry Updates: 

45 

46 

47 

Security 

Tax Credits Made Easy by Choosing 

ENERGY STAR® 

32 

39 

41 

Contents 

Thermal 

Comfort 

Laminated Glass, Providing 

Security against Terrorist Attacks 

How Does Fenestration Fit In 

41 

Fenestration 

Questions 

On the cover: The glass- 

NFRC Standards, Codes and Fenestration 

Research Activities 

BEC Corner 

50 Buyer’s Guide 

enclosed von der Heyden 

pavilion at the Perkins Library, 

renovated and expanded by 

Shepley Bulfinch Richardson and 

Abbott at Duke University, 

creates transparency by 

connecting the interior with 

nature and outdoor campus 

activity. 

Photo by: Albert Vecerka/ESTO. 

Summer 2006 5

Message from NIBS 

David A. Harris, FAIA 

With mold and 

other moisturerelated 

problems 

perpetuating, 

energy efficiency 

becoming more 

critical with 

escalating energy 

costs, and design 

professionals and 

constructors in 

need of reliable 

guidance, JBED 

will fill a critical 

void. 

WELCOME TO THE JOURNAL OF Building Enclosure Design (JBED)! The National 

Institute of Building Sciences and its Building Enclosure Technology and Environment 

Council (BETEC) is pleased to team with Matrix Group Publishing to produce 

this inaugural issue of the Journal of Building Enclosure Design. This new and 

important magazine will become an essential information source on research and 

development issues related to building enclosure systems for North America. 

With mold and other moisture-related problems perpetuating, energy efficiency 

becoming more critical with escalating energy costs and design professionals 

and constructors in need of reliable guidance, JBED will fill a critical void. 

Through the multi-disciplinary professional members of BETEC and Matrix’s 

publishing capabilities, facility professionals across North America will have a new 

and reliable source of information through which to improve the performance of 

exterior walls, below-grade, roof and fenestration systems and the related impacts 

on indoor environments. 

NIBS’ and BETEC’s past contributions are featured content of the Whole 

Building Design Guide (www.wbdg.org). They include the results of numerous research 

initiatives and symposia, the Envelope Design Guide and form a substantial 

portion of the basis for technical and editorial content of our biannual journal. By 

distributing it widely to members of NIBS councils, corporate, government and 

association personnel, design and construction professionals, and researchers and 

academics throughout Canada and the United States, the value of BETEC’s contributions 

will be greatly expanded. 

In addition to BETEC’s focus on building enclosure issues, NIBS and its other 

councils have, for nearly 30 years, addressed the broad range of facility-related 

issues through hundreds of multi-disciplinary and cooperative initiatives. They include 

health, safety, security, health care and educational facilities, natural and environmental 

hazard assessment and mitigation, information technology, standards 

and criteria development, facility life-cycle needs, life-lines research and information 

dissemination to name a few. Please visit NIBS website at www.nibs.org. We 

encourage your use of our products and seek your participation in our programs. 

Together we can successfully improve the performance of the built environment. 

We invite our readers to carefully review this inaugural issue and ask you to 

let us know how you like it. Please provide critical feed back to Matrix Group 

Publishing or NIBS so we can make this publication better and more responsive 

to your needs. 

David A. Harris, FAIA 

President 

National Institute of Building Sciences 

For NIBS membership information, go to www.nibs.org. 

WHAT IS NIBS 

NIBS is a non-profit, non-governmental organization bringing 

together representatives of government, the professions, industry, 

labor and consumer interests to focus on the identification and resolution 

of problems and potential problems that hamper the construction 

of safe, affordable structures for housing, commerce and 

industry throughout the United States. 

The Institute’s board of directors consists of 21 members. Six, 

which represent the public interest, are appointed by the President 

of the United States with the advice and consent of the U.S. Senate. 

The remaining 15 members are elected from the nation’s building 

community and include consumer and public interest representatives 

as well as representatives of industry. A majority of the 

NIBS’ board represents public interest sectors as prescribed in the 

authorizing legislation. 

For more information visit www.nibs.org. 

6 Journal of Building Enclosure Design

Message from BETEC 

Wagdy Anis, AIA, LEED A-P 

“The purpose of 

the Councils is to 

promote and 

encourage 

discussion, training, 

education, 

technology 

transfer, the 

exchange of 

information about 

local issues and 

cases, relevant 

weather conditions, 

and all matters 

concerning building 

enclosures and the 

related science.” 

WELCOME TO JBED, THE JOURNAL of Building 

Enclosure Design. 

The Building Enclosure Technology and Environment 

Council (BETEC), one of the councils of 

the National Institute of Building Sciences, along 

with Matrix Group Publishing, is pleased to lead 

the effort to publish the Journal of Building Enclosure 

Design, JBED. This new publication will quickly become 

an essential vehicle for the dissemination of 

information on research and development issues 

related to building enclosure science and technology, 

in full alignment with BETEC’s mission. 

With losses due to hurricane damage and other 

natural disasters, mold affecting and triggering the 

burgeoning asthma population, moisture accumulation 

determining the durability of enclosures and 

shortening their useful service lives, fossil fuel energy 

sources becoming threatened and energy 

costs escalating and the design and construction 

community in need of useful information and guidance, 

JBED is offered to provide just that. The 

United States represents all the climates of the 

world and designing enclosures for each climate 

and building use is a challenge this publication 

plans to address. 

One of BETEC’s important successes in the recent 

past is establishing the Building Enclosure 

Councils or “BECs” in different cities of the US, in 

partnership with the American Institute of Architects 

(AIA), following the successful precedent set 

in Canada. As of this writing, 13 BECs are in place 

in most of the climate zones, and at least 6 more 

are planned. 

I believe the BECs, as they mature, will help 

bring building science of the building enclosure to 

the mainstream. To contact the BEC’s, go to 

www.bec-national.org/ boardchairs.html. 

We will be bringing you news and events of the 

BECs on a regular basis in this publication through 

the “BEC Corner.” 

Another recent success of BETEC is the 

publishing of NIBS/ASHRAE Guideline 3: Commissioning 

the Building Enclosure. As of this writing, the 

publication is available for public review free for a 

limited time only, until July 21, 2006: 

www.nibs.org/ GL3.html. For the first time, commissioning 

the building enclosure has been organized 

as a process, in conjunction with ASHRAE 

/NIBS Guideline 0, The Commissioning Process. This 

has been a substantial effort that lasted two years, 

and your feedback would be very helpful. 

The Building Enclosure Design Guide, a huge effort 

of over a thousand pages, is now published on 

the web as part of the Whole Building Design 

Guide, www.wbdg.org and will be featured in future 

editions of JBED. 

This article will be a vehicle to bring you 

BETEC news and its directions in the future. 

BETEC membership is open to all organizations 

and individuals having an interest in BETEC’s 

goals. www.nibs.org/betecmem.html. 

We hope you enjoy this edition of JBED. Please 

send us your opinions and ideas regarding how to 

improve it. The JBED Editorial Board solicits the 

articles and submits them for peer review. It is important 

to make clear that in no way does NIBS or 

BETEC control or review the content or claims 

made by advertisers in JBED, nor is NIBS, BETEC 

or Matrix Group Publishing responsible for the use 

or application of any information provided in 

JBED. 

We look forward to hearing from you. Please 

encourage anyone you know who may be interested 

in receiving a copy of JBED to e-mail 

jbed@nibs.org. 

Thank you, 

Wagdy Anis, AIA, LEED A-P 

Chairman, BETEC 

Chairman, JBED Editorial Board 

Principal, Shepley Bulfinch Richardson and Abbott 

For BETEC membership 

information, go to 

www.nibs.org/betec 

All of Alaska in 

Zone 7 except for 

the following Borroughs 

in Zone 8: 

Bethel 

Northwest Arctic 

Dellingham 

Southeast Fairbanks 

Fairbanks N. Star 

Wade Hampton 

Nome 

Yukon-Koyukak 

North Slope 

Zone 1 includes: 

Hawaii 

Guam 

Puerto Rico 

The Virgin Islands 

Warm-humid below the 

white line 


Feature 

Dynamic, Integrated Façade Systems 

for Energy Efficiency and Comfort 

By Stephen Selkowitz and Eleanor Lee, 

Lawrence Berkeley National Laboratory 

SUMMARY 

In a world with growing concerns 

about global energy use and carbon emissions, 

and with limited short-term options 

for increasing renewable energy supplies, 

highly energy efficient and sustainable 

building design becomes a necessity. 

Buildings use more than 1/3 of all U.S. energy 

and more than 2/3 of all electricity— 

it is therefore difficult to change national 

energy use and carbon emissions without 

addressing energy use patterns in buildings. 

Architects design buildings with highly 

glazed façades in climates worldwide. It is 

impossible to “optimize” building performance 

with static glazings alone since 

sunlight/daylight intensity varies dramatically 

with location, orientation, climate 

and time. Providing optimal energy efficiency 

for owners, and thermal and visual 

comfort for occupants, requires dynamic, 

interactive façade systems to actively control 

solar gain, daylight and glare. Successful 

solutions require proper technology 

selection, integration between building 

systems and optimized sensing and control 

strategies. 

Although the concepts are well 

known, these solutions are not commonly 

available today as affordable, specifiable 

and reliable packages. We describe recent 

project results following several technology 

pathways that have made progress toward 

the goal of dynamic façade solutions. 

Automated motorized blinds and shades, 

integrated with a daylight responsive, dimmable 

lighting system can provide solutions 

today. 

Working with the New York Times, a 

full-scale mockup of part of a typical floor 

of a 52-storey, all-glass building was constructed, 

and a variety of interior motorized 

roller shades and dimmable lighting 

options were extensively simulated, 

10 Journal of Building Enclosure Design 

tested and optimized. Performance specifications 

were developed to guide competitive 

procurement and affordable new 

systems were developed that will shortly 

be installed and commissioned in the 

building, for occupancy in 2007. Looking 

forward, we also tested and simulated 

electrochromic “smart glass” façade prototypes 

in three side-by-side full size test 

rooms with integrated HVAC and lighting 

systems. Energy and demand impacts of 

alternate control strategies were also 

measured and occupant responses were 

also studied. 

The control and integration results 

from both projects demonstrate that dynamic 

façade technologies can provide desired 

energy performance levels, demand 

response and load management, and also 

reliably deliver visual and thermal comfort 

in indoor workspaces. 

INTRODUCTION AND BACKGROUND 

The “oil shocks” of the 1970s awakened 

many people to the realization that 

overall energy use in buildings could be 

reduced with better design and improved 

technology. In a nation where single glazing 

was the norm in most buildings, windows 

were commonly the thermally 

worst element from a perspective of both 

heat gain and loss. The regulatory response 

was typically to minimize window 

area and to require thermally improved 

technology, i.e. double glazing. The immediate 

crisis also stimulated a new look at 

passive solar heating and daylighting, two 

design approaches that attempt to capture 

benefits from window performance, 

but neither approach reached mainstream 

practice before energy availability and 

prices stabilized and the design profession 

returned to a largely “business-as-usual” 

approach. 

Thirty years later, new environmental 

challenges have made their way to the 

newspaper headlines and to the practice 

of building design and operations. At any 

given time, building designs reflect the influence 

of a wide range of issues and 

trends. These include not only the technical 

constraints of available technologies 

but also economic, cultural and business 

trends and market drivers. Glass is recognized 

as a key element in the architectural 

expression of the building, provides occupants 

with a visual connection to the outdoors 

and provides daylight indoors to enhance 

the quality of the interior work 

environment. The building envelope 

serves an important functional role to help 

maintain proper interior working environments 

under highly variable external environmental 

conditions. The primary technical 

challenges of envelope environmental 

control include heating, cooling and lighting 

energy use and electric demand, and 

the final design decisions impact not only 

the owner who pays for the energy use 

but society at large due to resource depletion, 

carbon emissions, and other related 

regional and global environmental impacts. 

The conventional approach to façade 

design in the U.S. has been for the architect 

and owner, to determine glazing 

areas and orientation, leaving the engineering 

team to select a glazing solution 

that provides some degree of damage 

control using static thermal and solar control 

technology. The strategy then required 

provision of large (typically oversized) 

HVAC systems to provide thermal 

comfort and provision of interior shading 

to manage glare and provide visual comfort. 

When highly glazed façades have 

been specified in the past the glass selection 

was normally heat absorbing and/or 

reflective, thus providing some control of 

radiant gain but at the expense of daylight.

Prior to the 1980s, most glazing was single 

glazed, and although double glazing is now 

the dominant glazing choice, many designs 

still use thermally unbroken metal framing, 

resulting in relatively high conductive/convective 

loads that are neutralized 

by powerful HVAC systems at the building 

perimeter. These peak perimeter zone 

heating and cooling loads are often the 

major factor in sizing building HVAC systems, 

adding significant cost to the building. 

Properly operated shades and blinds 

might reduce loads, but no engineer 

would trust that manual operation would 

consistently provide sufficient control to 

“rightsize” chillers and HVAC distribution 

systems. 

A variety of business, market and technical 

forces have conspired to change design 

practice over the last 20 years. Building 

energy codes and standards have been 

tightened, reflecting a growing societal interest 

in energy efficient, sustainable designs. 

Owners have shown a renewed interest 

in providing more comfortable and 

productive work environments in the context 

of “green buildings”. Glass and façade 

manufacturers now offer a wider range of 

affordable double glazing system solutions 

that provide better thermal and solar control 

without sacrificing daylight e.g. spectrally 

selective low-E glazings. 

These advances came at a fortuitous 

time because the growing interest in highly 

glazed façades makes new demands on 

designers and manufacturers. The new 

challenge is to provide a fully functional 

and integrated façade and lighting system 

that operates appropriately under a wide 

range of environmental conditions and addresses 

the full breadth of occupant subjective 

desires as well as objective performance 

requirements. These rigorous 

performance goals must be achieved with 

solutions that are initially affordable and 

cost effective and then must operate over 

long periods with minimal maintenance if 

they are to be accepted and purchased by 

building owners. The current high level of 

uncertainly and risk, both real and perceived, 

must be reduced by generating 

objective performance data that demonstrates 

the viability of these solutions. 

In prior studies we used extensive 

computer simulation studies to analyze 

and optimize the designs of high performance 

façades. In this paper we describe 

recent results from two field tests of 

integrated, high performance façade systems 

that, in partnership with manufacturers 

and building owners, are contributing 

toward reaching these challenging performance 

goals. 

PERFORMANCE REQUIREMENTS IN 

HIGHLY GLAZED BUILDINGS 

If all owner, occupant and society 

performance needs must be 

met with high performance 

façades, glazing systems alone will 

be inadequate. Glass selection 

might provide good performance 

where glazing area is judiciously 

limited on an orientation basis in 

climates that are not severe, but if 

one chooses to use large glazed 

areas on most orientations in a 

wide range of climates then new 

performance capabilities must be 

added to even the best of today’s 

glazing technology. 

Thermal losses in winter can be addressed 

by specifying highly insulated glazings. 

A standard, U.S. glazing today is a 

double glazed unit with low-E coating and 

gas fill, attaining a center glass U-value of 

about 1.4 to 1.6 W/m 2 -C in typical constructions. 

Even lower conductance levels 

may be needed, not so much as an energy 

saving strategy but to minimize thermal 

discomfort and condensation. Furthermore 

the overall conductance of the complete 

façade system is typically worse than 

the glazing alone since it includes the 

metal framing elements and glass edge 

conditions, so overall façade conductance 

can be 10 per cent to 40 per cent higher 

than the glass conductance, depending 

upon framing details and glass areas. The 

National Fenestration Rating Council 

(NFRC) has developed standardized, accurate 

methods to rate the performance 

of complete window and façade systems. 

Highly insulating glazings still require 

additional development but the bigger 

challenge is dynamic control of sunlight to 

modulate solar gain, daylight, view and 

glare. There are two fundamental issues 

to address in control of sunlight: 1) the 

mechanism(s) to physically control intensity 

e.g. absorption, reflection; and 2) the 

control logic by which the change in 

transmittance is triggered and activated. 

Finally one should note the challenge of 

simultaneously controlling sunlight admittance 

while admitting adequate daylight to 

offset electric lighting needs. These control 

issues are shown schematically in Figure 

1 below. In the remainder of this 

paper we focus on the sunlight/daylight 

control optimization issue. 

Figure 1 

Schematic of control logic to manage dynamic window system and dimmable 

lighting. A smart controller must be capable of responding effectively to a wide 

range of input conditions, shown on the left. 

THE CHALLENGE OF DYNAMIC CONTROL OF 

SOLAR GAIN AND DAYLIGHT IN ADVANCED 

FAÇADES 

We explored two pathways for developing 

high performance façades that are 

fully integrated with automated dimmable 

lighting systems, and are responsive to 

changing owner and occupant needs. We 

first examined technology that is widely 

available, although not commonly used, 

automated shades and blinds, to provide 

dynamic control of solar gain, daylight and 

glare. We then looked to the future and 

examined the use of emerging “smart 

glazings”, specifically electrochromic glazings. 

In both cases, integrated daylight 

dimming controls are essential to reduce 

lighting energy use, and in both cases control 

strategies that address occupant 

needs for comfort and performance are 

balanced against building owner needs to 

minimize building operating costs. While 

extensive parametric computer simulation 

of façade and building performance is a 

critical element of these studies, computer 

modeling alone is insufficient to address 

issues such as glare and subjective response 

to the indoor environment, and to 

understand and solve problems in a manner 

that leads to change in the marketplace. 

Therefore, each of these research 

efforts relied on field tests and each includes 

studies of human factor issues as 

well as engineering optimization. 


1. COMMERCIALLY AVAILABLE 

SOLUTIONS: AUTOMATED BLINDS 

AND SHADES 

Blinds and shades are used in most 

U.S. buildings today but unlike European 

experience, virtually none are motorized 

and few are externally mounted. The assumption 

is that that these shading systems 

are available for occupants to control 

localized glare and solar gain but they 

are not relied on to control building envelope 

performance. Accordingly, most energy 

standards do not provide any credits 

for systems that rely on occupant action 

since the response is unknown and uncertain. 

Furthermore, engineers will generally 

size HVAC systems assuming worst case 

operating procedures—e.g. that the shading 

systems are not operated as planned. 

Large glazed areas, even if heavily tinted 

and reflective, may be insufficient to fully 

control glare on sunny days. 

the U.S., nor are systems that further link 

the blinds to dimmable lighting controls. 

Beginning with “off the shelf” blind and 

lighting components, we developed and 

tested an integrated, automated blind and 

daylighting system in two identical sideby-side 

test rooms in a southeast facing 

office building in Oakland, CA (Figures 2.1 

and 2.2). Large cooling and lighting energy 

savings were achieved, peak electrical savings 

were measured and the resultant automated 

systems were acceptable to occupants 

in a limited occupancy study. 

Despite the success of the demonstration, 

the lack of a cost-effective delivery system 

managed by a single vendor or groups of 

vendors continues to limit use of such systems. 

The project illustrated the market obstacles 

from a building owner and manufacturer 

perspective in terms of who 

serves the “systems integrator” role when 

Figures 2.1 and 2.2 

Smart controls on the automated blind systems (left photo) keep direct sun out of the space, reducing glare and cooling loads. The same hardware 

system with different control strategies (right photo) admits sunlight to offset heating loads but creates excessive glare. 

AUTOMATED VENETIAN BLIND AND 

INTEGRATED DAYLIGHTING SYSTEMS 

Venetian blind systems are widely 

specified for control of solar gain and 

glare. Because both the optical properties 

of the slats and their tilt can be controlled, 

they provide a wide range of optical and 

solar control. But a number of field studies 

have shown that manually operated 

blinds are rarely controlled in an optimal 

manner. Adding sensors and controls and 

automating the blind operation should 

permit better control of both energy use 

and comfort, assuming that the proper 

control strategies can be successfully developed, 

implemented and maintained. 

These integrated, automated control 

systems are not yet commonly available in 


the different system elements are provided 

from different vendors. Development 

of smart, automated blind systems is 

more advanced in Europe and Japan. Although 

a growing number of these systems 

are now being installed in buildings it 

is still difficult to find measured performance 

data that clearly demonstrates the 

overall energy use of such systems. 

AUTOMATED MOTORIZED SHADE SYSTEMS 

AND INTEGRATED DAYLIGHTING CONTROLS: 

NEW YORK TIMES BUILDING 

A second widely used operable shading 

system is based on roller shades. 

Roller shade systems can utilize different 

fabrics encompassing a wide range of solar 

optical properties, ranging from blackout 

shades to highly transmissive veiling 

fabrics. Although mechanically simpler 

than blinds, once the fabric is chosen the 

shade systems have more limited optical 

control than blinds, largely based on their 

position between up and down. It is possible 

to layer blinds or use optically variable 

fabrics but this is not common practice. 

An extensive field test program was conducted 

using an automated shade system 

in conjunction with a high transmittance, 

all glass façade for the New York Times 

headquarters building, now under construction 

in New York City. The 52-storey, 

140,000 m 2 building will utilize fixed exterior 

shading and fritted glass in some locations 

(Figure 3.1) but will require interior 

shades for sun control and glare control 

and for thermal and visual comfort as well 

as energy management. 

The exterior of the building utilizes a 

transparent floor-to-ceiling, all-glass 

façade that encourages openness and 

communication with the external world, 

consistent with the owner’s dedication to 

creating a high quality work environment 

for their employees. Low partitions were 

used to reinforce the sense of openness 

and to let the daylight penetrate deeper 

into the space. The cruciform floor plan 

(Figure 3.2), with distances from interior 

offices to façade of less than 7.6 m, permits 

view in three directions from most


Left (page 12): Exterior view of an all-glass façade and 

shading system. Above: cruciform floor plan showing enclosed 

offices located toward the core. 

locations within the perimeter zone. With 

a generous ceiling height, a window-toexterior-wall 

ratio of 0.76 and a glazing 

transmittance of Tv=0.75, daylight was 

anticipated to be abundant throughout the 

entire perimeter zone even with the exterior 

fixed shading system. 

Overall solar heat gain would be a concern 

in any highly glazed façade. In this design, 

it is controlled with spectrally selective 

glazing (the glass solar heat gain 

coefficient is 0.39 and the U-factor is 1.53 

W/m 2 -°K) and with an array of exterior 

fixed ceramic rods designed to block and 

diffuse some sunlight as shown above. 

Even with these systems, the owner understood 

that the transparency of the 

façade would generate potential glare and 

visibility problems for employees using 

computers, so the owner wanted to explore 

the use of automated roller shades 

as a means of managing window glare. As 

well, conventional manually operated interior 

shades may have degraded many of 

the key design features that made the architectural 

design so compelling in the 

first place. 

The building owner had sufficient foresight 

to begin addressing these critical 

lighting quality and façade issues early 

enough in the design process while there 

was still time to explore potential dynamic 

shading options and to evaluate and 


procure them for the final building. A survey 

of the marketplace by the design 

team did not locate any vendors with 

suitable products that fully addressed the 

thermal and luminous issues in an affordable, 

integrated, and reliable package. 

While dimmable lighting and motorized 

shades have long been used as niche market 

products in corporate boardrooms, 

the challenge for the owner was to push 

the marketplace to respond with solutions 

with new, improved functionality, 

suitable for an entire building but at lower 

cost. 

Based on LBNL’s prior research and 

field testing, a partnership was created 

between The New York Times, its design 

team and LBNL to address this problem. 

A full-scale 401 m 2 daylighting mockup 

was constructed near the building site and 

a number of vendors were invited to install 

their existing shading and daylighting 

equipment. The mockup was extensively 

monitored by LBNL in partnership with 

the vendors over an 18-month field test, 

with support from the New York State 

Energy and Research and Development 


Authority (NYSERDA). 

FAÇADE PERFORMANCE RESULTS FROM THE 

NEW YORK TIMES DAYLIGHTING MOCKUP 

The project was structured around the 

availability of this unique full scale mockup. 

The New York Times mockup test 

program was designed to: 1) enable vendors 

to demonstrate features of their systems; 

2) fine tune their systems to meet 

the evolving requirements of the building 

owner; and 3) understand the benefits 

and limitations of each manufacturer’s approach 

to shade management and daylighting 

controls. A further objective of 

the public agencies supporting the research 

was to help broaden the market 

interest in these systems and design approaches 

with visits to the mockup from 

other design firms and owners. 

The fully furnished, full scale mockup 

reproduced the southwest corner of a 

typical floor (Figures 4.1 and 4.2). The 

mockup was divided into two test areas. 

Two different shade manufacturers and 

two different manufacturers of dimmable 

lighting systems installed systems in each 

area with different types of sensors and 

control strategies. The objective of the 

test was not to perform a side-by-side 

comparison of the two “competing” systems 

but rather to understand how vendor 

decisions regarding control infrastructure 

and design might impact actual field 

operation. The end goal of the monitoring 

phase was therefore not the selection of 

one or another of the manufacturers’ 

products in the mockup but the development 

of a performance specification that 

would be open for bid by any vendor. 

Over 100 engineering parameters 


Photograph of mockup interior (left) and RADI- 

ANCE nighttime rendering of the same space 

(right). RADIANCE simulations were used to explore 

shading and lighting issues for conditions that 

could not be tested in the mockup. 

were measured continuously (1x/min, 

24/7) in the mockup, including lighting energy 

use, work plane illuminance and distribution, 

various parameters related to 

visual comfort, control operations, exterior 

solar conditions, and other environmental 

parameters. Monitored data was 

collected over 9 months from December 

21 to September 21 to capture the full 

range of solar conditions. During this 

time, the manufacturers were permitted 

to tune their systems to obtain optimal 

performance and improve their designs. 

The building owner, upon seeing the effect 

of their initial control specifications, 

tweaked some control settings to obtain a 

system that better met their needs. In 

some cases, manufacturers altered their 

systems in response to interim performance 

data from LBNL when it was 

demonstrated that the owner’s specifications 

were not being met. 

At the end of the monitoring period, 

The New York Times incorporated what 

they learned into an open procurement 

specification. Procurement specifications 

for the lighting controls and for automated 

shading systems were let out to all eligible 

manufacturers for competitive bidding. 

The winning vendors were then invited in 

a further partnership with The New York 

Times and LBNL to demonstrate performance 

capabilities of their final systems 

in the daylighting mockup prior to installation 

in the headquarters building. The intent 

of this approach was to reduce risk 

and uncertainty in all aspects of the procurement 

process, leading to assured performance 

at lower costs, and motivating 

manufacturers to extend their product offerings. 

More detailed analysis 

of technical results 

is available on the 

LBNL website (see references). 

Initial testing 

demonstrated that the 

window and automated 

shade system provided 

useful daylight 

throughout the 13.4 m 

deep perimeter zone, 

enabling significant 

dimming of the electric 

lighting throughout 

much of the zone. For 

this building design, 

with its all-glass façade and minimal interior 

obstructions, even on the northwest 

side the daily lighting energy savings were 

20-40 per cent at 3.4 m from the window 

over the nine-month monitored period in 

Area A. The shading systems were controlled 

to provide a bright interior environment 

and control window glare. Lighting 

energy savings were substantially 

greater in zones daylit bilaterally from

oth the south and west façades in Area 

B. In this area of the mockup savings averaged 

from 50-80 per cent at 3 m from the 

façade and still achieved an average of 40 

per cent at 6 m. 

These daylighting savings were 

achieved with a shading control strategy 

that consistently blocked direct sunlight 

and adverse sky glare but also reduced interior 

daylight levels, lighting energy savings, 

and access to view. The fabrics under 

consideration in the roller shade systems 

had an openness factor of three per cent 

with an associated visible transmittance of 

about six per cent. 

To extend the test results, extensive 

simulation studies of the impact of different 

shade control strategies were conducted. 

A prototypical virtual floor was 

constructed for use with the Radiance 

daylighting simulation model. The occupants’ 

view conditions and glare at 22 different 

task locations on each floor were 

calculated for a lower floor (floor 6) with 

extensive external obstructions, and for 

floor 26 with largely unobstructed views. 

This modeling confirmed that specific 

shade fabric choices and control strategies 

would influence the magnitude of energy 

savings and likelihood of experiencing 

glare conditions. 

Controlled occupant studies were not 

conducted but over 200 Times employees 

had a chance to spend time in the mockup. 

The owner’s employees clearly preferred 

the brighter daylit space compared 

to the darker, less daylighted spaces that 

most currently occupy. They found the 

quality of daylight to be palpably different 

in the morning versus the afternoon and 

were delighted with the subtle shifts in 

color, intensity, sparkle and mood 

throughout the day. 

Glare control and the competing desire 

for openness and daylight remains a 

challenge. The mockup provided very 

powerful testing capabilities, allowed extensive 

exploration of alternate control 

strategies under a range of sun and sky 

conditions. Based on both mockup test 

results and extended simulations, in the 

building the shading systems will be fully 

automated to respond to direct sun and 

window glare and thus be responsive at 

each task location to the specific requirements 

of the occupants and work groups, 

window orientation, and degree of 


obstruction and/or daylight reflection 

from the urban surroundings. 

The automated shading and dimmable 

lighting not only provide energy savings 

but a demand response potential as well. 

Studies are underway to determine how 

to use the smart controls to bring the 

building to a “low power” mode of operation 

that would allow essential building 

functions to continue while substantially 

reducing overall electric power use on a 

hot summer day if the stability of the grid 

was threatened. The automated shades 

and dimmable lighting are a key element 

in the demand response strategy. The final 

step in this project will be to commission 

the installed systems and verify that performance 

meets the design specifications. 

Major construction will be completed in 

2006 with occupancy in 2007. 

2. THE ARCHITECTS’ HOLY GRAIL: 

SMART GLAZING SYSTEMS 

If the dynamic control of transmittance 

was incorporated directly into glazing layers, 

some of the limitations of motorized 

shades and blinds might be avoided. Researchers 

have been pursuing the quest 

for switchable “smart glazings” for over 

20 years and the laboratory accomplishments 

are now becoming available for initial 

purchase and use in buildings. As with 

shades and blinds, the actual energy and 

comfort performance in a building will depend 

on the interplay of the intrinsic 

properties of the materials and the operating 

strategy of the building. These operating 

strategies must be developed not 

only for energy and load control but to 

meet occupant needs in terms of comfort 

and productivity. As with the shade and 

blind studies above, field studies in test 

rooms and mockups are an important adjunct 

to the extensive computer modeling 

studies that have already been completed 

to quantify performance benefits and potential 

energy savings. 

FIELD TESTS OF ELECTROCHROMIC “SMART 

WINDOWS” 

In 1999, the window systems in the 

two test rooms in Oakland were retrofitted 

with a first generation electrochromic 

window. The optical system changed from 

a clear state with a transmittance of 51 

per cent to a dark state transmission of 11 

per cent. The system performed well 


although full switching could take in excess 

of 15 minutes and the coatings had a 

noticeable blue tint in the switched mode. 

Detailed technical results are available on 

our website. 

In 2002 we constructed a new test facility 

at LBNL with three side-by-side test 

rooms with unobstructed south views. 

The entire glazed façade (3.5 m x 4 m) for 

each room can be replaced. The lighting 

power and the heating and cooling in each 

room is individually monitored and the 

rooms have a full array of illuminance and 

luminance sensors for monitoring. Two of 

the rooms were fitted with electrochromic 

samples over the complete 

façade as shown in Figure 5. Since the 

prototypes were of limited size the current 

façade requires 15 glazing panels. 

Extensive engineering tests in the facility 

were conducted over a two-year period 

to explore the energy savings achieved 

with different control strategies. We operated 

the electrochomics over their full dynamic 

range, testing different control 

strategies designed to optimize lighting 

savings, cooling savings and visual comfort. 

We compared lighting and cooling loads 

with automated electrochromics to results 

from the room with fixed glazing and 

shading, with and without daylighting controls. 

The electrochromic systems were 

able to consistently beat the energy use of 

the conventional façade design but the detailed 

results were highly dependent on 

operating assumptions and specific control 

strategies. The testing focused on the 

challenge of the control optimization between 

glare control and daylighting energy 

savings, with associated studies of cooling 

impacts and peak demand impacts. 

We also conducted human factor studies 

in this facility (Figure 6) to determine 

desired operating and control parameters 

of the glazing and lighting systems and to 

better understand the issues associated 

with smart glazing control strategies. Early 

results suggest that the lowest transmittance 

level of the current glazing prototypes, 

three to four per cent, is usually adequate 

for most glare situations although 

additional glare control was desired by 

some occupants. However, switching the 

entire façade to very low transmittance 

levels to control glare often requires that 

electric lights be turned to full power levels. 

New architectural design approaches 

such as separate vision and daylighting 

glazings, as well as improved switching 

control strategies were then studied to 

address this issue. Initial results show that 

it is desirable to divide the façade into two 

elements that would be designed and controlled 

differently. A lower “vision” window 

might have a lower transmittance 

and would be designed to manage glare at 

a perimeter workspace. This will tend to 

have low transmittance values when sun 

and sky glare are present so that LCD 

screen visibility is not compromised. The 

upper “daylighting” window would have a 

higher visible transmittance and be managed 

dynamically to control solar gain but 

admit adequate daylight so that the primary 

room electric lighting is off or 

Figure 5 

Exterior view of LBNL Façade Test Facility. Two rooms 

at left have electrochromic prototypes installed, the room at 

right is a control room with spectrally selective glass and 

blinds. 

Figure 6 

Interior photo of façade test room configured for occupant 

response testing.


CCD photo of workstation (left) and false color luminance 

map (right) produced from image at left and 5 additional 

photos. Luminance map provides a dynamic 

range of 5000:1 

dimmed as much as possible. This approach 

adds to the design and control 

complexity but delivers better amenity 

and increased energy savings. 

Better tools are needed to quantify the 

visual environment in conjunction with 

subjective and objective user studies in 

these spaces. We have developed new 

glare assessment approaches using CCD 

images and processing of high dynamic 

range image data to quantify, display and 

understand these complex environmental 

parameters that directly impact occupant 

comfort, satisfaction and performance 

(Figures 7.1 and 7.2). These techniques 

can be used in the field to evaluate existing 

buildings as well as in a lab test environment. 

CONCLUSIONS 

A growing interest in daylighting and 

sustainable design has led architects in the 

direction of using highly glazed building 

façades. Balancing the need for view, glare 

control, thermal comfort with solar load 

control and daylighting energy savings is a 

complex challenge. In order for these designs 

to meet often contradictory performance 

objectives, they will need to 

have a degree of active, reliable management 

of solar/optical properties of the 

building envelope that has rarely been 

consistently and economically achieved in 

buildings. Some of the technologies to 

provide active control of fenestration 

transmittance and associated control of 

electric lighting in building interiors are 

now available and have been shown to be 

capable of good performance and others 

will emerge. 

However it will take better and cheaper 

hardware, additional exploration of systems 

integration solutions, new sensors 

and controls, improved commissioning, a 

better understanding of occupant needs 

and preferences, and better real time, 

adaptive controls to fully realize the potentials 

of these emerging technologies. 

Future building envelope design and operations 

will be increasingly integrated with 

other building systems to achieve these 

performance levels. 

REFERENCES 

Extensive additional information on 

these projects can be downloaded from 

several LBNL websites: 

• References for the New York Times 

project can be found at: http:// 

windows.lbl.gov/comm_perf/newyorktimes.htm. 

• References for the Electrochromics 

project can be found at: http://windows. 

lbl.gov/comm_perf/electrochromic. 

• A complete searchable list of LBNL 

window and daylighting references, 

from which current papers can be 

downloaded can be found at: 

http://windows.lbl.gov. 

ACKNOWLEDGEMENTS 

We acknowledge the active support of 

numerous LBNL colleagues on the teams 

that carried out the projects described 

here, and the participation of other partners 

and consultants referenced at the 

websites above. This work was supported 

by the Assistant Secretary for Energy Efficiency 

and Renewable Energy, Office of 

Building Technology, State and Community 

Programs, Office of Building Systems of 

the U.S. Department of Energy under 

Contract No. DE-AC03-76SF00098, by 

the California Energy Commission, Public 

Interest Energy Research Program, and by 

the New York State Energy Research and 

Development Authority. 

■ 


Feature 

All That Glass 

Is there an appropriate future for double skin façades 

By Donald B. Corner, 

Professor of Architecture, University of Oregon 

INTRODUCTION 

Building techniques have been shared 

across the Atlantic Ocean for hundreds of 

years. Anglo-American settlers preparing 

to move westward into the Appalachians 

were fortunate to have learned about log 

cabins from Scandinavian immigrants. Standardized 

2x4 light frame construction traveled 

from the United States to Europe and 

returned much later as the Swedish factory 

crafted house. 

In recent years we have seen the first 

landings of a new import, the double skin 

façade. American architects are attracted 

by the appearance and the performance of 

double skins, even though the benefits are 

hard to quantify. They will pursue this new 

option despite a growing body of technical 

literature that questions the effectiveness 

of the form (Lee, LBNL, 2006). We have 

had the same experience with the opening 

example of industrialized housing. 

There is a field, littered with well documented 

failures, that designers visit again 

and again because it is so seductive in concept, 

if not reality. The double façade is an 

equally powerful concept. Thus, American 

architects will try on these new enclosures, 

and their reasons for doing so will 

be as varied as they have been in Europe. 

As in Europe, their motivations will go beyond 

effective control of daylight and thermal 

comfort. 

This narrative examines frames of reference 

that have shaped European applications 

of the double façade and from this 

body of experience, outlines a critical perspective 

on the future of this technology in 

the United States. 

façade that is the focus of this paper. Double 

skins of any form include an outer 

façade, an intermediate space and an inner 

façade. The outer leaf gives the building 

weather protection and acoustic isolation 

where high noise levels are present on the 

exterior. The intermediate space can be 

used to buffer thermal impacts on the interior. 

Through the use of open slots and 

operable dampers in the glass planes, it is 

possible to ventilate the interstitial space 

on warm days and admit sun warmed air 

to the interior rooms on cool days. In 

most cases operable shading devices are 

placed in the intermediate zone where 

they are protected from damage. Double 

glazing of the inner façade provides the 

optimum thermal barrier, while single glazing 

of the outer façade is sufficient to create 

the buffer space. 

Double skins require the designer to 

sort through an imposing array of choices. 

A decision tree must include the following 

fundamental questions: 

• How much of the outer façade is glass 

and what is the relationship of that glass 

to the primary structure and to the 

other elements of building enclosure 

• What types of control are needed over 

the passage of light, heat, air and sound 

at the transparent portions of the 

façade 

• How will the two façade layers and the 

space between them be developed in a 

rational and effective construction 

strategy 

• How will access be provided to clean 

the glass and maintain the operable 

components located inside the buffer 

space 

An expansion of these basic points, 

prepared by this author, will appear in the 

forthcoming The Green Studio Handbook 

(Kwok and Grondzik, in press). Case studies 

and details can be found in widely distributed 

European texts (Herzog et. al., 

2005 and Oesterle, 2001). 

PLACE AND CULTURE 

As elements of architecture, enclosure 

A SUMMARY OF DOUBLE SKIN TECHNOLOGY 

Double skins are multiple leaf wall assemblies 

in the transparent or largely 

transparent portions of a building façade. 

They range from the vernacular storm 

window to the closely coupled, all glass 

Figure 1 - Office Block Remodel, Stuttgart, Germany, 1996. Behnisch Sabatke Behnisch. 


systems have a significant and fascinating 

cultural component. Façade openings in 

Europe have always had numerous “switches” 

in them, operated by the building 

Figure 2 - Hannover Messe A.G., Hannover, Germany, 

1999. Thomas Herzog + Partner. 

Figure 3 - Helicon Building, London, UK, 2000. Sheppard 

Robson International. 

Figure 4 - Plantation Place, London, UK, 2005. Arup Associates. 

Architects. 


user. Traditional windows in Italy have an 

outer layer of louvered shutters, glass in a 

casement sash, light filtering curtains and a 

solid inner shutter of wood. Each can be 

deployed to block, filter or admit elements 

of the exterior world. In the United States 

we have used building technology to eliminate 

switches, as insulating glass eliminated 

the storm window. 

European double façades are expanding 

the benefits of switches, using technology 

to automate rather than eliminate 

them. In commercial buildings a large percentage 

of the glass remains operable with 

building ventilation coming directly 

through the façade. The first new applications 

of double skins were “re-wraps” of 

existing buildings, such that the operable 

outer leaf works in tandem with the original 

façade to enhance building performance 

through both the heating and cooling 

seasons (Figure 1). This strategy remains 

one of the most cost effective applications 

of the double skin. 

From these beginnings, the new 

façades rapidly progressed to become 

spectacularly intricate machines that contribute 

to a wide variety of building climate 

functions. Thomas Herzog’s Hannover 

Messe A.G. is a mature example of a “corridor 

façade,” with the inner glass leaf set 

back on the floor slab around the entire 

perimeter of the occupied space (Figure 

2). The façade expression is dominated by 

its role in the ventilation scheme. With the 

service cores removed from the central 

block, the buffer space accounts for 22 per 

cent of the remaining slab area. This is an 

investment in passive strategies that few in 

the U.S. would be willing to consider. 

The quality and performance expected 

of German buildings is part of their culture 

and manifest in their regulatory system. 

Office buildings must provide workers 

with daylight and fresh air through an operable 

window within a specified distance 

from each station. German texts make it 

clear how these requirements have fueled 

the development of double skins (Oesterle, 

2001). However, as energy conservation 

goals have risen, all the components 

and systems have improved and the potential 

for savings through the addition of a 

second skin has become less. As the examples 

will show, German architects have become 

more focused and strategic in their 

use of the double façade. 

THEMES OF PRACTICE 

In London, the exuberant use of technical 

systems has long been part of the commercial 

building culture. The Lloyd’s Bank 

(1986, Richard Rogers) and the New Parliamentary 

House (2000, Michael Hopkins) 

both have ventilated façade cavities in addition 

to their more famous expressive elements. 

The engineers and architects at 

Arup and Arup Associates have had a 

formative influence on “high tech” work. 

Using extruded sections and machined fittings, 

in the 1980’s Arup crafted robust 

and expressive external shading devices 

that cantilever off the building façade (One 

Finsbury Avenue, London, UK, 1984, Arup 

Associates). The work of Peter Rice added 

large expanses of suspended glazing to the 

British vocabulary. Once these two themes 

of practice were firmly established, the 

double skin became a logical progression. 

Adding a glass leaf to the outside face of 

the cantilevered shading structure allows 

the fixed louvers to be exchanged for 

much more effective operable systems and 

admit diffuse light on overcast days and 

track the sun when shading is an issue. 

The Helicon Building in London offers a 

dramatic example (Figure 3). Engineered 

by Arup, the building has a monumental 

double façade suspended over the south 

entry. Inside the stack ventilated cavity are 

gigantic louvers. Not far away, Plantation 

Place offers a different integration of the 

two venerable themes (Figure 4). The 

façades are made with a repetitive unit 

curtain wall system. Close to street level 

the modules are matched to suspended 

external shades made of stone, in response 

to the context. As the floors 

mount, the plan steps back to form twin 

towers dominated by interactions through 

the skin. The same façade unit develops a 

cantilevered cavity with maintenance access 

and an outer leaf of glass shingles that 

are open jointed to discharge the heat absorbed 

in the small scale, operable louvers. 

This building does not function in all the 

modes of the German examples, but it 

also has far fewer moving parts. It is part 

of the trend in which architects are trying 

to capture the major benefits of a double 

skin through more efficient means. 

BRAND IDENTIFICATION 

The Arup offices in London occupy a rehabilitated 

building with a double skin

façade at the street corner. It is therefore 

one of the most potent of motivations, 

marketing. Arup is projecting a contemporary 

image of the environmentally responsive 

building that has enormous appeal to 

corporate clients. Returning to the Helicon 

Building, with the monumental façade, one 

must note that other faces are tempered by 

a much more reserved version of the same 

thermal chimney approach. The core of the 

building receives its light from an atrium 

space. The huge system above the entry 

hangs in front of a shallow band of offices 

no greater in volume than the façade cavity 

itself. That this flamboyant gesture survived 

the hard sums of a commercial project is a 

testament to the power of brand identification 

and the role of the double skin in realizing 

that ambition. Another vivid exemplar 

is a building on a prominent site in central 

Stuttgart (Figure 5). It has the shape of a 

teardrop with the pointed end reaching out 

toward a main thoroughfare. The plan becomes 

so narrow that fully one third of the 

outer glass leaf has nothing behind it except 

the cavity space. 

THE UNIVERSAL, ALL GLASS FAÇADE 

The RWE headquarters in Essen is a 

beautiful cylindrical tower that is considered 

by many in the field to be the most 

elegant of double skin façades (Figure 6). It 

faithfully realizes the historic imagery of 

Mies Van der Rohe’s project for an all glass 

skyscraper and strives to develop the 

“neutralizing wall” advocated by Le Corbusier 

many years ago. This building, and 

others like it, are driven by a renewal of 

modernist theory, now with the technical 

means available to try to realize those visions. 

The Essen tower is defined as a corridor 

façade, segmented at each floor 

plate. It is also a unitized, double curtain 

wall with cross-over ventilation between 

adjacent cells so that the intake and exhaust 

air streams are separated. The 

façade elements demonstrate a commitment 

to repetitive production, although 

they are so precise and intricate they 

should in no way be referred to as economical. 

The cylindrical shape optimizes 

the surface to volume ratio, but it also 

makes the building indifferent as to solar 

orientation. This is the double skin proposed 

as a universal solution that can be 

deployed with equal enthusiasm to the 

north, south, east or west. 

There is, in Frankfurt, a newer tower 

that makes an interesting comparison (Figure 

7). The work of Schnieder + Schumacher 

responds to the modernist legacy 

with equal intensity. Here the glass cylinder 

is pure, without accessory elements at 

the top or the base. The original concept 

called for buffer spaces that would ascend 

in a spiral similar to Norman Foster’s 

“Gherkin” in London (Swiss Re, 30 St. 

Mary Axe, 2004). In Frankfurt, the building 

has no major tenant to foot the bill and 

double skin techniques are reaching down 

into a speculative market that demands 

greater efficiency of means. 

As constructed, a square floor plan 

with a very simple glass façade is developed 

inside the protection of the outer 

cylinder. The difference between the two 

shapes produces four segmental buffer 

spaces, two in front of partitioned offices 

and two as “winter gardens” outside of 

open desk space. The cavities are segregated 

every four stories by a full circular 

floor plate. The outer leaf, executed skillfully 

by Gartner, has operable units in the 

upright triangles of the ornamental façade 

pattern. These ventilate the buffer spaces 

on demand. The scheme is beautiful in its 

conception, but again indifferent to solar 

orientation; a triumph of theory over the 

realities of nature. The cylinder is once 

more proposed to minimize surface area, 

but since the building is so often in cooling 

mode, a concern for skin losses is a suspicious 

motivation. 

GREEN ARCHITECTURE 

The double skin takes a different role 

on the palette of architects who try to 

connect to nature rather than neutralize it. 

Exemplary of this approach is the work of 

Behnisch, Behnisch and Partner, with climate 

engineering by the well known firm, 

Transsolar, also of Stuttgart. This team has 

worked closely on a number of projects 

including the NORD/LB headquarters in 

Hannover, Germany (Figure 8). For 

Behnisch and Transsolar, the double skin in 

not a preconceived solution, but just one 

of many tools taken up in order of their effectiveness. 

In fact, the double skin may be 

quite far down that ranked list. 

At NORD/LB the first concern is connecting 

the building occupants to the richness 

and variety of the environment outside 

the glass. This includes views, ample 

Figure 5 - Landesbank Baden Wurtemberg, Haus 5+6, 

Stuttgart, Germany, 2004. Wohr Mieslinger Architekten. 

Figure 6 - RWE A.G., Essen, Germany, 1997. 

Ingenhoven Overdiek Kahlen and Partner. 

Figure 7 - Westhaven Tower, Frankfurt, Germany, 

2003. Schneider + Schumacher. 

Figure 8 - Norddeutsche Landesbanke (NORD/LB), Hannover, 

Germany, 2002. Behnisch Behnisch and Partner.

daylight and natural ventilation through 

windows controlled by the occupants. A 

slender ring around a generous courtyard, 

NORD/LB has extremely shallow floor 

plates, even by German standards. Portions 

of the building have offices on only 

one side of social corridors. With the use 

of glass partitions, a spectacular quality of 

light washes through the building at all 

times. This is an architecture that intends 

to maximize the skin to volume ratio, not 

minimize it. 

Double skins at NORD/LB have been 


used in only two zones, and in both cases 

for very specific reasons. First, they have 

been applied to the long face of the building 

where needed to block traffic noise 

from a multi-lane boulevard. This again is 

driven by German space quality standards 

and sound walls are recognized as one of 

the corollary benefits that justify the double 

envelope (Osterle, 2002). A second 

application has been made on the southwest 

face of the 16-storey tower that was 

added to the scheme to provide offices 

for the board of directors. The entire 

building is fitted with automated, external 

shading louvers. At the higher levels these 

shades would often be forced to retract 

into their shelters on windy days if it were 

not for the protection offered inside the 

buffer space. The afternoon heat gain 

through this one exposure on breezy 

summer days was considered unacceptable, 

motivating the second leaf of glass. 

At the lower levels, where wind velocities 

never reach the critical level, the external 

louvers are free to deploy as needed. 

Where a covering layer of glass is not 

required by wind or acoustics, none is applied. 

This clearly demonstrates that in 

the climate of central Europe, shading is 

the design issues, not thermal losses, even 

for a building with such an extensive surface. 

There is an interesting cultural footnote. 

On the quiet streets of this German 

town, shading louvers can extend all the 

way down to the sidewalk without any 

sign of damage. In the United States we 

might need the outer glass just for protection 

from vandalism. 

The sound wall at NORD/LB happens 

to occur largely on a north face, so the 

double façade there returns little benefit 

in the dissipation of heat. However, it 

does have a second role in providing fresh 

air to offices that would otherwise face 

auto exhaust. The large interior courtyard 

of the building is a reservoir of clean air. 

This air is drawn through a flat plenum 

under the lowest office level. (Corresponding 

to the white volume at the base 

of the detail: Figure 9). In the relevant 

sections, baffles direct air into the base of 

the façade cavity and it is drawn by stack 

effect through louvers at the top of the 

façade. The occupants are then free to 

enjoy a clean and quiet source of fresh air 

through the operable windows of the 

inner skin. This simple transformation 

eliminates the need for vent panels in the 

sound wall; openings that would compromise 

the acoustic performance. 

Transsolar also teamed with Allmann, 

Sattler, Wappner on the design of an office 

complex in Munich (Figure 10). A low rise 

element again wraps the edge of the site 

with a really robust sound wall against the 

autobahn. There is an office tower in one 

corner with a more conventional form 

than NORD/LB. The scheme demonstrates 

a full palette of environmental 

strategies: shallow floor plate with easy ac-

cess to the perimeter, concrete structure 

with radiant cooling, operable glazing 

across the entire façade, displacement 

ventilation using a podium floor, a wind 

driven exhaust stack and a fan assisted 

supply sharing the same vertical shaft, an 

evaporative cooling tower on the roof operated 

at night, ground source wells operated 

during the day. Air flows in the 

rooms are boosted by small fan coil units 

at the perimeter that fit under the podium 

floor. These are fed with hot and cold 

water but no air duct system is required. 

Munich has district heating so there are 

no on-site strategies for that side of the 

energy equation. 

Fitting in among these strategies is a 

double façade for the tower. It is so simple 

in its concept and crisp in its detailing 

that it could easily be mistaken for a single 

leaf assembly (Figure 11). The façade is a 

unitized curtain wall with an overall depth 

that is not much greater than standard 

wind mullions. The inner leaf of insulating 

glass is divided at chair rail height into two 

operable units. The cavity is partitioned at 

the same point and contains operable 

shading louvers in the upper region. The 

outer leaf is a perforated stainless sheet in 

the lower zone and plate glass above. 

Generous amounts of ventilation air can 

be taken through the perforated metal by 

opening the lower sash. The larger, upper 

sash is the vision zone and the true double 

skin. By simply allowing the perforated 

metal to overlap this unit slightly at the 

top and the bottom, there is free ventilation 

of the cavity behind the outer leaf of 

glass. This can be used to dump heat gain 

from the shades or to admit a moderated 

air flow by opening the upper sash behind 

its protective outer leaf. It was first 

thought that projecting fins would be 

needed to create turbulence and to ventilate 

the cavities. Flow modeling revealed 

that the strips of metal mesh, top and bottom, 

were adequate on their own. 

It is remarkable how simple this double 

skin system has become. The key to 

the scheme is that maintenance access 

comes through the fully operable inner 

glass leaf. In the United States, this would 

in itself be a very radical proposition, but 

in Germany a large percentage of operable 

glass is a given in the building culture. 

For visual continuity, the low rise portion 

of the complex has the same cladding 

units on the courtyard façade, except that 

the outer leaf of glass in the upper zone is 

omitted. This repeats the lesson that protection 

of the external shading devices 

from wind velocities at height is the primary 

motivation for the double skin. Allmann, 

Sattler, Wappner and Transsolar 

have identified the performance attributes 

that are needed from the façades and 

achieved these with directness, clarity and 

true elegance. 

EXPLORATIONS IN THE AESTHETIC DOMAIN 

The technical benefits of the glass double 

façade have not yet been established 

with the certainty of those for the rainscreen 

wall. Nevertheless, we have already 

seen that, like the rainscreen, the 

double skin is a trigger for aesthetic explorations 

that run far beyond the functional 

basis of the concept. Herzog and De Meuron, 

Swiss architects of the first rank, 

completed very sophisticated double 

façades early in their rise to international 

prominence. Their “re-wrap” façade in 

Basle (SUVA Building, 1993) is a marvel of 

piston actuators and glazing technology. 

By contrast, their Laban center for Dance 

in London (Deptford) is wrapped in a simple 

layer of polycarbonate panels (Figure 

12). The wall section displays all of the attributes 

of a double façade: open grills at 

the base, operable vents at the inner leaf 

that draw air from the cavity, maintenance 

gangways between the skins that so far 

have seen limited use. But, these are not 

the driving forces behind the design. Subtle 

tinting of the polycarbonate gives the 

flush façades an abstract, lyrical quality as 

they hover above an earthy, post industrial 

context. Inside, the dance studios receive 

a serene wash of colored light so beautiful 

that the 2003 RIBA Stirling Prize could 

have been won for this effect alone (Figure 

13). 

The tour de force of glass façades remains 

Peter Zumthor’s Kunsthaus, Bregenz 

(Figure 14). Here the building is clad 

from parapet to ground plane with identical 

laminated panels. No other material is 

present except for the front door and the 

stainless steel brackets that support the 

glass. Inside is an equally minimalist structure. 

Each gallery fills a floor, with art displayed 

against the turned up edges of concrete 

“trays” that are suspended three 

times above one another like memo boxes 

Figure 9 - East façade detail, NORD/LB. Behnisch Behnisch 

and Partner. 

Figure 10 - Münchner Tor, Munich, Germany, 2003. 

Allmann, Sattler, Wappner. 

Figure 11 - Façade unit, Munchener Tor. Allmann, Sattler, 

Wappner. 

Figure 12 - Laban Centre for Dance, Deptford, UK, 2000. 

Herzog & de Meuron. 

Figure 13 - Studio interior, Laban Centre. Herzog & de 

Meuron. 


Figure 14 - Kunsthaus, Bregenz, Austria, 1997. Peter 

Zumthor. 

Figure 15 - Genzyme Center, Cambridge, MA, USA, 2003. 

Behnisch Behnisch and Partner. 

on the corner of your desk. Light 

penetrates the building at the tall interstitial 

spaces and filters into the galleries 

through a translucent glass ceiling. The 

façade cavity contains the steel framing 

necessary for the outer leaf of glass and 

extends below grade to light staff space in 

the basement. There are operable shading 

devices in the void, but the light levels 

across the ceilings drop off so quickly it is 

not clear how much shading is really needed. 

However, this is not a façade to be 

measured with instruments. The outer 

glass shingles overlap side-to-side and 

overhang top to bottom, producing a prismatic 

surface that is endlessly fascinating as 

the sun moves across the sky. While the 

interior defers completely to the featured 

works of art, the exterior represents a 


contemporary response to the expectation 

that a house for art should itself be 

art. So great has been the acclaim for this 

aesthetic that the use of open glass shingles 

has in return influenced more traditional 

double skins like that at Plantation 

Place in London or the Deutsche Post 

Tower in Bonn (2002, Murphy/Jahn). 

CONCLUSIONS 

There are certainly major themes that 

drive the design of glass façades: optimize 

the harvest of daylight to reduce lighting 

loads, reduce thermal gains in buildings 

that are almost always in a cooling mode, 

and perhaps control surface temperature 

at the inside face of the glass to maintain 

human comfort. A comprehensive analysis 

of costs and benefits in a double skin is difficult 

because it touches virtually every aspect 

of the building, from structural form 

to occupant behavior. Andrew Hall, head 

of the façade engineering group at Arup, 

cautions that double skins, in and of themselves, 

rarely save money or energy (referenced 

in this discussion was the seminal 

article by Gertis, 1999). The façade concepts 

must result in significant savings elsewhere 

in the design. A dramatic reduction 

in mechanical cooling equipment would be 

one such contribution. Hall acknowledges 

that there are also forces of market and 

fashion that brush aside rational analysis. 

He warns of architects who take the approach 

that, “in the double skin we have 

the solution, now what was the problem” 

To advance appropriate building we 

must have the patience and maturity to 

use the double skin as a complement to 

simple and logical controls of the building 

climate. Even though it is an intrinsically 

“natural” strategy, the double skin can be 

abused, thrown in the face of nature just 

as designers have done for decades with 

mechanical cooling. We must deliberately 

work our way down the list of green building 

strategies, applying the most effective 

first and the double skin only in its turn. 

NORD/LB shows us that the results can 

be a rich environmental experience as well 

as a good engineering solution. The Genzyme 

Center, also by Behnisch, is the best 

American application so far, but the façade 

systems were value engineered to the 

point that they have little of the elegance 

of the native German examples (Figure 

15). We must recognize this weakness in 

the American building culture. Facing our 

energy future, we cannot afford to be reductive 

in our thinking. While it is fair to 

demand true performance, we must also 

be willing to make pioneering investments. 

Over the history of architecture, the building 

façade was never meant to be inexpensive. 

It holds far too much importance, 

both technically and culturally. We must 

allow ourselves well reasoned excursions 

into the aesthetic domain. These have the 

power to inspire creative research into the 

effective means of architecture. 

ACKNOWLEDGEMENT: 

The interviews and site visits that form 

the basis of this article were funded by the 

John Yeon Center for Architectural Studies 

at the University of Oregon. 

INTERVIEWS: 

• Thomas Auer, Transsolar, Stuttgart, 

May 2005. 

• Peter Clegg, Feilden, Clegg, Bradley, 

London, April 2005. 

• David Cook, Behnisch Behnisch and 

Partner, Stuttgart, May 2005. 

• Andrew Hall, Arup Façade Engineering, 

London, April, 2005. 

• Stefan Holst, Transsolar, Munich, May 

2005. 

• Mikkel Kragh, Arup Façade Engineering, 

London, April, 2005. 

• Martin Werminghausen, Behnisch 

Behnisch and Partner, Boston, August, 

2005. 

REFERENCES: 

• Gertis, Karl. “Sind neuere Fassadenentwicklungen 

bauphysikalisch sinnvoll - 

Teil 2: Glas-Doppelfassaden (GDF)” 

Bauphysik, Heft 2/1999. Berlin: Ernst 

and Sohn, Wiley-VCH, 1999. 

• Herzog, Thomas and Roland Krippner, 

Werner Lang. Façade Construction Manual. 

Basle: Birkhauser, 2004. 

• Kwok, Alison and Walter Grondzik. 

The Green Studio Handbook. Oxford: 

Architectural Press, in press. 

• Lee, Eleanor and Lawrence Berkeley 

National Laboratory. “High Performance 

Commercial Building Façades.” Public 

Interest Energy Research Program: CEC 

500-2006-052-AT15. Sacramento: California 

Energy Commission, 2006. 

• Oesterle, Eberhard. Double Skin 

Façades. Munich: Prestel, 2001. ■

Feature 

Architectural Glazing for Sound 

Isolation (an Acoustician’s Perspective) 

By Jeffrey L. Fullerton, Acentech, Inc. 

ABSTRACT 

For most buildings, glazing is selected 

for its thermal or optical performance. 

However, there are numerous buildings 

where exterior noise impacts are a factor 

in whether the interior space will function 

properly. Often, the most important element 

for reducing intrusive noise is the architectural 

glazing. This paper discusses 

the acoustical tests and ratings of glazing 

systems, various upgrades to architectural 

glazing and several case studies where improved 

sound isolation from exterior 

noise was achieved using architectural 

glazing. 

INTRODUCTION: ACOUSTICS 101 

Sounds propagate through the air as 

pressure waves. Normal human ears are 

sensitive to a wide range of varying sound 

pressure. To simplify the representation of 

these acoustical pressure waves, the pressure 

levels are represented in a logarithmic 

ratio expressed in decibels, or dB. 

Human ears are more sensitive to midand 

higher- pitched sounds (the “treble” 

component), compared to lower frequency 

sounds (the “bass” component). This is 

represented by the so-called A-weighting 

filter for measuring sound, noted as decibels, 

A-weighted, or dBA. 

Since sound levels are reported in logarithmic 

decibels, they 

are inherently 

non-linear. 

As a result, comparing the loudness of 

various sounds may not be as simple as it 

appears. For example, studies of human 

responses to sound levels have shown 

that changes of 3 dB are considered a 

“just noticeable difference” and changes 

of 5 dB are considered to be “significant”. 

Changes of approximately 10 dB are perceived 

as a “doubling” of the sound level. 

A 20 dB change is perceived as being 

“four times louder”. 

To provide some perspective on various 

sound levels, the following environments 

or sound sources are described 

below. 

Rural Neighborhood: 30 to 40 dBA 

Urban Neighborhood: 40 to 50 dBA 

Speech (at 3ft): 55 to 80 dBA 

Traffic (at 100ft): 65 to 80 dBA 

Aircraft Overflights: 65 to 110 dBA 

ACOUSTICAL PERFORMANCE TESTING AND 

RATINGS 

The two primary types of acoustical 

tests for exterior glazing are either conducted 

in 1) a laboratory; or 2) in an installed 

condition, referred to as a 

field test. Based on these two 

types of tests, there are two ratings 

for quantifying the acoustical 

performance of glazing systems. 

1) Laboratory testing 

Laboratory testing is intended 

to provide a standardized 

and repeatable test of a 

building construction relating to 

its performance for sound transmission. 

The tests are standardized 

by ASTM E90-04, where all 

of the details regarding the laboratory, 

the test specimen, the test protocol, 

test conditions and measurement 

procedures are specified. The thoroughness 

of the standards is intended to pro- 


vide test results that are comparable and 

repeatable in any laboratory that meets 

the ASTM standards. A list of laboratories 

accredited by the National Voluntary Laboratory 

Accreditation Program is available 

at the National Institute of Standards and 

Technology website: www.nist.gov. 

There are a number of strengths and 

potential weaknesses to the results gathered 

from laboratory testing. It is important 

to understand that laboratory tests 

are generally conducted on a particular element 

of a building construction, rather 

than an entire composite construction. 

For example, manufacturers often test individual 

elements such as windows or 

doors in order to demonstrate their product’s 

specific sound transmission performance. 

While it is often useful to know the 

relative performance of one product versus 

another, it is often more important to 

relate that performance to the other elements 

of the façade in order to understand 

the performance of the composite 

construction. Also, keep in mind that laboratory 

tests are conducted under ideal 

conditions. Accordingly, the results from 

laboratory testing are generally considered 

to be the ideal performance of that 

product, and may not be as achievable 

when installed by a typical contracting 

crew. These considerations should be 

considered when applying laboratory test 

data to a specific project. 

2) Field testing 

Field-testing provides a means of conducting 

a test of an actual, installed construction. 

In most cases, these tests measure 

the performance of the entire façade 

rather than a particular element in the 

façade, though this is also addressed in the 

field test standard methodology. The field 

tests are standardized by ASTM E966-04, 

where all of the details regarding the installation, 

sound source, test protocol, 

test conditions and measurements are 

specified. The standard is intended to provide 

a methodology for comparing the 

test results to laboratory results or other 

field tests that are conducted to the same 

standard. 

The most significant strength to field 

testing is how the installed product performed. 

Depending on the quality of installation 

of the test specimen, the 

performance may closely represent what 

might be expected for a typical installation 

of that particular composite construction. 

ACOUSTICAL PERFORMANCE RATINGS 

The results from the sound transmission 

tests can be reduced to several single 

number ratings. The most commonly used 

rating is the Sound Transmission Class 

(STC), determined by ASTM E413-04. 

This rating is determined by comparing 

the sound transmission loss data from the 

test results to a weighted transmission 

loss spectrum that represents the STC 

contour. The one drawback of the STC 

rating is that it assumes a sound source 

with a spectrum similar to human speech. 

For this reason the STC rating is often a 

poor predictor of sound isolation for low 

frequency sources such as music, mechanical 

system or transportation noise (see 

below). An example of test data compared 

to the STC contour is shown in Figure 

1. 

More recently, another rating was developed 

which is called the Outdoor–Indoor 

Transmission Class (OITC). The 

methodology of this rating is defined in 

ASTM E1332. This rating is determined by 

calculating the difference between the 

product’s sound transmission loss performance 

and a standardized exterior 

source spectrum. The standardized 

spectrum is an average of three transportation 

spectra: a freeway, a railroad 

passby and an aircraft takeoff. 

The resulting number is intended to 

relate to the perceived sound levels in 

the interior receiving space as the result 

of an impact from a transportation 

source. At this time, this rating is not 

as widely used as the STC rating, 

however, it can often be calculated 

provided that sound transmission loss 

data for a product is available. 

There are several publicly available 

acoustical performance data sets for 

glazing. The two most common data 

sets are provided by Solutia (a Monsanto 

company, formerly named 

Saflex 1 ) and Viracon. These data sets 

provide the performance of only the 

glazing systems, without a window 

framing system. As a result, these data 

may somewhat overestimate the performance 

of a window product with a 

frame, particularly when the STC ratings 

of the glazing exceed STC 40. 

Figure 1 

Ratings of glazing systems in this range and 

higher may be adversely impacted by the 

incorporation of a window framing system, 

which often degrades the performance. 

ACOUSTICAL UPGRADES FOR 

ARCHITECTURAL GLAZING SYSTEMS 

Architectural glazing can vary dramatically 

in sound isolation performance. The 

following sections describe a variety of different 

window glazing options with different 

acoustical performance. 

1-inch thick insulated glazing unit: 

In many areas of the country, a common 

glazing assembly that is used on commercial 

projects is a 1-inch thick insulated 

glazing unit, consisting of 1/4-inch thick 

lites separated by a 1/2-inch thick airspace. 

This glazing generally provides a 

laboratory rating of about STC 35 and 

OITC 30, though depending on the frame 

it is installed in, the ratings may decrease 

by a few points. This glazing provides acceptable 

sound isolation from exterior 

noises in rural or quieter areas, or when a 

moderate amount of intrusive noise is acceptable. 

Insulated glazing unit with glass 

panes of different thicknesses: An alternate 

1-inch thick insulated glazing unit 


could consist of lites that have different 

thicknesses. For example, one lite might 

be 1/4-inch thick, while the other might 

be 3/16-inch thick, resulting in a 9/16-inch 

airspace. Laboratory test data indicates 

that this glazing unit can achieve a slightly 

higher STC rating of 37. This is attributed 

to a reduction of the resonance of the system 

by using the different thickness lites. 

However, it is interesting to note that this 

window achieves the same OITC rating 

(OITC 30) as the previous 1-inch insulated 

glazing. This would suggest that the increased 

performance indicated by the improved 

STC rating may not be noticeable 

to an occupant, if the exterior noise 

source is similar to the OITC standard 

spectrum. 

Insulated glazing unit with laminated 

glass: Another alternate of the 1- 

inch thick insulated glazing unit could 

comprise one lite that is laminated. The 

laminated lite could be 1/4-inch thick and 

be used in combination with another 1/4- 

inch thick lite separated by 1/2-inch to 

create a 1-inch thick glazing unit. Laboratory 

test data achieves an STC rating of 

39. This is also attributed to a reduction of 

the resonance of the system by using the 

laminated pane, which is a damped system. 

As with the previous example, it is 

interesting to note that this window 

achieves only a slightly improved OITC 

rating (OITC 31). The perceived difference 

of this glazing unit compared with 

the previous examples may not be noticeable 

to an occupant. 

Of practical interest, it is recommended 

that for acoustical reasons the laminated 

lite be installed on the interior of the 

glazing unit. This arrangement allows the 

lamination to remain closer to the occupied 

temperature, at which the lamination 

performs more effectively. Laminated 

panes that are subjected to colder temperatures 

perform similarly to non-laminated 

panes of glass. 

Insulated glazing unit with larger 

airspace: When the thickness of the window 

unit can exceed 1-inch, other options 

are possible for improving the sound isolation 

performance. For example, a 1-inch 

deep airspace between two 1/4-inch thick 

lites can improve the acoustical performance 

to a rating of STC 37; the OITC rating 

remains at 30, indicating that the perceived 

difference to the occupant may not 


be significant. The drawback of such a 

system is that the thicker insulated window 

unit may require a different (potentially 

non-standard) framing system to install 

this glazing unit. As a result, this may 

not be a cost-effective improvement to 

consider. 

“Storm sash” upgrade: In many remedial 

projects, it is not possible or costeffective 

to remove the existing window 

to improve the sound isolation. Many 

times the most effective solution is to introduce 

a secondary window system that 

captures an airspace of two-inches or 

more with respect to the existing window. 

Many people consider such an additional 

window akin to a “storm sash”. This 

type of upgrade can be performed on the 

exterior (if space allows) or interior (if the 

exterior of the building cannot be modified). 

With this upgrade, the airspace between 

the existing and new windows is a 

significant factor that largely determines 

the amount of sound isolation improvement 

that may be possible. It is suggested 

that airspaces of two-inches are the least 

that should be considered, but larger airspaces 

can provide even greater benefits. 

The thickness of the secondary sash is 

generally not considered as significant a 

factor. Testing on a recent project demonstrated 

that with an airspace of 5 inches, a 

1/4-inch secondary pane was the most 

cost-effective upgrade to implement 2 . The 

acoustical performance of systems that include 

the secondary sash can start at STC 

40 and OITC 33 and may even achieve 

higher sound isolation performance depending 

on the construction of the façade, 

depth of the airspace, or thickness of the 

secondary glazing. 

Potential issues to consider with 

upgrades: Acoustical upgrades to window 

systems can occasionally introduce 

the following detrimental effects: trapped 

condensation, thermal performance reductions, 

the need for heat treating of 

glazing, and difficulty in cleaning. 

Trapped condensation can result in any 

window systems that are not well sealed. 

This results from humidity entering the 

airspace between the two panes of glass 

and condensing on the cooler surface. 

The magnitude of the condensation is dependent 

on the humidity and temperature 

differences across the glazing system. It is 

occasionally possible to control this effect 

by using the building’s HVAC system to 

maintain a lower humidity level. Alternatively, 

it is also possible to introduce passive 

airflow vents for the cavity between 

the window system to maintain airflow 

that will minimize the condensation. 

The thermal performance with a secondary 

window system can decrease with 

larger airspaces. This is due to convection 

within the cavity transferring more of the 

heat to the colder surface and with a larger 

airspace, the convection can become 

more effective. Studies have shown this 

convection can reduce the thermal effectiveness 

of the window system. 

Airspaces between windows can trap 

heat that may build up to excessive levels 

within the cavity. As a result, manufacturers 

and installers often recommend heat 

treating the lites that create the cavity. 

This heat treating introduces a residual 

surface compression in the glass, which 

improves its ability to resist breakage 

from thermal stresses [citation WBDG]. 

The drawback of heat treating is the additional 

cost for the project. 

A practical issue with acoustical upgrades 

relates to cleaning the cavity between 

the two window systems. Typically, 

installed secondary window systems are 

not sealed and therefore present the potential 

for dust and dirt to enter the cavity. 

To clean within this cavity, it is necessary 

to allow for the secondary lite to be operable 

or removable. It is important to devise 

or select an operable or removable 

system that maintains a reasonable seal 

around the secondary sash when it is not 

being cleaned. Tests have demonstrated 

that cam locks and continuous hinges can 

provide the means to allow for the secondary 

sash to be operable and maintain a 

good acoustical seal. 3 

CASE STUDIES 

The following case studies all involve 

acoustical upgrades of window systems. 

They include projects at an extended stay 

hotel in an urban setting, commercial office 

space under a runway departure, and 

a residential development under a runway 

departure. 

Extended stay hotel in an urban 

setting: The patrons of the hotel were 

complaining of being awakened by construction 

activities in the neighborhood,

which began early in the morning. They 

were also complaining of late night bar patrons 

causing a commotion when they left 

the bars in the late evenings and early 

mornings. The hotel did not want to have 

any more disappointed guests or continue 

to foot the bill for refunds. 

The existing window systems consisted 

of operable double hung aluminum 

windows with 1-inch thick commercial 

grade glazing. The dimensions of the windows 

were about four feet wide by about 

four feet tall. The windows were mounted 

within sills that included an additional 

five inches inside the guestroom. The exterior 

of the building was an old masonry 

construction within interior stud framing 

and drywall. This substantial façade construction 

meant that the sound isolation 

weakness was the windows. 

The deeper than average sills provided 

a good amount of space for mounting secondary 

window systems inside the guestrooms. 

With this arrangement, the exterior 

of the building was not impacted 

visually, which helped the project avoid 

any review by the local architectural 

board. Testing after the installation 

demonstrated a substantial improvement 

of the sound isolation. The overall noise 

reduction was measured to be approximately 

7 to 10 dB better, which was perceived 

to be a noise reduction of 35 per 

cent to 50 per cent. This dramatically reduced 

the complaints from the guests, 

which greatly satisfied the hotel managers. 

They now market their guestrooms as 

providing superior sound isolation from 

the surrounding urban environment. 

Commercial office space under a 

runway departure: A new commercial 

office building was constructed in an area 

that had been previously used for industrial 

facilities. The site was less than one mile 

from a runway with the departure flight 

track passing directly over the building. 

Shortly after initial occupancy, tenants 

began to complain about noise. The noise 

from the departures was interrupting 

phone conversations and meetings. The 

developer requested a sound isolation upgrade 

that would provide effective sound 

isolation, but, at the same time, be as affordable 

as possible. 

A study of the noise impact yielded interesting 

results. It was learned that the 

runway operated infrequently under 

unique wind conditions that occur mainly 

in the spring and fall. In total, the runway 

was used for only about 15 per cent of 

the departures during the year. While this 

infrequent usage may seem to be a benefit, 

it was actually a detriment since it resulted 

in very intense use during those 

short periods. When these unique prevailing 

winds occur, every departing flight 

would use this runway, which meant that 

aircraft were passing over the site approximately 

every three to five minutes. This 

frequent departure schedule was particularly 

distressing to the tenants. Another 

interesting find from the complaints was 

that the noise was most bothersome on 

the side of the building that saw the backside 

of the planes as they departed; the 

occupants who would watch the planes 

approaching the building were not adversely 

impacted by the noise of the overflight. 

There were several significant issues 

relating to implementing the upgrades. 

The recently completed building was already 

partially occupied at the time of this 

work. This presented complications for 

accessing the windows, performing the 

upgrades and scheduling the work. Fortunately, 

the second of the two building that 

comprised the project was still in design, 

so the window upgrades being considered 

could be incorporated in the construction 

plans from the start. 

The base building windows were a 1- 

inch thick insulated glazing unit in individual 

window frame systems, or in two sections 

of curtain wall. The exterior façade 

of the building consisted of masonry with 

an interior stud construction, resulting in a 

fairly effective sound isolating construction. 

To determine the most cost-effective 

upgrades, in-situ testing was proposed 

with three different potential upgrades to 

be considered. The 3 interior sash options 

that were tested included a 1/4-inch thick 

annealed lite, a 1/4-inch thick laminated 

lite and a 3/8-inch thick annealed lite. A 

secondary framing system was installed 

within the existing window system to 

allow for quick changes between the various 

options. The frame was located 

where it achieved an airspace of five-inches 

from the base building windows. The 

tests included cam locks and a continuous 

hinged installation for facilitating the removal 

of the secondary lites. 

The test results demonstrated that the 

various options performed relatively similarly. 

The 1/4-inch thick annealed lite 

achieved an improvement of about 10 dB, 

while the 1/4-inch thick laminated lite 

achieved a reduction of 11 dB, and the 

3/8-inch annealed lite provided a 13 dB 

improvement. The contractor assisted 

with pricing the various options. The developer 

eventually determined that the 

1/4-inch annealed lite provided the most 

cost-effective option to implement. The 

tests also demonstrated that the cam 

locks provided slightly better performance 

over the continuous hinges. Based 

on the locations of the complaints, the 

upgrades were only performed on the 

two façades that faced the departing jet 

exhausts. The same upgrade was planned 

for the future office building project during 

the design. 

Residential Development under a 

Runway Departure: A new residential 

development was planned near the office 

building project described above. Based 

on the experience at the office buildings, 

there was significant concern with locating 

residences in this area. The most significant 

concern related to the potential 

for sleep disturbance due to late night or 

early evening aircraft operations. There 

was also concern about interference with 

conversations and listening to TV and 

music. 

Unlike the office buildings, the developer 

was required to demonstrate that 

their project would achieve an interior 

sound level goal recommended by the 

Federal Aviation Administration (FAA). 

The goal was to achieve a yearly daynight 

average sound level (abbreviated 

L DN ) of no more than 45 dBA. The airport’s 

own noise contours indicated that 

the proposed residential site was exposed 

to yearly day-night average sound 

levels exceeding 70 dBA. 

There were several complicating issues 

for this project. First, the annualized 

average sound levels do not take into account 

individual flight events. It is entirely 

possible to achieve the L DN 45 goal and 

still have significant sound levels intruding 

on the residence from individual departures. 

It was estimated that sound levels 

of 70 dBA were possible from louder aircraft 

departures. This sound level could 

result in sleep disturbance issues for the 


esidents. Another concern from the developer’s 

perspective was the cost of 

meeting this requirement. 

In order to understand the noise impacts 

on the proposed site, an analysis of 

over 1,500 aircraft operations was performed. 

These data provided a means to 

relate the aircraft type, departure time, 

departure height, and frequency of the 

departures to determine a representative 

sound spectrum at the exterior of the 

building. This sound spectrum was applied 

to the various windows that were 

being considered. Sound transmission 

level data from various window manufacturers 

were used to determine the interior 

sound levels for selecting acceptable 

windows for the project. This was compared 

to the sound isolation performance 

of the pre-cast concrete façade, 

which provided relatively good sound 

isolation performance for the non-glazed 

portions of the façade. 

The noise study and the discussions 

with the window manufacturers provided 

several useful results. First, it was 

possible to achieve the interior sound 

level goal with typical commercial grade 

glazing by limiting the size of some windows 

(the smaller window sizes reduced 

the exposure of the interior space to the 

aircraft noise). Second, the upgrades 

were installed in standard window framing 

systems to minimize the cost of the 

upgrades, as non-standard framing is 

often considerably more expensive. 

Third, the upgrades typically included 

laminations or deeper airspaces to 

achieve the interior sound level goal. 

Post-construction testing has demonstrated 

that the window performance is 

consistent with the program goals for 

noise reduction. Subjectively, aircraft departures 

were perceived as relatively 

quiet and unobtrusive to the residents. 

There is an interest in surveying the occupants 

to understand their day-to-day 

experience and perception of the aircraft 

noise impacts. 

CONCLUSIONS 

Architectural glazing can be selected 

to provide improved sound isolation for 

interior occupants of buildings. There are 

several existing standards for performing 

laboratory and field-testing, which includes 

the derivation of single number 

ratings (STC, OITC) for the test specimens. 

Various upgrades for improving 

the acoustical performance of glazing 

systems can be considered. There are 

several concerns to keep in mind and 

avoid when considering upgrades to window 

systems. These include glass thickness 

and type, and the depth of the airspace. 

Several case studies demonstrate 

that the use of architectural glazing can 

successfully improve the sound isolation 

for building occupants. 

REFERENCES 

1. Monsanto/Saflex, Acoustical Glazing 

Design Guide, 3.3-3.6, 1989. 

2. Fullerton, J. and Najolia, D. “Aircraft 

Noise Exposure along South Boston’s 

Waterfront Development.” Proceedings 

of Internoise 2002, The 2002 International 

Congress and Exposition on 

Noise Control Engineering, N400. 

3. Whole Building Design Guide website: 

www.wbdg.org 

■ 


Feature 

Occupant Thermal Comfort 

and Curtain Wall Selection 

By Susan Ubbelohde, UC Berkeley 

IN SUSTAINABLE BUILDING DESIGN, 

ANNUAL energy use becomes a primary 

metric for curtain wall performance. To the 

extent that the curtain wall allows undesirable 

thermal transfer, whether through admitting 

summer solar radiation or through 

winter heat loss, energy is used to counteract 

this transfer and keep the occupants 

comfortable. Current rating systems for 

sustainable performance, such as LEED, 

substantially reward reduced annual energy 

use (USGBC 2002). State building codes 

similarly emphasize annual energy use as a 

primary metric of building performance. 

Data from the state of California, however, 

indicate that energy costs in state 

buildings are equal to only five per cent of 

labor costs for the same buildings. This 

means that a one per cent increase in productivity 

of state employees is equal to 100 

per cent of the energy costs for the buildings 

that house those employees. If productivity 

can be related to occupant comfort, 

such comfort issues will challenge energy 

use as a primary measure of building performance. 

Sustainable buildings are delivering 

Figure 1 - View of the proposed building from the north 

indicating the northwest curtainwall and roof-top photovoltaic 

array (rendering courtesy of the architect). 

Figure 2 - (a) Full building section cut through NW and 

SE curtainwalls and (b) Plan for typical office floor. 


improved interior environments that result 

in increased occupant satisfaction, which is 

then reflected in documented increased 

productivity, recruitment and retention. A 

2003 report on sustainable building (Kats et 

al. 2003) cites productivity increases of 5 

per cent and absentee rates down 40 per 

cent after employees moved into the renovated 

VeriFone building in Costa Mesa, California. 

Similarly, the Firstside Center Building 

in Pittsburg, Pennsylvania which received 

LEED Silver Certification, reports increased 

productivity, reduced absenteeism, 

better recruitment and significantly lower 

turnover related to the improved interior 

environment. The Herman Miller SQA in 

Zeeland, Michigan, demonstrated increased 

productivity and significantly increased employee 

satisfaction over the previous facility 

(Herwagen 2000). 

More specifically, occupant thermal comfort 

is highly valued by office building occupants 

and research shows that many buildings 

fall short. Thermal comfort and 

acoustics are the only interior environmental 

factors that receive a less than satisfactory 

rating from 34,000 respondents in the Center 

for the Built Environment Web-based 

Occupant Survey (Huizenga 2003 and Abbaszadeh 

2006). Thermal comfort and ability 

to control indoor air temperature has 

been ranked as the most important and 

least satisfactory of interior environmental 

factors in office buildings (BOMA 1999). 

Occupant thermal comfort became a 

critical issue in the recent design process for 

a sustainable San Francisco, California office 

building (Figure 1). During the schematic design 

phase, analysis identified cooling loads 

as a major factor in building performance. 

Specifications related to cooling loads and 

energy use (Solar Heat Gain Factor, SHGF, 

and Visual Transmission, Tvis) became a 

prime factor in glazing decisions. However, 

as the design team moved in the design development 

and contract document phases, 

occupant thermal comfort during winter 

months became a critical issue in the final 

curtain wall design and specification. 

SCHEMATIC DESIGN: COOLING LOADS AND 

GLAZING SPECIFICATIONS 

This sustainable office building of 

267,000 square feet was designed for a 

height constrained downtown site. The 11- 

storey building fills out the volume of the 

site, with typical floor-plates that average 

140 feet by 184 feet around a central core 

(Figure 2 a and b). This develops deep office 

bays of 63 feet on the northwest and southeast 

orientations, with narrow bays 34 feet 

deep on the northeast and southwest. The 

floor to ceiling height, and therefore the 

head height for the daylight glazing, is held 

to 9 feet 10 inches due to height restrictions 

on the site and the deep beams necessary 

for the long spans. The northwest curtain 

wall is canted and fully glazed, while the 

northeast and southeast corners are developed 

as punched openings to reflect the design 

of the 1977 building to the northwest 

owned by the client. 

With the project tightly bounded in 

terms of building massing and orientation, 

the design team focused quickly on curtain 

wall performance issues. To identify the relative 

factors in building energy use (for example, 

heating, cooling, lighting, solar radiation) 

DOE2.1e modeling software was used for 

parametric analysis of envelope thermal 

loads. The input model described the entire 

building and was well defined with architectural 

detail that included surrounding site 

shading. A California Energy Code Title 24 

compliant envelope was developed for the 

base building. Hour-by-hour simulations of 

nine zones per floor and ten floors of offices 

were run with the San Francisco Typical Meteorological 

Year (TMY) climatic data (California 

2005). While San Francisco is undeniably 

a temperate climate zone, local 

conditions of fog, winter rains, cooling winds 

off the Pacific Ocean, and three to five day 

periods of “heat storms” caused by winds

from the California Central Valley provide a 

varied set of conditions and extremes for 

building performance. 

The initial runs, without lighting and mechanical 

systems, isolated and quantified 

heating and cooling loads attributable to the 

building envelope. Heating loads were relatively 

low, with the northeast and northwest 

zones demonstrating the highest demand. 

The southeast curtain wall developed the 

highest cooling loads due to solar radiation. 

The southwest façade benefited from some 

site shading conditions and the other orientations 

were less challenged by solar exposure 

(Figure 3). 

The overall annual cooling loads led the 

design team to place a high priority on daylighting 

and shading in the curtain wall design. 

A series of DOE2.1e parametric simulations 

for each orientation were run, using 

solar loads to compare and evaluate glazing 

types and shading strategies: spectrally selective 

glazing versus standard, exterior 

overhangs, interior light shelves, horizontal 

louvers, mullion caps, canted glazing, etc. 

Additional physical modeling using a mirrorbox 

artificial sky quantified the performance 

of two types of light-redirecting glass: insulated 

glass with specular internal louvers for 

the northwest clerestory glazing and lasercut 

prismatic glazing for the southeast 

clerestories (Figure 4). By the end of 

Schematic Design, the high performance 

spectrally selective glazing with redirecting 

clerestory glazing was selected. Shading devices 

for all orientations were designed to 

optimize daylighting performance and minimize 

summer cooling loads. 

With the cooling loads optimized, annual 

energy use simulations were developed to 

compare the performance of mechanical 

system options. A chilled water system with 

thermal storage was selected as it delivered 

the least annual operational cost and required 

the least kWh. 

DESIGN DEVELOPMENT: WINTER THERMAL 

COMFORT 

As the design moved into the DD phase, 

the design team and the owner were interested 

in eliminating the perimeter heating 

system. This would require maintaining the 

interior surface temperature of the curtain 

wall close to air temperature so that occupants 

near the window wall could remain 

comfortable, including on cold winter mornings 

during building start-up hours. By 

decreasing the overall U-value and thermally 

breaking the frame of the curtain wall assembly, 

the interior surface temperatures of 

the curtain wall could be controlled and the 

mechanical system would not be required 

to make up for radiant loss by the occupants 

to the building envelope. 

A full team including the architects, curtain 

wall contractors, glazing manufacturers, 

the construction administrator, the general 

contractor, daylighting and energy consultants, 

and a cost consultant developed a 

range of curtain wall options for consideration. 

The glazing specifications that impact 

cooling performance and daylighting (SHGF 

and Tvis) were consistent for all options, 

while the glass configuration, frame design, 

overall U-value and costs varied across the 

options. The U-values of the curtain wall assemblies 

are described in Figure 5. 

The final seven options were then evaluated 

by the metric that is well known and 

understood—annual energy use. The results 

(Figure 6) were convincing in terms of the 

contribution that daylighting would make to 

energy savings and the performance of the 

light redirecting glass. However, annual energy 

use did not make a clear case for any 

one of the curtain wall options, except to 

identify the worst performing (and least expensive) 

which had no thermal break in the 

frame and the best performing (and most 

expensive) option. 

Since these options had developed in 

large part due to concerns about occupant 

thermal comfort, it made sense to try to 

quantify the comfort performance of the 

seven curtain wall assemblies. Comfort is a 

much more difficult performance characteristic 

to quantify than energy use. Comfort is 

most evident when it is absent; discomfort 

causes complaints, reduced performance 

and local or individual modifications to a 

workspace such as sweaters, space heaters, 

desk fans and aluminum foil over windows. 

ASHRAE Standard 55 is the accepted standard 

for occupant thermal comfort in nonresidential 

buildings. Comfort is quantified 

by a calculated Predicted Mean Vote (PMV), 

an index that predicts the mean value of the 

votes of a large group of people on a sevenpoint 

thermal sensation scale. Additionally, 

the Predicted Percentage of Dissatisfied 

(PPD) quantifies the percentage of thermally 

dissatisfied people (ASHRAE 1992). 

The analytical process developed to predict 

winter comfort conditions throughout 

MBTU 

2.50 

2.00 

1.50 

2.00 

.50 

25 

20 

15 

10 

5 

0 

0 

Visionwall 

Cooling Loads 

Typical Floor 

1 2 3 4 5 6 7 8 9 10 11 12 

Visionwall 

Kawneer 

7500 w/ 

1.25" 

Alpen 

Product Data 

Building 

Geometry 

Fishey 

LOISOS + 

UBBELOHDE 

WW 

Improved 

w/ 

1.25" 

Alpen 

Month 

Figure 3 - Typical floor cooling loads. 

Figure 4 – Test cell of southeast façade mounted in artificial 

sky for tests. 1. Front Silvered Mirror 2. Redirecting 

Film 3. Building façade mounted in the side of Artificial 

Sky 4. Light Meter Array. 

71 

71 

69 

68 

67 

66 

65 

64 

63 

62 

61 

60 

59 

58 

Kawneer 

750 w/ 

1.25" 

Alpen 

WW 

Improved 

1.25" 

Alpen 

U-Values 

WW 

Improved 

w/ 

1" 

Alpen 

Kawneer 

7500 w/ 

VEI-2M 

WW 

Improved 

w/ 

VEI-2M 

ANALYTICAL PROCESS 

Window 5 

LBNL 

Therm 

LBNL + Partners 

Surface 

Temperatures 

Energy Use 

Glazing Performance 

Mean 

Radiant 

Temp 

WW 

Improved 

w/ 1" 

Alpen 

Kawneer 

750 w/ 

VEI-2M 

WW 

Improved 

w/ VEI-2M 

UCB Comfort 

UC Berkeley- 

ASHRAE 

PMV - PPD 

Radiant Asymmetry 

6000 

5000 

4000 

3000 

2000 

1000 

0 

WW Standard 

w/ 

VEI-2M 

Figure 5 - U-values of the seven curtain wall options. 

KBTU/Sq Ft/Year 

WWStandard 

w/VEI-2M 

kCal 

Summer 2006 33 

South East (8) 

West Corner (1) 

South West (5) 

North West (2) 

North east (4) 

South Corner (7) 

East Corner (6) 

Window-Assembly U-val 

Frame U-val 

Glass U-val 

No Okasolas Serraglaze 

Okasolar Serraglaze Included 

Figure 6 - Annual energy used of the seven curtain wall 

options, with and without daylighting contributions and 

light redirecting glazing. 

Weather Data 

(San Francisco) 

DOE2 

LBNL + Partners 

Air Temp 

Humidity 

Air Motion 

Metabolic Rate 

Clothing 

Figure 7 - Analytical process used for thermal comfort 

modeling of selected office bays.

the office floors was simplified by selecting 

five bays for simulation (NE corner, N, NW 

corner, S and SE corner). For each of these 

bays, the PMV and PPD was predicted for 

each square foot of the office bay starting at 

the window wall and moving 30 feet toward 

the interior. The comfort calculation 

methodology is described in Figure 7 (and in 

greater detail in Ubbelohde Buildings IX). 

Axonometric graphs were developed for 

Figure 8 - PPD results for the 

NE corner office bay with curtainwall 

option 1. The two horizontal 

scales represent distance 

from the skin of the building and 

the vertical scale represents 

PPD. 

Figure 9 - PPD results for the NE 

corner office bay with curtainwall option 

2. The two horizontal scales represent 

distance from the skin of the 

building and the vertical scale represents 

PPD. 

Figure 10 - Equal comfort graphic for best performing curtain 

wall option. 

Figure 11 - Equal comfort graphic for selected (middle) 

curtain wall option. 

Figure 12 - Equal comfort graphic for worst performing 

curtain wall option. 


each curtain wall option and each bay (Figures 

8 and 9). The degree of occupant dissatisfaction 

was reflected in the higher per 

cent PPD (graphed on the vertical axis) and 

the distance of dissatisfied occupants from 

the curtain wall (horizontal axis). The graphs 

quantified and compared the comfort performance 

of the curtain wall options in standard 

international comfort metrics and 

made visible the effect of the curtain wall 

temperature on occupant comfort. 

There is no direct correlation between 

PPD and the need for a perimeter heating 

system and the design team still needed 

some input on the issue of perimeter heat. 

By analyzing the hours per year of occupant 

discomfort with the best and middle performing 

curtain wall options, the annual energy 

use and cost of heat required in the 

perimeter zone was quantified. The annual 

levels of demand ($3,475 total annual heating 

costs for building perimeter zones for 

the best option and $7,494 for the middle 

option) enabled the owner to select individual 

radiant heaters rather than ducted 

perimeter heat as the backup system if 

there were occupant complaints. 

In additional conversations with the 

owner and design team a second strategy 

was developed to comparatively describe 

the comfort performance of the seven curtain 

wall options. A grid of mean radiant 

temperatures moving from the curtain wall 

back into the office bay was calculated for 

each curtain wall option. A sectional drawing 

of the office contained a desk located where 

the MRT equals 71˚F to 72˚F for each option 

(Figures 10-12). For the best performing 

option, the desk was located at the window 

wall, but as the curtain wall options 

allowed more thermal transfer, the desk 

was moved away from the wall to indicate 

locations of equal comfort. The description 

of potential floor area lost to discomfort (as 

much as 26,000 square feet with the unbroken 

frame option) was the most effective 

means of communicating the relationship 

between curtain wall performance and occupant 

thermal comfort. The owner selected 

the middle curtain wall of the seven 

based on cost and occupant comfort. 

CONCLUSION 

While annual energy use is an important 

metric for building and curtain wall performance, 

it cannot tell the whole story. Cooling 

loads and daylighting are highly effective in 

reducing annual energy costs for non-residential 

buildings but do not give a clear picture 

of the building performance during 

cooler mornings and winter months, even in 

a temperate climate like San Francisco. For 

this office building, analytical methods and 

descriptive techniques were developed by 

the authors to describe the thermal comfort 

implications of curtain wall design and specifications. 

REFERENCES 

• Abbaszadeh, S., L. Zagreus, D. Lehrer 

and C. Huizenga, 2006. “Occupant Satisfaction 

with Indoor Environmental Quality 

in Green Buildings.” forthcoming in 

Healthy Buildings 2006, Lisbon, Portugal. 

ASHRAE. 1992. Standard 55-1992R. 

• BOMA What Tenants Want: 1999 

Boma/Uli Office Tenant Survey Report. 

Urban Land Institute, January 1999. 

• California Code of Regulations. Nonresidential 

Compliance Manual For California’s 

2005 Energy Efficiency Standards. Publication 

Number: CEC-400-2005-006-CMF 

Published: April 2005 Effective Date: October 

1, 2005. www.energy.ca.gov/title24 

• Judith Heerwagen. “Do Green Buildings 

Enhance the Well Being of Workers Yes”. 

Environment Design and Construction, 2000 

• Huizenga, C. and Fountain, M. 1994-97. 

UCB Thermal Comfort Program version 

1.07 

• Huizenga, C., L. Zagreus, E. Arens and D. 

Lehrer. “Measuring Indoor Environmental 

Quality: A Web-based Occupant Satisfaction 

Survey.” Proceedings, Greenbuild 2003, 

Pittsburgh PA, November. 

• Kats, G., Alevantis, L, Berman, A. et al. 

The Costs and Financial Benefits of Green 

Buildings. A Report to California’s Sustainable 

Building Task Force, October 2003. 

• THERM. 

• Ubbelohde,S., Loisos, G. and Philip, S. “A 

Case Study in Integrated Design: Modeling 

for High-Performance Façades”. Building 

IX Proceedings. Performance of Exterior 

Envelopes of Whole Buildings IX, 

December 2004. 

• US Green Building Council. 2003. LEED 

(Leadership in Energy and Environmental 

Design) Reference Package for New Construction 

and Major Renovations. Version 

2.1. WINDOW5. 

•

Feature 

Window Comfort & Energy Codes 

By Jim Larsen, Cardinal Glass 

HEAT TRANSFER RATES THROUGH MOST windows are significantly 

greater than the adjacent insulated wall. This includes both 

winter heat loss and obviously summer heat gain. Figure 1 

demonstrates how quickly the roomside surface temperature of 

glass can drop in response to cold weather. 

It’s important to analyze window comfort implications before 

settling on an energy strategy that may compromise the livability 

of a space. As an example, take the situation of trading out “efficient” 

windows for an efficient furnace. On paper, the total energy 

consumption may look to be the same, but Figure 1 tells us 

that the occupant will be exposed to cold windows during the 

extreme weather. 

COMFORT BASICS 

Comfort can be evaluated with a statistical index called predicted 

percent dissatisfied (PPD) 1 . The calculation of PPD requires 

a knowledge of room conditions (air temperature, air velocity, 

humidity, and mean radiant temperature), and the occupant conditions 

(clothing level and metabolic rate). When comparing two 

conditions, a lower PPD is desirable as this reduces the risk of 

occupant discomfort. 

Some common examples where cold weather PPD will be 

improved (lower): 

• Increase thermostat setting; 

• Adding layers of clothing; and 

• Increase level of physical activity. 

During hot weather the converse of these will improve comfort 

as well as increasing air movement and/or reducing humidity. 

WINDOW SPECIFIC INPUTS 

Radiant conditions will be the primary driver on window comfort 

issues. Mean Radiant Temperature (MRT) expresses the occupant 

interaction with a window during cold weather. The value 

of MRT varies with the occupant location relative to the window, 

the size of the window and the room side surface temperatures 

(typically taken as glass temperature). Figure 2 compares three 

components of the MRT impact (size, proximity, and glass temp) 

at 70°F inside/0°F outside to the change in PPD near the thermostat 

(no MRT shift). 

Solar gains represent a high temperature radiant source that is 

handled independently of the room/ambient MRT. From research 

work performed by the Windows and Daylighting Group at 

Lawrence Berkeley National Laboratory 2 , a correlation has been 

developed that shifts the occupant comfort based on total solar 

gain. Figure 3 shows this offset for two levels of solar radiation 

and two levels of window solar gain. 

The National Fenestration Rating Council (NFRC) has completed 

a research project 3 that carries these comfort concepts 

forward in much greater detail than presented here. Interested 

Figure 1: Roomside Surface Temperature vs. Outdoor conditions 

Figure 2: PPD vs. Window Conditions and Thermostat Settings 

Figure 3: Solar Offset to Window Comfort 


eaders are encouraged to follow the 

reference listed for further background. 

COMFORT VS. CODE: A REAL WORLD 

EXAMPLE 

In 2003, the Building America program 

supported the development of a 

Habitat for Humanity duplex in the 

Chicago area. This structure used envelope 

improvements, which included 

low solar gain low-E windows, to 

achieve an energy performance that is 37 per cent better than 

the model energy code. The windows used in this project can be 

represented by the line labeled as ‘Quad’ pane in Figure 1. The 

winter design temperature in Chicago is about 0°F; reading up 

the quad pane line we see that the glass temperature will be approximately 

55°F at this design condition. Assuming this is adequate 

comfort—we can now compare the comfort implications 

from alternative energy strategies. 

The same energy performance can be accomplished using ordinary 

double pane windows along with a high efficiency furnace. 

The metrics listed below suggest, however, that these two structures 

are very different. 

1. Peak cooling loads increase by 18 per cent. This creates an 

extra burden for the electrical utility to generate sufficient 

electricity reliability during hot weather periods. 

2. Carbon emissions increase by 12 per cent. The Midwest uses 

mostly coal for electric generation. 

3. There will be 989 hours in the winter when the double pane 

glass is colder than the 55°F benchmark for the original low 

solar gain low-E. 

4. There will be 260 hours in the summer where, despite the 

presence of air-conditioning, more than 30 per cent of the occupants 

will be dissatisfied. This compares to 0 hours with the 

low solar gain low-E glass. 

5. The house with double pane windows is at risk for solar overheat 

760 hours during the swing season. This is not an energy 

consumption measure, but indicates the level of involvement 

needed by the home owner either through operation of 

drapes/blinds or opening of the windows to vent excess heat. 

All told this “equivalent” structure will be outside the comfort 


TABLE 1: EQUAL COMFORT FOR CHICAGO HOUSE 

Low Solar Gain Double Pane Single Pane 

Low-E Clear Clear 

Winter Thermostat Setting 70°F 72°F 73°F 

Summer Thermostat Setting 78°F 74°F 73°F 

Energy Increase vs. — 26% 50% 

Low Solar Gain Low E 

boundaries for 32 per cent of the hours in a year. Compare this 

to less than 10 per cent of the hours for the base case of low 

solar gain windows. 

The folly of the equipment for envelope trade-offs can be extended 

all the way to single pane windows. The combination of a 

high efficiency furnace plus a high efficiency air-conditioner gets 

the single pane windows back to an equal energy score, but the 

building space is now uncomfortable for 50 per cent of the hours 

in the year! 

Faced with uncomfortable windows a homeowner can chose to: 

1. Tough it out; 

2. Move away from the window; 

3. Leave the room; 

4. Add or remove clothing layers; 

5. Close the drapes and/or open the window; and 

6. Turn the thermostat setting to “comfort”. 

Table 1 shows that in spite of paper “equivalence”, homeowners 

could drive an energy increase approaching 50 per cent with 

a simple vote of the thermostat adjustment. 

CONCLUSIONS 

In comparison to most elements in the building envelope, 

windows are “first responders” to weather changes. Inefficient 

windows will be cold in the winter and hot in the summer. 

The general populace would expect an energy efficient house 

to be comfortable year round. If, as envelope designers, we allow 

paper trade-offs that fail the consumer comfort expectations, 

we’ve failed our professional responsibilities. More importantly 

these paper savings, given over to the control of a homeowner, 

could destroy any semblance of a national energy policy and lead 

to dramatic cost overruns and supply disruptions. 

REFERENCES 

1. ASHRAE 2005 Handbook of Fundamentals, Chapter 8; and 

Standard 55-2004. http://www.ashrae.org 

2. LBNL research paper available through ASHRAE via URL: 

http://resourcecenter.ashrae.org/store/ashrae/newstore.cgiite 

mid=7354&view=item&page=1&loginid=8813121&priority=none&words=window 

%20comfort&method=and& 

3. NFRC comfort research: www.nfrc.org/documents/ 

UCBThermalComfortFinalReportFeb72006.pdf 

4. Building America Habitat for Humanity duplex: www.eere.energy. 

gov/buildings/building_america/cfm/project.cfm/project=EEBA%202003%20HfH%20Duplex/state=IL/full=Illinois/city=Chicago 

■

By Valerie L. Block and Tammy Amos, 

DuPont Glass Laminating Solutions, Wilmington, DE 

PROTECTION AGAINST TERRORIST 

ATTACKS IS now a common theme in the 

design of government and commercial 

properties. Americans witnessed terrorism 

firsthand in 1995 with the bombing of the 

Alfred P. Murrah Federal Building in Oklahoma 

City that resulted in the deaths of 

168 men, women and children. Three 

years later, two United States embassies in 

East Africa were the targets of terrorist attacks 

that left 224 people dead and many 

more injured. These two events, and others 

like it that have occurred around the 

world, have led to a heightened awareness 

of the need for greater security in both 

government and commercial buildings. 

DIFFERENCES IN GLASS BREAKAGE MAKE A 

DIFFERENCE 

Annealed glass is made by floating 

molten glass over a bath of molten tin in a 

furnace. The glass ribbon is gradually 

cooled to room temperature through an 

annealing process that also removes residual 

stresses that may have formed during 

manufacturing. While there are many beneficial 

uses of annealed glass in buildings, 

after an explosion, annealed glass breaks 

into long, jagged shards that can cause serious 

injuries. 

Tempered glass is a safety glazing material, 

according to the Consumer Product 

Safety standard 16 CFR 1201. Tempered 

glass is made by reheating annealed glass in 

a furnace to approximately 1150 °F, which 

is then rapidly cooled by flowing air uniformly 

onto both surfaces. The cooling 

process locks the outer portion of the glass 

in a state of compression and the central 

core in tension. Although tempered glass is 

considerably stronger than annealed glass, 

it is not retained in its frame when breakage 

occurs. Instead the glass breaks into a 

myriad of relatively small pieces of glass. 

Laminated glass is often specified in 

windows, doors and façades needing blast 

protection because it provides impact 

safety. The interlayer used to bond two or 

more pieces of glass together provides 

glass retention after a bomb has been exploded, 

and in doing so, minimizes the 

chance of flying glass injuries to building 

occupants or passersby. In addition, this 

glass retention feature helps maintain the 

integrity of the building envelope against 

further vandalism after a terrorist attack 

has occurred. 

IMPACT RESISTANCE AND ENERGY SAVINGS 

Glass retention is desirable in glazing 

installed in seismic regions, as well as in 

residential and commercial fenestration 

intended for use in hurricane-prone areas. 

Impact resistant glazing in properly designed 

frames keeps a home or building 

intact during a severe weather event, protecting 

occupants and the structure itself 

from collapse and interior water damage. 

Window and curtain wall companies have 

applied the knowledge gained from impact 

testing of hurricane products to the 

development of products that offer bomb 

blast protection. 

Laminated glass not only contributes 

to the overall performance of the window 

by its ability to remain integral in its frame 

if breakage should occur, but it can also 

deliver acoustical benefits in terms of reducing 

outside noise. From an energy savings 

point of view, laminated glass can be 

made with high performance glass and/or 

coatings that result in a high visible light 

transmittance and low solar heat gain coefficient. 

While architects may specify laminated 

glass for security, the cost justification can 

often be measured in terms of energy savings 

expressed through lower utility bills. 

APPLICABLE STANDARDS AND TESTS 

ASTM F1642 Standard Test Method for 

Glazing and Glazing Systems Subject to Airblast 

Loading (available at www.astm.org) 

provides testing information for the glazing 

or fenestration system in either a shock 

tube or open-air environment. The 

Feature 

Laminated Glass, Providing 

Security against Terrorist Attacks 

Windows in the Wilkie D. Ferguson, Jr. Federal Courthouse, 

Miami, Florida were made with laminated glass to 

provide both hurricane impact and bomb blast protection. 

Historic renovation included blast resistant windows at the 

National Courts, Washington, D.C. Photo courtesy of 

Masonry Arts. 

standard also includes criteria for the classification 

of fragmentation. Currently, a specification 

to accompany the test method is 

under development. 

The ISC Security Design Criteria adopted 

by U.S. General Services Administration 

in 2001 requires a balanced design of window 

systems to four specified levels. At the 

minimum level, any glazing is acceptable. At 

the medium level and high levels, the preferred 

glazing systems include tempered 

glass with security film on the interior surface 

and attached to the frame, laminated 

glass, or blast curtains. Monolithic annealed, 

heat strengthened and wired glasses 

are unacceptable glazing products. 

Specifications for windows, skylights 

and glazed doors are provided in the U.S. 

Department of Defense Unified Facilities 

Criteria (UFC) Minimum Anti-terrorism 

Standards for Buildings. The UFC criteria 


eferences ASTM F2248 Standard Practice 

for Specifying an Equivalent 3-Second 

Duration Design Load for Blast Resistant 

Glazing Fabricated with Laminated Glass, 

a static design methodology. Except for 

retrofit applications, fragment retention 

film is not considered a glazing alternative. 

This year, the American Architectural 

Manufacturers Association published 

AAMA 510-06 Voluntary Guide Specification 

for Blast Hazard Mitigation for Fenestration 

Systems (available at www.aamanet.org). 

The document establishes 

standard test sizes for fenestration system 

evaluation and comparison. 

THE DESIGN PROCESS 

The design process may be different 

from project to project. In some cases, an 

experienced blast consultant will be required 

to conduct a vulnerability assessment 

and recommend blast loading requirements 

in terms of pressure and impulse, as well as 

the acceptable level of performance for the 

fenestration system. Blast consultants often 

design programs to test proposed systems—at 

laboratories with shock tubes or 

in an open-air arena setting. 

The U.S. State Department now has 

three standard designs for small, medium 

and large embassy projects that are constructed 

on a design-build basis. Blast resistant 

exteriors are part of the master 

plan for the security of these buildings. 

Fenestration design for embassies has 

been addressed by U.S. State Department 

standards, which call for a higher level of 

performance than other blast resistant 

window and curtain wall systems. Special 

attention has been given to attachments 

and frame details of these systems. One 

such system incorporates vertical and horizontal 

tubes or muntins that support the 

laminated glass in the window. The system 

is designed to transfer the load from 

the glazing to the structural muntins and 

frame and ultimately to the adjacent structure 

(Valerie Block and David Rinehart, 

“Security for U.S. Embassies,” Glass, June 

2004, pp 67-68). 

TRENDS FOR THE FUTURE 

As terrorist threats increase, the concern 

for building protection is expanding 

from government buildings—courthouses, 

military housing, and embassies—to 

commercial building projects. Because 

building codes in the United States represent 

minimum standards of construction, 

it is unlikely that mandatory requirements 

for security will be established any time 

soon for commercial construction. As a 

voluntary solution, building owners and insurance 

companies may be the pivotal 

force in driving the adoption of security 

glass solutions. 

It is clear that designers are placing a 

greater importance on the combined benefits 

of hurricane and seismic resistance, 

bomb blast and forced entry protection, 

and better acoustical and energy performance. 

Laminated glass installed in a properly 

designed fenestration system can deliver 

all of these benefits, but most 

importantly, it can protect people inside 

and outside of buildings from glass-related 

injuries and the buildings themselves from 

catastrophic collapse and damage. ■ 

Valerie Block is a Senior Marketing Specialist 

with DuPont Building Innovations, 

Wilmington, DE. Tammy Amos is a Marketing 

Specialist with DuPont Glass Laminating 

Solutions, Wilmington, DE. 


Feature 

How Does Fenestration Fit In 

Where have we been, where are 

we now and where are we going 

By Barry G. Hardman, National Building Science Corporation; 

James D. Katsaros, Ph. D., E. I. Dupont de Nemours and Company 

A SIMPLE PURPOSE 

Fenestration has one primary purpose 

and that is to hold glass. This article first 

reviews glass, then sash (that holds the 

glass in the window frame), then problems 

with today’s fenestration installations, 

and finally a new forward-looking 

concept currently under development— 

an installation process that utilizes gravitywater 

management principles. 

Glass has been an important building 

material for millennia and, until 1960, glass 

had very few changes. When the Pilkington 

brothers invented the float process 

for glass manufacture, it opened up the 

doors to a plethora of new and exciting 

glass products. 

Through 1960, glass was a fairly basic 

material, which came in just a few colors 

(clear, grey and bronze), which could be 

made obscure by rolling a pattern on it 

while it was still hot. 

RECENT INNOVATIONS IN GLASS 

In the past 40 years, glass manufacturing 

has become an extremely sophisticated 

industry that has developed glass that 

can be used for energy savings, safety, 

sound control, impact and blast resistance, 

photovoltaics, privacy (switchable 

New glazings with spectrally selective low-E coatings can 

reduce solar heat gain significantly with a minimal loss of 

visible light (compared to older tints and films). 

glass) and the list goes on. In the not too 

distant future, electrochromic glazing will 

contribute further energy optimization in 

commercial buildings. 

WINDOW FRAMES, SASH AND 

INSTALLATION INSTRUCTIONS 

At the turn of the last century craftsmen, 

carpenters and builders would build 

their walls in such a manner as to include 

the window frame. The craftsmen used 

common wooden mill stock which was 

designated by part numbers in the architect’s 

and mills’ catalogs, to integrate 

window sills, jambs and head frames into 

the building. They used proven water 

management details, such as slopes, 

shiplapping and drip chamfers. 

Architectural detail books often gave 

examples of good vs. faulty methods of integrating 

the frames (using the mill stock) 

into the wall. Window sills, for example, 

always ran well beyond the jambs and 

were sloped, allowing water to freely run 

off and be delivered to the outside of the 

cladding. The tops of window frames 

were also integrated with the cladding in a 

shiplap fashion that guaranteed water was 

drained to the exterior, using gravity. 

Sealants were not available, thus frame integration 

into the wall relied on known 

physics—simply stated, water likes to run 

downhill. 

SASH WAS INSTALLED LATER INTO THE 

WINDOW FRAME 

Around 1910, mill companies, which 

also provided the mill stock to the craftsman, 

usually manufactured sashes (the 

framework portion of the window that 

holds the glass), which could be either 

glazed or unglazed, and they were sold 

separately to the builder to install into the 

previously integrated window frame that 

was part of the wall. Everybody used the 

same sizes, mill stock and methods, therefore 

windows were uniform throughout 

the industry, and sizing was based on available 

glass, which was sold by even twoinch 

increments. 

PREASSEMBLED WINDOW UNITS—LOST 

INSTALLATION PRINCIPLES 

Early in the twentieth century, the 

United States was well into the Industrial 

Revolution and one of the innovations 

from that entrepreneurial time was the 

prefabrication of the window frame and 

the sash as a whole unit. Thus, the window 

as we know it today was born. 

Unfortunately, with that came the uncertainties 

of installing these pre-manufactured 

assemblies into the wall correctly 

with procedures that allow for good 

water management. 

WINDOW AND INTERFACE LEAKAGE 

DOCUMENTED 

Most windows eventually leak. In particular, 

the window-wall interface often 

leaks. That is why there was a need for a 

national consensus installation standard. 

Examine the abstracts for patents filed on 

window systems over the last couple ofcenturies—they 

attempt to address an 

ongoing problem—window leakage into 

the wall cavity. 


Studies define water and air leakage 

paths: 

• June 1980, Air Leakage in Newly Installed 

Residential Windows: Lawrence 

Berkeley Laboratory, University of California–Minnesota 

Energy Agency, John 

Weidt, Jenny Weidt, Prepared for the 

U.S. Department of Energy. Rate of Air 

Leakage through Installed Exterior 

Windows, Uninstalled, Windows and 

Jobsite. 

Conclusions: Manufacturers’ laboratorytested 

products always fell significantly 

short of the rating when in the field. Purchasers 

of products rely on ratings for 

product selection. Air Leakage is most 

severe in corners, interlocks, and sills. 

AAMA method of tabulating air leakage 

(by crack-foot length) was deemed misleading. 

Interface between window and wall: 

“The air leakage performance of the 

crack between the window unit and the 

wall has a significant effect on the air 

leakage performance of the entire window 

unit as installed.” 

• Durability by Design guideline published 

by the Partnership of Advancing 

Technology in Housing (PATH): “Most 

leakage problems are related to improper 

or insufficient flashing details or the 

absence of flashing.” 

• Water Penetration Resistance of Windows–Study 

of Manufacturing, Building 

Design, Installation and Maintenance 

Factors, By RDH Engineering Ltd., 

Vancouver 12/31/2002. “… the dominant 

leakage paths of concern are those 

associated with the window to wall interface, 

both through the window assembly 

to the adjacent wall assembly and 

through the window to wall interface 

with the adjacent wall assembly.” The 

study recommends redundant systems, 

sub-sill drainage for all windows. 

• Journal of Light Construction, November 

2003, based on CMHC / HPO 

study: “35 per cent to 48 per cent of 

newly installed windows were found to 

leak through the window unit itself, 

through joints between the window and 

the rough opening, or both.” 

“100 per cent of installed residential 

windows examined after years in service 

were found to leak either through the 

window unit itself or at points of attachment 

to the building.” 


NATIONAL CONSENSUS INSTALLATION 

STANDARD: ASTM E 2112 

Through 1995 there were no clear directions 

on how to install a window. In 

1995 an ASTM committee was formed to 

write the first fenestration installation 

standard. The first edition was published 

in 2001 and covered four basic methods 

to integrate windows into the wall and 

membrane to form a system. This document, 

known as E 2112 Standard Practice 

for Installation of Exterior Windows, Doors 

and Skylights, was developed with energy 

in mind, as significant energy losses were 

occurring due to the window-wall interface. 

E 2112 is loaded with excellent information, 

however, its one major drawback 

is that it assumes that windows don’t leak 

in their joinery. Any leak in the joinery, unfortunately, 

would become trapped in the 

wall cavity and be forced to the interior. It 

is common knowledge today that windows 

will leak in their corners, if not immediately, 

then at some point after their 

installation, when the weather-stripping, 

vinyl, sealants and other components succumb 

to UV exposure, moisture and thermal 

expansion. That is not necessarily a 

bad thing; it is not uncommon for the 

complexity of this product. Therefore, 

window manufacturers are acknowledging 

that there is a distinct possibility of corner 

leakage on their products sometime in the 

life cycle of the product. 

In 2001, the ASTM E 2112 committee 

started working on the next iteration of 

the document, which is being published 

this year (E 2112-06). This document 

recognizes the reality that there will be 

joinery leakage and provides details and 

methods to install a variety of sill pan 

flashings under the window. Admittedly, 

this is still just a recommended feature but 

the majority of the committee hopes that 

someday it will be required under windows 

where known joinery leakage occurs. 

The new standard also recognizes 

self-adhered flashing. 

Why is that so revolutionary Well, up 

until eight months ago there was no credible 

standard for determining the serviceability 

or durability of self-adhered flashings. 

There was no in-service track record 

of continued performance during their 

service life. In reality, eight months ago, 

duct tape or even masking tape would 

have been allowed to be used as “flashing”, 

as there were no standards. In 2005 

AAMA came to the rescue with AAMA 

711 Self Adhering Flashing standard. While 

the standard is still far from complete, for 

the first time it establishes criteria to be 

able to compare one product against another 

for a particular application. 

INNOVATIVE BUILDING MATERIALS ADD TO 

COMPLEXITY OF INSTALLATION 

The struggle which began early in the 

twentieth century continues today, even 

though we have developed a national installation 

standard and have sealants, 

membranes, weather-stripping, gasketing, 

and the list goes on. The fact is, every innovation 

seems to have added more complexity 

to the installation. And the struggle 

continues. 

REALITY CHECK—REMOVAL AND 

REPLACEMENT 

What do roofs, water heaters and windows 

have in common They all leak 

eventually and have to be replaced. They 

all have a limited lifespan which is less 

than that of the building. More energy-efficient 

versions are made available continuously. 

It is reasonable to assume that you will 

have to change your water heater in ten 

years so it has been installed in a manner 

that makes it fairly simple to remove. The 

roof has a predictable life as well and so 

replacement is easily accomplished. Best 

of all, for both the roof and the water 

heater, the removal is non-destructive to 

the rest of the building. 

Now the window installation, by comparison, 

is bizarre. They are installed and 

embedded in the wall so deeply that only 

destructive technology can be used to remove 

their deeply ensconced roots. They 

are glued, screwed, nailed, covered with 

membranes and cladding on the outside 

and then embedded by gypsum, plaster, 

paint, finish, stools and aprons, just to 

mention a few, on the inside. Why in the 

world do we install windows so deeply 

among the layers of the wall, that you literally 

cannot get it out without destroying 

the wall 

CODES AND CHANGES 

In spite of the integration of all building 

code bodies into the International Code

Council (ICC), one might expect that 

code would require quality window installation. 

Factually, there is very little in the 

code that deals with installation of fenestration 

and its flashing. In the past several 

code cycles a little language is starting to 

creep in, which primarily requires manufacturers 

to supply installation instructions 

to the builder at the time of delivery of 

the product. 

Which manufacturers, you may ask— 

windows, membranes, sealants, flashings 

Who knows The codes have embraced 

membranes to be installed on the exterior 

of the building, which is starting to come 

into effect now. Strangely, codes do not 

define flashing. The new version of E 2112 

clearly defines flashings and how they are 

used. 

MODULAR INSERT FENESTRATION SYSTEM: 

A NEW-OLD CONCEPT FOR INSTALLATION 

Consider a forward-looking concept 

where the builder is given a seamless, 

molded, robust receptor that is specially 

designed to marry with all standard windows 

and is based on standard sizes. Simplistically, 

this is a four-sided pan system 

which is molded and has no joints to leak. 

It integrates with the building’s water-resistive 

membranes and forces drainage to 

the outside of the cladding—just like the 

old master builders and architects knew, 

previous to the innovation of the preassembled 

window unit. 

This new system does not rely on the 

water being evacuated via the membranes 

in the wall cavity, but rather, diverts it immediately 

to the exterior of the cladding. 

Think of the benefit to the builder. He will 

be able to put the receptor in at any time 

when building the walls. This installation 

would then allow for a later window 

installation without penetration 

of claddings or membranes. 

The builder would then be 

able to finish the walls, add 

cladding, sheetrock, paint, clean 

the cladding—without the windows 

being in place. At a point 

when the builder felt it best to install 

the windows, he would 

come by and snap them into the 

receptors. Window manufacturers 

interviewed endorse the concept, 

as it will enhance the ability 

of the window to shed water to 

the outside, keep them clean and free of 

scratches during construction of the building 

and allow more flexibility for delivery. 

It will also keep them from being banged 

around on the job or stolen. The performance 

of the installed window would 

not be dependent on the skill and training, 

or lack thereof, of the installer. Current 

building practices have many different 

trades working around the fenestration 

openings, but the lack of coordination 

among them creates the difficulty with interface. 

PLANNED OBSOLESCENCE OF WINDOWS 

• Windows are the single largest contributor 

to energy loss in the exterior 

walls. 

• This loss translates to high energy bills 

and loss of comfort. 

• Cost of energy can be assumed to rise 

constantly and substantially over the 

lifetime of the building. 

• Allow for innovative technologies without 

prohibitive expenses and disruption. 

• The service life of a window is far less 

than the wall. It has to be replaced two 

to four times over the life of the building. 

• The labor cost to remove and replace 

windows and to repair the surrounding 

walls, interior and exterior, exceeds 

the cost of the window. 

Another important feature of the receptor 

system and methodology is that it 

will make for simple replacement of the 

window. Why is that important Because 

window technology is moving ahead in 

strides—self-cleaning glass, energy-efficient 

glass, photovoltaics, acoustical windows, 

impact-and blast-resistant glass and 

window systems. The list goes on. Without 

a doubt, manufacturers can agree that 

glass will continue to become more and 

more sophisticated, bringing more and 

more energy-saving concepts and comfort 

to the inhabitants of the building. The current 

destructive removal methods deter 

building owners from adopting innovative 

new window technologies sooner. 

RECENT TESTING OF PROTOTYPES 

Prototype receptor systems were installed 

in conjunction with two different 

EIFS systems. Specimen one used a liquidapplied 

water-resistive barrier (LWRB) 

over the substrate. Modular Insert Fenestration 

Systems (MIFS) product was installed 

on top of the LWRB. Additional 

LWRB was then applied over the MIFS installation 

flange with fiberglass netting. 

With specimen two, the MIFS frame 

was installed onto the substrate, then 

LWRB was applied over the substrate and 

over the MIFS attachment flange. Both 

specimens then had 1-1/2” Styrofoam installed, 

which was further coated with a 

1.5 mm cementitious acrylic coating. 

• ASTM E 330 Test Method for Evaluation 

of Structural Performance— 

The combined wall and fenestration 

products achieved a 45 psf positive and 

negative using a fenestration product 

that was rated at 25 psf. 

• ASTM E 331 Test Method for Static 

Water Penetration—The combined 

wall and fenestration products 

achieved 12 psf for 15 minutes. 

• ASTM E 283 Air Infiltration—Both 

combined wall/fenestration products 

measured 0.03 cfm per square foot 

(54 sq. ft. samples) at1.57 lb/ft2. 

CONCLUSIONS 

There are manufacturers now developing 

this concept. Changes are expected 

in window installations that are based on 

traditional gravity-based water management 

principles. The receptor approach 

requires the receptor to be built into the 

wall, is designed in such a way that the 

window can be simply snapped into the 

receptor without piercing the receptor or 

the cladding or the membranes. Even if 

the joinery at the corners of the windows 

leaked, it would not make any difference, 

because that leakage would be diverted to 

the outside of the cladding. 

■ 


By Rich Karney, 

U.S. Department of Energy 

Industry Update 

Tax Credits Made Easy by 

Choosing ENERGY STAR® 

THE U.S. DEPARTMENT OF ENERGY 

(DOE) and its fenestration partners were 

pleased with guidance issued by the Internal 

Revenue Service (IRS) earlier this year that 

recognized the value of the ENERGY 

STAR® label for windows. It is now easy to 

take advantage of Federal tax credits for 

windows by choosing ENERGY STAR®. 

The Energy Policy Act of 2005 introduced 

tax credits for building envelope 

components that meet minimum requirements 

of the 2000 International Energy 

Conservation Code (IECC) with supplements, 

or other applicable requirements. 

The legislation granted credits of 10 per 

cent of the cost of eligible improvements, 

not to exceed $500 ($200 for windows) 

over the length of the program—the 2006 

and 2007 tax years. Once the bill was 

passed and signed, ENERGY STAR® and 

energy-efficiency professionals looked to 

the IRS for guidance on how the credits 

would be implemented. 

In February of this year the IRS issued 

notice 2006-26, which outlined the specific 

requirements for eligible building envelope 

components and provided guidance on how 

eligibility was to be confirmed and documented. 

Notable provisions of the notice 

included an expansion of all references to 

the 2000 IECC, guidance for issuing and 

using a Manufacturer Certification Statement, 

and a special rule for ENERGY 

STAR® windows and skylights. 

The IRS effectively simplified many eligibility 

requirements by expanding references 

to the 2000 IECC, to also include the 2004 

Supplement to the 2003 IECC. This means 

that eligible envelope components may 

qualify for tax credits by meeting the requirements 

of the 2001 or 2004 Supplements 

to the IECC. The expansion allows 

products to qualify for the credit by meeting 

the simpler, but equally stringent, requirements 

of the 2004 Supplement. 

The IRS also addressed questions about 

consumers being burdened with determining 

and documenting compliance with the 

IECC by introducing protocols for manufacturer 

certification statements. A manufacturer 

of an eligible product may certify to a 

taxpayer that the component qualifies for 

the tax credit in a certification statement 

provided with the product. In turn, a consumer 

may rely on a manufacturer’s certification 

that a product is eligible when claiming 

the tax credit. Taxpayers will not need 

to submit the certification statement with 

their tax documents, but should retain the 

statement for their own records. 

A manufacturer of an eligible 

product may certify to a taxpayer 

that the component qualifies for the 

tax credit in a certification statement 

provided with the product. 

The greatest simplification for consumers 

came from a special rule that IRS issued 

for ENERGY STAR® windows and 

skylights. Recognizing that ENERGY STAR® 

qualified windows and skylights exceed 

IECC requirements nearly everywhere in 

the U.S., the IRS treats all ENERGY STAR® 

qualified windows and skylights as eligible 

products and allows consumers to rely on 

the ENERGY STAR® label, rather than a 

manufacturer’s certification statement, 

when determining if the product qualifies 

for the credit. As with the certification 

statement, a taxpayer does not need to 

submit the ENERGY STAR® label to the 

IRS, but should keep it for their records. 

Unfortunately, the special rule does not 

apply to ENERGY STAR® qualified doors, 

even though they also will nearly always exceed 

IECC requirements. DOE has encouraged 

all ENERGY STAR® manufacturing 

partners to provide certification statements 

with qualified doors and advises consumers 

to look for doors with these statements to 

ensure eligibility for the tax credit. 

The IRS guidance also covered products 

other than windows, doors, and skylights. 

Insulation materials or systems, metal roofs, 

and storm windows and doors are also eligible 

for the same $500 tax credit. Insulation 

materials must be primarily designed to 

reduce heat loss or gain, and metal roofs 

must meet or exceed ENERGY STAR® requirements 

in order to be eligible for the 

credit. Storm windows and doors are eligible 

if they meet IECC requirements when 

installed in combination with existing windows 

and doors. 

Additional incentives exist for energy-efficient 

fenestration and building envelope 

components through builder tax credits for 

energy efficient homes. The Energy Policy 

Act introduced a $2000 credit for new 

homes that have annual HVAC energy consumption 

that is 50 per cent less that that of 

a home constructed according to the 2003 

IECC, 1/5 of which must be associated with 

building envelope components. A $1000 

credit is also available for manufactured 

new homes with annual HVAC consumption 

of 30 per cent less than a home constructed 

to the 2003 IECC. IRS notice 

2006-27 defined eligible homes as those 

verified by a RESNET (or equivalent rating 

network) accredited certifier to meet the 

requirements prescribed in the legislation. 

The department looks forward to these 

credits advancing the market for energy-efficient 

building products. In addition to 

other financial incentives and energy benefits, 

federal tax credits are another asset for 

individuals and organizations that seek to 

market quality, energy-efficient products. 

For more information on these and 

other tax incentives, visit the ENERGY 

STAR® website at www.energystar. 

gov/taxcredits. 

■ 



By James C. Benney, NFRC Executive Director 

NFRC Standards, Codes and 

Fenestration Research Activities 

INTRODUCTION 

The National Fenestration Rating Council 

(NFRC) is a nonprofit (501(c)3) organization 

whose mission is to develop and administer 

comparative energy and related rating programs 

that serve the public and satisfy the 

needs of its private sector partners by providing 

fair, accurate and credible, user-friendly information 

on fenestration product performance. 

NFRC develops and publishes standards 

(see descriptions below) and administers a 

certification and labeling program to ensure 

accurate, uniform and credible energy performance 

ratings for all fenestration products; 

including windows, doors, skylights, curtain 

walls and storefront systems. 

TECHNICAL STANDARDS AND CODES 

NFRC standards are referenced in the International 

Energy Conservation Code 

(IECC), the International Building Code (IBC) 

and the International Residential Code (IRC); 

as well as ASHRAE 90.1 and 90.2; and many 

state and local energy codes, such as California’s 

Title 24. All NFRC standards are available 

at no charge on its website (www.nfrc.org). 

IECC REFERENCE 

IECC 102.5.2 Fenestration product rating, 

certification and labeling 

• U-factors of fenestration products shall be 

determined in accordance with NFRC 100 

by an accredited, independent laboratory, 

and labeled and certified by the manufacturer. 

• The solar heat gain coefficient (SHGC) of 

glazed fenestration products shall be determined 

in accordance with NFRC 200 by 

an accredited, independent laboratory, and 

labeled and certified by the manufacturer. 

NFRC STANDARDS 

• NFRC 100 (2004) “Procedure for Determining 

Fenestration Product U-factors”. 


Fenestration Product Solar Heat 

Gain Coefficient and Visible Transmittance 

at Normal Incidence.” 



Fenestration Product Air Leakage.” 


Fenestration Product Condensation 

Resistance Values.” 

NFRC CERTIFIED PRODUCTS DIRECTORY 

NFRC administers a voluntary certification 

and labeling program that provides assurance 

to architects, specifiers and code officials that 

fenestration products have been rated in accordance 

with NFRC procedures and by an 

independent, accredited lab. 

Those products that have been authorized 

for certification and manufacturers that 

have been licensed by NFRC are listed in the 

Certified Products Database. This database 

lists the ratings and attributes of hundreds of 

thousands of fenestration products and systems 

and is freely available on the NFRC 

website (www.nfrc.org). 

RESEARCH ACTIVITIES 

In addition, to these Programs, this nonprofit 

organization also spends a considerable 

amount of time, energy and money approving 

and funding fenestration product research. 

Since 2004, the NFRC Board of Directors has 

approved over $500,000 to fund research 

projects that serve its mission. Typically, research 

projects are related to improving the 

accuracy and dependability of its rating programs 

(including the basic science used in 

computer programs that model heat transfer 

mechanisms) or to develop new rating programs 

such as Thermal Comfort (see below). 

The following is a list of projects that have 

been recently completed or are in process of 

completion: 

• Effects of Surface Heat Transfer Coefficients 

on U-factor for projecting and highly 

conductive products; 

• Investigation of Heat Transfer Effects of 

Sloped and Ventilated Internal Cavities of 

Framing Systems; 

• Study of 3D corner heat transfer effects in 

fenestration products; 

• Development of a procedure (and model) 

for the U-factor rating of domed skylights; 

• Development of a procedure (and model) 

for SHGC and VT ratings of domed skylights; 

• Development of U-factor ratings for tubular 

daylight devices; and 

• Development of a thermal comfort rating. 

In addition, there are number of proposed 

research projects awaiting approval, including: 

• VT ratings for non-specular glazings; and 

• Research to support grouping rules and 

Condensation Resistance ratings for the 

Component Modeling Program. 

THERMAL COMFORT RATINGS 

Many NFRC members and stakeholders 

believe that thermal comfort is a missing component 

in our current rating system. There is 

a definite relationship between energy efficiency 

and comfort; and between comfort 

and productivity and personal satisfaction. 

Higher fenestration U-factor ratings tend to 

indicate colder interior window surface temperatures 

in the winter; leading to higher levels 

of discomfort and/or levels of dissatisfaction. 

The same can be true in terms of solar 

heat gain in the summer; where high levels of 

solar gain increases the interior surface temperatures 

of fenestration products to uncomfortable 

levels. These levels of dissatisfaction 

or discomfort depend upon a complex series 

of factors including the time of day, location, 

orientation, exposure, and distance from the 

window. The research being conducted is intended 

to assist NFRC in developing a Thermal 

Comfort Rating; which should providing 

additional information about fenestration performance 

to architects, specifiers and homebuilders. 

For more information about this program, 

or any of the on-going research projects at 

NFRC, please see our website at www. 

nfrc.org or contact our office in Silver Spring, 

Maryland at 301-589-1776. NFRC is also an 

AIA accredited information provider and offers 

courses to those firms interested in learning 

more about fenestration performance. ■


BEC Corner 

BOSTON-BEC 

By Richard Keleher 

Boston’s BEC has been getting 25 to 

30 attendees each month. We have begun 

a program of outreach to the larger offices 

in Boston and environs to improve 

attendance. Our co-chair, Maria Mulligan, 

is back after an extended maternity leave 

and she is beginning to work on improving 

the quality of our monthly presentations. 

Presentations of note that we have 

had are; Mineral fiber cavity insulation by 

Dr. John Straube, ABAA adhered sheet air 

barrier specifications by Mark Kalin, 

Through-Wall Flashings by Len Anastasi, 

and Rainscreen Cladding Systems by our 

chairman, Richard Keleher. We also had 

our first ever “roadshow,” where three 

experts from the BEC went out to the 

surrounding region and presented a sequence 

of three two-hour sessions on 

building science (heat, air, moisture), the 

management of liquid water and specifying 

the building enclosure. For more information 

on our presentations, projects, 

membership and contacts, tour our website, 

www.bec-boston.org. 

CHARLESTON-BEC 

By Nina Fair 

Building Enclosure Council-Charleston, 

had its initial organizational meeting 

in October, 2005. Regular meetings 

started in January, 2006. BEC-Charleston 

has generated a lot of interest and excitement 

in the design and construction communities. 

Our recent and planned programs 

are: 

• February 2006 Meeting 

Topic: ASTM E 2112 Standard for 

Window Installation with Proper 

Flashing 

Presenter: Mr. Barry Hardman with 

National Building Science Corporation 

• March 2006 Meeting 

Topic: Metal Wall Rainscreen & 

Moisture Control 

Presenter: Mr. Andrew Laiewski with 

Centria Architectural Systems 

• April 2006 Meeting 

Topic: ASHRAE 90.1 Energy Code 

Envelope Compliance 

Presenter: Mr. Dennis Knight, P.E. of 

Liollio Architecture 

• May 2006 Meeting (Joint meeting 

with ASHRAE Charleston) 

Topic: Cool Roofs 

Presenter: Dr. William Miller of Oak 

Ridge National Laboratory 

• June 2006 Meeting: 

Topic: “Flashing: The Good, the Bad 

and the Ugly” 

Program: Hands-on exploration of 

flashing materials, details and related 

issues 

• August 2006 Meeting: Thursday, 

August 24, 6:00 – 7:30 PM 

Topic: NFRC Certification and 

Programs 

Presenter: Bipin Shah, Director of 

Programs, National Fenestration 

Rating Council (NFRC) 

COLORADO-BEC 

By Ned Kirschbaum 

BEC-Colorado’s inaugural meeting 

was on August 10, 2005 and we have met 

on the first Wednesday of each month 

since then. Attendance has consistently 

been between 15 and 25 participants including 

architects, engineers, contractors, 

subcontractors and suppliers. Presentations 

have included a computation fluid 

dynamics case study, detailing of windows 

in brick veneer walls, the ins and outs of 

horizontal waterproofing systems, a roofing 

systems overview, snow country roof 

design: materials, assemblies, and moisture 

management, fluid applied air barriers, 

building science principles in cold and 

very cold climates, weather-resistive barriers, 

and best (and worst) practices for 

exterior stucco in Colorado. 

In the future we hope to jointly host, 

with the University of Colorado and 

BETEC, a one day building science seminar. 

We are also planning to create a halfday 

seminar on building envelope design 

in very cold, snowy climates, given by 

local BEC members. 

DC-BEC 

By Tim Taylor 

The inaugural meeting of the DC-BEC 

occurred in February of 2005 at the 

Washington DC offices of Gensler. Since 

then, the DC-BEC has hosted approximately 

a dozen meetings on selected aspects 

of building enclosure design. Topics 

have included basic design criteria for curtain 

walls, including wind, water and air, 

shadow box design guidelines, fundamental 

architectural design considerations for 

existing and new blast resistant building 

envelopes, firestop design of spandrels, 

building envelope thermal testing, the 

new NIBS Building Envelope Design Guide, 

building structural deflections and exterior 

cladding, selecting roofing systems for 

long term performance, the what, when, 

where, why and how of air barrier design, 

carbon fiber reinforcement of precast 

concrete panel cladding. Future topics for 

the fall include exterior wall maintenance 

systems design, the National Fenestration 

Rating Council’s latest rating system and 

water management within exterior walls. 

Our meetings are an hour long, are held 

at 4 pm on the first Wednesday of each 

month except in July, August and December, 

when we suspend the meetings in observance 

of vacations and end of the year 

parties. They are attended by facilities 

owners, developers, architects, exterior 

wall consultants, exterior wall cladding 

subcontractors, and manufacturer representatives. 

Attendance is free and those who attend 

can earn a continuing education unit 

which is automatically reported by filling 

out a sign-up sheet. 

To contact the BECs, go to www.bec-national.org/boardchairs.html 


BEC Corner 

HOUSTON-BEC 

By Andy MacPhillimy 

AIA Houston is joining the national initiative 

by AIA National and the National 

Institute for Building Sciences by establishing 

BEC-Houston, an open forum to promote 

discussion, education and the transfer 

of information and technology among 

all stakeholders in buildings enclosures— 

owners, architects, engineers, consultants, 

manufacturers, installers, contractors and 

others. We are excited about this opportunity 

to raise regional expertise, skill and 

the understanding of building exterior enclosure 

construction, resulting in the improvement 

of the quality of design, the installation 

and the maintenance. A kick-off 

meeting was held on May 24th and was attended 

by a diverse group of those interested 

in the mission of BEC-Houston. 

In the coming weeks we will be 

establishing the steering committee to set 

the vision and mission of BEC Houston 

and the program committee to develop 

the series of speakers, panels and work 

shops needed to accomplish the vision and 

mission established by the steering committee. 

MINNESOTA-BEC 

By Judd Peterson 

From our inception on February 14, 

2006, the BEC-Minnesota has scheduled 

monthly meetings involving both lectures 

by experts about specific aspects of the 

building envelope, and informal round table 

discussions about preferred section detailing 

of the building envelope. Speakers have 

included Kim Bartz of WR Grace Company 

and Brent Anderson of BA Associates 

about air/water/vapor barriers on backup 

construction and sheathing; Dan Braun and 

Dan Johnson of Architectural Testing, Inc. 

about the range of possible field tests for 

exterior building envelopes; Craig Hall of 

WL Hall and Wausau Windows about critical 

detailing of window and curtainwall 

openings and primary seals. 

Upcoming lectures include Bob Moran, 

Northeast Regional Technical Representative 

of BASF Polyurethane Foam Enterprises, 

talking on Spray Polyurethane Foam Insulating 

Air Barriers in the exterior envelope; 

Chemrex Technical representatives 

will discuss all aspects of sealant application, 

including chemical compositions, 

compatibilities, incompatibilities, proper 

uses depending on the type of sealant, 

primers, application conditions; and Craig 

Thompson, Technical Representative of 

the Copper Development Association, 

talking on copper sheet metal enclosures 

and detailing, with examples formed and 

fabricated at the seminar by McGrath 

Sheet Metal. 

Our BEC participants have voiced appreciation 

for the access to critical building 

enclosure expertise, and the extended resources 

and advice from other BEC peers. 

PORTLAND-BEC 

By Rob Kistler 

In the short period since the introductory 

meeting held in December 2005, the 

Portland-BEC has developed into a well 

attended monthly seminar hosted at various 

architect and contractor offices. 

Consisting of roughly equal numbers of 


manufacturing representatives, contractors 

and architects, the seminars have attracted 

between 30 and 45 people. The 

topics, presented by local and national experts, 

have alternated between the theoretical 

and the practical. Seminar topics 

range from Portland cement plaster, and 

air and moisture infiltration and barriers, 

to seminars on barrier compatibility with 

sealants, and envelope acoustics. Adding 

interest to each seminar, a “detail of the 

month” that is relative to the topic is displayed 

and discussed prior to the presentation. 

The “BEC Programming Group,” 

which is responsible for developing the 

programs and lining up speakers is also 

working towards producing a two-day 

seminar to take place in November 2006. 

Interested parties can find out more in formation 

at www.aiaportland.com/ (Member 

resources) (Committees). 

SEATTLE-BEC 

By Dave Bates 

The Seattle Building Enclosure Council 

or SeaBEC as we call it, is almost halfway 

through its second year and it has been a 

good adventure so far. We have a governing 

board of six with diverse backgrounds; 

contractor, owner’s rep, architect, product 

rep, building envelope consultant and 

an architectural consultant with the NW 

Wall and Ceiling Bureau. Our membership 

is more diverse with students, developers, 

contractors, architects, engineers, envelope 

consultants, construction defect attorneys, 

building department personnel, 

product reps and industrial hygienists. We 

meet the third Thursday of every month, 

from 5-7pm with the exception of July and 

August. The Board meets once a month 

year-round. Our membership base is currently 

at 110 members and we have had 

anywhere from 35 to 82 people attend 

our monthly meetings. 

Our membership fees cover the cost of 

our meeting rooms, air fare and lodging 

for our chair to attend the national BEC 

and BETEC meetings and necessary operational 

expenses such as our annual audit. 

We charge 50 dollars for a single membership 

with student memberships gratis. 

Member firms and product reps sponsor 

refreshments at our meetings which typically 

include sandwiches. Meetings consist 

of 1/2 hour networking session, 15 minutes 

of business and an hour+ program. 

Programs are diverse and have included a 

window testing demonstration, discussion 

of the Washington State Condominium Act 

relating to building envelope, air barriers, 

curtain walls, sealants, and structural 

forensic investigation practices to name a 

few. 

We have two committees in place, one 

for education/programming and another to 

help define third-party building envelope 

inspectors as allowed for by the Condominium 

Act. We also have a web site 

under construction, www.seabec.org and 

are sponsoring a golf tournament in the 

fall. Our goals for the future are to educate 

contractors, help the local AIA chapter 

with building envelope seminars and workshops, 

forge ties with the University of 

Washington Architecture and Building 

Construction programs, collaborate with 

BEC Portland and continue operating as a 

respected forum for discussion and learning 

of building envelope issues. ■ 


Buyer’s Guide 

AIR BARRIERS 

Dupont Building . . . . . . . . . . . . . . . . . . . . . . .7 

AIR AND VAPOR BARRIERS 

Carlisle Coating & 

Waterproofing . . . . . . . . .outside back cover 

ARCHITECTS 

HKS Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 

ASSOCIATION 

National Fenestration Rating Council . . . . . .25 

BUILDING DESIGN SERVICES 

Wauters Design GPP LLC . . . . . . . . . . . . . . .30 

BUILDING ENVELOPE ARCHITECTS 

Conley Design Group Inc. . . . . . . . . . . . . . .17 

BUILDING PRODUCTS 

Georgia Pacific . . . . . . . . . . .inside front cover 

BUILDINGS SCIENCE & RESTORATION 

CONSULTANTS 

Read Jones Christoffersen . . . . . . . . . . . . . .48 

CERAMIC TILE ADHESIVES 

ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .35 

CONCRETE MODIFIERS & SEALERS 

ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .35 

CONCRETE ROOF TILES, MODIFIERS & 

SEALERS 

ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .35 

CONSULTANTS 

Patenaude-Trempe Inc. . . . . . . . . . . . . . . . . .50 

ELASTOMERIC ROOF COATINGS 

ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .35 

ENGINEERS 

Sutton-Kennerly & Associates Inc. . . . . . . . .30 

EXTERIOR INSULATING FINISH SYSTEMS 

ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .35 

FENESTRATION CONSULTANT 

National Building Science Corporation . . . . .38 

FLUID APPLIED AIR & MOISTURE 

BARRIERS 

Prosoco Inc. . . . . . . . . . . . . . . . . . . . . . . . . .13 

GLASS & GLAZING 

Cardinal Glass . . . . . . . . . . . . . . . . . . . . . . . . .9 

GLASS COATINGS 

AFG Glass . . . . . . . . . . . . . . .inside back cover 

GLASS FABRICATIONS 


GLASS MANUFACTURING 


INSULATING GLASS 


INSULATION 

Knauf Insulation . . . . . . . . . . . . . . . . . . . . . . .3 

INSULATION MANUFACTURER 

Johns Manville . . . . . . . . . . . . . . . . . . . . . . . .44 

MEMBRANE/VAPOR BARRIER 

CertainTeed . . . . . . . . . . . . . . . . . . . . . . . . .31 

MANUFACTURER REFLECTIVE ROOF 

COATING • LEED COMPLIANT 

Karnak Corporation . . . . . . . . . . . . . . . . . . .18 

MASONRY 

Mortar Net USA Ltd. . . . . . . . . . . . . . . . . . .15 

METAL ROOF COATINGS 

ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .35 

MULTI-DIRECTIONAL DRAINAGE 

BARRIER 

Valeron Strength Films . . . . . . . . . . . . . . . . .36 

ROOF DECKS 

Global Dec-K-ING . . . . . . . . . . . . . . . . . . . .49 

ROOF DECKS & BALCONIES/ 

WATER PROOFING & ROOFING 

Skyline Building Systems Inc. . . . . . . . . . . . .22 

ROOFING MANUFACTURER 

GAF Materials . . . . . . . . . . . . . . . . . . . . . . . . .4 

SIDING, WOOD, VINYL FIBER CEMENT 

ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .35 

WATER PROOFING 

CETCO Building Materials Group . . . . . . . .40 

WATERPROOFING, RESTORATION 

The Waterproofing Company Inc. . . . . . . . .13

(JBED) - Summer 2006 - The Whole Building Design Guide

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