jbed journal of building enclosure design · tive of actual performance, since additional heat flow...

An official publication of the Building Enclosure Technology and EnvironmentCouncil (BETEC) of the National Institute of Building Sciences (NIBS)

Journal of Building Enclosure DesignJBEDSummer 2007

Experts in Design,Construction andthe Advancementof the Industry

Experts in Design,Construction andthe Advancementof the Industry

PRSRT STDU.S. Postage

PAIDPembina, NDPermit No. 14

TheBESTof theBECS:

TheBESTof theBECS:

Summer 2007 5

Published For:NIBS / BETEC1090 Vermont Avenue, NW, Suite 700Washington, DC 20005-4905Phone: (202) 289-7800Fax: (202) [email protected]

Published by:MATRIX GROUP PUBLISHINGPlease return all undeliverable addresses to:16516 El Camino RealSuite 413, Houston, TX 77062Phone: (866) 999-1299Fax: (866) 244-2544

PRESIDENT & CEOJack Andress

SENIOR PUBLISHERMaurice P. LaBorde

PUBLISHER & DIRECTOR OF SALESJoe [email protected]

EDITOR-IN-CHIEFShannon [email protected]

EDITORJon Waldman

FINANCE/ACCOUNTING & ADMINISTRATIONShoshana Weinberg, Pat Andress, Nathan [email protected]

DIRECTOR OF MARKETING & CIRCULATIONJim Hamilton

SALES MANAGERNeil Gottfred

MATRIX GROUP PUBLISHING ACCOUNT EXECUTIVESTravis Bevan, Albert Brydges, Lewis Daigle,David Giesbrecht, Rick Kuzie, Miles Meagher,Marlene Moshenko, Declan O’Donnovan, Ken Percival, Brian Saiko, Vicki Sutton, Jason Wikis

ADVERTISING DESIGN James Robinson

LAYOUT & DESIGNJ. Peters

©2007 Matrix Group Publishing. All rightsreserved. Contents may not be reproduced byany means, in whole or in part, without theprior written permission of the publisher. Theopinions expressed in JBED are not necessarilythose of Matrix Group Publishing.

Features:10 Evaluating Energy Efficiency

Using Whole-BuildingSimulation Tools

16 ASTM C 652 Bricks: Less isGood

20 Transitions: How to DesignFacade Interfaces

24 Reflections on the WindowWall

29 Air Barriers: Walls MeetRoofs

33 Curtain Wall Mock-upTesting

Contents

Messages:

07 Message from NIBS President, David A. Harris

08 Message from BETEC Chairman, Wagdy Anis

Industry Updates:

46 BEC Corner

50 NIBS Application

On the cover: New Yorkcity’s Chrysler Building isknown for its art deco crown.Learn more about distinctivecharacteristics of exterior wallsin Henry Taylor’s article onpage 33.

36 Perimeter Joints

39 Rain Screens: The NewStandard

41 Characterizing Air Leakage inLarge Buildings: Part I

JBED

24

33 41

Curtain WallTesting

Window Walls

Air

Le

akag

e

50 BETEC Application

48 Buyer’s Guide

Summer 2007 7

Message from NIBS

THE GREEN BUILDING MOVEMENT hasalways been with us. If it hasn’t, it shouldhave been. Energy conscious design, mini-mizing waste, recycling, using renewableresources and the like should be integral tothe design and construction of all buildings.

Today, we’re bombarded with invita-tions to conferences focusing on buildinggreen and green buildings. To me, it makesmore sense for us to focus our energies onimproving the full range of building per-formance—security, safety, appearance,durability and functionality—to name just a

few. Each of these performance needscompetes with the others for its share ofspace during design, for dollars during con-struction and for other resources over abuilding’s life cycle. Design professionals,constructors and building owners mustproperly balance these needs and costs.

We can get rating points for using sus-tainable materials such as recycled wall-board, non-VOC emitting carpet and ceilingtile, and increased insulation in the buildingenvelope. But if we don’t look at total build-ing performance, all of our “green” effortsmay be for naught. If the building is in a hur-ricane zone and we haven’t provided ade-quate tie-downs for the rooftop equipment,much of that equipment can be blownaway, opening the roof system to hurricanelevels of rain, which will soak the insulation,saturate the drywall, ceiling tile and carpet,leaving the interiors in ruins. What have youaccomplished?

The Journal of Building Enclosure Design(JBED) brings the design professional’s at-tention to whole building performance.Look beyond the low hanging fruit of

sustainability to the high performance build-ing concept. The U.S. Congress deservesstrong praise for its foresight and wisdom inestablishing the high-performance buildingsprogram to create high performance goalsand accompanying metrics for public andprivate buildings of the future.

The building envelope is a large and im-portant portion of the building. Improvedenvelope performance will improve build-ings and systems life spans, building opera-tion and maintenance, occupant productivi-ty, safety and security, as well as mission andsystems performance. JBED and theBETEC’s focus will continue to be the im-provement of the building envelope forgreener, sustainable and high performancebuildings.

Please send us your comments and sug-gestions for additional topics for JBED. And,in the interest of recycling, please pass thisissue along to a colleague.

David A. Harris, FAIAPresidentNational Institute of Building Sciences

David A. Harris, FAIA

WELCOME TO THE SUMMER2007 edition of the Journal of BuildingEnclosure Design (JBED)!

This edition is a tribute to theBuilding Enclosure Councils (BECs)of the U.S., all eighteen of them(www.bec-national. org/board-chairs.html) and their cousins andpredecessors in Canada. The BECs,a partnership between the AIA andthe National Institute of Building Sci-ences, are truly an untapped forcethat is discovering its potential in the

influence it can have on the design, construction, product devel-opment and advancement of a unique and rapidly developingrollercoaster of focus on how buildings perform in their environ-ments, in all of the eight climate zones of North America.

With a new national focus on energy efficiency, the carbonfootprint of buildings and their contribution to climate change,this represents a unique time in the history of North America tomake an impact, and they are truly taking this to heart. The BECsare working as a group, through the formation of a Research Co-ordinating Committee of the Building Enclosure Technology andEnvironment Council (BETEC) a council of the National Instituteof Building Sciences. In addition to the almost daily communica-

tions that are conducted nationally, they are putting on a majorinternational conference, the Building Enclosure Science and Tech-nology Conference (BEST 1), the first of a series that will be heldevery two years, in alternate years to the Canadian NationalBuilding Envelope Council (NBEC) conferences held every twoyears. BEST 1 promises to be an international conference thatfulfils the BETEC mission of technology transfer to mainstreamdesign, research and construction, closing the loop between re-search and practice, and at the same time challenging previousperceptions and beliefs, identifying future research needed in thatesoteric and mysterious world of building science, and presentingthe cutting edge of building science knowledge and practicestoday.

BEST 1 will be held on June 11 and 12, 2008 in Minneapolis,Minnesota. It will be hosted by the progressive BEC chapter, BECMinnesota, which is already busy organizing an event that promis-es to be an amazing step in the focus on durability and the indoorair quality of buildings. One track will be “Bugs Mold and Rot IV”,and the other will be the energy efficiency of buildings, withspeakers who are leaders in building science from all of NorthAmerica and Europe. Stay tuned, it will be an event not to miss!

Now to this edition of JBED, which is dedicated to bringingthe best technical presentations that have been presented to theBECs…and more! They have been brought to you here, for yourenjoyment and for posterity! So join me in enjoying these scholar-ly papers and we certainly welcome your comments, suggestionsand reactions.

Wagdy Anis, FAIA, LEED APChairman BETEC BoardChairman, JBED Editorial BoardPrincipal, Shepley Bulfinch Richardson and Abbott, Boston, MA

8 Journal of Building Enclosure Design

Message from BETEC

Wagdy Anis, FAIA, LEED AP

UPCOMING EVENTSDon’t forget the top conference of them all, the BETEC /

DOE / ORNL / ASHRAE Thermal Performance of the ExteriorEnvelopes of Whole Buildings X International Conference, De-cember 2-7, 2007, Sheraton Sand Key Resort, ClearwaterBeach, Florida. It is held once every three years, and is thebuilding science conference to attend! BETEC will be cele-brating its 25th anniversary there, with a special dinner youcan sign up for.

BETEC will also be holding its open board meeting and itsResearch Coordinating Committees will also be meetingduring this conference, so please participate and join BETECin its mission in bringing the best of building science to NorthAmerica.

See you there!

For more information, go to www.ornl.gov/sci/buildingsor check out the advertisement on page 49!

RECENT TRENDS TOWARDS GREENER BUILDING havebrought whole-building energy performance into the spotlight.Building and mechanical system designers typically use manufac-turer’s published R-values and U-factors in their wall and roof as-semblies to meet prescriptive building energy code requirements.However, the use of such product properties alone is not indica-tive of actual performance, since additional heat flow paths arenot accounted for in these values (for example, losses or gains dueto thermal bridging through steel stud-framed walls or discontinu-ous insulation at floor slab edges). Similarly, the reported U-fac-tors for window, door and curtain wall systems are based on labo-ratory performance testing that does not account for thesubstantial heat loss at the window perimeters that often occurs intypical window installations1. Accurate simulation of window per-formance is critical, as fenestration heat loss/gain in a buildingoften exceeds that of the opaque (insulated) walls and dominatesthe envelope loads.

This article examines the differences in calculated envelopeloads for a variety of cladding and fenestration systems using botharea-weighted manufacturer’s insulation values and integrated sim-ulation of connections, such as window-to-wall interfaces. We alsoexamine the effects of relatively minor component changes on theperformance of the whole building, including strategic selection ofwindow and glazing types, and varying insulation thickness andplacement. Based on our review, we provide strategies for maxi-mizing the effectiveness of whole-building energy simulations.

PARAMETRIC STUDY OF OVERALL R-VALUE IN A SIMULATEDBUILDING

Simpson, Gumpertz & Heger Inc. recently performed a seriesof analyses determining the effects of cladding, windows and glaz-ing types on the overall insulating value of a generic rectangular,two-story, light commercial office building. The building was mod-eled as slab-on-grade construction, with continuous R-24 roof in-sulation and continuous strip windows on the second floor only.The first floor contained no fenestration; for modeling purposeswe assumed that the first floor was fully opaque. We modeled thisbasic building using a variety of wall systems, presented in Figure1 A and Figure 1 B, summarized as follows:• Wall System 1 – Composite (uninsulated) 1/2 in. (12.7 mm)

thick metal panels over insulated (R-19 [RSI-3.35]) 6 in. (0.152m) steel studs, non-thermally broken aluminum strip windowswith insulating glass units (IGUs), and steel studs discontinuousacross the 2nd floor slab edge.

• Wall System 2 – System 1 with steel studs continuous acrossthe 2nd floor slab edge.

• Wall System 3 – System 1 with brick masonry veneer in placeof metal composite panels.

• Wall System 4 – Composite 2 in. (0.051 m) insulated (R-14[RSI-2.47]) metal panels over uninsulated 6 in. (0.152 m) steelstuds, thermally-broken aluminum strip windows, and steelstuds continuous across the 2nd floor slab edge. We determined the heat flow properties of the building


Feature

By Jason S. Der Ananian and Sean M. O’Brien, Simpson, Gupertz & Heger Inc.

Evaluating Energy Efficiency UsingWhole-Building Simulation Tools

Figure 1 A - Wall System Descriptions.

Figure 1 B - Wall System Diagrams. System 4 Note: Panels include horizontal joints at3 ft (0.9m) on center and vertical joints at 36 ft (11 m) on the center.

Wall System DescriptionsWall Cladding 6” (0.152m) R-19 (6” [0.152m]) Aluminum Thermally Broken Insulating Glass Low E Insulation Continuous atSystem Steel Stud Batt Insulation Strip Window Frames Unit (IGU) Coating 2nd Floor Slab Edge

Framing Windows

1 yes yes yes yes

1a yes yes N/A N/A N/A

1b yes yes yes yes yes

2 yes yes yes yes yes

2a yes yes yes yes yes

2b yes yes N/A N/A N/A yes

3 yes yes yes yes

3a yes yes yes yes yes

3b yes yes N/A N/A N/A

4 yes yes yes yes yes yes yes

4a yes yes N/A N/A N/A yes

4b yes yes yes yes yes yes

1/2”(2.7mm) uninsulated compositemetal panels

1/2”(2.7mm)uninsulatedcompositemetal panels

4”(0.102m)brick masonryveneer

2” (0.051m)insulated (R-14 [RSI-2.47])compositemetal panels yes

w/argon fill

Yes = System includes this featureN/A = Not applicable

enclosures using the Therm 5.2 computer program, developed bythe Lawrence Berkeley National Laboratory, a 2-dimensional,steady-state finite element simulator. For consistency, we per-formed all simulations using an interior temperature of 69.8°F(21°C) and an exterior temperature of -0.4°F (-18°C), with a 12.3mph (5.5 m/s) airflow perpendicular to the exterior surface of thecomponent, based on the NFRC 100-2001 standard for determin-ing fenestration product U-factors. We modeled all IGUs withrigid aluminum spacer bars.

We performed separate analyses of each major component ofthe building enclosure to determine their individual insulating val-ues and then calculated the weighted insulating value of the entirewall from the component values. For window perimeters, wesimulated the effects of heat transfer through the perimeter wallsin addition to heat transfer through the windows themselves. Theenclosure consists of the following components:• Base of wall (at slab-on-grade);• Field of opaque wall;• Slab edge (at second floor level);• Window sill;• Field of window (center of glass area), including vertical mul-

lion effects;• Window head; and• Roof edge (horizontal heat flow only).

We determined the boundaries of our model for each compo-nent by reviewing the initial simulation results to establish the adia-batic end conditions—the points at which heat flow occurs in onlyone dimension, then “cutting” the section in that location. Figure2 illustrates this concept for an example window sill cross section.

For simple, layered systems of building materials with heatflow in one dimension, such as concrete block walls with continu-ous insulation, the overall R-value (expressed in (hr*ft2*°F)/btu[m2*K/W]) is simply the sum of all component R-values: Roverall = Rlayer1 + Rlayer2 + ….. + RlayerX (equation 1)

In this case, adding continuous R-5 (RSI-0.88) insulation to anR-10 (RSI-1.76) wall will increase the overall insulating value to R-15 (RSI-2.64). This is also known as “series” heat flow.

The overall R-value was chosen as the final indicator of thermalperformance, as R-values are more commonly recognized than

their inverse, the overall heat transfer coefficient, or “U-factor”(btu/(hr*ft2*°F [w/m2K]). The U-factor is a measure of the totalheat flow through a given material thickness (or a given compo-nent) by conduction, convection and radiation. It is commonlyused to define a weighted average conductance for the variousmaterials in an assembly. When applied to windows, the U-factoraccounts for convection and radiation within and between airspaces in glazing systems. The relationship between the U-factorand the overall R-value is: Roverall = 1 / Uoverall (equation 2)

Hence, the overall R-values that we calculated account forconvection and radiation in addition to conduction.

For multi-dimensional heat transfer, U-factors must be used tocalculate overall heat flow. This is due to the physical phenome-non of heat flow occurring along the path of least resistance, alsoknown as “parallel” heat flow. Since all of the components that weanalyzed were of different size, we performed an area-weightedcalculation to determine the composite U-factors for the wall sys-tem, based on a unit width of 12 in. (0.3 m): Uoverall = (Area1 * U1 + Area2 *U2 + ….. + AreaX *UX) /(Area1 + Area2 + ….. + AreaX) (equation 3)

Using U-factors in Equation 3 takes into account the increasedheat flow through conductive components, such as steel studs,placed in parallel with non-conductive components such as insula-tion. Where these parallel heat flow paths exist, adding R-5 insula-tion to the stud cavity will not necessarily produce a correspon-ding R-5 increase in the overall R-value of the system, as thepotential effect of insulation is reduced by the increased heat lossthrough the other components of the system.

GENERAL RESULTS OF OVERALL R-VALUE STUDYUsing the equations above, we calculated overall R-values for

each system. Figure 3 presents the calculated overall R-values forthe systems analyzed.

THERMAL BRIDGING AND INSULATION DISCONTINUITIESThermal bridging through steel studs or discontinuities in insu-

lation at floor slab edges leads to relatively high heat loss from thevarious wall components.2 Given its relatively low weight, highstrength and ease of erection in the field, light-gauge steel framing

Summer 2007 11

Figure 2 - Selection of component size. Figure 3 - Overall system R-values.

System Overall R-Value (RSI-value)1 4.8 (0.85)

1a 10.8 (1.9)

1b 5.5 (0.97)

2 5.0 (0.88)

2a 5.7 (1.0)

2b 11.6 (2.0)

3 4.8 (0.85)

3a 5.4 (0.95)

3b 10.2 (1.8)

4 7.1 (1.25)

4a 12.6 (2.22)

4b 7.5 (1.32)

is widely used for both interior and exterior building walls. Howev-er, steel is also a highly conductive material, with a thermal conduc-tivity more than 1000 times that of typical building insulation. In atypical sheathed wall with glass fiber batt insulation between steelstuds spaced 16 in. on center, the studs create an efficient path forheat to bypass the insulation (Figure 4). The addition of steel studstypically reduces the overall R-value of the wall by approximately 50percent. This loss is accounted for in some energy codes throughrequirements for continuous insulation outboard of steel-framedwalls. The addition of continuous insulation outboard of the studs,which helps to isolate them from the exterior of the building, resultsin a slight reduction in the effects of thermal bridging through thestuds. The net effect of this reduction is often an increase in overallR-value that exceeds the R-value of the insulation component alone.

Similarly, although to a lesser degree, joints between the insulat-ed metal panels analyzed in System 4 have thinner or no insulation.The effect of these discontinuities at the panel joints alone reducesthe overall insulating value of the panels by approximately 10 to 15percent.

In some steel stud-framed buildings, the studs on each level aresupported on floor slabs that bypass the stud cavity insulation. Ther-mal inefficiencies, such as these slab edges (Figure 5), can have siz-able impacts on building performance. The clearest example of this is between Systems 1a and 2b, where insulating the

slab edge improves the overall R-value of the enclosure by approxi-mately 8 percent. Comparing the basic component R-values to theoverall system R-values in Figure 3, it becomes clear that simplecalculations based on product data can significantly overestimatethe overall thermal performance of a wall system.

FENESTRATIONWindows, curtain walls and other components typically have

much less thermal resistance than opaque wall and roof sections. Modern aluminum-framed assemblies employ features such as

multi-pane IGUs and low-conductivity thermal breaks to reduceheat flow. However, due to the already low thermal resistance ofthese components, even properly functioning assemblies may ex-perience condensation problems. Consequently, small thermalbridges through framing members and perimeter constructions canhave a significant impact on overall heat loss. To minimize the riskof these problems, the insulating components should be made con-tinuous with the insulation in the adjacent construction.

Due to the nature of parallel heat flow, a disproportionateamount of heat is lost through building windows when compared totheir contribution to building surface area. Comparing Systems 1with 1a, the R-value of the windowless wall system is nearly doublethe R-value of the wall system when windows are included. This issomewhat counterintuitive, as the windows account for less than 20percent of the overall building surface area (not including the roof)The use of thermally broken windows can have a significant impacton overall R-values, as the windows are typically a primary source ofheat loss. Figure 6 shows a graphic temperature plot of the System1 vs. System 4 windows. Without complete thermal breaks, theSystem 1 windows remain significantly colder and have less than halfof the insulating value of the thermally-broken System 4 windows.In some buildings, cold frame temperatures may contribute to con-densation problems as well as increased heating and cooling costs.

GLAZING SELECTION Selection of glazing systems can have significant impacts on

overall system performance. Figure 7 presents the center-of-glassthermal resistance and Solar Heat Gain Coefficients (SHGCs) forthe glazing systems used in the study. The SHGC is the fraction ofincident solar radiation that is transmitted through the system. A


Figure 4 - Computer simulation results showing effects of thermal bridging throughsteel framing.

Figure 5 - Computer simulation results showing effects of thermal bridging at slab edges.Figure 6 - Computer simulation results showing the effects of thermally brokenwindow frames.

SGHC of 0.702 means that 70.2 percent of incident solar radiation istransmitted through the glazing. Consequently, a lower coefficientrepresents a decrease in solar heat gain, which can increase heatingloads but decrease cooling loads. For example, the addition of a low-e coating (e=0.04) to the IGUs in System 1 provides a 15 percent in-crease in the overall R-value of the building enclosure—a significantincrease in performance relative to the cost of adding the coating.

Small changes such as the addition of argon gas to improve IGUperformance can also have moderate impacts on overall enclosureR-values. For example, the addition of argon-fill to IGUs with a low-ecoating in System 4 provides a 6 percent increase in overall R-valuefor the building enclosure. As with the low-e coating discussedabove, this is a significant increase in performance given the relativelylow cost of the argon fill.

PARAMETRIC STUDY OF WHOLE-BUILDING ENERGY REQUIREMENTS INA SIMULATED BUILDING

Utilizing the overall R-value (Figure 3) and SHGC data (Figure7), we performed a series of whole-building energy simulations of allvariants of Systems 1 and 4 for the generic office building describedin Section 1.1. We used the EnergyPlus 1.4 computer program, de-veloped by the U.S. Department of Energy to simulate the effects oftime-varying interior and exterior environmental conditions, as wellas the effects of solar radiation (i.e., solar heat grain through win-dows) and internal heat loads.

All options were analyzed using slab-on-grade construction and aflat roof system with R-24 insulation. The simulated rectangularbuilding (100 ft [30.48 m] x 75 ft [22.86 m] in plan) was orientedwith the long dimension on an east-west axis. The building includedtwo stories with opaque walls on the first floor and continuousperimeter strip windows on the second floor.

In order to provide a more realistic estimate of building envelopeloads, simulated occupant and occupant-related loads for a typical of-fice building were used. All simulations included basic heating andcooling systems, as the goal of this analysis was a generic comparisonof system performance. For these models, the simulated mechanicalsystem provided exactly enough heating, cooling, and ventilation tomeet the building loads based on a prescribed occupancy schedule.

GENERAL RESULTS OF WHOLE-BUILDING ENERGY ANALYSESFigure 8 presents the total heating and cooling energy calculated

for all variants of Systems 1 and 4. In addition, the peak cooling loadfor each system is presented in the last column. The peak coolingload is the maximum cooling power of the system, and representsthe cooling power required to maintain the design interior tempera-ture on a summer design day.

The results from the whole-building energy simulation for thebuilding heating loads are generally consistent with the results fromour overall R-value simulations. The internal heat loads, such as peo-ple and equipment, that we simulated will reduce the heating de-mand for mechanical system in the building, since they provide addi-tional heat to the space. For alternate occupancies in a similarbuilding, such as residential or retail spaces, the mechanical systemloads may be greater due to the lack of this additional heat. Internalbuilding loads, combined with solar heat gain through windows, pro-vide 100 percent of the winter heating requirements for the Miami,FL cases.

In general, the building heating loads make up less than 10 per-cent of the total load, with the remaining 90 percent attributed tocooling. The effects of latent (moisture) loads or the use of “econo-mizer” cooling are not included in this simulation. Simulation of thesevariables is relatively complex, involves the selection of specific me-chanical system components and equipment sizes, and is beyond thescope of a general comparison.

Due to the complexity of building cooling loads, the comparativeloads that we calculated may not represent the actual cooling loadsthat a real-world building would experience. However, the resultsdo illustrate several relevant trends:• System 4a vs. System 1a (Chicago): System 4a, despite having a

more efficient building envelope, has a slightly higher overall cool-ing load than the less efficient System 1a. This appears to be dueto the higher insulating value of the walls and windows retainingmore heat from interior sources. The same occurs between Sys-tem 4 and System 4a in Miami. The use of argon-filled IGUs in-creases the thermal resistance of the envelope, but as a result re-duces the loss of heat from interior sources and increases thecooling loads.

• System 4 vs. System 4a (Miami): The overall cooling load for abuilding without windows (System 4a) is over 25 percent lessthan the building with windows. This illustrates the potentiallysignificant contributions of windows to building cooling loads.

Summer 2007 13

Figure 8 - Summary of Heating and Cooling Energy for Wall Systems.

Figure 7 - Insulating Glass Unit performance characteristics.

1/4” (6.35mm) clear 2.1 - 0.702 -

glass, 1/2 (12.7mm)

airspace, 1/4” (6.35mm)

clear glass

1/4” (6.35mm) clear 3.4 62% 0.378 46%

glass w/low-e

(e=0.04) coating on #2

surface, 1/2” (12.7mm)

airspace, 1/4" (6.35mm)

clear glass

1/4" (6.35mm) clear 4.1 21% 0.374 46%

glass w/ low-e (e=0.04)

coating on # 2 surface,

1/2" (12.7mm) argon fill,

1/4 (6.35mm) clear glass

Glazing Assembly (all Effective % SHGC* %dimensions nominal) R-value Increase Decrease

* SHGC = Solar Heat Gain Coefficient

System Windows Heating Energy Cooling Energy Total Load Peak Cooling Load

1 – Chicago Non low-e 39,470,492 323,137,208 362,607,700 207,174

4 – Chicago Low-e 22,544,532 315,256,842 337,801,374 189,017

42.88% 2.44% 6.84% 8.76%

1 – Miami Non low-e 0 627,430,538 627,430,538 206,607

4 – Miami Low-e 0 584,980,452 584,980,452 188,132

0.00% 6.77% 6.77% 8.94%

1a – Chicago None 21,199,529 251,632,630 272,832,159 155,850

4a - Chicago None 17,372,286 256,052,105 273,424,391 154,500

18.05% -1.76% -0.22% 0.87%

1a – Miami None 0 474, 399,687 474,399,687 167,434

4a – Miami None 0 474,130,258 474,130,258 167,763

0.00% 0.06% 0.06% -0.20%

1b – Chicago Low-e 32,914,018 304,873,553 337,787,571 192,933

4b – Chicago Argon low-e 19,935,520 320,255,018 340,190,538 188,841

39.43% -5.05% -0.71% 2.12%

1b – Miami Low-e 0 585,744,457 585,744,457 191,923

4b – Miami Argon low-e 0 587,420,462 587,420,462 188,172

0.00% -0.29% -0.29% 1.95%Percentages listed represent reduction (or increase) in loads

Yearly Totals Whole Building (btu)

• System 1b vs. System 1 (Miami); The use of low-e coated IGUs(System 1b) reduces the overall building cooling load by approxi-mately 7 percent. In addition, the building heating load is reducedby 20 percent when low-e IGUs are included. These incrementalimprovements justify the added material expense of low-e IGUs.Also of interest is the peak cooling load, which determines therequired capacity of the mechanical cooling equipment. Whileoverall energy usage will determine space conditioning costs,lowering the peak cooling load for a building may produce an up-front cost savings if the cooling equipment can be downsized.

CONCLUSIONSCode prescribed R-values for wall/roof assemblies, when used

exclusively in building designs, generally do not account for heat flowdue to thermal bridging at structural components, window sur-rounds and floor slabs. In addition, they do not account for solar heatgains as dictated by fenestration selection and placement, or glazingtype. Consequently, the use of product R-values to generate energyload estimates is an oversimplification of actual performance charac-teristics and may result in misguided expectations and inadequateperformance of installed heating and cooling equipment. Our com-parative R-value calculations and whole-building energy simulationsshow that relatively small details, such as the use steel stud framingor low-e glazing, can significantly influence the required loads for abuilding depending on the climate zone in which the building is located, underscoring the need for careful analysis of whole-buildingenergy performance.

Whole building simulations can also provide designers with a rela-tively inexpensive method of performing cost-benefit and life-cyclecosting analysis on alternate building components. This may rangefrom selecting alternate glazing systems to optimizing the location ofwindows to maximize winter heat gain (reducing heating loads) andminimize summer heat gain (reducing cooling loads). This type of op-timization is not possible with traditional, steady-state load calcula-tions.

Based on our analysis, we present the following guidelines for de-termination of whole-building energy performance:• Do not rely solely on product or code-prescribed R-values as a

measure of thermal performance.• Calculate the performance of individual building envelope com-

ponents, especially the intersections between assemblies such asopaque walls and windows, to determine the effects of these in-tersections on the overall system performance.

• Calculate effective R-values for entire wall sections from theircomponent parts for use in whole-building simulations. Eachunique wall section and glazing system should be modeled sepa-rately.

• Apparently minor changes in occupancy or mechanical equip-ment can have significant impacts on overall building perform-ance. These aspects of the building should be modeled to matchthe actual building use and construction as closely as possible toprovide a more realistic estimate of overall energy consumption.

• Parametric analysis of building system options, including glazingorientation, can be used once a model is complete to performcost-benefit analysis of building options and optimize the overallperformance of the building. Given the relative ease with whichan options analysis can be performed, the potential for long-termenergy savings is likely to far outweigh the up-front cost of theanalysis. As energy prices climb higher and the demand for “greener”

buildings increases, the use of whole-building energy simulation isevolving from a purely academic exercise to a critical tool in buildingdesign. �

Some of the analysis discussed in this article is derived from a re-cent project with CENTRIA Architectural Systems that includedthermal simulation of their Formawall Dimension Series insulatedmetal panels.

Jason Der Ananian is a Senior Engineer in the Boston office of Simp-son, Gumpertz & Heger Inc. He can be reached [email protected]. Sean O’Brien is a Senior Staff Engineer in theNew York City office of Simpson, Gumpertz & Heger Inc. He can bereached at [email protected].


REFERENCES1. O’Brien, S.M., “Finding a Better Measure of Fenestration

Performance: An Analysis of the AAMA Condensation Re-sistance Factor”, RCI Interface, May 2005.

2. O’Brien, S.M., “Thermal Bridging in the Building Envelope:Maximizing insulation effectiveness through careful de-sign”, The Construction Specifier, October 2006.

INTRODUCTIONBrick is one of the oldest building prod-

ucts, being used in many ancient structures,yet still remains a popular and competitivewall cladding today. Brick is very durable,producing a long product life, greater than100 years, with very little maintenance re-quirements. Brick contributes to air qualityby eliminating the need for paint or adheredfinishes, thereby reducing volatile organiccompounds (VOCs). Brick reduces the po-tential for mold growth. Fire safety andwind-borne debris impact resistance are in-creased with brick construction. Bricks donot emit toxins to the environment whenexposed to fire. Bricks provide thermalmass, reducing energy requirements byslowing the transfer of heat and cold. Brickare typically manufactured regionally, so thetransportation distance is minimized. Brickscan be recycled, with old brick, culled brickfrom the manufacturing process, and wastebrick from construction, being ground upand used for landscaping chips and brickdust. Brick produces no hazardous waste.

Brick provides many advantages as an exte-rior wall covering.

Brick manufacturing was mechanized inthe late 1800s with the development of ma-chines to produce molded brick (Borcheltand Carrier, 2007). These bricks were solid,with no cores. The extrusion manufacturingprocess was developed in 1875, and is stillin use today. Although the original extrudedbrick did not contain any cores, manufac-turers were soon producing cored brick, asthis resulted in reduced weight and im-proved drying and burning characteristics.The current specification for facing brick,ASTM C 216, was first introduced in 1947.The brick could have up to 25 percent cor-ing, and was considered to be solid forstrength calculations. This has remained un-changed until today. In 1967, a change wasproposed to C 216 that would allow up to40 percent coring. Rather than incorporatethe increased coring into C 216, ASTM C652 was introduced in 1970 as a specifica-tion for hollow brick. Currently, ASTM rec-ognizes both C 216 and C 652 as facing


Feature

By Richard Bennett, University of Tennessee andJim Bryja, General Shale Products Corp.

ASTM C 652 Bricks: Less is Good

Figure 1 - Comparison of ASTM C 216 solid brick (25 percent coring) with C 652 hollow brick (28 and 32 percent coring).

brick. The specifications have similar re-quirements for durability, appearance andtolerances on chippage, distortion and size.The primary difference is the amount ofcoring.

Due to advances in the manufacturingprocess, brick manufacturers are increas-ingly producing hollow facing brick, whichhas greater than 25 percent coring. Figures1 and 2 compare bricks with differentamounts of coring. This paper examinessome of the aspects of hollow bricks.

PROPERTIES OF HOLLOW BRICKSPhysical properties

Hollow facing brick will have voids inthe 26-35 percent range for typical brickveneers, as opposed to the current 25 per-cent. This will reduce the weight of thebrick. Modular size bricks, 7 5/8 x 2 1/4 x 31/2 in. (194 x 57 x 89 mm), will weighabout 1/3 pound (1 1/2 N) less; engineersize bricks, 7 5/8 x 2 3/4 x 3 1/2 in. (194 x70 x 89 mm), will weigh about 1/2 pound(2 1/4 N) less.

The National Brick Research Center(Sanders, 2006) examined the physicalproperties of over ten different brick types.For each brick type, a hollow brick wascompared to a solid brick. Properties ex-amined were compressive strength, flexuralbond strength, cold water absorption, boil-ing water absorption, saturation coefficient(C/B ratio) and the initial rate of absorption.For all brick types there was no significantdifference between the properties of thehollow brick and the solid brick. Hollowbrick can be expected to behave similarly tosolid brick, having the same durability andsimilar structural performance properties.

Fire resistanceThe fire rating of masonry is determined

based on the equivalent thickness. Theequivalent thickness is simply the actualbrick thickness times the percent solid. Fora given actual thickness, a hollow brick willhave a smaller equivalent net thickness thana solid brick. However, codes allow a higher

rating per equivalent thickness for hollowbrick than solid brick. This is based on actualtesting and the fact that air is an excellent in-sulator. Based on the 2006 InternationalBuilding Code, ASTM C 216 solid brick (ac-tual 25 percent coring) will have approxi-mately a 1 hour rating. A hollow brick with30 percent voids will have a rating of ap-proximately 1.1 hours or greater than theASTM C 216 brick.

Thermal performanceBrick veneer walls are known to improve

the thermal performance of structures dueto their thermal mass. Thermal mass has thedesirable properties of reducing the ampli-tudes of, and delaying in time, heat transfersthrough building sections under real world,dynamic conditions. Experimental work andmonitoring of test structures has shown thatbrick veneer structures do save heating andcooling energy.

Brown and Stephenson (1993) testedseven different wall specimens using a guard-ed hot box. One specimen was a 3 1/2 in.(90 mm) steel stud wall with 1/2 in. (12 mm)gypsum on the interior and exterior, R-12glass fiber insulation between the studs, and1.0 in. (25 mm) stucco on the exterior face.A similar specimen had 3 1/2 in. (90 mm)brick veneer with a 1 in. (25 mm) airspace.The brick veneer over steel stud wall speci-men had a measured thermal transmittance,the U-value, of 30 percent less than thetransmittance of the stucco over steel studwall specimen. Biblis (2005) monitored theactual energy consumption of ten differenttest houses in Auburn, Alabama. The unitwith plywood siding used 5.1 percent moreenergy in the cooling period from June 8 toSeptember 15, and 9.2 percent more energyin the heating period from January 1 to April4 than the brick veneer structure.

The enhanced energy performance ofbrick veneer structures comes from twosources. One source is the mass of the brickand the other source is the insulating valueof the brick and cavity. Obviously reducingthe mass of a brick by increasing the coringwould reduce the thermal mass benefits ofthe brick. However, hollow brick have bet-ter insulating properties than a solid brickdue to the air in the voids.

Simulation of the energy use of buildingsin Chicago, San Francisco, Denver, Tampaand Washington showed virtually identicalthermal performance of C 216 and C 652

bricks (Bennett et al, 2007). The decreasein thermal mass was offset by the increasedthermal resistance. The use of hollow brickwill not reduce the known energy benefitsof brick.

CONSTRUCTION WITH HOLLOW BRICKSAlthough the use of hollow brick may

result in a slight increase in mortar usage,studies performed at the National Brick Re-search Center (Sanders, 2006) and by abrick manufacturer showed the increase tonot exceed the industry standard estimateof seven bags of mortar per 1000 brick.

Masonry walls of hollow brick have thesame resistance to moisture penetration aswalls made of solid brick. The most impor-tant factor in reducing permeability is work-manship, irrespective of the type of mason-ry unit (Grimm, 1987). Modern day cavitydrainage wall construction also provides ex-cellent moisture resistance, even if waterdoes penetrate the brick wall.

The reduced weight of hollow brickmakes it easier on the laborer and themason. The coring percentages with hollowfacing brick are not sufficiently large to re-quire face shell bedding. The mason caneasily make a full bed, with furrowed mor-tar, identical to current construction prac-tice. In other words, hollow brick can belaid in the same manner, and with the sameproductivity, as solid brick, with the lighterweight reducing mason fatigue.

Hollow brick construction will result in

Summer 2007 17

Figure 2 - Comparison of ASTM C 216 solid brick (22 percent coring) with C 652 hollow brick (30 and 34 percent coring).

wall claddings with less mass, which is ofbenefit in seismic and structural design. Theforce in seismic design is directly propor-tional to the mass, so a reduced mass re-sults in a smaller force. With more munici-palities across the country adopting seismiccodes, including areas where there hasnever been seismic design, the use of hol-low brick will be advantageous. The lighterweight also reduces the load on founda-tions, lintels and shelf angles.

ENVIRONMENTAL BENEFITS OF HOLLOWBRICKS

Environmental aspects, or the “green-ness” of a project, are measured in severalways. Three ways will be examined here;the National Home Builders Association(NAHB) Green Homebuilding Guidelines,the National Institute for Standards andTechnology Building for Environment andEconomic Sustainability (BEES), and theU.S. Green Building Council Leadership inEnergy and Environmental Design (LEED).

The National Home Builders Associa-tion (NAHB) specifically mentions C 652hollow brick as an alternative to C 216brick under the second guiding principle,Resource Efficiency, of the Green HomeGuidelines. The National Institute for Stan-dards and Technology Building for Environ-ment and Economic Sustainability (BEES)program is a systematic methodology forselecting building products that achieve the most appropriate balance between

environmental and economic performancebased on the decision maker’s values. TheBEES analysis is based on the weight of abrick. Lighter weight brick reduce emis-sions during manufacturing and require lessfuel for shipping. The typical flatbed truckcan haul 26 cubes of C652 brick as com-pared with 23 cubes of C216 brick, aneleven percent savings for a trip.

Brick construction enables a designer toachieve several LEED points in a single ma-terial. These include Materials and Re-sources 5.1 credits the use of materials ex-tracted and manufactured within 500 miles

of the construction site. These LEED creditpoints can be met by selection of face brick asan exterior material, and can be enhanced bythe choice of hollow brick over solid brick.

CONCLUSIONSHollow bricks are increasingly being pro-

duced by brick manufacturers. They come inthe same sizes, types, colors and textures assolid brick. Hollow brick have similar physi-cal properties to solid brick and provideequivalent or slightly better performancecharacteristics. Hollow brick provide important environmental benefits, reducing


REFERENCESASTM C 216-07, Standard Specifica-

tion for Facing Brick (Solid MasonryUnits Made from Clay or Shale).

ASTM C 652-05a, Standard Specifica-tion for Hollow Brick (Hollow MasonryUnits Made from Clay or Shale).

Bennett, R.M., Kelso, R., and Bryja, J.(2007). “Thermal Performance of Hol-low Brick Veneer Walls.” 10th NorthAmerican Masonry Conference, TheMasonry Society, 158-164.

Biblis, E.J., “Experimental Determina-tion of the Energy Requirements forCooling and Heating Different Single-story Residential Structures.” ForestProducts Journal, 55(3), 2005, pp. 81-85.

Borchelt, J.G., and Carrier, J. (2007).“The History of Void Area and Face ShellThickness Requirements in USA Brick.”10th North American Masonry Confer-ence, The Masonry Society, 584-595.

Brown, W.C., and D.G. Stephenson,“Guarded Hot Box Measurements of theDynamic Heat Transmission Characteris-tics of Seven Wall Specimens – part II.”Transactions, ASHRAE, 99(1), 1993, pp.643-660.

Grimm, C.T. (1987). “Water Perme-ance of Masonry Walls: A Review of theLiterature.” Masonry: Materials, Proper-ties, and Performance, ASTM SpecialTechnical Publication 778, 178-199.

NAHB Model Green HomebuildingGuidelines (2006). National HomeBuilders Association.

Sanders, J.P. (2006). The Effect ofVoid Area on Wall System Performance.National Brick Research Center, Clem-son University, Anderson, SC.

environmental impacts both in manufactur-ing and transportation. Hollow brick en-hance the already substantial benefits ofbrick construction. �

Richard Bennett, PhD, PE, is professor of civiland environmental engineering at the Univer-sity of Tennessee. He is a member of ASTMand the Masonry Building Code Committee.Jim Bryja, PE, SE, is manager of engineeringservices at General Shale Products Corp.,Johnson City, Tennessee. He chairs the Na-tional Brick Research Center (NBRC) WallSystems Committee.

THE WALL PERFORMS A number of functions. The elements responsible forperforming these functions must be continuous throughout an enclosure, particu-larly at the transitions (for example, at the interfaces of fenestration with adjacentassemblies). A discontinuity almost always causes a functional weakness or out-right failure. In my practice I use a system of layering that helps me accomplish

the principles of facade engi-neering. I visualize layers forwaterproofing, thermal insula-tion, vapor retarder, air barrier,etc. The goal is to keep all lay-ers continuous, no matterwhat part of vertical or hori-zontal section of building enve-lope is analyzed.

Figure 1 and Figure 2 arean example of an analysis per-formed on curtain wall details.The building enclosure’s layersare represented with colored,dashed lines. In this example,not only are all the major lay-ers kept continuous, but alsono sealant is used to performany essential facade function.This type of rainscreen detail isseldom seen in the U.S. Therain screen wall is unfamiliar tomany contractors and comeswith a greater initial cost forowners.

The typical layers include:weather screen, insect or birdscreen, vapor-permeable wa-terproofing, vapor-imperme-able waterproofing, thermal in-

sulation, acoustical insulation, fire isolation,smoke isolation, vapor barrier and air seal.Special layers may include blast resistance,burglar resistance and bullet resistance.

Most of these functions can also betagged with the required unit and value, forexample fire rating min 1hr, vapor retardermax 1 perm (57 ng/s•m2•Pa), air barrier min45 psf (2,155Pa), etc. This is particularlyuseful where the values change, for exam-ple where horizontally positioned R20 (RSI-3.10) insulation transitions into vertical R10(RSI- 1.76) insulation.


Feature

By Karol Kazmierczak and Dan Neeb, Halliwell Engineering Associates

Transitions:

Figure 1. Details to be analyzed.

Figure 2. Analysis of details.

Figure 4.

How to Design Facade Interfaces

Figure 3.

Bird screen interrupted at each mullion of a stepped curtain wall.

Some materials perform more thanone function. The most demanding appli-cations will require particular focus on thechoice of the proper material and connec-tions. In this example, the perimetermembrane acts as the waterproofingmembrane, the vapor retarder, and theair barrier all in one. In this case the mostdemanding function is the air barrier be-cause a membrane material has to resistperhaps 20psf (958Pa) positive and nega-tive pressure differential or more, andtransfer the load to the assembly. Designwind pressure establishes the perform-ance criteria and describes the in-serviceneed for physical durability of the layer, asopposed to the 1.57psf (75Pa) air perme-ance testing pressure listed in ASTME2178 which merely establishes accept-ability as an air barrier material.

In Figure 1 and Figure 2, one wouldspecify a thick, puncture-and-tear-resist-ant elastomeric membrane, mechanicallyclamped at its terminations. A metal flash-ing would be inappropriate because of thevertical movement the flashing has to ac-commodate at the head.

Once one determines exactly whatfunction is performed by the particularmaterial, one is more likely to avoid com-mon mistakes. One common mistake inthis example is the placement of insula-tion below the bottom mullion and abovethe top mullion. As a result of this action,condensation forms on the interior side ofthe vapor barrier in cold climates. Onceone realizes where the vapor barrier is lo-cated, this mistake should not happen.See Figure 5, reprinted from “Glass andMetal Curtain Wall Systems” (R. L.Quirouette, http://irc.nrc-cnrc.gc.ca/pubs/bsi/82-3_e.html).

All sections of the enclosure openinghave to be designed in one process: jamb,head, spandrel, sill, etc. The layers pic-tured at each section must be located atthe same respective wall depth and posi-tion around a perimeter of an opening.Otherwise, a wall would be non-con-structible, or gaps in the corners wouldbe created. A common error of this kindis demonstrated by the two details repro-duced below which belong to the same,straight masonry opening, according tothe elevation.

Note in Figure 6 how the distancebetween the face of the curtain wall and

the brick veneer varies. The analysis ofthe weather shield continuity allows foran early detection of such an error. Theanalysis of the details above reveals alsosome other problems. We encourage thereader to analyze these details in context(available at www.wbdg.org/design) andcompare with the logic presented in thisdiscussion.

The major facade layers are penetrated

at the anchors. The support functionshould be decoupled from the need forsealing; these two functions are typicallydone by different trades and specifiedseparately. See Figure 7. The thermal in-sulation is discontinuous, bridged by con-ducting elements and the vapor retarderis placed on its outer side, suggesting thedetails are unsuitable for a cold or mixedclimate. Note the incorrect placement of

Summer 2007 21

Figure 5. Source: R.L. Quirouette, “Glass and Metal Curtain Wall Systems”.

Figure 6.

Figure 7.

air barrier, sealed to the non-continuous bottom tran-som. This error is particularly evident at the corners of acurtain wall. This is also a potential problem when a de-signer decides to use a transom different than a mullion,either for economy or aesthetics—see Figure 8 show-ing a corner of a curtain wall sill.

The principle of continuity holds true no matter whatscale is considered. In the scale of the whole building, adesigner has to determine where the layers are locatedwith regard to all rooms and partitions. Typically, the for-gotten spaces are those above suspended ceilings ofoverhangs, resulting in bursting, frozen plumbing in coldclimates. According to ASHRAE statistics, frozen sprin-kler pipes are the biggest single cause of mold in NewYork City.

See Figure 9 showing the properly conditionedoverhang space and the photograph showing the uncon-ditioned space separated thermally from the building bythe insulated wall. See Figure 10 for magnified detail ofthe curtain wall head from the good example above.

A different, but equally important example is a fre-quent violation of fire and smoke compartmentalizationin cavity walls. Typically a rated slab is bypassed by anexterior wall cavity, which in turn opens to the buildinginterior at deflection joints, and is not sealed by ratedmaterials at the fenestration openings’ perimeters aboveand below.

Fire and smoke transmission among compartments isfurther assured by stack or chimney effect. See Figure11 for detailed drawings of a masonry wall with a looselintel in a high-rise building and the photographs taken inFigure 13 and Figure 14, in the field. In this example,the outer sheathing of the backup wall is made of com-bustible plastic foam. The distance between the looselintels and the slabs varies from floor to floor; the result-ing gap effectively connects compartments. The design-er not only forgot about the fire code, the building is lo-cated in a cold climate zone too. As a result, the risk ofcondensation is increased because the thermal insulationlayer is interrupted, and is unprotected by a vapor re-tarder; thermal bridging is effected by concrete, metal,and wood elements. The spacing of brick veneer ties donot meet code, but this problem is irrelevant to the cur-rent discussion. See Figure 12.

The photos in Figure 13 were taken when the brickveneer was already being erected, after the substratehad been accepted by the masons. The joints aroundwall panels remained unsealed; an observer can seethrough the crack. Moisture problems are likely to de-velop due to the condensation induced by an unpre-dictable pattern of air leakage and discontinuity of thedrainage plane. The mechanical system may negativelypressurize the interior walls and suck the humid outsideair inside in summer; a positive pressure in the apart-ments would blow the moist interior air to the outsidein winter. The interruptions of both the lintel and thethru-wall flashing ensure chimney effect in the wall


Figure 11.

Figure 10.

Figure 8. Examples of transom discontinuity.

Figure 9.

cavity. A transfer of insects, odors and sound among apart-ments through the open cavity are among probable side ef-fects.

The photos in Figure 14 show the misalignment betweenthe face of insulating sheathing and concrete. The tape readsover 2 in. (5 cm). In the above drawings, construction toler-ances, particularly the cast-in place concrete tolerance is notanticipated. The air barrier was installed in a discontinuousfashion which creates problems.

Continuity must also be maintained through movementjoints. An average curtain wall typically has several movementjoints differing in direction and magnitude of designed move-ment. Typically the floor deflection joints are most vulnerable.Each layer has to be constructed in such a way as to accom-modate the designed movement.

The process of design sometimes requires compromises. Ifyou follow this method, you will soon discover that manypopular design practices, materials and systems don’t work,and no economical method may exist to solve the problemand keep the layers continuous. Remember, there are twoprice tags attached to each compromise: the long term costand the initial cost. Many good solutions are available fromcountries employing sophisticated construction techniques, in-cluding Great Britain, Germany and Canada. My favorite ex-ample is thermally broken lintels and balcony slab systemsproduced by foreign manufacturers. See Figure 15 and Fig-ure 16. There is an increasing demand for them in NorthAmerica. �

Karol Kazmierczak is a forensic building enclosure specialist at Halliwell Engineering Associates. He is a registered architect inNew York and is the founding chairman of the Miami Building En-closure Council. He specializes in curtain walls and architecturalglass with particular focus on thermodynamics. Dan Neeb is a Senior Forensic Architect for Halliwell Engineering Associates. He is entering his twenty fifth year in practice as a Registered Architect and, in that capacity, has provided investiga-tive and analytical services in a variety of projects, ranging fromcomplete systemic envelope failure as a result of catastrophicevents to component failures associated with construction de-fects.

Summer 2007 23

SUGGESTED LITERATURE:American Society of Heating, Refrigerating, and Air-Conditioning

Engineers, “Applications Handbook” Chapter 42 “Building En-velopes.”

R.L. Quirouette, “Glass and Metal Curtain Wall Systems.” NRC,1982. http://irc.nrc-cnrc.gc.ca/pubs/bsi/82-3_e.html

Thomas Herzog, “Facade Construction Manual.” Birkhauser,2004.

Figure 16.

Figure 12.

Figure 13.

Figure 14.

Figure 15.

JOINT BTW. STUD WALL AND CONC. COLUMN INTERRUPTION OF BOTH LINTEL AND FLASHING

MISALIGNMENT BTW. STUD WALL AND CONCRETE SLAB INTERRUPTION OF BOTH INSULATION AND AIR BARRIER

THE GLAZED ALUMINUM WINDOWwall synonymous with high-rise, multi-fam-ily residential construction reflects a con-tinuing trend toward transparency withinthe practice of architecture, more typicalof its commercial office building context.Through the window walls’ aesthetic asso-ciation to curtain wall, it appears to havecreated for itself a cost-driven nichethroughout major United States cities, yetclear performance criteria and compre-hensive details are still needed to ensure asuccessful project.

MODERNIST ORIGINSOriginal window wall compositions,

which some could argue may be tracedback to the early decades of Modernism,relied principally upon a “barrier” ap-proach to resist rainwater penetration.However, as air and water leakage prob-lems became systemic, the design of thewindow wall adopted similar principles torain screen design, including secondaryflashings, receptors and sub-sills, heel-beads in the glazing pocket, back-panssealed to framing at opaque panels and in-ternally-drained systems to overcomethese issues.1

Throughout the United States today,the Modern aesthetic has been adopted bydesigners of high-rise residential buildings.

However, many construction documentslack informed criteria for window wallperformance, including design pressure, airand water penetration resistance, andglazing systems coordinated with thestructural and mechanical characteristics ofthe specific building design—all informa-tion critical in procuring and installing asystem that will meet the expectations ofthe owner and end-user with regard tolong term durability and performance.

INDUSTRY DEFINITIONPerhaps some of the confusion is due

to the lack of a clear definition of a win-dow wall. While industry guidelines can beuseful in defining the general configurationof each system, performance definitionsare less clear. Consider the following wide-ly held definitions:• Fenestration: Openings in a building

wall, such as windows, skylights andglass doors designed to permit the pas-sage of air, light or people.2

• Curtain Wall: Any building wall, of anymaterial, which carries no superim-posed vertical loads, i.e. any “non-bear-ing” wall.3

• Metal Curtain Wall: An exterior cur-tain wall which may consist entirely orprincipally of metal, or may be a com-bination of metal, glass and other

surfacing materials supported by orwithin a metal framework.4

• Window Wall: A type of metal curtainwall installed between floors or betweenfloor and roof and typically composed ofvertical and horizontal framing members,containing operable sash or ventilators,fixed lites or opaque panels or any com-bination thereof.5

As the industry definition of window wallsuggests “metal curtain wall”, it is not sur-prising that the term “window wall” is fre-quently misunderstood, even by those in thedesign and construction professions whoseresponsibility it is to properly design, specifyand install these systems. To address thisconcern, it is critical to understand windowwall fundamentals related to structure andresistance to uncontrolled air and water infil-tration.

THE INFLUENCE OF STRUCTUREThe design, engineering and installation of

a curtain wall, and the inter-relationship be-tween the structure and the curtain wall, aretypically well understood issues. This in-cludes compensating for movement withinthe wall components themselves, relativemovement between the components, andrelative movement between the walls andbuilding frame to which it is attached.6 In ad-dition, movements caused by temperature


Feature

By Fiona Aldous, Wiss, Janney, Elster Associates, Inc.

Reflections on the Window Wall

Figures 1.1 and 1.2 - Cantilevered bays of window wall assemblies typical in high-rise resi-dential construction.

Figures 2.1* and 2.2** - Common deflection header or movement anchors provided by manufacturers of win-dow wall assemblies. It is important to verify receptor joinery also accommodates movement if used. * Detail Courtesy of www.oldcastleglass.com/ww 2.5 4.5-6 elevation.php** Detail Courtesy of www.wausauwindow.com/resources/details/4750-6250%20RX.pdf

changes, wind action, gravity forces and de-formation and/or displacement of buildingframe must also be factored.7 To further re-inforce the issue, AAMA states, “to disre-gard such movements in designing the wallis an urgent invitation to trouble.”8

The movement considerations outlinedabove extend without exception to the de-sign and installation of window walls. How-ever, as window walls typically incorporatepre-designed window products, along withthe potential for less experienced installersand manufacturers migrating from the tradi-tional residential market, the structural andmovement considerations are often over-looked. Window “gateway” minimum re-quirements, such as size, may not equate towindow wall openings—attachment andloading calculations may not be performedto guide installation and product choices,and deflection of the structure may not beaccommodated in the window wall design.In determining the extent to which thestructure will impact the window wall de-sign, typically the fraction of a span L/360 isutilized as the deflection limit for concretemembers; however it is suggested that themaximum expected deflection, being, “thesum of creep deflection from permanentloads, the ‘elastic’ deflection from transientloads, and the deflection effects of shrinkageand temperature change”9 must also be con-sidered.

This is particularly critical with post-ten-sioned concrete slabs such as those typicallyutilized in high-rise residential construction,where allowable design live and dead loaddeflection at the center of continuous spans

often results in 3/8 in. (9.7 mm) of move-ment, unless factors more stringent due touse/occupancy, or requirements of the initialdesign program are outlined. At cantileveredslabs such as those typically associated withprojecting bay windows and window wall“stacks” this can be an important considera-tion (Figures 1.1 and 1.2). A review of thestructural design and the resulting deflectionallowance, in addition to thermal and sealantcompression characteristics will consider-ably impact the design of the window walland interface conditions, including air barrierand sealant continuity without which, theperformance of the entire exterior wall maybe compromised. Properly specifying theseissues, and including either a deflectionheader or movement anchor (Figures 2.1and 2.2) as the basis of design is recom-mended in consultation with the structuralengineer.

AIR AND WATER PENETRATION RESISTANCEIn part, the appeal of the window wall is

derived from its operable and/or fixed litesor panels, and the available manufacturingdiversity. However, to conceive this notionas straight forward is to recognize the con-flicts, deal with the occasional whim and un-derstand the cumulative intent of all the ap-plicable industry standards, and ultimatelydefine a clear performance specificationbased upon a practical, durable and sustain-able approach! The air and water perform-ance criteria established by the AmericanArchitectural Manufacturer’s Association(AAMA) (Figure 3), are generally acceptedin the industry and can be used as a guide.

However, when considering these standardsas a guide it is also important to note:• Typically, AAMA designated windows are

tested as individual units. Rarely, if ever,are they tested in a window wall configu-ration that typically includes “ganged” or,less often, but more problematic,“stacked” mullions, receptor frames, andsimilar accessories—all components thatsignificantly impact the overall perform-ance.

• Maximum allowable air infiltration hastraditionally been defined by ASTM E283and AAMA/WDMA/CSA 101/I.S.2/A440-05, and are calculated based on squarefoot area or frame size (crack length).WDMA/AAMA/CSA Technical Joint In-terpretation 06-05, dated 14 February2007 stated: “the overall frame size isdefined as the part of window fitting intorough opening.”10 As such, for a fixed andan operable unit utilizing a common sub-frame, the area used to calculate net airinfiltration through that assembly in-cludes, by definition, the entire squarefoot area of the assembly, including thesub-frame (Figure 4), and not the indi-vidual lite as tested to gain AAMA-desig-nation. This can fundamentally alter proj-ect-specific test results for a windowwall assembly, often leading to confusionregarding what constitutes a “passing”grade during pre-construction mock-upand or field air infiltration testing. Thestandards, as currently written must bethoroughly understood by the designprofessional or construction specifier-when crafting the specification.

Summer 2007 25

System and Industry Standard: Water Penetration Resistance per Air penetration Resistance perASTM E331, ASTM E547 and ASTM E283AAMA 501.1.

AAMA/WDMA/CSA 101/I.S.2/A440-05R - Residential, 15% x *DP 75 Pa (1.57psf) and allow for LC - Light Commercial, 1.5 L/s.m2 (0.3 cfm/sf)C - Commercial, HC - Heavy CommercialHC - Heavy Commercial 15% x *DP 300Pa (6.24 psf) and allow for (Compression seal & Fixed) 1.5 L/s.m2 (0.3 cfm/sf)AW - Architectural Windows 20% x *DP 300Pa (6.24 psf) and allow(Compression seal & Fixed) for 0.5L/s.m2 (0.1 cfm/sf)CW-DG-96-1 and AAMA MCWM-1-89Curtain Wall 20% x *DP 0.08 L/sm (0.06cfm/sf) of wall area

plus per linear meter (foot) of crack for the operable window units (if any)

Figure 3 - Typical water and air performance criteria established by the American Architectural Manufacturer’s Associa-tion (AAMA) Note: For complete product listing of maximum allowable air leakage, see AAMA/WDMA/CSA101/I.S.2/A440-05, Clause 5.3.2.1, Table 6. p.52 * DP = Design Pressure

Figure 4 - Although comprised of both fixed and operable lites, the area ofthe rough opening is used to determine air infiltration and not the individuallite. Isolating the individual lite during testing can prove useful in determin-ing possible areas of excessive air leakage.

continued on page 28

When specifying window wall assembliesutilizing multiple individual, AAMA-designat-ed window units “ganged or stacked” to-gether into a single floor-to-floor glazedarea, it is recommended to establish waterpenetration resistance and allowable airleakage of the entire window wall assembly,and laboratory and/or field tests to validateperformance. Note that AAMA allows a 33percent reduction in pressure for field tests,which often results in testing that may notreplicate the actual design pressures towhich the building is exposed. This informa-tion is critical to establish early in the proj-ect, rather than relying on the publishedperformance test data or test standards foreach of the window wall component parts.

INTEGRATED PERFORMANCEAs areas of window wall glazing often

comprise whole exterior walls of resi-dences, the designer should carefully andholistically evaluate the impacts of solar heatgain (SHG), glare, UV impact on interiors,Condensation Resistance Factor (CRF), U-factor, and allowable air leakage relative tothe HVAC design. A recent investigation ofair tightness studies on commercial buildingenvelopes identified tightening of the enve-lope in accordance with Air Barrier Associa-tion of America’s (ABAA) recommended airleakage allowance of 0.02 L/s.m2 at 75 Pa(0.04 cfm/sf at 0.3 in. H2O) and “predictedpotential annual heating and energy cost sav-ings for these buildings ranged from 2 per-cent to 36 percent with the largest savingsoccurring in the heating-dominated cli-mates.”11 High-rise residential building fa-cades, incorporating window wall designsare moving towards emulating commercialbuilding facades. However, considerationshould be given to the internal residentialenergy-consuming functions which dramati-cally contrast with those of commercialbuildings. Functions such as operable lites

and associated higher air infiltration al-lowances, individually controlled HVAC unitsand less controllable relative humidity levels,and full height vision glazing (typically with-out sun shading devices) all inter-relate withthe window wall. Hence, the widespreaduse of the window wall should be ponderedin the context of energy-related perform-ance factors which may not yet be fully ap-preciated.

DETAILSThe cladding at the slab edge adds fur-

ther complexity and is typically the weakestaspect of both the performance and designof the window wall (Figures 5.1 and 5.2).Not only must the slab edge cover accom-modate the intricacies of the drainage of thewindow wall system, but also provide coor-dinated air and water resistance while ad-dressing the concerns of thermal discontinu-ity such that it does not contribute to thedevelopment of condensation, meet the in-tent of the energy codes by installation ofsufficient insulation and properly interfacewith adjacent construction. Three-dimen-sional drawings identifying conditions at slabedges (Figures 6.1 and 6.2), balconies,doors, secondary flashing and receptor sys-tems, integration with adjacent wall (barrieror drainage) and/or roof systems, and ac-commodations for movement and air pres-sures associated with high-rise buildings,should all be considered in the overall detail-ing and specifying of the façade which incor-porates window wall.

The window wall provides a modern costand schedule-driven alternative to the curtainwall and although it is conceptually simple, therequirements for successful design, installa-tion and long term durability are complex.The window wall requires thorough detailingof the slab edge condition by the designer andcareful execution by the contractor. Overall,the window wall warrants careful and

comprehensive consideration, and funda-mentally clear performance criteria and de-tailing before inclusion in the design of high-rise residential buildings. �

Fiona Aldous is a building envelope consultantwith Wiss, Janney, Elster Associates, Inc.(WJE). She has extensive experience in thepeer review, commissioning and investigation/repair of various building enclosures with proj-ects across the United States. She can bereached at [email protected].


REFERENCES1. Stéphane Hoffman, Adaptation of

Rain-Screen Principles in Window-WallDesign. p.1-2 The Exterior Envelopesof Whole Buildings VIII Conference.

2. ANSI /AAMA / WDMA, Voluntary Per-formance Specification for Windows,Skylights and Glass Doors 101/I.S2/NAFS-02, p.16.

3. AAMA, CW-DG-1-96 Curtain WallDesign Guide Manual, 2005, p.2.

4. Ibid.5. Ibid.6. Ibid., p.137. Ibid.8. Ibid.9. W.G. Plewes and G.K Garden, CBD-

54. Deflections of Horizontal Structur-al Members, June 1964, http://www.irc.nrc-cnrc.gc.ca.

10.WDMA/AAMA/CSA Technical Joint In-terpretation 06-05 and AAMA/WDMA/CSA 101/I.S.2/A440-05, sec-tion 8.2.1 and Fig. 27.

11.Steven J. Emmerich, Timothy P. McDowell and Wagdy Anis, “Investigationof the Impact of Commercial BuildingEnvelope Airtightness on HVAC Ener-gy Use” U.S. Department of Energy,Office of Building Technologies, 2005.p.34.

Figures 5.1 and 5.2 - Problematic slab edge interfaces require special attention.

Figures 6.1 and 6.2 - Three dimensional concept sketches and CADdetails aid in understanding how the window wall and slab edge coversystem interfaces with adjacent construction while maintaining accom-modation for movement of the structure, and air/moisture barrier con-tinuity.

ABSTRACTThis paper briefly reviews what an air

barrier is and why it is needed, the designinfluences on and the functional require-ments of air barriers, and then documentsthrough case study format the ways toachieve continuity between walls androofs. The basic environmental influenceson the enclosure managed by air barriersin buildings are the air pressures on thebuilding enclosure. The air barrier systemprovides the air-tightness of the buildingenclosure by resisting the air pressures onthe building enclosure and transferringthose forces without displacement or rup-ture to other building enclosure systemsand finally to the building’s structuralframe. The air barrier must continue toperform its functions for the intendedservice life of the enclosure assembly.

A case study, the Worcester TrialCourt building in Worcester, MA, de-signed by Shepley Bulfinch Richardson andAbbott, Architects, with Wiss, Janney, El-stner Associates, Inc, Engineers, Archi-tects and Material Scientists, acting asRoof Consultants providing quality assur-ance during the construction phase, willbe used as a case study to demonstratecontinuity of air barriers, specifically thecontinuity between walls and roofs.

BENEFITS OF AIR BARRIERSContinuous air barriers provide the

pressure boundary that separates the inte-rior environment from the exterior, includ-ing below grade components of the enclo-sure. Controlling infiltration andexfiltration enables the HVAC system toperform as designed without disruption,enhances human comfort, saves energy,controls condensation and reduce the like-lihood of pollutant entry into buildings andthe migration of pollutants within build-ings. They improve the wind performanceof certain roof systems1, and are an essen-tial component of high-performance

building enclosures2 for buildings that arefully heated and/or conditioned.

The four basic requirements of air bar-riers are:• Air impermeability• Continuity• Structural support• Durability

AIR IMPERMEABILITYAir barriers are composed of materials

that are air impermeable to a great de-gree. Materials that have an air perme-ance of 0.004 cfm/ft2 at 1.57 psf (0.02 L/s.m2 at 75 Pa) or less when tested to ASTME 2178 meet the basic requirement formaximum allowable air permeance.

CONTINUITYMaterials are assembled together with

tapes and sealants, or applied as self-ad-hering sheets, or fluid-applied to formopaque assemblies. Assemblies shouldmeet a maximum air permeance of 0.04cfm/ft2 at 1.57 psf (0.2 L/s.m2 at 75 Pa)when tested to ASTM E2357.

Assemblies are connected togetherwith flexible air impermeable joints toform an air barrier system. An air barriersystem (the entire building enclosure, in-cluding below grade components) shouldmeet air permeance criteria of 0.4 cfm/ft2

at 1.57 psf (2 L/s.m2 at 75 Pa) of the ther-mal envelope pressure boundary whenthe whole building is tested to ASTM E779 or similar test.

STRUCTURAL PERFORMANCEThe air barrier must be rigidly sup-

ported to transfer the design wind loadsgusts (negative and positive) safely with-out tearing, widening of holes at fasteners,or displacement against adjacent materi-als. Continuous, persistent lower air pres-sures acting on joints, such as stack effector HVAC fans, can work to loosen someadhered membranes and tapes.

Summer 2007 29

By Wagdy Anis, Shepley Bulfinch Richardson and Abbott andWilliam Waterston, Wiss, Janney, Elster Associates, Inc.

Air Barriers: Walls Meet Roofs

Feature

Figure 1.

Figure 2.4 Flow around a building in a boundary layer.

Figure 3. Plan view of roof with contours showing nega-tive pressure distribution. From Leutheusser, H.J., Uni-versity of Toronto, Department of Mechanical Engineer-ing, TP 604, April 1964, Fig 15. 10.7.

Figure 4.

DURABILITYSince the air barrier is often inaccessi-

ble within the envelope layers, it needs tolast as long as the intended service life ofthe assembly.

AIR LEAKAGE THROUGH THE ENVELOPEUnlike the moisture transport mecha-

nism of diffusion, air pressure differentialscan transport hundreds of times morewater vapor through air leaks in the enve-lope over the same period of time.3 Airleaks can be one of three different modes:• Diffuse flow, such as flow through air

permeable materials.• Orifice flow, such as flow through a

crack between the window frame andthe wall.

• Channel flow: Channel flow is by farthe most serious from a condensationstandpoint. Air moving through thebuilding envelope materials can en-counter a dewpoint temperature andcan condense within the envelope in aconcentrated manner, wherever thoseair leaks may be (Figure 1).

AIR PRESSURES ON BUILDINGSThere are three major air pressures on

buildings that cause infiltration and exfil-tration:1. Wind Pressure: Wind pressure tends

to pressurize a building positively on thefaçade it is hitting, and as the wind goesaround the corner of the building it cav-itates and speeds up considerably, cre-ating especially strong negative pressureat the corners, and less strong negativepressure on the rest of the buildingwalls and roof (Figure 2, Figure 3).

2. Stack Pressure: Stack Pressure iscaused by a difference in atmosphericpressure at the top and bottom of abuilding due to the difference in tem-perature, and therefore the weight ofthe columns of air indoors vs. out-doors in the winter, and reversed forbuildings in hot climates with air condi-tioning indoors. Stack effect in heatingclimates can cause infiltration of air atthe bottom of the building and exfiltra-tion at the top, as seen in Figure 4. Incooling climates, the reverse happens.

3. HVAC Fan Pressure: Fan Pressure iscaused by HVAC system pressuriza-tion, usually positively, which is fine incooling climates but can cause incre-mental envelope problems to wind andstack pressures in heating climates.HVAC engineers tend to do this to at-tempt to reduce infiltration, and with itpollution and disruption of the HVACsystem design pressures.Figure 5 shows each of these pres-

sures on its own, and a combined diagram.

CODE REQUIREMENTSMassachusetts, since 2001 has had air

barrier requirements in the building code.5

Those air barrier code requirementsare summarized as follows:• A continuous plane of air-tightness

must be traced throughout the buildingenvelope with all moving joints madeflexible and air-tight;

• The air barrier material in a systemmust have an air permeance not to exceed 0.004 cfm / sf at 0.3” wg (1.57psf) [0.02 L/s.m2 @ 75 Pa];

• The air barrier “system” must be ableto withstand the maximum positive andnegative air pressure to be placed onthe building and transfer the load to thestructure;

• The air barrier must not displace underload or displace adjacent materials;

• The air barrier material used must bedurable or maintainable;

• Connections between roof air barrier,wall air barrier, window frames, doorframes foundations, floors over crawl-spaces, and across building joints mustbe flexible to withstand thermal, seis-mic, moisture and creep buildingmovements; the joint must support thesame air pressures as the air barriermaterial without displacement;

• Penetrations through the air barriermust be made airtight;

• Provide an air barrier between spacesthat have significantly different temper-ature and/or humidity requirements;

• Lighting fixtures are required to be air-tight when installed through the airbarrier;

• To control stack pressure transfer tothe envelope, stairwells, shafts, chutesand elevator lobbies must be decou-pled from the floors they serve byproviding doors that meet air leakage


Figure 5.

criteria for exterior doors, or the doors must be gasketed; and• Functional penetrations through the envelope that are normal-

ly inoperative, such as elevator shaft louvers and atrium smokeexhaust systems must be dampered with airtight motorizeddampers connected to the fire alarm system to open on calland fail in the open position.Of course there are many products formulated to qualify as air

barriers materials. Some of these, as well as specifications, techni-cal help, etc. can be found at www.airbarrier.org.

LOCATION OF THE AIR BARRIERThe air barrier, unlike the vapor retarder (since its function is

to stop air, not control diffusion) can be located anywhere in theenvelope assembly. It can be on the warm in winter side, inwhich case it can also control diffusion and would be a low-permvapor barrier material. In that case, it is called an air/vapor barri-er. Or it can be on the cold side of the wall, in which case itshould be vapor permeable (5-10 perms or greater). Vapor re-tarders, when used, must always be placed on the high vaporpressure side of the insulation.6 For examples of this, visitwww.mass.gov and search “energy code details”.

(Figure 6, Figure 7 and Figure 8) of air barrier system de-sign continuity and structural integrity, taken from the referencedetails published by Massachusetts at www.state.ma.us/bbrs/en-ergy.htm.

Air barriers on the exterior side of the insulation: Air barriersthat are subject to thermal changes are more difficult to keep air-tight for the life of the building, because of the integrity of thejointing tape or sealant over a long period of time. The best tapesfor non-moving joints are:• Silicone (extruded) bedded in wet silicone;• Wet silicone reinforced with fiberglass mesh;• Other fluid-applied elastomeric air barriers products, rein-

forced with fiberglass mesh; and• Self-adhering modified bitumen with surface properly primed.

In short, if you can avoid the above, the building will be moredurable, longer.

ROOF AIR BARRIERSThe roof membrane can be considered an air barrier since it

is designed to withstand wind loads, if it is fully adhered. Mechan-ically fastened and ballasted roof systems, because they displaceand momentarily billow or pump building air into the system, donot perform the required functions of containing air without dis-placement. In those cases, another air barrier must be providedin the system. Either a self-adhering modified bitumen air andvapor barrier on the inboard side of the roof system (interiorconditions and weather-dependent), or two layers of asphalt feltmopped down with asphalt, or similar air barrier. Those layersmust be designed to withstand design wind loads without dis-placement. One of the vital concepts, that of continuity with thewall air barrier, is paramount. A pre-construction conference onroofing must include a discussion of the connection between theroof air barrier and the wall air barrier, and the sequence of mak-ing that air-tight and flexible connection. It is also important toensure compatibility between materials coming together. Pene-trations into roof systems such as ducts, vents, roof drains, etc.

must be dealt with perhaps using spray polyurethane foam orother sealant, or membranes to air-tighten those penetrations atthe selected air barrier layer.

CASE STUDYWorcester Trial Court, Worcester, MAArchitect: Shepley Bulfinch Richardson and Abbott

The Worcester Trial Court in Worcester Massachusetts is de-signed to house 27 courtrooms for Superior, District, Juvenile,Housing, Probate and Family Courts. There are five floors andpenthouse, totaling 427,000 square feet. It is the first CM at riskproject undertaken by the Division of Capital Asset Managementin the Commonwealth of Massachusetts.

Worcester Trial Court is a steel framed structure with con-crete floors, brick, cast stone, EIFS and glass walls with a series ofhigh sloped and low slope roof areas. The high sloped roofs arestanding seam lead coated copper panels with cornices, soffitsand internal gutters. The low sloped roof areas consist of threeroof types, a TPO fully adhered membrane, built-up roofingmembrane installed in hot asphalt and a modified bitumen roofingsystem in cold adhesive. These roofs are terminated at metaledges, parapets and rising walls with internal drains and scuppers.All of the roofs incorporate high levels of insulation, six inches ofextruded polystyrene insulation or polyisocyanurate insulation.

Summer 2007 31

Figure 6 - The Worcester Trial Court under construction with finished metal roofing inplace.

Figure 7 - Structure, vapor retarder, insulation and decking under construction.

Photos from the construction of the roofing systems are in-cluded with attention to the terminations and integration withthe air barrier systems. References are made to the constructiondetails. Locations examined are the wall/roof intersection at theparapet walls, the roof edge and the rising wall locations. Thesloped roof to the skylight construction will be shown. Intersec-tion of the air barrier wall against the underside of the metal deck

is examined to illustrate the connections required for continuityof the air barrier.

Figure 6, Figure 7, Figure 8, Figure 9 and Figure 10 aresample photographs of the conditions during construction

CONCLUSIONAn air barrier system is an essential component of the building

envelope of fully heated and/or conditioned buildings, so thatthose buildings’ mechanical systems can perform as intended, andthe enclosure be durable and sustainable. Building codes shouldrequire air barriers systems, and building designers and buildersshould be aware of the consequences of ignoring building air-tightness. �

This article reprinted, with permission, from the Proceedings ofthe RCI 22nd International Convention, Orlando, Florida, March 1-6,2007. ©2007 RCI. All rights reserved.

Wagdy Anis, FAIA, LEED AP is a principal focuses on building scienceand building enclosure design excellence with Shepley BulfinchRichardson and Abbott, architects, planners and interior designers, aninternational practice based in Boston, MA, USA, and is the chairmanof BETEC, a council of the National Institute of Building Sciences. William Waterston, AIA, RRC is a Senior Associate and Project Man-ager for Wiss, Janney, Elster Associates, Inc. in their Boston area of-fice. He has experience in project management, construction docu-ment preparation, and specification writing. With over 15 years ofspecific experience in roofing products and systems, his knowledge ofmodified and built-up roofing systems is extensive. Waterston’s workat WJE includes the investigation, evaluation, and design of roofingand waterproofing systems. He is an active member of the BuildingEnvelope Committee of the Boston Society of Architects.


BIBLIOGRAPHYAir Leakage in Buildings, Wilson, A.G. CBD 23, NRC 1961Wind on Buildings, Dalgliesh, W.A., Boyd, D.W., CBD 28,

NRC 1962Wind Pressure on Buildings, Dalgliesh, W.A., Schriever,

W.R., CBD 34, NRC 1962Control of Air Leakage is Important, Garden, G. K. CBD

72, NRC 1965Stack Effect in Buildings, Wilson, A.G., Tamura, G.T

REFERENCES1. A Guide for the Wind Design of Mechanically Attached

Flexible Membrane Roofs: NRC-IRC-47652E.2. Investigation of the Impact of Commercial Building Enve-

lope Airtightness on HVAC Energy Use 2005, NISTIR7238, by Emmerich, S., McDowell, T., and Anis, W.

3. The difference between a vapor barrier and an air barrier:Quirouette, R.L. http://irc.nrc-cnrc.gc.ca/pubs/bpn/54_e.pdf.

4. Figures 2 and 3: Building Science for a Cold Climate: NRC,Hutcheon, N., Handegord, G.

5. 780 CMR 1304.3.6. ASHRAE Handbook of Fundamentals 2005.

Figure 10 - Air barrier on wall at roof edge, extends under cornice.

Figure 8 - Detail of sloped roof edge.

Figure 9 - Modified detail of diagonal wall meeting underside of metal deck. Note foamfilling flutes of deck.

MOST OF US CAN QUICKLY IDENTIFYthe TransAmerica Building in San Franciscoby its pyramidal shape, the John Hancockbuilding in Chicago by its skeletal frame de-sign, and New York City’s Chrysler Buildingby the art deco crown. Further, FrankLloyd Wright’s Falling Waters nestled over astream in western Pennsylvania is equallyidentifiable.

These structures are identified by thedistinctive characteristics of the exteriorwalls. Importantly these same exteriorwalls are the primary barrier between na-ture’s outside elements and the interior en-vironment. It is the performance of thesewalls that we will discuss here.

The walls of many residential and low-rise buildings rely on conventional, provenconstruction methods without extensivepre-construction testing to validate the abili-ty of the walls to resist air infiltration, waterpenetration and structural loads. Often, wallperformance is compromised because ofthe cost of performing quality assurance,pre-construction tests. Instead, the buildingowner often relies on the reputation of thematerial suppliers and the represented per-formance of their products coupled withthe building contractor’s assurance of the in-tegrity of the finished building.

However, high-rise (skyscrapers) andother monumental buildings require mil-lions of dollars to construct the wall enve-lope, and that wall system is often—or gen-erally—a unique design of various materialsand components. Therefore the investmentin pre-construction performance qualifica-tion tests is financially justified. This testingprocess provides an ideal time to examinetransition details between different materi-als, to further develop unique features andto train the construction/installation crewson the proper methods and installation se-quence to effect a sound wall installation.

This curtain wall, as it is frequentlycalled, is exposed to the harshest of na-ture’s elements: intense sunlight raising sur-face temperatures to as high as 180ºF(82.2ºC), extremely cold air temperatures

to 0ºF (-17.8ºC) or colder, hurricane windloads with concurrent flying debris, earth-quakes and building movement, heatloss/gain and condensation, noise pollutionand more. Therefore these unique curtainwalls require sufficient scrutiny to validatelong term performance before, during andafter these extreme events.

Historically the project architect ac-cepted total responsibility for all of theproject details from concept through com-pletion. The architect would develop thesignature building by considering theowner’s perception, project costs, the in-tended use or function, the surroundingarea, etc. He/she would follow through byproviding a performance specification,quality assurance procedures, shop draw-ing review and approvals, and the many di-verse details involved in creating a new,monumental structure. An important func-tion was the hand-in-hand research the ar-chitect would cultivate with the reputablesuppliers and contractors to assure the re-sults that the owner expected.

Today the architect has been removedfrom many of these functions and responsi-bilities. The architect often merely pro-vides concept drawings of many aspects ofthe project which are then turned over tothe construction manager who pushes theresponsibility down the chain to the sub-contractors, suppliers and installers. Now,more than ever before, the architect mustrely on the project specifications for pre-qualification mock-up testing and qualityassurance during the installation processwith the hope that the CM does not value-engineer this important function out of theproject.

A full-service independent testing labo-ratory can provide the services necessaryto evaluate the performance of these com-plex wall systems pursuant to the specifica-tions and desires of the architect. Whoeveris responsible for evaluating the mock-upperformance should coordinate the mock-up construction and testing protocol thatprovides assurance that the intent of the

Summer 2007 33

By Henry Taylor, Architectural Testing, Inc.

Curtain Wall Mock-up Testing

Feature

Curtain wall mock-up being finalized and inspected priorto initiating the test sequence.

View of curtain wall mock-up from inside the test chamberprior to testing.

Sloped glass wall system being prepared for testing.

Interior detailed view of jamb anchor into concrete sub-strate.

Noise pollution has created increasingdemand for the knowledge of acousticalperformance of the building’s wall system.Highway, aircraft and other industrial nois-es can be dampened by a thoroughknowledge of the specific noise sourcecoupled with the products that can atten-uate the specific frequencies generated.An OITC (Outdoor-Indoor TransmissionClass) rating of the components will be agood indicator for selection of windowsand some other components. Increasingly,demands for acoustical testing of the cur-tain wall mock-up is being required toverify the anticipated performance and tohelp identify sources of leakage so im-provements can be included during the in-stallation of the wall system on the proj-ect.

After mock-up testing has been com-pleted, the results accepted and the finalmock-up detail has been properly docu-mented, it is equally important to assurethat the final curtain wall fabrication andinstallation duplicate the approved designresulting from the testing program. Oftenyour testing agency can provide the con-sulting necessary to follow through withthis important function, inspecting the in-stallation and performing in situ tests tofurther validate that the “delivered” build-ing will perform as expected.

Consultation with the engineers andtechnicians of a competent, independent,and experienced testing laboratory willprovide the information necessary to helpassure that the monumental building will perform as expected for many yearswithout extensive and unnecessary maintenance. �

Henry Taylor is president and founder of Ar-chitectural Testing, Inc. They have eight lab-oratory locations across the United Stateswith over 700 feet of test wall dedicated tomock up testing.

architect’s specifications and quality assur-ance program are met.

A basic mock-up test will include air in-filtration, static and dynamic water penetra-tion, and design load and structural over-load tests (typically 1.5 times the designload). Generally several optional tests areadded to this basic sequence. For examplea repeat of the air infiltration test and thestatic and dynamic water penetration testsare conducted after the mock-up has beenstressed by the design load test. Similarly,building movement caused by the live anddead loads expected on the structure isoften simulated on the mock-up after whichthese same tests are again repeated.

Other critical tests include the thermalmovement caused by extreme temperaturechanges of the building materials. A curtainwall is composed of many different materi-als with a wide range of expansion createdby temperature changes thereby creatingchallenges for maintaining air and waterseals. Often the mock-up is enclosed withinan insulated chamber where air tempera-tures are cycled from the low design tem-perature (say 0ºF, -17.8ºC) to the expectedhigh surface temperatures caused by infra-red heat from the sun (up to 180ºF,82.2ºC). Then a repeat of the air and watertests are generally conducted to evaluateperformance after several temperature cy-cles which represent environmental expo-sure and stress.

Accurate heat loss (thermal transmit-tance or u-value) tests are, of necessity,performed in a sophisticated chamber; dur-ing this same test process an accurate Con-densation Resistance Factor (CRF) can, andshould, be obtained. Knowledge of the u-value is important for specifying HVAC sys-tems, but the American Architectural Man-ufacturers Association has a documentAAMA 507 that has proven to be a valuabletool to predict thermal performance of cur-tain wall systems.


Mock-up composed of ribbon windows and natural stone.

Three story mock-up being prepared for air infil-tration tare procedure.

Roof soffit and support capping a curtain wallmock-up with many angles, transitions, and ma-terials.

Dynamic water infiltration test using an aircraftengine on a 55 feet high mock-up. Uniform load testing of roof structure of a sunroom using sandbags. Catastrophic failure of ribbon window during testing.

UNDERSTANDING THE ISSUEThe joint between the floor assembly and the exterior wall faces

many challenges: to limit the spread of flames and smoke, control airmovement, contain the spread of contaminants and provide acousticisolation. When the joint is required to be fire-rated, then tested as-semblies are required which further complicate the decision becauseof ambiguities in the code, conflicting manufacturer’s data, the lack ofreliable test methods and inconsistent interpretations by local codeauthorities. Selecting the proper system for this joint is not at all clearand no single easy response is available. Also, each architect and engi-neer must make their own professional judgment. I am not suggestingthat this paper establishes a guideline, let alone a standard. Instead,the paper is meant to point out the performance issues, suggest solu-tions and make recommendations for future testing.

The joint configuration occurs in several categories: rated walls in-tersecting rated floor assemblies, non-rated walls intersecting ratedfloor assemblies, rated walls intersecting non-rated floor assembliesand finally non-rated walls intersecting non-rated floor assemblies.Each of these four categories can be further broken down into sub-categories based on if the wall spans from floor-to-underside of slababove or if the wall spans past the outside edge of the slab (curtainwall). One of the more problematic categories is when curtain wallspans past the edge of a rated floor assembly and will be the focus ofthis paper. For the purposes of this paper, only non-combustible com-mercial construction with concrete floor slabs will be considered. Sys-tems that require a gypsum board, plaster or other ceiling membraneto provide a rated floor/ceiling assembly are not included. I am pre-senting this paper not as a code or fire safety expert but as a practic-ing architect who must face these decisions almost daily. The article isbased on the results of material found using normal research prac-tices, for example Google searches, code reviews and manufacturer’sliterature.

WHY SHOULD AN ALUMINUM FRAMED CURTAIN WALL BE CONSIDEREDA DIFFERENT CONDITION?

Much of the confusion regarding the wall-to-floor joint centersaround one particular type of exterior wall, specifically curtain wallframed with aluminum extrusions and infilled with glass. Aluminumframed glass curtain wall systems do not otherwise receive special at-tention in the code. They are typically allowed as a non-rated, non-combustible assembly and they do not appear to carry any special riskof failure when compared to other non-rated, non-combustible exte-rior wall assemblies.

The risk of the wall and glass failing before the time rating of thetest is frequently touted as a reason to treat these walls differently.However, protecting against flames jumping from floor to floor is cov-ered in other portions of the code. Currently by code it would be

possible to have many other exterior wall assemblies and these wallswould be allowed to have windows that extend to the underside ofthe floor slab and start again at the top of the floor slab. I cannot con-clude that the interruption of a floor slab substantially increases pro-tection against the jumping of flame to the next floor and likewise findit is not reasonable to focus differently on aluminum framed curtainwalls.

CODE REQUIREMENTSLimiting the passage of flame and the products of combustion is a

well understood requirement in the protection of life and property.Protecting the inevitable gap at the intersection of the exterior walland floor is no exception. The concern about the “void” between thefloor and exterior wall construction is because this gap, to quote IBC2006 Commentary, “clearly requires sealing to prevent the spread offlames and products of combustion between adjacent floors”. Fulfillmentof that requirement at this particular location in a manner that is ac-ceptable to both the spirit and letter of the code becomes somewhatconfusing because of the limitations of testing methods and becauseexterior walls are frequently not required to be a fire-resistive ratedassembly. Additionally, the merging of the three major U.S. code writ-ing bodies into the ICC, the evolution of the IBC since 2000 and in-formation provided by fire stopping manufacturers have left many ar-chitects, engineers and even code authorities unclear.

From the code, it appears reasonable to assume sealing of thejoint at the exterior wall/floor interface is an independent issue fromprotecting against the spread of fire vertically up the building resultingfrom the heat of the fire breaking out glass and then leaping to thenext floor. In IBC 704.9 “Vertical Separation of Openings” the re-quirements for protection against this occurrence (except in low-risebuildings) are rated spandrel, rated horizontal flame barriers or fullysprinklering the building. There are no limits placed on the size, place-ment or rating of fenestration; in other words, the entire wall couldbe made of glass and would still comply with 704.9, provided thebuilding is fully sprinklered. I have not found evidence for a significantnumber of losses resulting from flames jumping floors in sprinkleredbuildings. This is significant because it seems logical not to considerhow long glass, or even the non-rated wall assembly itself will stay inplace in the selection and detailing of the joint sealer because thatsafety precaution is addressed through requirements of 704.9.

At this time the model code (2006 International Building Code willbe used for the sake of this article) allows two test methods for theexterior curtain wall/floor intersection (Section 713.4). The first,ASTM E119, tests the materials essentially independent of the sur-rounding construction. The second, ASTM E2307-04 “Standard TestMethod for Determining Fire Resistance of Perimeter Fire BarrierSystems Using Intermediate-Scale, Multi-story Test Apparatus”


By David W. Altenhofer, AIA, RMJM Hillier

Perimeter Joints What’s the right thing to do at the joint between the floorassembly and an exterior wall?

Feature

attempts to recreate test conditions more similar to in-place fieldconditions. E2307 was added to the 2006 IBC and there is a chance itmay supersede E119 in future editions based on the commentary andthe long history of proposed code revisions, many of which are spon-sored by firestopping manufacturers. The two test methods results indramatically different system designs, although the materials are simi-lar. It is important to note the slightly different wording of the codefor each. For E119 the code requires materials or systems capable ofpreventing the passage of flame and hot gases “where subjected toASTM E119 time-temperature conditions”. For E2307 the require-ment is, “installed as tested in accordance with ASTM E 2307”.

The question is, should architects and engineers require systemswhich comply with E2307 or is E119 sufficient? It appears that thetwo methods differ substantially in that the E119 method allows useof materials that are proven by test method to “generically” resist thepassage of flames and smoke but have not been tested for the exactconfiguration of the final use. E2307 attempts to create a more realis-tic test configuration, however, by doing so it now creates a require-ment for the exterior wall to stay in place for a prescribed period oftime, which is over and above the code requirement for that wall.

The International Firestop Council claims that “Designing the wallto keep the firestop system in place for the rated period of the flooris an obvious necessity” to meet the “letter of the law” of the buildingcodes, which is directly in conflict with my interpretation of the coderegarding E119. E2307 also appears to add requirements for protec-tion against flames jumping from floor to floor which is properly de-scribed elsewhere in the code as discussed above. I do not find theextra requirements of E2307 over E119 to be logically applied orconsistent with other areas of the code. The logic of using materialstested “generically” for the resistance to the passage of smoke andflames does seem to have other applications in the code, such as forpenetrations of nonfire-resistance–rated assemblies (Section 712.4.2).

Therefore, I conclude that using materials or systems properly in-stalled and tested in compliance with E119 as acceptable to protectthe fire-resistant joint between a rated floor and an unrated curtainwall. Architects and engineers should also review their approach earlywith the code Authorities Having Jurisdiction (AHJ) as they ultimatelyhave to approve the joint system. Finally, each architect and engineerwill have to decide for themselves which approach suits the particularrequirements for each of their projects.

ADDITIONAL PERFORMANCE REQUIREMENTSBeyond the code requirements, the joint between the exterior

wall and the floor slab, no matter how they are joined or rated, mustalso perform several other tasks. For nearly all buildings, the joint willneed to perform these tasks continually as compared to the relativelyunlikely event of a fire and therefore are very important to the prop-er functioning of the building. The joint must provide acoustic isola-tion between floors and this is particularly true when there is no sus-pended ceiling.

It is desirable for the joint to stop the movement of air betweenfloors. This becomes more important if the building is very tall be-cause of the increased pressures resulting from stack-effect. Forbuildings utilizing under floor air distribution it is imperative to makethe joint air tight to control air distribution. In buildings with concernsfor the distribution of contaminants such as hospitals or labs, main-taining the perimeter floor joint airtight becomes important.

Common to all joints is that they must be able to accommodate dif-ferential movement between the wall and the floor. Finally, the jointsystem is frequently installed before the building is completely water-tight. Therefore, the joint should resist a reasonable period of expo-sure to sun and moisture without deleterious effect.

To adequately design joints against these performance criteria ispresently difficult because they are not tested against these criteria.For the time, it is reasonable to make sure that approximately 4 inch-es (100 mm) of mineral wool or similar non-combustible filling isstuffed into the joint and well supported from the slab edge. An elas-tomeric fire-resistant sealant material covering the mineral woolshould be at least 1/4 in. (6 mm) and preferably 1/2 in. (13 mm) thickto provide for proper two sided sealant adhesion and the ability towithstand cyclic building movement. Of course, this has to be withinthe installation methods prescribed by the approved test.

A MORE APPROPRIATE APPROACH TO TESTING?In my opinion, it is highly unlikely to find a means to test this

joint for actual performance in a fire. In instances when the codedoes not require the exterior wall assembly to remain in place forany prescribed length of time it is illogical to create a test methodthat requires the wall assembly to stay in place for a prescribedlength of time. Performance of the joint to resist flames andsmoke from a fire that does not cause failure of the wall beforethe rated time of the floor after aging and cyclic movement of thejoint system is extremely important and not currently covered byeither test method. Additionally, there are many other perform-ance criteria that could genuinely provide additional protection of

Summer 2007 37

life and property. A more appropriate testshould be conceptualized as follows:• If the wall is otherwise allowed by the

building code to have 0 hours fire-resist-ance rating, the test should not be de-signed to expect the wall to last as long asthe slab or even some portion thereof. If awall falls away or glazing breaks out, as al-lowed by code under the “Vertical Pro-tection of Openings” section, then thereis no reason to expect the perimeter sealto continue to perform.

• Attachment of the sealing system shouldbe to the floor assembly only, since this isthe component whose integrity the seal issupposed to protect.

• Testing should address anticipated buildingmovement and the seal should still per-form after long term cyclic movement.

• Testing should address the real worldcondition of a fire not immediately adja-cent to the exterior wall.

• Testing should include a reasonable airseal performance value after movement.

• Testing should include resistance to dete-rioration from a short exposure to theweather to simulate current installationmethods and still meet relevant perform-ance criteria.Some propose that E2307 should include

sprinklers, which are commonly included inmany buildings, especially those with alu-minum and glass curtain wall. I do not sub-scribe to that theory as fire stopping and jointprotection is part of the passive fire resist-ance features of a building and other similarfire stops are not tested with sprinklers. �

David Altenhofen, AIA CSI CCS is an AssociatePrincipal and Technical Director of the Philadel-phia Office of RMJM Hillier, a 1,000 person in-ternational architecture firm. He is active inthe AIA, BETEC and is widely published and lec-tures frequently at local, national and interna-tional events.


REFERENCESArticle from UL regarding current trends.

Glass industry news digest regarding ICCdirection.

International Firestop Council presentationregarding fire-resistant joints.

Perimeter_Curtain_Wall.ppt

www.ul.com/tca/spring05/

www.usgnn.com/newshearings

AS THE POPULARITY OF rain screencladding systems continues to grow, sodoes the need for test methods and per-formance guidelines for such systems. Tothis end, the American Architectural Manu-facturers Association (AAMA) has recentlypublished AAMA 508-07 Voluntary TestMethod and Specification for PressureEqualized Rain Screen Wall Cladding Sys-tems.

The new standard quantifies the per-formance of pressure-equalized rain screen(PRWC) systems, the most sophisticatedrain screen cladding system. PRWC systemsfeature high venting and good drying capa-bilities, while substantially reducing pressuredifferentials that drive water through theexterior cladding. Ventilation is a built-incomponent of the joinery of such systems,which employ a separate air barrier anddrainage plane to carry incidental water outof the system. Compartmentalization al-lows the system to maintain constant pres-sure and minimize the amount of water thatbypasses the exterior screen.

Before the establishment of the newAAMA standard, any manufacturer couldclaim to have a pressure equalized rainscreen product on the basis of an assump-tion of perfect air and water barrier, butthere was no recognized way to verifythese claims. Various commercially availablesystems relied upon the air barrier anddrainage plane that are commonly providedby others—not by the manufacturers of thePRWC systems. Since AAMA 508-07 waspublished, manufacturers have been able tocompare the performance of their productswith others on the market without depend-ing solely on the air and water barrier quali-ty.

In general, water leakage is driven byfive forces: kinetic forces, gravity, surfacetension, capillarity and pressure differen-tials. Any number of these forces can beacting on water penetrating the building

envelope; the goal of a design is to eliminateor minimize their effects. Kinetic forcesrefer to the horizontal velocity wind-drivenrain drops possess. The momentum cancarry them directly through sufficientlysized openings into the envelope interior.The actual rain screen cladding serves tokeep most of this water out of the system.Gravity, capillarity, and surface tension canall be combated with appropriately de-signed flashings or drip edge. Pressure dif-ferences between the cladding exterior andinterior generated by mechanical systems,stack effects, and wind also act to forcewater through. Pressure equalized systemswere designed specifically to resist thismechanism of leakage and is an importantcharacteristic of the system to be tested.

Basic ASTM and AAMA test methodsmake up the bulk of 508-07, includingASTM E 283 Standard Test Method for De-termining Rate of Air Leakage Through Ex-terior Windows, Curtain Walls, and Doors

Under Specified Pressure DifferencesAcross the Specimen; ASTM E 331 Stan-dard Test Method for Water Penetration ofExterior Windows, Skylights, Doors, andCurtain Walls by Uniform Static Air Pres-sure Difference; ASTM E 1233 StandardTest Method for Structural Performance of

Summer 2007 39

Rain Screens: The New StandardAAMA 508-07 Voluntary Test Method and Specification forPressure Equalized Rain Screen Wall Cladding SystemsBy Jennifer Pollock, Architectural Testing, Inc.

Feature

Figure 1 - Pressure Equalization Cycling Chart.

Before the establishment of the

new AAMA standard, any

manufacturer could claim to have

a pressure equalized rain screen

product on the basis of an

assumption of perfect air and

water barrier, but there was no

recognized way to verify these

claims.

Exterior Windows, Curtain Walls, andDoors by Cyclic Static Air Pressure Differ-entials, and AAMA 501.1, Standard TestMethod for Water Penetration of Windows,Curtain Walls, and Doors Using DynamicPressure.

AAMA 508-07 actually takes into ac-count imperfections that commonly occurduring the installation of the air/water barri-er system. The Air Barrier Association ofAmerica recommends a 0.15L/s/m2 air leak-age rate, but the new standard increasesthis rate to 0.6 L/s/m2 ± 10 percent to ac-count for the anticipated field defects in theas-built conditions of the air and water bar-rier. The ASTM E 283 Air Leakage test isperformed at a specified pressure differen-tial of 75 Pa (1.57 psf), which is roughlyequivalent to a 11 m/s (25 mph) wind ve-locity. The test is completed both prior toand after the rain screen cladding is installedover the air/water barrier. The purpose ofthe air leakage test is not to validate theperformance of the air/water barrier butrather to determine what impact the instal-lation of the rain screen cladding has on theoverall air leakage of the composite assem-bly. Testing performed by Architectural

Testing has indicate that the air leakage ofthe assembly can change as much as 10 per-cent when the cladding is installed.

The ability of pressure equalized rainscreen cladding to control water intrusion isdetermined by observing the amount ofwater that contacts the air/water barrier.The test assembly is subjected to both stat-ic water and dynamic water tests (ASTM E331 and AAMA 501.1, respectively) and theamount of water penetrating the rainscreen is observed and recorded after eachtest. The standard also requires documen-tation of the nature of the water penetra-tion, such as specific observations on thequantity and location of continuous stream-ing of water and/or misting occurring on theair/barrier surface, and/or water dammingin any channels. Accredited laboratorieswhich perform the test must record anddocument in the report the amount ofwater penetrating the rain screen and con-tacting the air/water barrier; the AAMA 508test limits the amount of water that con-tacts the air/water barrier to five percent ofthe total wall area. The five percent criteri-on was established by the task group basedon the resulting data from research testing.

In addition to limiting the water contactingthe air/water barrier, the standard also pro-hibits the accumulation of water dammingin the system.

Pressure equalized rain screen claddingsrely on the capability of the system toachieve equilibrium when wind and othernatural forces create pressure changes onthe exterior of the cladding. Since this is theprimary mechanism used to control waterpenetration, the standard also requires test-ing to validate the pressure equalizationcharacteristics of the wall system. Utilizingthe ASTM E 1233 test method, cavity pres-sure readings are recorded in three loca-tions—on the exterior and in two interiorchambers—and plotted over time to deter-mine the pressure equalization perform-ance. The recorded pressure data is thenpresented graphically to determine thepressure difference between the interiorand exterior chambers as well as the lagtime for equalization (Figure 1). AAMA508 restricts lag time to 0.08 seconds andthe interior pressure to at least 50 percentof the exterior pressure.

All wall cladding, whether pressureequalized or not, is subjected to some windloading. Structural testing per ASTM E 330is included in the AAMA 508 specification asan option to validate the structural charac-teristics of the wall system. The specifica-tion does not attempt to specify a reductionfactor for pressure equalized cladding how-ever some industry experts suggest that aproperly designed and constructed rainscreen wall cladding may have to withstandas much as 75 percent of the full designpressure due to rapid changes in outside airpressure.

The AAMA Task Group has workedhard to ensure fair and accurate testingmethods with meaningful performance re-quirements, but AAMA 508-07 is only thebeginning of that work. Also under devel-opment are voluntary standards for drainedand back-ventilated rain screen wallcladding systems and perhaps barrier wallsystems. �

Jennifer Pollock is a project engineer with Ar-chitectural Testing, Inc., and is a graduate ofLafayette College with a degree in MechanicalEngineering. She is a member of the AAMAworking task group and has performed numer-ous tests using the AAMA 508 test methodsand specification.


THE FAN PRESSURIZATION TESTPressure testing to determine the air tightness of a building’s en-

closure is conceptually simple. A variable speed fan is used to eitherexhaust air from a building or supply air to a building. This changesthe building’s air pressure relative to the outdoors—hence thename Pressure Testing. To some, this name may be a little confusingbecause most tests are done by exhausting building air.

When a mass of air is exhausted or supplied to a building, the in-door/outdoor pressure relationship changes until the same mass ofair enters or exits the building through leaks in the building enclo-sure. Once this mass balance is reached, the induced pressure dif-ference stabilizes. The magnitude of the pressure difference be-tween inside and outside depends on the size and shape of the leaksin the building. The smaller the leaks the greater the pressure differ-ence has to be to reach this balance.

Measuring the two variables—the air flow rates and the inducedair pressure differences—provides data that can be used to charac-terize the building’s air tightness. The quality of the resulting datadepends on how well these two variables are measured. This iswhere the conceptual simplicity of the test meets real world com-plexity. Wind, occupants, equipment limitations, and the skill andknowledge of the person doing the test impact the test’s overall ac-curacy.

WHY PRESSURE TEST A BUILDING?Besides having fun doing weird things in buildings if you are a

building science geek, or making some money if you are a busi-nessperson, there are many reasons for conducting fan pressuriza-tion tests, such as:• To determine whether a building enclosure (or a zone within a

building) meets tightness specifications (Potter 2007). Airtight-ness may be specified to conserve energy (Emmerich 2007) orto reduce water vapor migration (Brennan 2002).

• To compare the tightness of a building to other tested buildings(Emmerich 2007).

• To determine whether air pressure control can reasonably beexpected to solve a problem in an existing building. For examplepressurizing wall cavities to prevent the entry of hot, humid out-door air or depressurizing a crawlspace to prevent the entry ofradon-laden air (Brennan 1997).

• To develop a “calibrated” airflow model of an existing building.Airflow modeling software (example, CONTAM) can be used topredict the effect of changes in the enclosure or mechanical sys-tems on airflows through the building. Such a model can be test-ed against measured airflow and induced pressure data.If the test is being conducted to compare the results to a target

airtightness, as the British Part L energy code requires (Potter

2007), or to compare the building airtightness to other buildings,specific details of the test must be standardized. Weather condi-tions, the state of windows and doors, treatment of intentionalHVAC openings through the building shell, and the location and set-up of test fan equipment must be considered.

You will need to carefully measure air flows and pressure differ-ences and conduct uncertainty analysis to ensure the accuracy ofthe result. There are a number of protocols that can be followed in conducting the test:• The British Air Tightness Testing and Measurement Association

(ATTMA) Standard 1: Measuring Air Permeability of Building En-velopes (contains guidance for large buildings);

• CGSB 149.15-96 Determination of the Overall Envelope

Summer 2007 41

By Terry Brennan and Michael Clarkin, Camroden Associates Inc.

Characterizing Air Leakage in Large Buildings: Part I

Figure 1 - Acalibratedblower door.

Figure 2 - Multiple blowerdoors used in buildings withleakage areas too large for asingle blower door.

Feature

Airtightness of Buildings by the Fan Pressurization Method Usingthe Buildings Air Handling Systems (contains guidance for largebuildings);

• E 779 – 03 Standard Test Method for Determining Air LeakageRate by Fan Pressurization (does not specifically address largebuildings); and

• E 1827 – 96 (Reapproved 2002) Standard Test Methods for De-termining Airtightness of Buildings Using an Orifice Blower Door(does not specifically address large buildings).If, however, you want to know how many cubic feet per minute

of exhaust air it would take to depressurize a crawlspace by 4 Pas-cals, the test would need to be conducted differently and the resultsare likely to be used to design an intervention in a building relatedproblem. There are no published protocols for conducting a diag-nostic test of this kind.

This article focuses on pressure testing the entire enclosure of alarge building (“large” meaning “not single family residences”). Mostof the building tightness data collected in the United States has beenfor single family residences. A much smaller number of other build-ing types have been tested. For non-residential buildings tightnessdata has been reported for low-rise, mid-rise and high-rise build-ings: for offices, banks, restaurants, food markets, theaters, schools,warehouses, rowhouses and apartment buildings. They have rangedin size from several thousand to several hundred thousand squarefeet. Many of these buildings present issues that do not occur whilepressure testing single family buildings (Emmerich 2007).

PLANNING THE TESTThe purpose of the test, how you are going to conduct it, and

what equipment you will use should be well understood andplanned well before going into the field. For example, are you goingto use a blower door, the building’s air handler or some othermethod of providing the air flow needed for the test? Where areyou going to measure the pressure differences and with what in-struments? Not that the plan won’t change once it encounters thereality of field measurements, but come prepared or failure is likely.

The purpose of the test determines how much of the buildingyou are going to test. To determine if the building meets airtightnessspecifications the entire exterior shell of a building—defined by thethermal or air pressure boundary of the building would be tested.For other purposes a smaller enclosure within a building may betested (example, a special use area like a swimming pool or a fruitripening room). In apartment buildings air sealing each apartmentreduces transport of air contaminants and odors to neighboringunits, reduces accidental outdoor airflows through the building andimproves the distribution of intentional ventilation air. In this case itmay be as important to pressure test each apartment as the entirebuilding enclosure.

Collect background information. You need information on thebuilding itself—the enclosure and the HVAC systems. Architecturaland mechanical drawings are very helpful. The people who maintainthe building, the HVAC equipment and controls are a wealth of in-formation. They are needed on the day of the test to answer ques-tions, open doors and set the HVAC systems to the state you wouldlike during the testing (without setting off fire alarms or sprinklers,freezing coils or otherwise damaging equipment or controls). It isbest to schedule the test when the fewest people are likely to be inthe building opening doors and windows, turning exhaust fans onand off, or doing other things that interfere with your test.

Identify the pressure boundaries of the zone to be tested. Thepressure boundaries may be well defined and implemented. Possi-bly they were not clearly defined in the design documents duringthe design of the building. The location of the actual pressureboundary can be determined during a pressure test by making pres-sure drop measurements across each layer of the enclosure. This isan advanced topic and is not covered in this article. When theboundaries of the zones to betested have been identified, thesurface area of the enclosingwalls, ceilings and floors and theenclosed volume can be calculat-ed. This information will be need-ed so the results of the test can benormalized. Normalizing leakageto the surface area of the enclo-sure allows comparison to targettightness levels or to the normal-ized tightness of other buildings.

Get an understanding of theHVAC systems. Locate each ex-haust outlet and outdoor air inlet.Locate each air handler. Tracesupply and return ducts andplenums. Identify outlets, inlets,


Figure 3 - Infiltec G-54 trailer mounted calibrated blower for testing large buildings.

Figure 4 - Measuring total exhaust flows by summing flow through exhaust grilles(NOTE: This misses air leaks in the ductwork).

Figure 5 - Measuring air flow through an outdoorair duct by pitot tube traverse.

ductwork and air handling equipment that breaches the bound-aries of a test zone. Plan to air seal the HVAC openings that willcompromise the test enclosure. The HVAC inventory may also beuseful if it turns out that using the ventilation equipment in thebuilding is the best way to pressure test the enclosure.

Estimate the amount of air flow that will be needed to achievethe required pressure difference. An estimate can be made by cal-culating the area of the enclosure and multiplying that area bymeasured or target normalized leakage rates for buildings of thetype under consideration (ATTMA 2007, CGSB 1996). An on-linecalculator for estimating the amount of airflow needed to pressuretest a building can be found at www.infiltec.com/inf-ukstd.htm.Determine how the airflows will be provided and measured—seethe next section.

MAKING THE TESTOn the day of the test you will need to be able to close all the

intentional openings in the enclosure, open all the interior doorsand turn off all the ventilation equipment. In many buildings thebuildings and grounds personnel will be needed to get these thingsdone. An HVAC controls contractor may be needed to turn offthe ventilation system.

You will also have to prepare the building:If the whole building is one test zone

• Close exterior doors and windows• Open interior doors

If the test zone is a portion of the whole building• Close exterior doors and windows• Isolate test zone from surrounding building• Close doors• Tape off supply diffusers and return grilles that connect to

ducts or equipment outside the test zone• Determine whether adjacent zones should be open to out-

doors or closed• Close outdoor air intakes and exhaust outlets• Dampers• Gravity dampers• Plastic, foam board and tape

MEASURING AIRFLOWThere are three basic strategies for providing known airflow

rates to depressurize or pressurize the building:• Blower doors: variable speed, calibrated blower doors are

available from two U.S. companies (the Energy Conservatoryand Infiltec) and one Canadian company (Retrotec). Blowerdoors are available in a range from 5000 to 8000 cfm. Airflowthrough blower doors is easily and accurately measured withthese units. They are easy to install in a door opening. With alittle effort and creativity they can be installed in windows, ac-cess hatches or more unusual openings. Multiple blower doorscan be used on one building to achieve higher airflows and todistribute the induced pressure differences throughout a build-ing. Distributing the air pressure becomes more important asthe size and the number of rooms and floors in a building in-crease. Figure 1 shows a photo of a single blower door usedin a research project on unplanned airflows in small commer-cial buildings in New York State (NYSERDA 2006). Figure 2

shows two blower doors being used to test a movie theater inthe same project.

• Trailer mounted fans: Infiltec manufactures a trailer mounted cal-ibrated, variable speed fan that produces flows between 20,000and 60,000 cfm. This unit is ideally suited for large buildings withfew interior floors or partitions. Problems producing uniform in-door/outdoor pressure differences can occur in more complexbuildings. For example, consider a trailer mounted fan depres-surizing the first floor of a six story building, that has two fireegress stairwells open into the lobby. All the air depressurizingthe top five floors must be drawn through the open stairwelldoors. The first floor may be depressurized to a significantlygreater extent than the upper floors because the stairwell doorsmay form a bottle neck, creating a two or three zone problem.Additional smaller fans depressurizing the upper floors usingwindows or rooftop access can be used to even out the depres-surization.Besides the fabled Super Sucker (used for research purposes atthe National Research Council of Canada), currently there is onetrailer mounted fan in North America owned by Jeff Knutson atA. A. Exteriors in Wisconsin. One interesting aspect of this fan isthat it is powered by a gasoline engine rather than an electricmotor. This makes the unit more flexible than would be the case

Summer 2007 43

Figure 6 - Temporary ductwork on outdoor air intake allows pitot tube traverse.

Figure 7 - Fan powered capture hood measuring flow from a rooftop exhaust fan. Thismethod provides good accuracy but is limited to flows equal to or less than the flow of thecalibrated fan. Photo courtesy of CDH Energy Corporation and New York State EnergyResearch and Development Authority.

if a twenty horse power electric motorwas used to power the fan. You don’texactly just plug that big an electricmotor into the nearest outlet. Figure 3shows a photo of the trailer mountedG54 being used to pressure test an810,000 square foot warehouse. TheG54 is ideal for testing large open build-ings. Accurate flows are easily meas-ured. Distributing the pressure differ-ences across the enclosure surfaces isnot hampered by internal partitions andfloors.

• The ventilation equipment in the build-ing (exhaust or outdoor air flows) canbe used to pressurize or depressurizethe building. In the United States duringthe late 1980’s and early 1990’s thistechnique was used (Persily 1986). Themajor advantage of this method is thatthe air handling equipment is already atthe building. There are three commondifficulties with this method: measuringthe airflow through ventilation systemsis often time-consuming and tedious;flow measurements made on air han-dling equipment that is part of the venti-lation system are likely to have greater

uncertainty than flows measured using a calibrated fan door or trailer mountedfan unit (extra effort is required to en-sure data quality); there may not beenough outdoor air or exhaust air ca-pacity to achieve the desired pressuredifference or number of flow-pressuredata pairs to meet the data quality ob-jectives for the test. The only protocolfor pressure testing large buildings usingthe building air handlers is the Canadianstandard CGSB 149.15-96. There aretwo additional references that are help-ful (PECI 2005, Lee 1998). The PECIdocument is a protocol developed to bepart of a commissioning guide. Theother document is a Master of ScienceThesis. A number of Test and Balanceguides provide protocols and methodsfor measuring outdoor airflow throughair handlers and exhaust fans (ASHRAE2005, SMACNA 2002). Two researchprojects that studied unplanned airflowsin non-residential buildings contain de-scriptions of additional methods formeasuring airflows through air handlersand exhaust fans (Cummings 1996a and1996b, 1997, Henderson 2006). There

are a number of techniques for measuringairflow:

• Measure the velocity of air in ductworktraversing multiple locations (e.g. usingpitot tube, hot wire anemometer orvaned anemometers).

• Measure airflow through a duct using anorifice (e.g. flow measurement stationsbuilt into the system. NOTE: flow sta-tion accuracy should be validated usingone of the other flow measurementmethods).

• Measure airflow through diffusers or ex-haust grilles using calibrated flow hoods.

• Measure exhaust or outdoor airflowthrough rooftop intakes or exhaust usinga flow compensated shroud and cali-brated fan. �

Up next issue, Part II: how to measure pres-sure differences and figuring out what all thefacts and figures actually mean, plus a completereference guide for both Part I and Part II of thisseries.

Terry Brennan and Michael Clarkin are buildingscientists who work at Camroden AssociatesInc. They have been pressure testing buildingssince 1981.


BOSTONBy Boston-BEC staff

In 2006 The Boston Society of Architects’ Building EnclosureCouncil (BEC-Boston) established a sub-committee to develop anawards program to recognize building enclosure design and con-struction. After six months of hard work the sub-committee, led byWei Lam (Morrison Hershfield Corp.) and Ann Coleman (Wiss, Jan-ney, Elster Associates, Inc.), is proud to announce the first annualBuilding Enclosure Design Award. A big thanks to all of the commit-tee members who have contributed their time and knowledge: AlecStevens (DMI, inc), Jeff Wade, (Add Inc.), Jonathan Baron (SGA Ar-chitecture, Inc.), Richard Panciera (Elkus-Manfredi), Richard Keleher(BEC-Boston Chair), Keith Yancey (Lam Partners, Inc.), Wagdy Anis(Shepley Bullfinch) and the folks at BSA.

The competition will consider projects by evaluating aspects ofheat, air, moisture, day lighting control, in-service performance, col-laboration and other innovations related to the building enclosure.Outstanding innovation and excellence in these areas will be thebasis for selecting a winning project and runner-up projects to berecognized during a BSA/BEC-Boston sponsored event during BuildBoston 2007 (buildboston.com). The intent of the award is to pro-mote best practice, innovation, and a transfer of information andtechnology related to building enclosure design.

A distinguished panel of judges from the industry has been select-ed. They include:

Wagdy Anis FAIA of Shepley Bulfinch Richardson & Abbott; DavidAltenhofen AIA of Hillier Architects; Desmond McAuley AIA ofChilds Bertman Tseckares Inc.; Daniel Lemieux AIA of Wiss, Janney,Elstner Associates, Inc.; Mark Lawton P.Eng. of Morrison HershfieldLimited; Paul Stoller, Director of Atelier Ten; Chris Benedict R.A.,Principal of Architecture and Energy Limited; and, Keith Yancey AIA,P.E. of Lam Partners, Inc.The competition is open to built projectsthat conform to the Massachusetts State Commercial Building Codeand were completed after January 1, 2002 and before January 1,2006. For more information about the competition go to:www.BEC-Boston.Org.

CHARLESTONBy Nina M. Fair, AIA, CCS, LEED AP

Rodeos are not common occurrences in quaint, historicCharleston, South Carolina, but on May 11, 2007, BEC-Charlestonhosted a wild and wooly Window Flashing Rodeo! The rodeo wasoriginally conceived by board member (and director of hair-brainedschemes) Larry Elkin in response to ASTM Call for Papers for their“Up Against the Wall” Symposium. The Rodeo took on a life of itsown, sweeping up all BEC members, designers, contractors, suppli-ers and manufacturers in its path.

The event was open to 50+ participants forming 11 teams com-prised of local construction professionals and trades-people whoparticipate in BEC. Each team was provided with a standardized wallmock-up with a rough opening and a nail-flange window. The teams

were required to develop a design for their window installation incompliance with requirements set forth in:• The window manufacturer’s installation instructions;• The 2003 International Residential Code;• ASTM E 2112 Standard Practice for Installation of Exterior Win-

dows, Doors and Skylights;• The weather resistive barrier manufacturer’s instructions; and• The flashing manufacturer’s instructions.

The teams then installed their windows in accordance with theirdesigns. Once installed, the assemblies were tested in accordancewith ASTM E 1105 Standard Test Method for Field Determination ofWater Penetration of Installed Exterior Windows, Skylights, Doorsand Curtain Walls by Uniform or Cyclic Static Air Pressure Differ-ence. No exterior cladding or perimeter sealants were installedtherefore the moisture loading on the window/wall interface wasgreater than in-service conditions.

Each team reported to the group a summary of their design, in-stallation process and testing results. These results revealed areas ofconflict between the design requirements and some difficulties in im-plementing the designs. Teams also learned about the benefits of de-sign mock-ups and commissioning to identify design and constructionproblems. The anecdotal data provided by this workshop should beutilized by the publishers of the design and installation documents aswell as the testing standard to influence future.

Recent and upcoming programs for BEC-Charleston are:• September 2007 Meeting: Sustainability in Masonry Construc-

tion by Chris Bupp of Hohmann and Barnard; and• October 2007 Meeting: Advanced Building Science Seminar by

Jacques Rousseau and Rick Quiroette.

CHARLOTTEBy Phil Kabza, FCSI, CCS, AIA

The Building Enclosure Council-Charlotte is wrapping up its firstyear with planning toward an upcoming year of activities that will in-clude a concentrated look at the building enclosure issues of schoolconstruction with our area school district facility leaders, panel dis-cussions featuring construction management staff, and an examina-tion of commercial and institutional roofing issues and options.

In addition to our half-day kickoff event, we have featured pre-sentations on:• Moisture and mold control in new construction• Roof/wall and plenum details in thermographic analysis• Recent litigation issues in building envelope failures• Introduction to WUFI

We’re looking forward to the coming year and appreciate thesupport and information exchange with BEC leaders around thecountry.

DALLASBy George M. Blackburn, AIA, BEC-Dallas Chair

The BEC-Dallas chapter is in its third year of operation and


Industry Update

BEC Corner

convenes it’s meetings on the second Tuesday of each month at theAIA-Dallas office meeting room at 1444 Oak Lawn, Suite 600, Dallas,Texas 75207. Contact George M. Blackburn, AIA for information onBEC-Dallas programs and meetings at 972-466-1103. BEC-Dallas isa sub-committee of AIA-Dallas and Paula Clements, AIA- Dallas Ex-ecutive Director, has agreed for AIA Dallas to handle all of BEC-Dal-las finances, and to publicize all meetings and programs of BEC-Dal-las.

The Weatherization Partners (Tyvek) has graciously agreed to paythe $200 copyright fee to the artist, Deb Gordon, for the BEC-Dal-las Logo design copyright.

BEC Dallas was one of the sponsors of the WUFI workshop con-ducted in Dallas on February 1 and 2, 2007 presented by the OakRidge National Laboratory Building Envelope Program, and received$1,700 from the Building Science Corp. for the revenue sharingarrangement.

John Edgar, Senior Technical Service Manager with Sto Corp.gave an excellent presentation on building enclosure science featur-ing air and water barriers at the April meeting.

There are some interesting and informative programs on mason-ry, waterproofing, air barriers, and the Residential Energy Codescheduled in the coming months. We are also planning on conductinga fenestration flashing competition in the fall, with contractors, archi-tects and architecture students participating.

HOUSTONBy Andy MacPhillimy, AIA, LEED AP, Principal Director, Education Studio

BEC Houston has just completed its first year of full successfulprograms that range from Green Roofs to “Acoustical Considera-tions in the Design and Construction of Exterior Walls.” The mostattended was a discussion of “The most Common Design and Con-struction Issues” related to the building exterior by a panel that in-cluded an owner, a general contractor, an architect and roofing andglazing subcontractors. There was general consensus by panel mem-bers that creating a close collaborative working relationship by allteam members was the best at identifying and resolving design andconstruction issues early. A WUFI Training session was conducted for22 people brining a higher level of technical expertise related tobuilding envelop to the Houston consulting community.

Looking to the next year of programs BEC Houston and the localASHREA chapter are working together to conduct joint programson such topics as “Interaction of the Envelop and Mechanical SystemDesign”, Building Envelope, IAQ and Ventilation Effectiveness.

MINNESOTABy Judd Peterson, AIA, BEC-Minnesota Chair and Jodelle Senger, AIA, LEED AP

The BEC-Minnesota is excited to announce that the first everBEST 1 (Building Enclosure Science and Technology) Symposium tobe held in the United States is scheduled for June, 2008. Mark yourcalendars! This two day symposium will be held at the Minneapolis Convention Center and BEC-Minnesota will be the localhosts. BEC-Minnesota is working with other state BEC chapters,NIBS, BETEC and AIA to plan and fund this exciting event. ThisAmerican symposium will take place on a bi-annual basis, alternatingyears with the Canadian Building Science & Technology Conference.

The BEST 1 Symposium will offer two educational tracks and sixteenindividual sessions. One track will address building health issues:Bugs, Mold, and Rot IV. The other track will focus on energy efficien-cy and new technologies: Energy Efficiency in Buildings. Abstracts ofsubmitted papers are currently being reviewed and certain, selectedpapers will be assigned and presented at sessions during the sympo-sium. Additional information can be found on the BETEC website.BEC-Minnesota will soon host a webpage on the AIA Minnesotawebsite with symposium-related links and additional information.

In addition to planning the BEST 1 Symposium, we continue tohave our monthly meetings at AIA Minnesota offices. Recent speak-ers and topics have included Dan Headley of Pella Windows: qualitywood window construction; Wayne Westerbrook of SpecMix/TCCMaterials: mortar and mortar mixes; Reed Gnos of 3M: firesafing inthe exterior envelope; Wilbert Williams of DOW CORNING and BillMcCann of Chemrex BASF: pros and cons of silicone andpolyurethane sealants; James Flanigan and Matt Breyer of Centria: theadvantages of insulated metal panels; Tom Wickstrom of Spec 7group: blind side, exterior waterproofing applications. We’ve alsowatched a PBS program, titled “Design: e2”, which features six dif-ferent segments addressing green/sustainable design. These segmentshave inspired BEC-Minnesota to research exterior envelope compo-nents and systems that not only excel in our Minnesota climate, butalso address the preservation of our natural resources and global en-vironment. The program, Design: e2, was purchased online viaPBS.org and is highly recommended for individual viewing or for in-house office seminars.

PORTLANDBy Rob Kistler, The Facade Group, LLC

The Portland BEC completed this years presentations in July witha well attended discussion of Acoustics. We learned how to mitigateunwanted noise through a curtain wall and other issues that havearisen with the high rise condominium market. We kicked off thisyear with a panel discussion of sustainable practices and the forcesthat hold us back from doing more environmentally friendly designs.Through the year we held presentations on how to design and con-struct a viable eco-roof and the differing theories of the layering ofthe systems. Monitoring systems for either instantaneous feedbackon water infiltration or life cycle building monitoring systems werepresented in the spring followed by a packed room presentation onfenestration systems from residential face sealed systems throughunitized curtain walls to monolithic point fixed glass walls. September6 will be our kick off meeting for the next year with a wrap up pres-entation of a membrane compatibility and adhesion study. We are inthe planning phase of our full day Fall Symposium which this year willoccur Friday, October 26, 2007.

SEATTLEBy David K. Bates, AIA, Olympic Associates Company

Seabec is “cooking with gas.” As we enter our third year, the dustis settling around the administrative foundations and we formed newcommittees to assist the Board of Directors. We have a diversemembership base of approximately 130 and are formulating a cam-paign to attract more architects and contractors. We are reaching outto the University of Washington Schools of Architecture and BuildingConstruction along with community colleges and other trade groups.

Summer 2007 47

ARCHITECTURAL GLASSOldcastle Glass . . . . . . . . . . . . . .26, 27

ARCHITECTURAL WINDOWSOldcastle Glass . . . . . . . . . . . . . .26, 27

ASSOCIATIONS/INSTITUTIONSABAA . . . . . . . . . . . . . . . . . . . . . . . . .7AISC . . . . . . . . . . . . . . . . . . . . . . . . .35ASHRAE . . . . . . . . . . . . . . . . . . . . . . .8Indoor Air Quality Association . . . . . . . . . . . . . . . . . . . .9

BUILDING ENCLOSURECONSULTANTSConstruction Consulting International . . . . . . . . . . . . . . . . . .40

BUILDING ENVELOPEARCHITECTS CONSULTANTSConley Design Group Inc. . . . . . . . .48


Buyer’s Guide

SEABEC’s Education Committee takescare of our programming needs and a “virtu-al” Public Relations Committee has beenstarted to get the word out to the industry.A Task Force produced a document to helpguide people through the revised Washing-ton State Condominium Act. After over ayear, this task is completed and we haveposted the work product on our web site,www.seabec.org.

It is interesting running an organizationthat is essentially a “virtual organization” – Ilike to think that puts us a little more intothe green arena pushing more bites and lesspaper. In the last two years we had pro-grams covering below grade waterproofing,metal siding, Washington State Energy Codeupdates, green roofs, designing for access,windows, window installations and wraps,air barriers, bond breakers and sealant, and apresentation on the Washington State Uni-versity test facility to name a few.

Over the last year, we have again benefit-ed from the generosity of our member firmsand vendors who generously sponsoredmeeting snacks and beverages. 2006/2007was good. 2007/2008 will be great! �

BUILDING PRODUCTSGeorgia Pacific . . . . .inside front cover

BUILDING SCIENCE &RESTORATION CONSULTANTSCamroden Associates Inc. . . . . . . . .45Read Jones Christoffersen . . . . . . . .44

ENGINEERED CURTAIN WALL &WINDOW WALLOldcastle Glass . . . . . . . . . . . . . .26, 27

ENGINEERSSutton-Kennerly . . . . . . . . . . . . . . . .37

ENTRANCE SYSTEMS SPARE PARTSOldcastle Glass . . . . . . . . . . . . . .26, 27

GLASS & GLAZINGCardinal Glass Industries . . . . . . . . .18

INSULATION MANUFACTURERKnauf Insulation . . . . . . .outside back cover

MANUFACTURER REFLECTIVE ROOF COATINGLEED COMPLIANTKarnak Corporation . . . . . . . . . . . . . .6

MASONRYMortar Net . . . . . . . . . . . . . . . . . . . .38

RAINSCREEN STUCCOASSEMBLYStuc-O-Flex International . . . . . . . . .3

ROOFING MANUFACTURERGAF Materials . . . . . . . . . . . . . . . . . .4

STRUCTURAL ENGINEERING,DESIGN & CONSULTANTSWJE . . . . . . . . . . . . . . . . . . . . . . . . . .14

VAPOR BARRIERSEl Dupont Building . . . . . . . . . . . . . .15

WATERPROOFINGSto Corp . . . . . . . . . .inside back cover

WEATHER BARRIERCosella Dorken Products Inc. . . . . .19

JOIN BETECBuilding Enclosure Technology and Environment Council

1090 Vermont Avenue, NW, Suite 700 | Washington, DC 20005-4905Tel: (202) 289-7800 | Fax: (202) 289-1092 | www.nibs.org/BETEC

To become a member of the Building Enclosure Technology and Environment Council, please complete and return the following application form:

Name: ______________________________________________ Title: ___________________________________________________

Company: ______________________________________________ Address: _____________________________________________

City: ______________________________________________ State: _________________ ZIP Code: _________________________

Telephone: ______________________________________________ Fax: ________________________________________________

E-Mail Address: __________________________________________

JOIN NIBSNational Institute of Building Sciences

1090 Vermont Avenue, NW, Suite 700 | Washington, DC 20005-4905Tel: (202) 289-7800 | Fax: (202) 289-1092 | www.nibs.org

Membership ApplicationMembership in the National Institute of Building Sciences is open to all interested parties as provided in the enabling legislation. Individu-als are eligible to become either public interest or industry sector members. Organizations that wish to support the Institute in achievingits objectives may become sustaining or contributing organization.Name ______________________________________________ Title ___________________________________________________Company ______________________________________________ Addres: _____________________________________________City ______________________________________________ State _________________ ZIP Code _________________________Telephone ______________________________________________ Fax ________________________________________________Nature of Business/interest areas: _________________________________________________________________________________

Annual Contribution $ __________________________ � Payment Enclosed � Bill Me � Charge to my MC/VISA/AMEX:Account No. __________________________________________ Exp. Date_______________ Name on Card _____________________________________________Billing Address _________________________________________________________________The National Institute of Building Sciences is a nonprofit organization with an Internal Revenue Service Classification of 501(c)(3) tax exempt status. Contributions to all 501(c)(3) organizations are tax deductible by

corporations and individuals as charitable donations for federal income tax purposes.

Signature ____________________________________________ Date ___________________________

Send information on the following council/committee: � BSSC � BETEC � FIC � IAI � FMOC � MMC

DUES PAYMENT:� Check or Money Order enclosed payable to BETEC � Please bill my Credit Card: � AMEX � MC � VISA

Account No. ___________________________________________________ Exp. Date _________________________

Cardholder’s Name _____________________________________________ Billing Address ________________________________________________

City __________________________________________ State _____________ ZIP ___________________________

Signature ______________________________________________________ Date _____________________________

MEMBERSHIP CATEGORY:� Individual Member - $100� Corporate Member - $250

(optional alternate member)

RESEARCH COORDINATINGCOMMITTEES:I will participate on the following ResearchCoordinating Committees (RCC’s):� Heat Air and Moisture� Fenestration� Membranes� Materials and Resources� Existing Building Enclosures

� Education� Window Security Rating and Certifi-

cation System

OPERATIONAL COMMITTEES:I will participate on the followingOperational Committees (OC’s):� Technology Transfer� National Program Plan

� Network for the Advancementof Building Science

ALTERNATE MEMBER INFORMATION(corporate members only):

Alternate Name: ________________Alternate Title: _________________Alternate's RCC's and OC's: _____________________________________

� INDUSTRY SECTOR MEMBER:Open to any individual in the follow-ing categories: Building construction;labor organizations; home builders;building or construction contractors;producers, distributors or manufac-turers of building products; tradeand professional associations; organ-izations engaged in real estate,insurance or finance; research andtesting of building products; andcode and standard organizations.ANNUAL CONTRIBUTION: $150

� PUBLIC INTEREST SECTORMEMBER: Open to any individualin the following categories: Feder-al, state and local government,consumer organizations, nonprofitresearch and educational organiza-tions, the media, architects, pro-fessional engineers or other designprofessionals, and retirees.ANNUAL CONTRIBUTION: $75

� SUSTAINING ORGANIZA-TION: Open to organizations inthe public interest or industry sec-tors desiring to provide additionalsupport for and participation withthe Institute to achieve the goalsand objectives. Sustaining organi-zations may designate up to fiveindividuals from their organizationto be Institute Members. ANNU-AL CONTRIBUTION: $1000

� CONTRIBUTING ORGANI-ZATION: Organizations makingcontributions to the Institute inan amount substantially exceeding$1000. Contributing organiza-tions are accorded the samerights and privileges as sustainingorganizations and such otherrights and privileges as authorizedby NIBS’ Board of Directors.ANNUAL CONTRIBUTION:$______________________

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jbed journal of building enclosure design · tive of actual performance, since additional heat flow...

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