JBED
Journal of Building Enclosure Design
An official publication of the Building Enclosure Technology and Environment
Council (BETEC) of the National Institute of Building Sciences (NIBS)
Winter 2007
Airtightness of
Commercial Buildings:
Taking Notice, Finally
Pembina, ND
Permit No. 14
PAID
PRSRT STD
U.S. Postage
Contents
JBED
Published For:
NIBS / BETEC
1090 Vermont Avenue, NW, Suite 700
Washington, DC 20005-4905
Phone: (202) 289-7800
Fax: (202) 289-1092
nibs@nibs.org
www.nibs.org
Published by:
MATRIX GROUP PUBLISHING
Please return all undeliverable addresses to:
16516 El Camino Real
Suite 413, Houston, TX 77062
Phone: (866) 999-1299
Fax: (866) 244-2544
PRESIDENT & CEO
Jack Andress
Features:
12
16
26
32
38
42
SENIOR PUBLISHER
Maurice P. LaBorde
PUBLISHER & DIRECTOR OF SALES
Joe Strazzullo
jstrazzullo@matrixgroupinc.net
Air Barrier Systems Defined
Impacts of Airtightness
on Energy Use
Commissioning Airtight Building
Enclosures
Calculate the Costs, Prove the
Performance
Under Floor Air Distribution: The
Good, The Bad and the Ugly
26
PreConstruction
44
Definition 48
Air Tightness: The British
Experience
New Test Standards for the
Building Enclosure
A Critical Review of the Use of
Double Façades for Office
Buildings in Cool Humid Climates
EDITOR
Jon Waldman
FINANCE/ACCOUNTING &
ADMINISTRATION
Shoshana Weinberg, Pat Andress,
Nathan Redekop
accounting@matrixgroupinc.net
DIRECTOR OF MARKETING &
CIRCULATION
Jim Hamilton
SALES MANAGER
Neil Gottfred
SALES TEAM LEADER
Donna Billey
MATRIX GROUP PUBLISHING
ACCOUNT EXECUTIVES
Travis Bevan, Albert Brydges, Lewis Daigle,
George Gibson, Rick Kuzie, Ron Morton,
Declan O’Donnovan, Ken Percival, Melvin
Ramos, Vicki Sutton, Darcy Tkach, Jason Wikis
ADVERTISING DESIGN
James Robinson
LAYOUT & DESIGN
J. Peters
©2007 Matrix Group Publishing. All rights
reserved. Contents may not be reproduced by
any means, in whole or in part, without the
prior written permission of the publisher. The
opinions expressed in JBED are not necessarily
those of Matrix Group Publishing.
Double
Façcades
EDITOR-IN-CHIEF
Shannon Lutter
shannonl@matrixgroupinc.net
12
Messages:
06
08
From NIBS President, David A. Harris
48
From BETEC Chairman, Wagdy Anis
Industry Updates:
06
54
57
Calendar of Events
BEC Corner
NIBS Application
08
56
57
Calendar of Events
On the cover: To Come
BETEC Application
Buyer’s Guide
Winter 2007 5
Message from NIBS
David A. Harris, FAIA
This new and
important journal
is becoming an
essential
information
source on
research and
development
issues related to
building enclosure
systems for North
CALENDAR OF INDUSTRY EVENTS
America.
FEBRUARY
Event: CTI Annual Conference
Date: February 4 – 7
Web: www.cti.org
Event: MCAA Annual Convention
Date: February 25 - March 1
Web: www.mcaa.org
Event: FILTECH 2007
Date: February 27 - March 1
Web: www.filtecheuropa.com
Event: Refrigeration & Air Conditioning Exhibition 2007
Date: February 27 - March 1
Web: www.racexhibition.com
Event: aqua-therm
Date: February 27 - March 2
Web: www.msi-fairs.com
Event: CLIMATIZACIÓN
Date: February 28 - March 3
Web: www.ifema.es
WELCOME BACK TO THE JOURNAL OF Building Enclosure Design (JBED)! The National Institute of
Building Sciences (NIBS) and its Building Enclosure
Technology and Environment Council (BETEC) are
delighted to this. Matrix Publishing Group informs us
that JBED has grown by more than 10 per cent over
the inaugural issue. Readership has greatly increased
too, as the demand for copies of the first issue far
exceeded the number printed.
Hundreds of names have been added to the subscription list. The value of BETEC’s contributions
will continue to expand through JBED’s widening distribution to members of not only NIBS councils, but
high-level corporate, government, and association
executives, as well as design and construction professionals, and researchers and academics throughout Canada and the United States. The results of numerous research initiatives and symposia and the
Envelope Design Guide (featured content of the
Whole Building Design Guide at www.wbdg.org)
continue to form a substantial portion of the basis for
technical and editorial content of JBED.
This new and important journal is becoming
an essential information source on research and
development issues related to building enclosure
systems for North America. A primary area of
focus in this second issue is on the air-tightness of
commercial buildings and how to achieve the
best thermal efficiency results. JBED will continue
to provide BETEC’s focus on building enclosure
MARCH
Event: NADCA Annual Meeting
and Exposition
Date: March 5 - 8
Web: www.nadca.com
Event: ACCA Annual Conference
and Indoor Air Expo
Association: The Air Conditioning
Contractors of America
Date: March 6 - 8
Web: www.indoorairexpo.com
Event: International Roofing Expo
Date: March 6 - 8
Web: www.theroofingexpo.com
Event: ISH 2007/Aircontec/IKK
Building Forum
Date: March 6 - 10
Location: Frankfurt, Germany
Event: Cairo 10th International Conference on Energy and Environment
Date: March 11 - 15
Web: www.eecairo.com
6 Journal of Building Enclosure Design
issues, in addition to featuring contributions from
NIBS and its other councils on a broad range of
facility-related issues, such as safety, security,
health care and educational facilities, natural and
environmental hazard assessment and mitigation,
information technology, standards and criteria development, facility life-cycle needs, life-lines research, and information dissemination to name
just a few. Please visit the NIBS website at
www.nibs.org. We encourage you to use our
products, participate in our programs, and provide useful feed-back on critical issues affecting
the building industry in North America. Together
we can successfully improve the performance of
the built environment.
We invite our readers to carefully review the second issue of the journal and ask you to let us know
how you like it. Let us know how we are doing toward meeting our goal of providing a new and reliable source of information through which to improve the performance of exterior walls,
below-grade, roof and fenestration systems and the
related impacts on indoor environments. Please provide critical feed back to Matrix Group Publishing or
to NIBS, so we can make this publication better and
more responsive to your needs.
David A. Harris, FAIA
President
National Institute of Building Sciences
Event: Corrosion 2007 Conference and Expo
Date: March 11 - 15
Web: www.nace.org/c2007/
APRIL
Event: China Refrigeration 2007
Date: April 4 - 6
Web: www.cr-expo.com/en/
Event: BuildingEnergy07
Date: March 13 - 15
Web: www.buildingenergy.nesea.org
Event: ASTM E06 meeting: Performance of Buildings
Date: April 15 - 18
Web: www.astm.org
Event: International Indoor Environmental Technology and Products Exhibition and Forum
Date: March 16 - 18
Location: Shanghai, China
Event: HARFKO 2007/ Heating,
Air-Conditioning, Refrigeration and
Fluid Exhibition
Date: March 21 - 23
Web: www.harfko.com
Event: Canadian Conference on
Building Science and Technology
Date: March 22 - 23
Location: www.nbec2007conference.com
Event: Ammonia Refrigeration Technology for Today and Tomorrow
Date: April 19 - 21
Location: Ohrid, Macedonia
Event: IARW-WFLO Annual Convention and Trade Show
Date: April 21 - 26
Web: www.wflo.org/hq/convention
MAY
Event: AIA National Convention &
Design Exposition
Date: May 3 - 5
Web: www.aiaconvention.com
Message from BETEC
Wagdy Anis, AIA, LEED A-P
The airtightness of
the opaque
envelope has been
largely ignored by
the design,
construction and
regulatory
communities, but,
as you will see from
the articles, it is of
strategic
importance to our
resource efficiency
as a nation, and to
the proper
integration,
performance and
durability of the
building systems.
WELCOME TO THE WINTER 2007 edition of
JBED, the Journal of Building Enclosure Design. Before I talk about this edition, I would like to address a serious omission in the inaugural edition of
JBED. The content of the inaugural edition was
captured from the fall 2005 BETEC symposium of
the same title, Comfort and Productivity: The Fenestration Factor. That symposium was organized by
veteran BETEC board member Herb Yudenfriend,
who has been the fenestration Research Coordinating Committee chairman for 20 years. It was an
excellent symposium, a true technology transfer in
the BETEC tradition, which made for the resounding success of the inaugural edition of JBED;
so a profuse thanks, Herb, and my apologies for
the omission.
The theme of this landmark reference edition
depicts the struggle of the US research, design,
construction and regulatory sectors in dealing with
(or not) the airtightness of the building enclosure;
by the lack of establishment of performance limits
on air leakage of the opaque envelope in codes,
and the non-existence of verification requirements. The airtightness of the opaque envelope
has been largely ignored by the design, construction and regulatory communities, but, as you will
see from the articles, it is of strategic importance
to our resource efficiency as a nation, and to the
proper integration, performance and durability of
the building systems. We also bring you news from
across the ocean, reporting on the progress being
made by Britain on airtightness, since the L2 Requirements were passed in 2002, and enhanced in
2006.
The Department of Energy sees infiltration control as a national priority. A multi-year research
project has been started at Oak Ridge National
Labs funded by the Air Barrier Association of America, in partnership with the Department of Energy,
to study the holistic effects of air leakage in buildings, including the energy and moisture impacts.
Now, to every rule there is an exception. This
is true of this edition of JBED since it includes an
Event: National Conference on
Building Commissioning
Date: May 2 - 4
Web: www.peci.org/ncbc/
Event: CLIMA 2007 - WellBeing
Indoors
Date: June 10 - 14, 2007
Web: www.clima2007.org
Event: Commercial Construction Show
Date: May 15 - 17
Web: www.cc-show.net
Event: CIB World Building Congress 2007
Date: May 21 - 25
Web: www.cib2007.com
Event: Rebuild Iraq 2007
Date: May 7 - 10
Web: www.rebuild-iraq-expo.com
8 Journal of Building Enclosure Design
article that does not consider the theme of the
edition, airtightness. Rather, it expands on the
theme of the inaugural edition. One of the important concerns of the DOE’s research community is
the mistaken perception by the design community
that double façade glass buildings save energy—
the scholarly article by Dr. John Straube and Randy
van Straaten included in this edition of JBED goes a
long way towards debunking that myth, placing
enclosure design choices in their true perspective
by doing a comparative analysis focused on energy
conservation.
Finally, I would like to report to you some
exciting news: the National Institute of Building
Sciences (NIBS) on behalf of The Building Enclosure Technology and Environment Council
(BETEC) has signed a memorandum of understanding with RCI, Inc. (formerly Roof Consultants Institute), to collaborate and coordinate
in activities such as symposia and the Building
Enclosure Councils (BECs) nationwide
(www.bec-national.org). For membership in
BETEC and NIBS, see the forms enclosed
herein.
Stay tuned for the BETEC Spring 2007 Symposia on membranes, to be held in conjunction
w i t h B E C - Po r t l a n d a n d B E C - S e a t t l e ,
(SEABEC); and of course last but not least, the
BETEC/DOE/ORNL/ASHRAE Thermal Performance of the Exterior Envelopes of Whole
Buildings X International Conference, December 2-7, 2007, Sheraton Sand Key Resort,
Clearwater Beach, Florida. This event is held
once every three years, and is the building science conference to attend. For more information go to www.ornl.gov/sci/buildings/.
See you there!
Wagdy Anis, AIA, LEED AP
Chairman BETEC Board
Chairman, JBED editorial board
Principal, Shepley Bulfinch Richardson and Abbott
Boston, MA
JUNE
Event: BETEC Fenestration Syposium and Washington Update
Date: July 6 - 7
Web: www.nibs.org
Event: Roomvent 2007
Date: June 13 - 15
Web: www.roomvent2007.org
JULY
Event: International Conference
on Heat Transfer, Fluid Mechanics
and Thermodynamics
(HEFAT2007)
Date: July 1 - 4
Web:
www.africaspecials.com/HEFAT2007
Feature
Air Barrier Systems Defined
By Gary Osmond, Henry Company
MASSACHUSETTS WAS THE FIRST STATE
to regulate a minimum performance criterion for the building envelope by adopting the
Massachusetts Energy Code in January 2001.
The code regulates a number of issues related to building science technology, design and
energy conservation. More recently Minnesota and Wisconsin adapted similar codes
that identify key elements in the building envelope design to increase thermal performance and prevent uncontrolled air leakage.
Today’s architect sees the value in a well
designed building envelope system, incorporating air barrier membranes into their construction documents. The selection process
to specify the right air barrier membrane system will depend on a number of factors,
with the best time to make that decision
during design development. Some key factors to consider are:
• Seasonal exterior to interior design temperatures, impact of extreme weather conditions;
• Wall construction types, connections, deflection and building movement;
• Cladding (rain screen) system, location of
secondary rain barrier;
• Cladding anchors and/or brick ties, wall
openings and other penetrations; and
• Location and placement of thermal insulation.
Although there are a number of products
that may exhibit resistance to air leakage, it
should be understood that air barriers are
more than a line on the drawing, they need
to be designed as a “system”, in other words,
continuity through the six sides of a box that
represents a building. In this article, we will
focus on fluid-applied air barrier materials and
self-adhered sheet membrane air barrier materials as part of the whole air barrier system.
Fluid-applied air barrier membrane systems provide a complete monolithic uniform
coating over the intended substrates. They
are applied to a specific wet film thickness
specified by the manufacturer, which serves
a number of issues including; long-term durability, elongation/recovery, crack bridging,
water resistance, gasket effect (self-sealing)
and ability to effectively seal rough surfaces
such as concrete block. It is important to
note that manufacturers test products at
specific thicknesses to achieve the required
test criteria; if applied at less than the specified thickness, the system will not perform as
expected or designed.
Fluid-applied membranes are categorized
as water vapor permeable or non permeable
(vapor retarding) air barriers. Permeable air
barriers restrict the flow of air, but allow slow
vapor diffusion and are typically referred to as
the “air barrier”. Non-permeable air barriers
restrict the flow of air and vapor; they are
“air/vapor barriers”. Due to their location in
the wall, both permeable and non-permeable
air barriers may also be required to resist rain
as a water barrier.
Fluid-applied membranes can be further
broken down to be summer grade or winter
grade when referring to the time of application.
Summer grade or water-based air barriers are
low in VOC’s, can be applied to “green” or
freshly-poured concrete and provide excellent
elastomeric properties. Winter grade or solvent-based air barriers allow the contractor to
continue with the applications during temperatures below 40 degrees F (4C).
Fluid-applied air barrier systems must also
include the use of compatible sheet or transition membranes to span cracks and voids, provide positive connections to window frames in
During and after construction shots
of the cancer research center at
SUNY Albany in Rensselaer, NY,
shows a system Air-Bloc 33 permeable, fluid-applied air barrier,
UV-resistant coating, and a Trespa, METEON composite panel
system outboard air barrier. The
architect was Einhorn, Yaffe and
Prescott of White Plains, NY, and
the air barrier subcontractor was
Cornerstone Waterproofing of
Cooperstown, NY.
12 Journal of Building Enclosure Design
wall openings, roofing and waterproofing systems as well as flashing membranes. For ease
of application and conformity to the “system
approach”, transition membranes are typically
self-adhered sheet membranes. As will be discussed below, self-adhered membranes provide the same degree of air and vapor control
necessary to achieve the continuity and integrity of the system design.
Self-adhered sheet air barriers are an excellent alternative to fluid-applied membranes. Subject to details and application issues which may be too difficult for a
fluid-applied, self-adhered air barriers provide fully bonded protection against uncontrolled air leakage. Self-adhered membranes
are also categorized as permeable and nonpermeable, summer grade or winter grade;
all must be resistant to liquid water penetration. Self-adhered sheet air barriers must
also rely on compatible fluid-applied products for terminations, mastics and sealants.
PERMEABLE OR NON-PERMEABLE: CLIMATE
Based on the diverse climate conditions
through out the U.S., selecting the right air
barrier for the building envelope can not be
considered as an “out–of-the-box” design.
However, for water vapor performance reasons we can consider northern cold climate
conditions, mixed midrange climate conditions and hot, humid climate conditions.
For both cold and mixed climates, the
ideal cavity wall design would consist of the
exterior cladding, air space, thermal insulation layer, non permeable combination
air/vapor barrier on CMU backup wall or
sheathing board over steel studs with interior gypsum wall board. The performance advantages of this design are that it maintains a
continuous plane of air tightness, the vapor
barrier is on the warm or controlled temperature side of insulation (reducing stresses on
the membrane), there is no thermal bridging,
and the membrane is at a temperature
above the dew point of the indoor air based
on acceptable levels of indoor relative humidity. For hot humid climates, substituting a
permeable air barrier would allow this wall
design to dry towards the interior. This wall
design is sometimes criticized as too thick, so
Smart Wall Assemblies vs. Smartest Wall Assemblies
Smart Wall Assembly: If the air barrier is also a vapor barrier (i.e. an air-vapor barrier), it must be located on the
“warm side” of the primary insulation. This requires that all of the insulation be positioned in the exterior wall cavity.
The smart wall design works well but is considered a “thick wall design” because positioning all the insulation in the
cavity results in a thicker wall section.
The Smartest Wall Assembly shows how vapor permeable air barrier systems allow for a designer to move the primary insulation into the stud wall (i.e. in the form of batt insulation) and reduce the wall section thickness. Because vapor permeable air barriers are not “vapor barriers” they do not have to be located on the warm side of the
primary insulation. In cold northern climates, where a vapor barrier is required, the vapor barrier can be separated
from the air barrier, and positioned on the interior side of the wall.
Smart Wall Assemblies
The National Museum of the American Indian (NMAI) is a new Smithsonian Museum in Washington, DC. The Smith Group
was the architect for the building, using a
Blueskin SA sheet membrane air/vapor barrier with BASF Walltite sprayed polyurethane
foam insulation behind sandstone.
Smartest Wall Assemblies
the resulting gross to net floor areas ratio
may not be acceptable and there could be
additional cost concerns related to masonry
ties and shelf angles.
A somewhat thinner wall design for cold
climates would consist of exterior cladding,
air space, a layer of insulation over a permeable air barrier on sheathing board over steel
studs with insulation in the stud cavity, an interior vapor retarder and gypsum wall board.
The benefits of this design are that it still
maintains a continuous plane of air tightness,
the vapor retarder, is at the warm-in-winter
side of insulation, there is reduced thermal
bridging, and the temperature of the sheathing is above the dew point of the indoor air
based on acceptable levels of relative humidity. The key advantages of this design is that it
recognizes nominal R-value v. effective Rvalue of a wall design that includes stud cavity
insulation. Thermal bridging through steel
studs can reduce the nominal R-value of the
wall by 60 per cent. Un-insulated sheathing
board placed over the steel studs will be at
air temperatures below the dew point of indoor air. Insulation placed outside of the
sheathing board and steel studs stops heat
Is sheet the best solution? Sometimes there is difficulty when
using a sheet membrane system with pre-installed brick ties
and penetrations. Fluid-applied systems can be less costly to
install and may produce better results in some cases.
transfer and maintains the sheathing at a
temperature above the dew point.
For mixed mid range climates, where the
summer temperature period and winter temperature period are about equal in length,
many experts agree permeable air barriers
are the best option. Typical wall designs may
include exterior cladding, air space, a permeable air barrier on sheathing board over insulated steel studs with interior gypsum wall
board. A vapor retarder is typically not needed. In this design assembly, in addition to controlling air leakage the air barrier must also
provide two other critical functions: water
vapor control and resistance to rain penetration. If either of these requirements are ignored, condensation and moisture damage
will lead to the premature deterioration of the
walls. The performance value of this design is
maintained by a continuous plane of air and
rain tightness thorough out the building envelope which includes connections to roofing
and foundation waterproofing systems.
Building wraps are commonly used as
suitable protection to rain, in other words as
a building paper and are rarely detailed and
constructed as a structurally supported or
continuous air barrier system; such construction may result in significant energy consumption due to uncontrolled air movement.
For humid climates, the building science
remains the same, but vapor pressure conditions are reversed. A successful cavity wall
system design may include exterior cladding,
air space, and non-permeable air/vapor barrier over the back-up wall with all insulation to
the interior. The performance benefits of this
design are that it provides a continuous plane
of air tightness over the exterior enclosure of
The Marina Bay Tower in Quincy, MA, used Georgia
Pacific’s Dens Glass Gold Sheathing (yellow in photo),
Henry’s Air-bloc 31 membrane (a liquid emulsion, vaporpermeable air barrier), Dow 1” extruded polystyrene insulation (light blue), and an Alucobond panel system.
the building, the vapor retarder is on the warm
side of insulation, there is no thermal bridging,
and the air/vapor barrier is placed in a location
above the dew point of the outside air.
FLUID-APPLIED OR SHEET MEMBRANE?
Fluid-applied air barrier membrane systems provide a complete monolithic uniform
Winter 2007 13
coating over the intended substrates when
applied to a specific wet film thickness. The
selection process can be narrowed down to
simply permeable or non-permeable, based
on the location of insulation and application
climate conditions. The advantages of properly installed fluid-applied membranes is that
they are faster to apply, since no priming of
the wall is required and less preparation of
the substrate is needed. Transition membranes and associated priming may be required in 20 per cent or less of the entire
wall and water base options allow placement
on green or uncured concrete.
Insulation adhesives that are combined as
air/vapor barriers are an excellent method of
improving thermal performance. The adhesives hold the insulation tight to the wall and
reduce thermal short-circuiting by preventing the convective air loops between the
plane of insulation and air/vapor barrier.
In open joint-panel-type rain screen systems such as METEON® by Trespa, UV resistant vapor permeable air barriers are available. The above would be common for a thin
wall design and would consist of rain screen
cladding, air space, a UV resistant permeable
air and rain barrier over the exposed insulating
sheathing or sheathing board, insulated steel
studs with interior vapor retarder and gypsum
wall board. The performance advantage of this
design is that it provides a continuous UV resistant rain and air barrier. There are other
fluid-applied products available that are fire resistant with low flame spread and smoke development ratings if they are required in noncombustible wall systems.
BRICK TIES AND OTHER PENETRATIONS
When considering objects attached through
the air barrier such as masonry ties, metal panel
clips, Z girts and brackets, both fluid-applied and
self-adhered air barriers have advantages over
other types of air barriers. Fluid-applied and selfadhered sheets are fully bonded to the substrate, lateral movement of moisture between
the substrate and membranes is eliminated.
Fluid-applied air barriers remain malleable and
elastomeric providing a gasket effect when mechanical fasteners are used. Self-adhered membranes with SBS modified compounds are
renowned for their self-sealing characteristics
around screw penetrations. When brick ties are
already in place, the most cost effective method
will be a fluid-applied system.
CONCLUSIONS
Although local codes and regulations may
not address air infiltration control performance criteria, the proper application of building science to enclosure design dictates that
air barriers should not be ignored. If your
project includes a layer of insulation to guard
against conductive heat losses, then so should
your project need an air barrier to reduce the
likelihood of condensation and conserve energy due to infiltration control. Selecting the
appropriate product for the application starts
with getting the best advice possible.
The first principles of exterior wall design
needs to consider the following:
• Design a continuous plane of air tightness. Trace continuity with your pencil
throughout building envelope details and
assembly transitions;
• Design a complete structural positive and
negative load transfer system. Similarly,
design air barrier connections to withstand the loads;
• Design a continuous plane for rain control;
• Provide a continuous plane of insulation;
• Avoid thermal bridging;
• Use appropriate analysis of water vapor
control. Understand the permeance of
the different layers; and
14 Journal of Building Enclosure Design
• Accommodate building movement and
construction tolerances. Remember,
Construction is not a precise process.
Design professionals, architects and consultants commonly rely on qualified manufacturers’ product representatives to provide
reliable technical building science knowledge
but this information cannot begin and end
with a data sheet. It is important to select
products with a proven history of performance. Well written, technically correct air
barrier system specifications are as crucial to
the construction documents as understanding the details. Air barriers are “systems” assembled of many materials and components,
not just a product with a low air leakage rate.
A knowledgeable product representative
will listen to the architect’s design criteria,
understand the regulations and help the designer apply current technology to help select the appropriate products. Many building
enclosure consultants have been working
with air barrier systems in an effort to control moisture through wall assemblies for
years and understand the damage caused by
poor details and construction practices.
Architects and building owners should
consider retaining an enclosure consultant to
directly assist in the enclosure design. Consultants will often continue their contracted
involvement through the bid and submittal
review process and the construction phase.
Once a suitable design has been detailed
and specified, air barrier manufacturers
should join the architect or consultant in attending pre-construction meetings as well as
providing separate on-site observations. Air
barrier designed systems depend upon proper installation for continuity and effectiveness. A qualified consulting firm will help ensure the building envelope, including the air
barrier, is successfully installed. An effective
air barrier system will be one that is supplied
by a reputable air barrier manufacturer,
properly installed by a qualified air barrier installation contractor, and inspected by a qualified building envelope consultant.
■
Gary S. Osmond CET, CSC has 28 years
of experience in the building and construction technology industry. The last eight years
have specifically been focused on the air
barrier, waterproofing and roofing industry.
Osmond is the Manger, Building Science,
Henry Company, Building Envelope Systems.
He may be reached at (416) 432-4168 or
gsosmond@henry.com.
Winter 2007 15
Feature
Impacts of Airtightness on Energy Use
By Steven J. Emmerich, Building and Fire Research Laboratory, National Institute of Standards and Technology
INTRODUCTION
The energy use in commercial buildings due to infiltration has received little
attention in the United States. However,
as improvements have been made in insulation, windows, etc., the relative importance of these airflows has increased. Despite common assumptions that envelope
air leakage is not significant in office and
other commercial buildings, measurements have shown that these buildings are
fairly leaky. Infiltration in commercial
buildings can have many negative consequences, including reduced thermal comfort, interference with the proper operation of mechanical ventilation systems,
degraded indoor air quality (IAQ), moisture damage of building envelope components and increased energy consumption.
Since 1997, the Building Environment
and Thermal Envelope Council of the
National Institute of Building Sciences
has sponsored several symposia in the
U.S. on the topic of air barriers for
buildings in North American climates.
Others have also published articles on
the importance of air leakage in commercial buildings (Anis 2001, Ask 2003,
Fennell and Haehnel 2005). However,
the focus of these conferences and publications has largely been air barrier
technology and the non-energy impacts
of air leakage in buildings.
Over the last 20 years, engineers in
the Building and Fire Research Laboratory at the National Institute of Standards and Technology (NIST) have studied the issue of airtightness of
commercial buildings including development of airtightness measurement
methods, compilation of a database airtightness measurements, and analysis of
the energy impacts of infiltration in
commercial buildings. This article presents the most complete set of measured
U.S. commercial building airtightness
data and describes two simulation studies on the impact of airtightness on
building energy use.
16 Journal of Building Enclosure Design
AIRTIGHTNESS DATA
In 1998, Persily published a review
of commercial and institutional building
airtightness data that found significant
levels of air leakage and debunked the
“myth” of the airtight commercial building. In 2005, Emmerich and Persily updated the earlier analysis for the U.S. by
including data from over 100 additional
buildings. The 2005 update reports on
measured envelope airtightness data
from over 200 U.S. commercial and institutional buildings assembled from
both published literature and previously
unpublished data. The buildings include
office buildings, schools, retail buildings,
industrial buildings and other building
types.
The airtightness of building envelopes is measured using a fan pressurization test in which a fan is used to
create a series of pressure differences
across the building envelope between
the building interior and the outdoors.
The airflow rates through the fan that
are required to maintain these induced
pressured differences are then measured. Elevated pressure differences of
up to 75 Pa are used to override weather-induced pressures such that the test
results are independent of weather
conditions and provide a measure of
the physical airtightness of the exterior
envelope of the building. ASTM Standard E779 (ASTM 2003) describes the
fan pressurization test procedure in detail. In conducting a fan pressurization
test in a large building, the building’s
own air-handling equipment sometimes
can be employed to induce the test
pressures.
The airtightness data presented here
are collected from a number of different studies that use different units and
reference pressure differences (see
Emmerich and Persily 2005 for sources
of data). Air leakage data were available
for 201 U.S. commercial and institutional buildings that were tested for a
variety of purposes but were not randomly selected to constitute a representative sample of U.S. commercial
buildings. None of the buildings are
known to have been constructed to
meet a specified air leakage criterion,
which has been identified as a key to
achieving tight building envelopes in
practice. The results are presented
here as airflow rates at an indoor-outdoor pressure difference of 75 Pa normalized by the above-grade surface
area of the building envelope. When
necessary, this conversion was based on
an assumed value of the flow exponent
of 0.65. The values of envelope airtightness are given in units of m 3 /h•m 2 ,
which can be converted to cfm/ft 2 by
multiplying by 0.055.
The average air leakage at 75 Pa for
t h e 2 0 1 b u i l d i n g s i s 2 8 . 4 m 3/ h • m 2,
which is essentially the same as the average for U.S. buildings included in the
earlier analysis by Persily. This average
airtightness is tighter than the average
of all U.S. houses but leakier than conventional new houses based on a large
database of residential building airtightness (Sherman and Matson 2002). The
average of the U.S. commercial buildings is also similar to averages reported
by Potter (2001) of 21 m3/h•m2 for offices, 32 m 3 /h•m 2 for factories and
warehouses, and 26.5 m 3/h•m 2 for superstores built in the United Kingdom
prior to new building regulations that
took effect in 2002.
The airtightness data were also analyzed to assess the impact of a number
of factors on envelope airtightness including number of stories, year of construction, and climate. It is important to
note that the lack of random sampling
and the small sample size limits the
strength of any conclusions concerning
the impacts of these factors. Also, not
all of these parameters were available for
all buildings in the database. Figure 1
(Page 23) is a plot of the air leakage at
75 Pa vs. the number of stories of the
building and shows a tendency toward
more consistent tightness for taller
buildings. The shorter buildings display
a wide range of building leakage. This
result is consistent with the earlier
analysis by Persily (1998).
Figure 2 (Page 23) is a plot of the
air leakage at 75 Pa vs. the year of construction of the building for buildings
built more recently than 1955. While
common expectation is that newer
commercial buildings must be tighter
than older ones, the data gives no indication that this is true. This result is
also consistent with the earlier analysis
by Persily (1998), despite the addition
of numerous newer buildings in this
dataset. However no attempt has yet
been made to specifically study the
achieved airtightness in U.S. commercial buildings constructed with a continuous air barrier such as currently required in Massachusetts.
Figure 3 (Page 23) is a plot of the
air leakage at 75 Pa vs. the climate
where the building is located as measured by annual heating degree-days base
18C for buildings of 3 stories or fewer
(189 of the buildings). The data indicate
a general trend toward tighter construction in the colder climates. Although
there are data from numerous locations,
there is little data from the northern
U.S. and even less from the western
U.S. If possible, future efforts should
focus on collecting data in those regions.
ENERGY IMPACT STUDIES
Recently, NIST has published the results of two simulation studies of the
energy impact of airtightness in U.S.
commercial buildings. Emmerich et al.
(2005b) reported on an estimate of the
national energy liability of infiltration in
U.S. office buildings by performing simulations for 25 prototype buildings using
a coupled building thermal and multizone airflow analysis tool. Using the
same simulation technique, Emmerich
et al. (2005a) conducted a simulation
study in support of the consideration of
an air barrier requirement by the
American Society of Heating Refrigerating and Air- Conditioning Engineers
(ASHRAE) SSPC 90.1 committee.
Continued on Page 20
TABLE 1: SUMMARY OF MODELED OFFICE BUILDING CHARACTERISTICS
No.
Floor
Area
(m2)
Floors
Year
Location
Lighting
Load
(W/m2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
576
604
743
929
1486
2044
2601
3716
3902
4274
13 935
16 723
26 942
26 942
27 871
28 800
53 884
67 819
68 748
230 399
1022
1208
1579
38 090
46 452
1
3
1
2
2
2
4
5
2
3
6
6
11
6
12
10
19
10
28
45
2
2
2
9
14
1939
1920
1954
1970
1969
1953
1925
1908
1967
1967
1968
1918
1929
1948
1966
1964
1965
1957
1967
1971
1986
1986
1986
1986
1986
Indianapolis, IN
Toledo, OH
El Paso, TX
Washington, DC
Madison, WI
Lake Charles, LA
Des Moines, IA
St. Louis, MO
Las Vegas, NV
Salt Lake City, UT
Cheyenne, WY
Portland, OR
Pittsburgh, PA
Amarillo, TX
Raleigh, NC
Fort Worth, TX
Minneapolis, MN
Boston, MA
New York, NY
Los Angeles, CA
Greensboro, NC
Tucson, AZ
Scranton, PA
Pittsburgh, PA
Savannah, GA
Receptacle Weekly
Load
Operating
(W/m2)
Hours (h)
22.2
18.0
22.5
25.4
28.2
20.3
18.0
21.1
23.5
28.0
23.6
19.1
18.0
19.7
21.8
23.1
24.8
29.7
26.5
25.5
18.5
18.5
18.5
16.1
16.1
7.1
6.2
6.9
7.5
7.5
6.7
6.2
7.2
5.5
7.6
6.7
5.0
7.1
6.5
7.3
6.6
6.8
9.6
8.1
8.4
7.5
6.2
7.5
8.3
5.8
83
83
83
83
83
77
77
77
84
86
84
105
168
77
168
105
105
86
102
102
77
84
77
102
102
Effective
Leakage
Area
at 10 Pa
(cm2/m2)
15
15
10
7.5
5
10
10
10
7.5
5
5
10
10
10
5
5
3.33
5
3.33
3.33
5
5
5
3.33
3.33
TABLE 2: SUMMARY OF ANNUAL INFILTRATION RESULTS (H-1)
Building
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Average
when
system
is off
0.27
0.57
0.14
0.14
0.12
0.16
0.29
0.22
0.12
0.10
0.13
0.25
NA
0.28
NA
0.2
0.14
0.12
0.19
0.13
0.11
0.10
0.12
0.063
0.075
Average during system operation
Negative
0.54
0.91
0.56
0.45
0.45
0.48
0.64
0.47
0.42
0.40
0.41
0.62
0.40
0.58
0.61
0.56
0.37
0.39
0.44
0.40
0.42
0.26
0.41
0.40
0.40
Neutral
0.31
0.70
0.16
0.12
0.13
0.20
0.40
0.22
0.12
0.10
0.15
0.26
0.20
0.35
0.19
0.22
0.13
0.12
0.19
0.12
0.14
0.10
0.14
0.058
0.081
Positive
0.15
0.52
0.026
0.013
0.015
0.066
0.23
0.085
0.026
0.015
0.044
0.089
0.087
0.19
0.031
0.05
0.023
0.071
0.057
0.006
0.027
0.033
0.025
0
0.003
Average for all hours
Negative
0.40
0.74
0.35
0.29
0.28
0.31
0.45
0.34
0.27
0.25
0.27
0.48
0.40
0.42
0.61
0.42
0.28
0.26
0.34
0.29
0.25
0.18
0.25
0.27
0.27
Neutral
0.29
0.64
0.15
0.13
0.12
0.18
0.34
0.22
0.12
0.10
0.14
0.26
0.20
0.31
0.19
0.21
0.13
0.12
0.19
0.12
0.12
0.10
0.13
0.061
0.079
Positive
0.21
0.55
0.086
0.076
0.066
0.12
0.26
0.16
0.070
0.057
0.088
0.15
0.087
0.24
0.031
0.11
0.067
0.095
0.11
0.056
0.074
0.067
0.076
0.025
0.031
Winter 2007 17
Continued from Page 17
SIMULATION TOOL
McDowell et al. (2003) describes the
details of the coupling of the CONTAM
and TRNSYS simulation tools used for
the two studies. CONTAM is a multizone airflow and contaminant dispersal
program with a graphical interface for
data input and display (Walton and Dols
2005). The multi-zone approach is implemented by constructing a network
of elements describing the flow paths
(ducts, doors, windows, cracks, etc.)
connecting the zones of a building. The
network nodes represent the zones,
each of which are modeled at a uniform
temperature and pollutant concentration. The pressures vary hydrostatically,
so the zone pressure values are a function of the elevation within the zone.
The network of equations is then
solved at each time step of the simulation.
TRNSYS (Klein 2000) is a transient
system simulation program with a
modular structure that is a collection
of energy system component models
grouped around a simulation engine.
The simulation engine provides the capability of interconnecting system
components in any desired manner,
solving the resulting equations, and facilitating inputs and outputs. The
TRNSYS multi-zone building thermal
model includes heat transfer by conduction, convection and radiation,
heat gains due to the presence of occupants and equipment, and the storage of heat in the room air and building mass.
U.S. OFFICE BUILDING STUDY
To study the national impacts of infiltration and ventilation rates on the
energy usage of buildings, it was necessary to conduct simulations of airflow
and energy usage for a set of different
building types and locations. The
source for the building set was a statistical analysis completed by the Pacific
TABLE 3: SUMMARY OF HEATING AND COOLING LOAD RESULTS
Annual Loads with
Annual Loads with Infiltration
No Infiltration (MJ/m2)
(MJ/m2)
No.
Heating
Net Cooling
Heating
Net Cooling
1
398
186
530
202
2
593
134
922
146
3
80
226
100
228
4
150
311
173
301
5
112
167
135
163
6
39
353
62
377
7
236
178
388
175
8
183
213
266
221
9
25
190
34
200
10
27
283
34
264
11
24
26
45
25
12
138
30
236
29
13
179
246
229
234
14
49
205
158
160
15
33
617
32
599
16
16
431
18
417
17
33
286
67
257
18
8.8
117
15
116
19
63
311
91
284
20
1.3
110
2.2
107
21
21
278
36
263
22
12
394
16
378
23
40
109
64
106
24
3.4
141
6.0
139
25
8.9
305
8.8
299
20 Journal of Building Enclosure Design
Northwest Laboratory (PNL) which
defined 25 buildings to represent the
commercial office building stock of the
United States (Briggs et al. 1987, Briggs
et al. 1992 and Crawley et al. 1992). A
summary of the buildings with some
key modeling parameters is shown on
Table 1 including airtightness values
based on the Persily (1998) dataset and
engineering judgment. Other simulation details are discussed in McDowell
et al. (2003).
To study the effects of building pressurization on infiltration and energy use,
the models were simulated with positive, negative, and neutral building pressures. The positive and negative building
pressures were created by setting the
return airflow rate 10 per cent lower
and higher, respectively, than the supply
airflow rate. The simulation models did
not include detailed equipment models
so all results are presented in terms of
the zone heating and cooling loads that
must be met to maintain the thermostat
setting.
RESULTS
Table 2 summarizes the calculated
annual average infiltration rates for all
25 buildings, including all three pressurization cases and the averages when the
systems are on and off. The overall annual average infiltration for positive
pressurization cases ranges from 0.025
h-1 to 0.55 h-1 with an average of 0.12 h-1.
For negative pressurization cases, the
average infiltration rates increase and
range from 0.18 h-1 to 0.74 h-1 with an
average of 0.35 h -1. The neutral pressure cases fall in between.
Table 3 summarizes the predicted
annual heating and cooling loads per
unit floor area for all 25 buildings including both the zero infiltration case
and one of the three infiltration conditions. For buildings 1, 2, 3, 6, 7, 8, 9,
and 12, the infiltration case included in
Table 3 is the neutral pressure case,
since the systems for those buildings in
the PNL set were such that pressurization of the building would not be expected. For the remaining buildings, the
case shown is the positive pressurization case. Additionally, the cooling loads
presented for buildings 1, 2, 3, 5, 8, 9,
11, 12, 18, 20, 23, 24, and 25 are net
cooling loads obtained by subtracting
the portion of the cooling that may be
met by an “ideal” economizer (either
mechanical or operable windows) from
the total cooling load.
Figure 4 (Page 23) shows the impact of infiltration on individual building
space loads as a percent of total load
relative to the no infiltration case.
Weighted by the floor area represented
by the buildings, infiltration is responsible for an average of 33 per cent of the
heating load in U.S. office buildings. For
cooling, infiltration can either increase
or decrease the load depending on the
climate, presence of economizer capability and other building factors. On average, infiltration was responsible for a
3.3 per cent decrease in cooling load,
but resulted in a significant increase in
cooling load in several cases.
U.S AIR BARRIER REQUIREMENT STUDY
Emmerich et al. (2005a) reported on
a simulation study of the energy impact
and cost effectiveness of improving envelope airtightness in low -rise U.S.
commercial buildings to provide input
to the ASHRAE SSPC 90.1 committee
in its consideration of adding a continuous air barrier system requirement to
the standard. Such an air barrier system
is the combination of interconnected
materials, flexible joint systems, and
components of the building envelope
that provide the airtightness of the
building. The current standard includes
detailed quantitative limits for air leakage through fenestration and doors but
only very general qualitative guidance
for the opaque portion of the building
envelope (ASHRAE 2001). For example,
the Standard requires sealing, caulking,
gasketing, or weather-stripping such locations as joints around fenestration
and doors, junctions between floors,
walls and roofs, etc. However, there is
no quantitative air leakage limit specified for either the wall and other envelope components or the building as a
whole. This might be considered analogous to requiring that care be taken
when installing insulation without requiring any minimum R-value.
Annual energy simulations and cost
estimates were prepared for a two
story office building, a one-story retail
building, and a four-story apartment including a 3ft (0.92m) plenum per floor.
The internal gains for the occupied
spaces include lighting, receptacle loads,
and occupants. These gains are all applied using a peak value and fraction of
peak schedule. The lighting peak is 1.0
W/ft2 (10.8 W/m2), the peak receptacle
load is 0.63 W/ft 2 (6.8 W/m 2), and the
peak occupancy density is 5 persons/1000 ft2 (53 persons/1000 m).
The retail building is a one-story
building with a total floor area of
12,100 ft 2 (1125 m 2 ), a window-towall ratio of 0.1 and a floor-to-floor
height of 13ft (3.9m) including a 3ft
(0.9m) plenum. The lighting peak is
1.5 W/ft≤ (16.2 W/m 2), the peak receptacle load is 0.24 W/ft2 (2.6
W/m 2), and the peak occupancy density is 15 persons/1000 ft 2 (162 persons/1000 m 2).
TABLE 4: INFILTRATION AND HVAC ENERGY COST SAVINGS FOR TARGET OFFICE BUILDING
City
Annual Average
Gas Savings
Electrical
Total Savings
Infiltration (h-1)
Savings
Baseline Target
Bismarck
0.22
0.05
$1,854 42%
$1,340
26%
$3,195
Minneapolis
0.23
0.05
$1,872 43%
$1,811
33%
$3,683
St. Louis
0.26
0.04
$1,460 57%
$1,555
28%
$3,016
Phoenix
0.17
0.02
$124 77%
$620
9%
$745
Miami
0.26
0.03
$0
0%
$769
10%
$769
TABLE 5: INFILTRATION AND HVAC ENERGY COST SAVINGS FOR TARGET RETAIL BUILDING
City
Annual Average
Gas Savings
Electrical
Total Savings
Infiltration (h-1)
Savings
Baseline Target
Bismarck
0.20
0.02
$1,835 26 %
$33
2%
$1,869
Minneapolis
0.22
0.02
$1,908 28 %
$364
18 %
$2,272
St. Louis
0.24
0.01
$1,450 38 %
$298
9%
$1,748
Phoenix
0.13
0.00
$176 64 %
$992
14 %
$1,169
Miami
0.21
0.01
$6
98 %
$1,224
14 %
$1,231
TABLE 6: SUMMARY OF CALCULATED SCALAR RATIOS
Two Story Office Building Bismarck
Minneapolis
Masonry Backup Wall
First cost
$12,054
$12,054
Scalar
3.8
3.8
Steel Frame Building - Taped sheathing (Option 1)
First cost
$4,612
$4,612
Scalar
1.4
1.4
Steel Frame Building - Commercial Wrap (Option 2)
First cost
$325
$325
Scalar
0.1
0.1
One Story Retail Building Bismarck
Minneapolis
Masonry Backup Wall
First cost
$7,287
$7,287
Scalar
3.9
3.2
Steel Frame Building - Taped sheathing (Option 1)
First cost
$2,604
$2,604
Scalar
1.4
1.1
Steel Frame Building - Commercial Wrap (Option 2)
First cost
$176
$176
Scalar
0.1
0.1
St. Louis
Phoenix
Miami
$12,054
4.0
$12,054
16.2
$12,054
15.7
$4,612
1.5
$4,612
6.2
$4,612
6.0
$325
0.1
$325
0.4
$325
0.4
St. Louis
Phoenix
Miami
$7,287
4.2
$7,287
6.2
$7,287
5.9
$2,604
1.5
$2,604
2.2
$2,604
2.1
$176
0.1
$176
0.2
$176
0.1
Winter 2007 21
The HVAC system modeled for the
office building included water-source
heat pumps (WSHPs) with a cooling
tower and a boiler serving the common
loop. Each zone had its own WSHP rejecting/extracting heat from the common loop. The HVAC system modeled
for the retail building was a packaged
rooftop unit including a DX cooling coil
and a gas furnace, with a separate system for each individual zone. The St.
Louis, Bismarck and Phoenix buildings
included economizers. The heating setpoint is 70F (21.1C) with a setback
temperature of 55F (12.8C) and the
cooling setpoint is 75F (23.9C) with a
setup temperature of 90F (32.2C).
Three different airtightness levels
(no air barrier, target, and best achievable) were modeled in each building.
The values for the no air barrier level
varied for each location, while the target and best achievable construction
cases were the same for all locations.
The values for the no air barrier
(i.e., baseline) case were established
through an analysis of the airtightness
data available at the time of the study.
First, the dataset was adjusted by excluding buildings older than 1960 (even
though examination of the data by U.S.,
Canadian and U.K. authors have found
no trends toward increased airtightness
in more recent buildings), all industrial
buildings, and one extremely leaky
building. The data were then divided
REFERENCES
Anis, W. 2001. “The Impact of Airtightness on System Design”, ASHRAE Journal Vol. 43, No. 12.
ASHRAE. 2001. Energy Standard for Buildings Except Low-Rise Residential Buildings. ASHRAE
Standard 90.1; American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
ASHRAE. 2005. Handbook of Fundamentals. American Society of Heating, Refrigerating and AirConditioning Engineers, Inc.
Ask, A. 2003. “Ventilation and Air Leakage”, ASHRAE Journal Vol. 45, No. 11.
ASTM. (1999). E779-99, Standard Test Method for Determining Air Leakage Rate by Fan Pressurization. West Conshohocken, PA: American Society for Testing and Materials.
Briggs, R., Crawley, D., and Belzer, D. (1987). Analysis and categorization of the office building stock.
GRI-87/0244 by Battelle, Pacific Northwest Laboratory, for Gas Research Institute.
Briggs, R., D. Crawley, and Schliesing, J.S. (1992). Energy requirements for office buildings. Volume 1,
Existing buildings. GRI-90/0236.1 by Battelle, Pacific Northwest Laboratory, for Gas Research Institute.
Crawley, D., and Schliesing, J. (1992). Energy requirements for office buildings. Volume 2, Recent and
future buildings. GRI-90/0236.2 by Battelle, Pacific Northwest Laboratory, for Gas Research Institute.
Emmerich, S.J. and Persily, A.K., Airtightness of Commercial Buildings in the U.S. (2005) AIVC Conference, Brussels, Belgium
Emmerich, S.J., McDowell, T., Anis, W., Investigation of the Impact of Commercial Building Envelope
Airtightness on HVAC Energy Use (2005a) NISTIR 7238, National Institute of Standards and Technology,
Gaithersburg, Maryland
Emmerich, S.J., Persily, A.K., McDowell, T.P. Impact of Infiltration on Heating and Cooling Loads in
U.S. Office Buildings (2005b) AIVC Conference, Brussels, Belgium
Fennell, H.C. and J. Haehnel. 2005. Setting Airtighness Standards. ASHRAE Journal, Vol. 47, No. 9.
Klein, S. (2000). TRNSYS – A transient system simulation program. Engineering Experiment Station
Report 38-13. Solar Energy Laboratory, University of Wisconsin-Madison.
McBride, M.F. 1995. “Development of Economic Scalar Ratios for ASHRAE Standard 90.1R”, Proceedings of Thermal Performance of the Exterior Envelopes of Buildings VI, ASHRAE.
McDowell, T.P., Emmerich, S., Thornton, J. and Walton, G. (2003). Integration of Airflow and Energy
Simulation Using CONTAM and TRNSYS. Proceedings of ASHRAE Transactions, Vol. 109, Part 2.
Olivier, D. 2001. “Shattering the energy barrier” Building Services Journal: April 2001.
Persily, A.K. (1998). Airtightness of Commercial and Institutional Buildings: Blowing Holes in the
Myth of Tight Buildings. Proceedings of Thermal Performance of the Exterior Envelopes of Buildings
VII, pp. 829-837.
Potter, N. (2001). Air Tightness Testing – A Guide for Clients and Contractors. BSRIA Technical
Note 19/2001.
Sherman, M.H. and Matson, N.E. (2002). Airtightness of New U.S. Homes: A Preliminary Report.
LBNL-48671, Lawrence Berkeley National Laboratory.
22 Journal of Building Enclosure Design
into north (Standard 90.1 climate zones
5 and above) and south (Standard 90.1
climate zones 4 and below) subsets for
the North American buildings only. Unfortunately, the available data are inadequate to support a breakdown by the
individual climate zones. Finally, within
those North and South subsets, average
airtightness was calculated for short
buildings (three stories and less) and tall
buildings (four stories and up) as the
data demonstrate that the tall buildings
are tighter on average. The average
measured value from the short buildings in the south was used as the baseline value in the warmest climate
(Miami) and the average measured
value from the short buildings in the
north was used as the baseline value in
the coldest climate (Bismarck). The values for the remaining locations were assigned by linearly interpolating between
these values using the number of heating degree days (HDD) for the location.
As a result, the baseline whole building
air leakage values with no air barrier
are as follows, in units of L/s-m 2 at 75
Pa (cfm/ft2 @ 0.3 in H2O):
• Miami: 2.3 cfm/ft2 (11.8 L/s-m2)
• Phoenix: 2.2 cfm/ft2 (11.1 L/s-m2)
• St. Louis: 1.8 cfm/ft2 (9.1 L/s-m2)
• Minneapolis: 1.4 cfm/ft2 (7.2 L/s-m2)
• Bismarck: 1.3 cfm/ft2 (6.6 L/s-m2)
In addition to the baseline level, all
buildings were modeled at two levels of increased airtightness. Both published building airtightness data and current commercial buildings airtightness standards were
considered in selecting these levels. The
“target” level was selected to represent a
level of airtightness that can be achieved
through good construction practice, while
the ‘best achievable’ level is based on the
tightest levels reported for nonresidential
buildings. About 6 per cent of the buildings listed in the database would meet the
selected target airtightness level (0.24
cfm/ft2 (1.2 L/s-m2)). Achieving the tightest
level (0.04 cfm/ft2 (0.2 L/s-m2)) would require an aggressive program of quality
control during construction and airtightness testing, combined with efforts to
identify and repair any leaks.
RESULTS
As shown in Tables 4 and 5, the annual average infiltration for the office
and retail buildings with the baseline air
leakage rate ranges from 0.13 h -1 to
0.26 h-1 depending on the climate. Reducing the air leakage rate to the target
level reduces the annual average infiltration rates by an average of 83 per
cent for the office building and 94 per
cent for the retail building (note that
outdoor air ventilation requirements
are met for these buildings through operation of the mechanical ventilation
systems).
Tables 4 and 5 also summarize the
annual heating and cooling energy cost
savings for the office and retail buildings
at the target air leakage level relative to
the baseline level. The annual cost savings are largest in the heating dominated climates.
COST EFFECTIVENESS
As described in Emmerich et al.
(2005a), a cost effectiveness analysis of
the air barrier energy savings was conducted using the scalar ratio methodology (McBride 1995) employed by
ASHRAE SSPC 90.1. This cost analysis
was performed to put the calculated
energy savings in context using estimated values of the costs associated with
the air barrier measures. As seen in
Table 6, the majority of cases with two
exceptions (the office building with masonry backup in climate zones 1 and 2)
have a Scalar Ratio less than 8 for the Target case.
SUMMARY
Despite common assumptions about
“sealed” commercial buildings, the available U.S. building airtightness data indicate
that commercial buildings are similar to
typical U.S. houses and, significantly, the
data shows no trend toward improved
airtightness for newer buildings. Although
this airtightness database includes over
200 buildings, any general conclusions
from this analysis are still limited by the
lack of random sampling.
Two recent simulation studies using a coupled multi-zone airflow and building thermal
modeling tool demonstrate that the energy
impact of infiltration in U.S. commercial buildings is substantial—up to one third of HVAC
energy use—and that cost effective measures
are available to save much of this energy for
many buildings in most U.S. climates.
Figure 1 - Normalized building air leakage vs. height of building (in stories).
Figure 2 - Normalized building air leakage vs. year of construction.
Figure 3 - Normalized building air leakage vs. climate (in heating degree-days base 18C).
Figure 4 - Per cent of space loads due to infiltration
Winter 2007 23
Further study is needed to boost the
knowledge of energy impacts of commercial building airtightness. Additional measured airtightness data should be collected
including for new buildings constructed
with continuous air barriers and in underrepresented regions such as the Northern
and Western U.S. Additionally, field studies documenting energy savings would be
helpful. Finally, the potential for tightening
and saving energy in the vast stock of existing buildings should be demonstrated in
sound field studies.
■
ACKNOWLEDGMENTS
This work was sponsored by the US.
Department of Energy, Office of Building
Technologies under Interagency Agreement No. DE-AI01-01EE27615.
Steven Emmerich has been a research engineer in the Indoor Air Quality and Ventilation
Group of the Building and Fire Research Laboratory at the National Institute of Standards
and Technology since 1992. He is currently
Chair of ASHRAE’s Technical Committee 4.3
Ventilation Requirements and Infiltration. He
can be reached at (301) 975-6459.
24 Journal of Building Enclosure Design
Feature
Commissioning Airtight Building Enclosures:
The Importance of the Pre-Construction Phase
Commissioning Process
By Kevin D. Knight, Retro-Specs Consultants Ltd. and Bryan J. Boyle, Retro-Specs Consultants Ltd.
TODAY’S DESIGN AND CONSTRUCTION of commercial buildings is placing new
challenges and demands on one of the oldest
industries known to man. As the world population increases, we are forced to live in areas
which were previously unoccupied—areas
which often possess extreme climates. As
such, the requirements for environmental
separation between exterior environment
and interior occupied space have increased.
Additionally, energy use has become a global
concern and buildings represent one of the
most significant users of non-renewable energy resources and contributors to greenhouse
gas emissions.
26 Journal of Building Enclosure Design
To this end, the building designer is not
only the artist that will create the aesthetics
of the building, but he now has the responsibility of selecting materials and designing systems that are both energy efficient and
durable. In some cases, the expected service
life of the building may be, in relative terms,
short (25 years or less). In other instances,
the building is considered a “monument”,
with an expected service life in excess of one
hundred years. As a result, the onus falls upon
the designer to understand the concepts of
occupied space use, aesthetics, budget and
the science of environmental separation.
Prior to 1950, most building enclosures
were comprised of simple building materials
and constructed by master tradesmen and
qualified, experienced installers. Today, building enclosures include many different materials installed by multiple trades, and as a result,
it becomes difficult for each trade to know
how to coordinate his work with the overall
installation of the other building enclosure
components. Compounding the problem is
the potential for chemical and physical incompatibilities between these materials and adjoining systems. The general contractor must
schedule construction so that all of the materials can be installed into an assembly, and the
different assemblies joined for a complete
functional building enclosure. With the need
to build throughout the whole year, numerous environmental conditions are faced—
rain, snow, humidity, and T of 140F
(60C)—and yet materials must be installed
within recommended installation tolerances.
Given all of these challenges, the potential for
failure of one or more building enclosure
components increases dramatically. These
conditions require advanced planning to ensure that the construction satisfies the design
intent and ever-changing energy code requirements, and provides a robust and
durable building enclosure that will function
over the full life cycle of the building.
Some contractors have developed
their own quality control (QC) programs,
but rarely do these programs address the
building enclosure in a complete and holistic manner. For this reason, there is a recognized need for a specialized discipline
to commission the building enclosure to
address environmental separation and
provide for an effective building enclosure, the requirements of which include: a
thermal barrier to provide insulating properties; a vapor retarder to reduce the diffusion of moisture through the building
enclosure; drainage planes to effectively
manage water infiltration; and an air barrier to control the movement of air through
the building enclosure. To address these
issues, the National Institute of Building
Sciences (NIBS) has developed a guideline
for the commissioning of building envelopes: NIBS Guideline 3-2006 Exterior
Enclosure Technical Requirements for the
Commissioning Process. Specifications are
also now readily available for building enclosure separation project management,
coordination and commissioning.
When one thinks of building enclosure
commissioning, or in fact, any procedures to
ensure a functional building enclosure, the
focus usually falls upon the work-in-progress
phase of construction. Specifically, what inspection and testing procedures will be conducted during construction (or even postconstruction) to ensure an effective building
enclosure? But, in actuality, many issues that
may arise during the construction process,
such as inconstructable details and other design issues, material incompatibilities, scheduling or sequencing conflicts with detailing assumptions, confusion or disagreements over
testing procedures, and a myriad of others,
can be eliminated through proper commissioning procedures conducted during the preconstruction phase of the project. The remainder of this article will focus on some of
the procedures conducted prior to the start
of construction that can greatly reduce the
number of issues encountered during the
work-in-progress phase of the project.
PRE-CONSTRUCTION PROCEDURES
With so many different design options
and with the variety of different climates
under which we build, the matrix of different system-climate combinations is so
large that it becomes impossible to effectively “standardize” a testing protocol applicable to any building (for example, employing off-site testing for performance of
materials and/or predetermined assemblies as the sole means of quality assurance). Buildings need to be viewed as individual projects with requirements peculiar
to each project. Once an understanding of
the aesthetics, performance requirements, climatic conditions and expected
design life of the building has been gained,
the selection of materials and their placement within the building enclosure can be
made.
The building enclosure commissioning
process begins early in the design phase of
the project with the aforementioned functions diligently examined for their performance requirements, both individually
and together as one functioning system.
Reviews of the drawings and specifications
are made, generally at 50 per cent, 90 per
cent and 100 per cent completion, that
consider constructability, the correct
building science, material selection, and
continuity between assemblies and systems (as the functions of different systems
must not be compromised at junctions).
While the final details will often change to
suit the selected components and assemblies used in the successful tender (bid),
these details are also reviewed prior to
being constructed. Concurrent to the design review, testing and inspection protocols to be used throughout the project are
developed, including designating specific
test standards and procedures, review of
contractor quality control programs and
third-party quality assurance (QA) programs.
Prior to awarding the contract, a review
of the tender submittals should be made to
confirm compliance with tender documents. After the award of the contract,
meetings are conducted to ensure all parties involved in the construction of the
building enclosure understand their responsibilities. These meetings usually require the
participation of the owner, designer, building envelope commissioning agent, general
contractor, appropriate subcontractors, and
third-party inspection/testing agencies or
consultants. The general contractor will
submit the construction schedule, and at
this time, the sequence of installation of an
assembly can be examined to ensure all
components can be installed as designed.
Often, details have to be revised to accommodate a different scheduling sequence
than originally envisioned. QC and QA programs are reviewed so all parties understand who is responsible for what activities.
Any environmental protection issues should
be addressed by the general contractor to
protect both work-in-progress and finished
work.
The next phase involves construction of a
mockup or mockups of typical wall sections
to prove the functionality of the assembly, to
identify any design or construction concerns,
and to set a benchmark level of acceptance
for the project. Four different types of mockups can be considered:
• An off-site laboratory setting is not uncommon for large or high-performance
projects, and usually involves testing for
air, thermal, and water penetration, and
ability to withstand structural stress loads.
• On-site “stand-alone” mockups allow for
the opportunity to work out any problems before the construction process begins. As the mockup is constructed and
tested on-site, testing is usually more limited than what can be conducted in a laboratory setting. The benefit to on-site
testing is that the mockup is exposed to
conditions for which the remainder of the
construction can be reasonably expected
to be exposed.
• Designating a portion of the final construction of the mockup is fairly common,
and like stand-alone mockups, is more
limited in what can be tested. Unlike
stand-alone mockups however, if problems are encountered, projects may be
delayed due to the time needed to correct issues found during testing.
• Small mockups are often constructed for
review of details that could not be included in the larger, start-up mockup. Ultimately, the type and number of mockups
required will depend upon the size, complexity and performance requirements of
each individual project.
Test results for the mockup must satisfy
the performance requirements of the project, but be careful with the test results! Consider a mockup of the air barrier system,
where the sample area consists of more than
one component. Testing may reveal air leakage within the system, although the amount
of leakage detected may be within the allowable leakage as specified in the tender documents. However, if the leaks are concentrated in one area, the amount of leakage might
not be within the allowable amount if it were
not “diluted” over a large test area. In other
words, there may be a point failure within the
tested area (or a failure of an individual component), but the result is diluted over the
total test area giving a misleading “pass” result. For this reason, it is imperative that the
tester have a comprehensive understanding
of the test method, and ample experience
conducting the test in question. It is one thing
to be able to run a test and publish a result—
it is quite another to be able to go beyond the
numbers to provide an accurate analysis of
what the numbers represent.
Once the mock-up is approved we move
on to the construction phase of the project
where the testing and inspection programs
designed during the pre-construction phase
Winter 2007 27
can now be implemented. Although this article has stressed the importance of the preconstruction phase commissioning, by no
means should this undermine the importance
of commissioning during the work-in-progress
phase. Think of it as if it were a building,
where the pre-construction phase commissioning is seen as laying the foundation for a
successful project. Once the foundation is laid,
work-in-progress inspection and testing can
be used as a tool to help ensure that construction continues on the right path to providing a
functional building enclosure.
■
28 Journal of Building Enclosure Design
Kevin Knight is President, and Bryan
Boyle is Operating Manger, of Retro-Specs
Consultants Ltd., a firm based in Winnipeg,
Manitoba, Canada, specializing in building
envelope commissioning, inspection and
testing. The pair have collaborated on numerous publications and research projects in
the areas of building science and building
enclosures, and their work published through
Canada Mortgage and Housing Corporation
(CHMC), ASTM, and other architectural and
trade journals. Knight is also a founding
member of the Air Barrier Association of
America, is a contributing editor for the
Journal of Architectural Coatings and a
Board Member of the Building Environment
and Thermal Envelope Council (BETEC), and
sits on the ASTM E06 subcommittee and
the ULC Standards Committee for Air Barriers.
If you would like a copy of the Building
Envelope Environmental Separation Project
Management, Coordination and Commissioning Specification, please contact RetroSpecs Consultants Ltd. at (800)-837-3207
or at retrspec@mts.net.
Feature
Calculate the Costs, Prove the
Performance
By Tony Woods, Canam Building Envelope
SUMMARY
THERE IS A GROWING NEED in the
building community to demonstrate the
benefits of high-performance enclosure
design. The relationship between the performance of the building envelope and energy expenditure is well understood by
many in the community, but often less so
by clients, owners and managers. Hard
numbers presented in an organized format help consultants and engineers present information to clients, helping them to
justify an investment in enclosure construction and materials.
That need is currently being met by
energy calculation software such as the
Canadian-made ALCAP (Air Leakage
Control Assessment Procedure) system.
ALCAP is a sophisticated and accurate
building energy simulation program used
to determine the energy savings that can
be achieved by air sealing large buildings
to create air barrier continuity. ALCAP, as
demonstrated further in this article, helps
create a detailed energy use and cost-benefit analysis breakdown in easy to understand format. It deals with cooling as well
as heating and electrical calculations to determine demand reduction and includes
124 weather locations in Canada and 210
in the US. In addition, the ALCAP report
has recently included a specific table
showing the potential benefits associated
with reducing the size of heating and cooling equipment (systems).
Software such as this creates a clearer
understanding of what many in the community already know—a high-quality
building enclosure heightens building performance in energy use, structural soundness, occupant comfort, indoor air quality
and mechanical system function.
INTRODUCTION
Most industrial, commercial and institutional buildings in North America suffer
from uncontrolled air leakage. The only
32 Journal of Building Enclosure Design
remedy is to include a continuous air barrier in new construction or retrofit existing
buildings to create air barrier continuity.
Air leakage occurs through cracks,
gaps, holes, pores in materials and other
openings in the building envelope. Air flow
is the result of pressure differences. When
air leaks, it takes with it heat, water vapor,
smoke, pollutants, dust, odors, allergens
and anything else it can find and carry. Energy moves from regions of high to regions of lesser potential: hot to cold, high
pressure to low, and so on.
There are three major sources of
pressure that cause air to leak: wind pressure, stack pressure and HVAC fan pressure. Of the three, wind is usually the
greatest. When averaged out over the
course of a year, it is about 10-15 mph
(0.2-0.3psf or 10-14Pa) in most locations
in North America?. If it hits the building
straight on, air enters the envelope on the
windward side and exits on the other
three sides and at the top, through the
roof. If the wind hits at an angle, air exits
the building on the two leeward sides and
the roof.
Stack effect, also sometimes referred
to as chimney effect, is caused by buoyancy or the simple physics lesson that hot air
rises. The weight of the column of conditioned air inside the building compared
with that outside creates a pressure difference across the building envelope. The
taller the building is, the greater the stack
pressure will be. Warm, conditioned air
escapes through holes at the top of the
building and at the roof. The resulting
lower pressure at the bottom of the building draws in air from the surrounding environment.
The third pressure comes from the
mechanical system itself. Mechanical engineers and on-site managers often choose
to bring in makeup air to increase pressure and overcome the infiltration at the
base of the building. Unfortunately, this in-
creases pressure at the top, causing more
exfiltration problems in that area. It is
amazing how often duct penetrations
through curbs on the roof are not sealed
and vented mechanical rooms are not
compartmentalized.
It has been proven that a leaky building
envelope contributes to poor energy efficiency, primarily through the increased
burden on the building’s mechanical systems. Air leakage through the building envelope can lead to unnecessary heat loss
in winter or heat gain in summer, poor indoor temperature and humidity control,
and excessive energy consumption as the
building’s HVAC system struggles to compensate for these losses
A study by the National Institute of
Standards and Technology (NIST), Investigation of the Impact of Commercial Building
Envelope Airtightness on HVAC Energy Use,
released in mid-2005, showed that the inclusion of an air barrier system in four
sampled types and sizes of building can reduce air leakage by up to 83 per cent,
representing a large reduction in energy
consumption and operating costs: potential gas savings of greater than 40 per cent,
and electrical savings of greater than 25
per cent.
Field experience has shown similar results in the real world. Dean Brigham,
business development manager for Comstock Canada Ltd., a national design-build
construction, multi-trade contracting and
facilities management firm, has found significant savings can result from simple air
sealing retrofits.
“A building with proper envelope sealing can benefit from a heating system that
is 20 to 30 per cent smaller, and usually
less expensive, than one with uncontrolled air leakage,” he says. “Eliminate
the uncontrolled air leakage and you get a
typical four- to five-year payback in natural gas savings coming directly out of reduced heating consumption, with the op-
tion to upgrade the plant with smaller,
more efficient capacity which yields annual
savings.”
ASSESSMENT AND CALCULATION
The capability of energy-use and savings calculation software is best demonstrated with field data. Calculating potential energy savings is a three-stage
process: 1) a field survey, 2) estimating airleakage flow rate and appropriate corrective measures, 3) calculating potential savings and cost/benefit analysis.
ALCAP uses simple methods for evaluating infiltration and exfiltration flows. The
airflow through the building envelope depends on the size of air leakage path and
the operating pressure differential between the conditioned space and the outdoors. The objective of the field survey is
to record the air leakage paths in the
building and to define the equivalent total
air leakage area. Each component of the
air leakage area is treated independently
in determining its air flow characteristics
and their contribution to the whole. It
may include visual observations, in-situ
window assembly air leakage tests and
blower door tests.
Calculations of air leakage flow rates
are based on the measurement of effective pressure differentials across the building envelope. This is based on the combined effects of the stack, wind and
mechanical pressures, hourly weather
data for the location (mainly outdoor temperature and wind speed and directions)
and the operating schedule of the indoor
air distribution system.
The whole building energy simulation
uses these air leakage flow rates to calculate the building heat loss/heat gain and to
estimate peak demand and energy use.
Proposed retrofit air sealing measures are
applied to the base model and provide estimated potential reductions in both demand and consumption savings.
The ALCAP methodology is illustrated
below with a real-life case study of a condominium building in Mississauga, Ontario,
Canada.
FIELD SURVEY
Major air leakage paths were discovered in this building at exterior doors,
window joints, duct penetrations, interior
doors, roof/wall intersections, conduits
passing through floors and elevator shafts
and vents on the roof. Air sealing measures that would reduce the heating load
and improve occupant comfort included:
Weather-stripping common area
doors:
• Smoke shaft;
• Stairwell;
• Exterior and underground doors; and
• Doors to roof/elevator, garbage and
•
•
•
•
•
mechanical rooms.
Re-weather-stripping windows:
Sealing and caulking;
Soffit/wall joints;
Fire cabinets; and
Around windows.
AIR LEAKAGE FLOW RATES
In Table 1, we can see that this condominium has an air leakage area of about
TABLE 1
Air-sealing
measures
Doors
Number
(a)
Exterior
Interior
Conduits
Windows Awning
Walls
Electrical
receptacles
Shafts
Pipes
Electrical
service
Totals
43
63
11
W/s, ft
(b)
Seal, ft
(c)
W/s,
ft2/ft
(d)
0.0159
0.0104
860
1, 260
989
1,449
37,184
32,820 0.0104
35
0.0159
Seal
ft2/ft
(e)
0.0039
0.0173
0.0209
0.0029
0.0104
68
21
0.0032
0.0282
100
0.2791
W/s, ft2 Seal/ft2
(f ) =
(g) =
(b x d) (c x e)
1.26
0.38
1.23
0.23
0.07532
36.58 9.6872
0.034432
Total, ft2
(h) =
(f +g) x a]
1.6581
1.4773
0.07532
46.2723
0.0344
0.073168 0.0731
0.180768 0.1807
39.09
8.599392 8.599392
19.20983 58.3030
TABLE 3
Month
Degree Days (F)
January
1423 (791 C)
February
1276.2 (709 C)
March
693.6 (578 C)
April
730.8 (406 C)
May
147.6 (82 C)
June
July
August
September
185.4 (103 C)
October
480.6 (267 C)
November
804.6 (447C)
December
1294.2 (719 C)
Total for the year
7380 (4,100 C)
Energy Savings
Natural Gas, ft3
657,623.08
(18, 619 m3)
589,455.48
(16, 689 m3)
336,317.04
(9,522 m3)
168,653
(4,775 m3)
20,450.28
(579 m3)
34,083.80
(965 m3)
132,873.84
(3,762 m3)
259,990.52
(7,361 m3)
596,272.24
(16,882 m3)
2,795,683,96
(79,153 m3)
$ USD/ CDN
4,092 (4,841 CAD)
3,668 (4,339 CAD)
2,092 (2,476 CAD)
1,049 (1,242 CAD)
126 (150 CAD)
212 (251 CAD)
826 (978 CDN)
1617 (1,914 CDN)
4,389 (3,709 USD)
20,580 (17,394 USD)
Winter 2007 33
2
2
5.4185 m (58.3 ft ) or about 2.9
2
2
2
2
cm /m (5.111 in /ft ) of envelope area—
which shows that the building envelope
can be described as ‘loose’? using this classification:
2
2
• Tight building: Less than 0.7 cm /m
2
2
(1.18 in /ft ) of building envelope area;
2
2
2
2
• Average: 0.7 to 1.6 cm /m (1.18 in /ft
2
2
to 2.79 in /ft ) of building envelope
area; and
2
2
2
2
• Loose: 1.7 to 3.6 cm /m (2.9 in /ft to
2
2
6.34 in /ft ) of building envelope area.
2
• The total air leakage area (5.418m ) or
2
(58.3ft ) was distributed as per the
field observations. Major air leakage
paths were found at the below grade
and the ground floor levels and at the
top floor and penthouse level.
The estimated monthly average air
leakage rate is shown in Table 2. The
heating season is assumed from mid-September to end of May. Higher indoor/outdoor temperature differences during the
winter months of December to February
lead to higher air leakage rates.
ESTIMATES OF ENERGY AND COST SAVINGS
Estimated total cost of air leakage control measures to upgrade this condo was
$99,846 (84,400.67 USD). Assumptions
used to estimate energy and cost savings
included:
• Air sealing measures would be about
60 per cent effective in curtailing air
leakage based on previous field experience;
• Weather data based on 30-year climate normals and monthly average
weather data for Mississauga;
• Fuel prices and calculated cost savings
using utility data provided for the
building previous calendar year. Current, and any indicated price increase
in energy costs, is used.
TABLE 2
Month
January
February
March
April
May
September
October
November
December
34 Journal of Building Enclosure Design
Air leakage Rate, ft3/s
514.97
489.18
360.26
257.48
154.35
205.92
309.05
360.26
499.57
• Building operating data and schedules
as provided by property management;
• Overall building interactive effects
(solar and internal gains and other
loads) and purchased space heating
consumption estimated at about 67
per cent of total heat losses; and
• Retrofit measures assumed to reduce
overall air leakage by 40 per cent.
Table 3 (Page 33) shows month-bymonth energy savings associated with airsealing measures.
Energy analysis also showed that the
air sealing measures would reduce the
peak space heating demand by about 275
kW (about 940 kBtu/hr) on coldest days
during the winter months.
consultants, engineers and building envelope specialists to work toward making better buildings that will last longer,
are more energy efficient, and more
comfortable and safe for residents. ■
Tony Woods is President of Canam Building Envelope Specialists Inc. Canam offers a
comprehensive range of environment and
energy-related services in all types of buildings. He is also past president of the Ontario
Building Envelope Council. He can be
reached at 905-890-5866 extension 222 or
twoods@canambuildingenvelope.com.
REFERENCES
1
Air Barrier Systems in Buildings, Anis,
Wagdy AIA, Whole Building Design
Guide, www.wbdg.org , a program of
the National Institute of Building Sciences (NIBS).
2
CMHC Surveys of mid- and highrise apartment buildings. CMHC, Ottawa.
3
Determination of Peak Demand
and Energy Savings Associated with
Air Leakage Measures for High-rise
Apartment Buildings, Ontario Hydro,
by Scanada Consultants Limited.
PROVING THE PERFORMANCE
The information compiled and calculated above shows how controlling air leakage at one Mississauga condo can reduce
heating load and energy consumption. Energy service professionals, energy management consulting firms, incentive-providing utilities and government
departments are currently using similar
calculation summaries to make decisions
in favor of envelope upgrades.
Proof of the connection between a
retrofitted building envelope and reduced
HVAC operating costs is available from
many documented projects conducted by
the author’s company. Simple air sealing
of roof/wall joints in Toronto single-story
schools has delivered 17 per cent average
energy cost reductions; perimeter air sealing of high-rise apartments in Ottawa and
Toronto showed an average of more than
10 per cent in electrical demand and
about nine percent in consumption. A
similar project performed in Muskoka,
Ontario for the Gravenhurst High School
cost $5696 USD ($6,740CAD) and saved
$4135 USD ($4,893CAD) in the first two
winter months.
Energy calculation software allows
complex information, as seen in the example above, to be presented in a clear
and easy-to-demonstrate manner. It
helps justify the investment in envelope
upgrades by creating a clearer picture
of the role a high-quality, high-performance building enclosure plays in reducing energy costs and load specifications
of HVAC systems. This, in turn, helps
foster a culture of cooperation among
Winter 2007 35
Feature
Under Floor Air Distribution:
The Good, The Bad and the Ugly
By Wagdy A. Y. Anis, AIA, LEED AP
NOT ONLY ARE UNDER FLOOR Air Distribution (UFAD) systems considered in conjunction with green building and sustainable
environments, but they are promoted on the
basis of energy efficiency, better comfort and
indoor air quality, and other important benefits harder to quantify, such as reduced absenteeism and greater productivity. This
paper does not cover all the design requirements. It reviews the benefits and advantages of UFAD systems, the potential pitfalls
and problems, and the architectural design
and construction requirements to produce a
successful design and installation. Most critical to the success of these buildings is the air
tightness of the building enclosure.
A BRIEF HISTORY OF UFAD
Ancient Uses of UFAD: Roman bath
houses and villas (Figure 1) sometimes used
radiant heating using heated air floor
plenums.
Prior to 1960s: Heating and ventilation
applications (Monticello, Houses of Parliament, Chicago Auditorium, Metropolitan
Opera House, Frank Lloyd Wright’s Imperial
Hotel in Tokyo).
1960s to Current: Clean rooms and
computer rooms; cooling of sensible loads
(floor return for contamination control, floor
supply for thermal control).
1990s to Current: Flexible workspaces;
heating, cooling, and ventilation of interior
and perimeter zones.
THE GOOD
Under Floor Air Distribution (UFAD) systems have many benefits compared to Conventional Air Distribution (CAD) systems:
1. ENERGY CONSERVATION
Energy is saved due to several reasons:
• Due to the greater effectiveness of displacement ventilation, less air is required,
therefore fan power is reduced.
• Due to the higher air delivery temperature (about 10F or 5.6C higher than
overhead distribution systems) the
chillers operate at a higher Coefficient of
Performance (COP) using less energy.
38 Journal of Building Enclosure Design
• Another reason less energy is used is because the window for using free cooling
or economizer cycle is increased due to
the higher delivery temperature.
2. PLUG AND PLAY
• Receptacle power and data/telephone are
available virtually everywhere. Floor outlets are provided with a plug-in “whip”, so
that they can be moved around by building maintenance, not an electrician.
• Because the plenums are pressure-controlled using variable speed fan controllers and pressure sensors, the building
can be extremely easy to test, adjust, balance and commission, if the building enclosure air-tightness and other measures
are observed.
3. INDOOR AIR QUALITY
Due to the cleaner air quality delivered to the breathing zone, occupant satisfaction with the indoor environment is
considerably higher and occupant complaints are minimized. One of the big features of UFAD is that the building occupants have greater control over their
environment by easily adjusting the
dampers in the outlets (Figure1), relocating outlets if they are in inconvenient locations, or using a different outlet type
that can move the air in a different pattern, or by increasing or decreasing the
number of outlets (LEED EQ 6.2 Controllability of Systems).
Optimistically under LEED, UFAD may
help obtain these credits:
EA
Pre-requisite 2: Minimum Energy
Performance Required
Optimized Energy Performance Up
to 10.
EQ Prerequisite 1: Minimum IAQ
Performance Required
Increased Ventilation Effectiveness: 1
Controllability of Systems (NonPerimeter Spaces): 1
Thermal Comfort: 1
ID
Other innovations that have not been
recognized: 4
THE BAD AND THE UGLY
ENERGY INEFFICIENCY
Picture a mechanical system where the
ducts are open-ended, unsealed and in an
unconditioned space or on the exterior of
the building. If the building enclosure is not
tight, conditioned air losses can cause the
building to become extremely energy inefficient. Building plenums can lose conditioned
air directly to the exterior (Figure 3) or
lose the air from supply plenum to return
plenum (Figure 4), or to other interior
shaft-ways or spaces. A famous GSA federal courthouse, recently designed and
built which achieved LEED Gold, was reportedly a nightmare to get the plenums
pressurized and took months of expensive
dismantling, sealing and commissioning in
order to get it functional. It is still too
leaky, causing multiple other building problems including condensation and corrosion
of floor components. The building was
modeled using DOE 2.1 to provide an energy efficiency of 46 per cent better than
ASHRAE 90.1 - 1999, but in fact it reportedly uses three times the energy per
square foot annually as an older building
across the street that incorporates a conventional overhead air distribution system.
LACK OF ACCESS
The floor layout has to be drawn similar to a reflected ceiling plan, to coordinate outlet locations with workstation
walls and partition locations. Tiles under
partitions and workstation walls are not
moveable without dismantling the workstation or wall (Figure 5); that makes it
impossible to reconfigure the layout.
Floor fan boxes, fan-coil units and
other air distribution devices typically
have filters that need replacement. Furniture layouts need coordination with tile
locations so that heavy furniture including
file cabinets, bookshelves, tables, etc. do
not impede easy access to those filters for
removal/replacement. The same is true
for controllers, valves, etc.
Continued on Page 40
CASE STUDY
BOSTON COLLEGE ADMINISTRATION BUILDING
Shepley Bulfinch Richardson and Abbott, Architects, Boston, MA
Figure 1 - Roman villa incorporating a hypocaustum
Figure 2 - Better indoor air quality due to displacement ventilation causes greater occupant comfort and satisfaction.
Figure 4 - Conventional curtain
wall floor to slab connections are
not air-tight.
Figure 3 - Plenum
losses due to leaky
enclosure.
Figure 8 - Mechanical system consists of four rooftop units
serving the four quadrants.
Figures 11 and 12 - Membrane flashings and air barrier
window transition membranes.
Figure 13 - Airtight Slabto-curtain wall joint.
Figure 14 - By staggering the
carpet tile and floor tile joints,
the plenum is effectively sealed.
Boston College requires its buildings to be designed to be compatible with and contextual
to its Gothic campus. The granite and limestone heavily articulated façade for this administration building does just that in an elegant design solution (Figure 6 and 7). The building plan is
conceived of in four quadrants; each quadrant is served by an air handling unit supplying each
floor from of a vertical duct shaft (Figure 8).
The building was conceived of for quick reconfiguration to serve a transient population. This
was the biggest driver for the UFAD system design. The exterior enclosure is designed with a
continuous air barrier system using the rigid insulation sheathing boards and peel-and-stick membranes as well as spray polyurethane foam for joints and penetration sealing (Figures 9 and 10).
All window membrane transitions from the insulating sheathing were effected using modified bitumen peel-and stick membrane (Figures 11 and 12). A sealed membrane physical connection joint was then installed between the inside face of the window frame and the membrane; additionally window perimeters were foamed with spray polyurethane foam sealant.
Wall air barrier is connected to roof air barrier and foundations. Most importantly, at curtain wall perimeters, curtain wall spandrel areas must be designed with sealed metal backpans;
the perimeter seal curtain wall-to-slab connection is mineral wool fire-stopping with a one inch
(25 mm) thick poured smoke sealant on top, that effectively separates the supply from the return plenum (Figure 13) in an airtight manner.
Concrete-filled tiles were used in a stringer-less installation. The plenum was air-tightened
using the rubber-backed carpet tile installed with joints staggered relative to the tile joints. (Figure 12). Carpet tile adhesive remains tacky for easy reconfiguration.
CONCLUSIONS
• Design and build the building enclosure with a continuous air barrier system;
• Provide fully sealed and fire-stopped plenum;
• Compartmentalize UFAD plenum in accordance with the fan service zone;
• Provide ventilation fans with VFD’s and operable dampers controlled by pressure sensors;
• Provide for catastrophic water leak: structural collapse: Indirect drains with solenoid
valves activated by water sensors/alarms;
• Insulate slabs-on-grade and slab projections;
• Seal conduits especially to thermostats;
• Seal pipe penetrations through slab and through tile (Figure 14);
• Do not use MC cable; it’s leaky;
• Filters on fan boxes and fan coil units need access;
• Coordinate outlet locations with workstations and walls;
• Coordinate outlet locations with walls and workstations so that tiles are moveable;
• Pressure test plenums (blower door). Leakage 12 per cent maximum is achievable;
• Users’ manual is needed to explain how occupants can become comfortable and how
to adjust the system;
• Provide longer “whips” on outlets for flexibility;
• UFAD building properly designed uses less energy than a CAD system; and
• Fewer occupant complaints than conventional buildings.
BIBLIOGRAPHY
Underfloor Air Distribution (UFAD) Design Guide, ASHRAE, Bauman, F.
REFERENCES
1 Air Barrier Systems in Buildings, Anis, W., www.wbdg.org/design/airbarriers.php.
2 Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC Energy Use, Emmerich, S.J., McDowell, T., Anis, W., http://fire.nist.gov/bfrlpubs/build05/PDF/b05007.pdf.
Wagdy Anis is a principal and Director of Technical Resources at Shepley Bulfinch Richardson and Abbott, architects, planners and interior designers in Boston, MA , USA
(www.sbra.com). He serves as chairman of the Building Enclosure Technology and Environment Council. Anis can be reached at wanis@sbra.com.
Winter 2007 39
Figure 5 a/b - Coordinated and uncoordinated outlet locations
Figure 6 and 7 - Façade design and detail.
Figures 9 and 10 - Insulating sheathing taped air barrier with sealed joints and penetrations.
Continued from Page 38
A basic decision (that affects the structural design) has to be made whether the core
area of the building that includes exit stairways, elevators, restrooms, janitor’s closets is also served with the UFAD system,
or whether it will be structurally designed
with the slab at the finish floor level and
served with a conventional overhead system. Concerns are: hygiene, wetting of
the plenum, accessibility of plumbing, and
pest infestation. Transitions at fire separations at elevators and stairs are another
complication and concern.
CLEANLINESS OF THE PLENUM
The documents must clearly spell out
the controlling of human waste such as
food during construction, and require a
level of cleanliness that is not left to subjective opinion. Integrated Pest Management is also required during construction.
A method of anticipating a catastrophic
water leak and dealing with the water and
associated alarms must be provided. The
structure probably will not be designed to
hold that much water. Emergency drains
must be airtight and cannot depend on a
trap filled with water to prevent loss of air
into the drain. The drain must have an airtight damper that will remain shut under
normal air pressure, but open under
water flow. One way to accomplish that is
to install a solenoid valve in the drain line
activated by the water alarm.
AIR-TIGHTNESS OF THE ENCLOSURE
The building enclosure must be designed with a continuous air barrier
system1 for the success of a UFAD building. Care with tight material selection,
sealing of joints between materials and
sealing of the joints between assemblies of
the exterior enclosure is vital, as is sealing
of all penetrations. Ordinary buildings, not
built with air barrier technology and an airtightness standard cannot successfully incorporate UFAD systems. The National
Institute of Standards and Technology
(NIST) has analyzed the air leakage rates
of commercial buildings2 and discovered
that the average building built in the U.S is
extremely leaky. In the South, buildings are
built even leakier than in the North. Coupling a leaky envelope with a UFAD system is like putting open-ended unsealed
ductwork in unconditioned spaces.
■
40 Journal of Building Enclosure Design
Feature
Air Tightness: The British Experience
By Nigel Potter, BSRIA
42 Journal of Building Enclosure Design
require a lower air tightness target to achieve
the required Target carbon dioxide Emission
Rate (TER). These same regulations (technically equivalent) have now been adopted in
Northern Ireland. The calculation methodologies for determining the design carbon dioxide
emission rates are included in SAP2005 for
the domestic sector and SBEM
(www.NCM.BRE.co.uk) for the non-domestic sector.
All air tightness tests should be carried
out by accredited organizations and be in accordance with ATTMA1 Technical Standard 1
(which can be downloaded from
www.ATTMA.org). This is notionally equivalent to the new draft ISO 9972, except r2
needs to be above 0.98.
BSRIA was a founder member of ATTMA.
In over twenty years of testing, it has carried
out air tightness tests on well over 3,000 commercial buildings. It developed a fleet of “Fan
Rovers” many years ago, which essentially consist of 1.31yrds (1.2m) diameter axial flow fans
mounted on trailers and powered, via rear
power take offs, by 1.05 gallons (4 litre) Land
Rover Discovery petrol engines. The fans are
capable of delivering up to 40 m3.s-1 of air into
a building, so that when up to four are lined up,
very large distribution warehouses can be tested for compliance. At the other end of the
Air Permeability M3/Ch
Air Permeability
UNINTENTIONAL AIR LEAKAGE IS A
major source of energy loss in the UK building stock. Only recently, however, has it become a regulatory requirement to restrict it.
Although test methods have been recognized
for twenty years, and some advanced clients
have required building testing for the last 15,
only now that it is enshrined in the Building
Regulations is it becoming mainstream.
It first appeared in the Building Regulations for England & Wales in 2002, which required all buildings with a gross floor area
greater than 1195 yd2 (1,000 m2) to be air
tightness tested, and to achieve an air permeability less than 10 m3/(h.m2) at a test
pressure of 50 Pascals. This is the amount of
air required to pressurize the building divided by the envelope area. For air permeability, the envelope area is defined as the area
of the internal surface of external walls, roof
and ground floor slab, as opposed to air
leakage index, which excludes the area of
the ground floor slab.
In April 2006 the regulations were further
revised, which made it a statutory requirement for all non-domestic buildings to be air
tightness tested along with all different dwelling
types. Essentially all new air-conditioned or
mechanically ventilated buildings need to
demonstrate that they will use 28 per cent less
energy than a building built to the 2002 regulations. Naturally ventilated commercial buildings should use 23.5 per cent less energy and
dwellings should use 20 per cent less energy
compared with an identical notional building
built to the 2002 regulations. These energy
savings are expressed in kg of CO2 per square
metre.
Whilst there is a blanket maximum air
permeability of 10 m3/(h.m2), many buildings
scale, BSRIA uses single fan blower doors for
the domestic sector and with a full range of fans
caters for all building sizes.
From twenty years of experience BSRIA
has found a wide variety in the performance of
buildings, but with generally improving performance.
WAREHOUSES AND RETAIL UNITS
A survey of a dozen factory/warehouse
units, late 1980’s to early 1990’s revealed air
permeability values which were typically
around 20 m3/(h.m2) and usually in the range of
15 to 25 m3/(h.m2) (see chart). Superstores
were very much in the same very leaky category. Now, 90 per cent of factory/warehouse
units pass the required 10 m3/(h.m2) for the
Building Regulations and indeed approximately
70 per cent achieve an air permeability less
than 5 m3/(h.m2). There are quite a few retail
store operators who have demanded a better
standard of air tightness than required by the
regulations. For instance, Tesco require the
equivalent of an air permeability of less than 2
m3/(h.m2) for all their new stores and they are
the largest superstore chain in the UK (40 per
cent market share). BSRIA has also carried out
consultancy and tests on Tesco stores in
Poland and Hungary, which passed the required design standard—which only proves
that it can be done despite language difficulties!
Since these building types can contain construction details which can be replicated with
ease, they are out performing most other
building types from an air tightness point of
view. Well before the 2002 Building Regulations came in, an analysis of the air tightness
performance of the top 300+ superstores
tested was undertaken and the results are
presented in the attached figure below.
B&Q, which is a large and National DIY
retail chain compared the heating energy
consumption of two of their (naturally ventilated) stores — 100,000 square feet each.
One with an air tightness of 4.0 m3/(h.m2)
consumed 35 per cent less energy than a
store with an airtightness of 8.5 m3/(h.m2).
OFFICES
A variety of air tightness tests were undertaken in office buildings in the early 1990’s and
the air leakage index (envelope area excludes
ground floor) varied from 10 to 40 m3/(h.m2).
The overall conclusion of this study was that
older buildings tended to be more airtight than
new buildings and buildings with an air leakage
index greater than 20 m3/(h.m2) suffered from
lack of thermal comfort control and complaints
from the occupants.
Since the introduction of the 2002 Building
Regulations only 60 per cent of new office
buildings meet an air permeability of 10
m3/(h.m2) at the first air tightness test and
10 per cent of offices have an air permeability greater than 15 m3/(h.m2). Most office buildings are to a unique design and in
general, insufficient attention is applied to
air sealing details.
HOSPITALS AND SCHOOLS
Most hospitals and schools fail the required air permeability criteria by a wide
margin. They all tend to be unique designs
with too little attention being paid to air sealing details at the design stage. They are also
generally subject to cost pressure at the procurement stage.
COLD STORES
There has been an industry standard of
an air permeability of 0.3 m3/(h.m2) for quite
a few years for cold and chill stores. In general terms, they are designed and built by
specialist contractors and do not have any
difficulty in achieving the air tightness target.
Failures, which are few, are usually down to
poorly fitting loading bay doors.
DWELLINGS
BSRIA has carried out in excess of 300
tests on new dwellings during the last year
mostly for developers coming to terms with
the new Building Regulations. On average 83
per cent of dwellings tested passed the required standard of 10 m3/(h.m2). The chart
(see chart, page 42) indicates that almost a
third achieve an air tightness half of that re-
quired by the regulations. Apartments
achieve the required airtightness criteria
more easily than dwellings. It also appears
that conventional brick and blockwork construction techniques are slightly worse, on
average, than timber frame dwellings.
CONCLUSION
An air permeability standard of 10
m3/(h.m2) is not an arduous target to meet in
general terms, but architects and building
contractors need to pay far more attention
to air sealing details at the design stage. This
is particularly relevant where different subcontractors are employed and where no
specific details are given as to how they deal
with the interfaces.
NOTE
1
Air Tightness Testing & Measurement
Association.
■
Nigel Potter has worked for BSRIA for over
36 years and pressure tested a house some 30
years ago and a factory building 24 years ago.
NP is also a member of the ATTMA technical
committee. Potter designed and developed the
BSRIA ‘Fan Rovers’ and mini fan rover.
Winter 2007 43
Feature
New Test Standards for the Building
Enclosure
Edited by Richard Keleher, AIA, CSI, LEED AP
THIS ARTICLE HAS BEEN PREPARED to inform the readers of four new test standards
that will assist in achieving high performance
building enclosures.
This content is intended to provide the
reader with an understanding not only of the
state of current development for standards and
testing associated with air barriers, but also to
identify the great dearth of work in this area
and the need for a contributing effort by other
building professionals.
The recognition and acceptance of the
need for air barriers in building construction is
a new development in the industry that affects
many areas of interest and much need for development. Prior to 2003, air barrier testing
was very limited in scope and practice. Initial
efforts identified individual building materials in
their capacity to resist the movement of air.
PART ONE: THE FAMILY OF AIR
BARRIER STANDARDS
By Laverne Dalgleish, Building
Professionals Consortium Inc.
Requirements for air barriers are becoming more common in project specifications and, as a consequence, the need
for air barrier standards has grown.
Figure 1 - The Family Tree for Air Barriers
44 Journal of Building Enclosure Design
As work began on the development of
an air barrier standard, it became obvious
that a single all encompassing standard
would not be practical. It would be large,
cumbersome and not very easy to use.
There was a concern that manufacturers
would have to undertake larger scale testing
every time they made a small change in their
material and/or system. Therefore it was
decided to “break down” the requirements
for air barriers into manageable segments.
This family of standards covers a multitude of requirements and types of material that may be used as air barriers. The
first step in the development process was
to develop a “family tree,” so to speak
(Figure 1), for the standards and identify
and to define exactly what we meant
when we used the term air barrier.
Like any standard, getting agreement
on terminology and definitions was the
first challenge in the development
process. The development of the family
tree for air barriers (Figure 1) provided a
means to bring together all of the different usages of the term air barrier.
To develop the standards family tree,
the complete air barrier in a building was
deemed the air barrier system. This
would apply to all the requirements for an
airtight plane on all six sides of the building and includes the requirements for installation of an air barrier.
When we apply air barriers to buildings, we identify a main material to perform the function of the air barrier. On
the other hand, we have multitudes of
materials that are all ultimately assembled
together and connected with the primary
“air barrier” material to create air barrier
assemblies: There are roof assemblies,
wall assemblies, window assemblies and
so forth. The same approach was taken
with air barriers. The air barrier system
defines the complete air-tightness plane of
the building; it is broken down into different assemblies, which led to the creation
of an air barrier assembly standard (ASTM
E 2357 Standard Test Method for Determining Air Leakage of Air Barrier Assemblies—see Part Two of this article). Also in
this category is an air test for leakage of
air through the sides of windows (ASTM E
2319 Standard Test Method for Determining Air Flow Through the Face and Sides
of Exterior Windows, Curtain Walls, and
Doors Under Specified Pressure Difference (see Part Three of this article).
The following standards have been
added to the family tree and are still
under development:
• Air barrier component standards: Air
barrier assemblies are broken down
into the “big” pieces of material and
the subsequent component materials
used to join the “big pieces” together;
• Standard for air barrier installation and
air barrier assembly site audit or inspection: Each material needs to be installed under field conditions;
• Standard for air barrier material/assembly durability: Some air barrier materials are non-maintainable and buried
within a building assembly;
• Air barrier definitions: The term air
barrier was being used to describe a
multiple of situations, so terms needed
to be defined; and
• An air barrier design guide: Further
input from the design professionals
identified that guidance was needed
from the industry as how to design an
air barrier system for a building.
Some of these standards are simply test
methods, such as the standard for air barrier
materials. As many materials may be used to
provide the air barrier function, there needed to be a standard way of determining the
air permeance of a material. Currently,
there is a published ASTM standard as a test
method to determine the air permeance of
STAY TUNED FOR NEXT ISSUE
In the next issue, Jennifer Pollock (Architectural Testing, Inc., 717-764-7700)
will write about AAMA 508-05, a Voluntary Test Method and Specification for
Pressure Equalized Rain Screen Wall
Cladding Systems. This new test method
establishes, for the first time, a way of
comparing the performance of pressureequalized rain screen systems. Specifiers
can now specify equal systems based on
common test results. Manufacturers will
be able to compare the performance of
their products to their competitors without placing undue reliance on the performance of the air barrier behind their
systems. A whole segment of the market
that was unable to prove its performance
prior to the advent of this test method
will now be able to promote its products
in a rational and comprehensive way.
building materials (ASTM E 2178-03 Standard Test Method for Air Permeance of
Building Materials). However, this is a test
method only and as such does not include
performance requirements for a material.
The performance requirement for an air
barrier material of 0.02 L/(s·m2) @ 75 pascals therefore needs to be identified in the
project specifications and/or building code.
PART TWO: AIR BARRIER
ASSEMBLIES
ASTM E 2357-05 Standard Test Method for
Determining Air Leakage of Air Barrier Assemblies
By Lance E. Robson Jr., AIA, BET
Building Envelope Technologies, Inc.
In 2005, the American Society of Testing
and Materials approved the Standard Test
Method for Determining Air Leakage of Air
Barrier Assemblies, E 2357-05. This is the
first standard to provide a holistic approach
to the testing of air barrier assemblies utilized in building enclosures. ASTM E 2357 is
ostensibly a laboratory test. Previous standards development efforts associated with
air leakage have been limited to fenestration
components when considered as building assemblies. Test Method E 2357 allows a proponent to establish the air leakage rate of a
complete assembly that incorporates materials and accessories. This procedure measures the air leakage of a representative air
barrier assembly before and after exposure
to specific conditioning cycles and then assigns a rating dependent upon the results.
Utilizing this standard, material manufacturers can now provide a reasonable comparative analysis of an air barrier assembly’s
performance. The standard incorporates the
testing of two specimen panels with an option for a third. The first specimen panel is
approximately 8 by 8’ in area, representing
an opaque wall. The specimen preparation
includes typical seaming and sealing processes for the air barrier materials and for securing the air barrier material. The second specimen incorporates panel one, and also
includes several different penetrations representing those most typically incurred in a
building enclosure design.
Each specimen is conditioned and is tested
under static pressure loads ranging from 25300 pascals. Each is subsequently tested under
sustained cyclic and gust loads varying from
400-1200 pascals. The basic air leakage rate
reporting is presented based upon a 75 pascal
pressure difference for the opaque wall area.
The mechanics of the testing are directly analogous to that of ASTM E783, Test Method for
Measurement of Air Leakage through Installed
Exterior Windows and Doors.
In the fall of 2006, a new standard was
proposed to ASTM for the testing of air barrier systems. This testing standard is intended primarily for field applications wherein
multiple air barrier assemblies are combined
so as to provide a complete air barrier system for a selective building enclosure system. The intent is to establish the sufficiency
of the installation conditions when various
Figure 2
Air barrier assembly test.
Winter 2007 45
assemblies are combined to provide for the
building enclosure. Currently, the only means
of testing similar to this is to utilize whole
building fan pressurization. Unfortunately,
this testing is often completed after the air
barrier systems are constructed and, as such,
no longer permit the effective evaluation of
their performance. ASTM Committee
E06.41.05 Task Group has undertaken this
task and is currently establishing a work item
for the further development of the standard.
PART THREE: AIR LEAKAGE AT
WINDOWS
By Vince Cammalleri, AIA, Simpson
Gumpertz & Heger Inc.
ASTM Standard E2319-04 Standard Test
Method for Determining Rate of Air Leakage
Through The Face and Sides of Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen.
As the architectural community becomes
increasingly aware of the effects of air leakage
through building envelopes and building codes
begin to adopt mandatory air barrier requirements, building designers and specification
writers are faced with the difficult challenge of
detailing durable air seals at critical junctures
between building components. Key among
these junctures is the window/wall interface,
where successful integration of flashings, air
seals, vapor retarders and thermal barriers
depends, in large part, on the profile, performance and other design characteristics of
the window frame.
The traditional standard for determining air
leakage through windows (ASTM E 283),
measures air leakage through the test specimen, but does not discriminate between leakage through the face of the frame and through
the sides of the frame. Consequently, the task
of designing reliable air seals at the window
surrounds is complicated because the specific
paths of potential air flow through and around
the window assemblies are ambiguous. The
new standard, ASTM E 2319, addresses this
ambiguity by adopting a more complex testing
procedure that includes additional steps to
measure and report air flow through the sides
and face of the specimen separately.
The additional information provided
through E 2319 is particularly useful when design conditions dictate that the air barrier be
sealed to the window frame at a location other
than the exterior face of the window, which is
where the air seal occurs when a face-sealed
or barrier wall approach is used. Since weeped
46 Journal of Building Enclosure Design
cavity wall and rainscreen approaches are
commonly used for improved performance
and durability, a test standard to allow testing
of windows for use with these kinds of assemblies was needed. ASTM E 2319 fills this void.
It can also help clarify potential paths of air flow
through window assemblies that do not have a
clearly-defined air barrier plane, or that are
vulnerable to condensation from indoor air
leakage through the sides of the frame. Examples of such conditions include the following:
• Interior air barrier termination: Air
barrier sealed to interior surface of window frame. Outdoor air leaking through
the sides of the window frame can by-pass
the air barrier or circulate within the window frames, cooling the interior surface of
the frame and increasing the possibility of
condensation. This applies, among other
cases, when the interior gypsum wallboard
is the air barrier, or when an exterior air
barrier or window flashings turn into the
window opening and extend to the inboard surface of the window frame.
• Clad wood windows with nailing
flanges: Air barrier sealed to nailing flange
that is not designed to be the air barrier
plane of the window system. Air leakage
may occur at nailing flange attachment to
window, or at corners that are not fused
or continuously welded.
• Humidified buildings: Air barrier sealed
to exterior face of window system in humidified, pressurized buildings with multiple-glazed window units (usually with integrated blinds). Interior air leaking through
the sides of the frame can penetrate the interstitial glazing cavity and condense.
The test report for ASTM E 2319 is required to include a detailed drawing showing
the air seal between the test specimen and the
test chamber, clearly indicating the location of
the air seal relative to the specimen frame. This
detailed information further enables the designer to understand the peculiarities of a particular
window product, and to design the air seal at
the window/wall juncture accordingly.
As is the case with E 283, E 2319 is applicable to exterior windows, curtain walls, and
doors and is intended to measure only leakage
associated with the assembly and not the installation; it does not purport to address air
leakage between the assembly and the wall
opening. The new provisions for measurement of air leakage through the sides of the
frame are provided to inform specification
writers of the potential leakage through the
specimen at the window surrounds, and to
guide designers in drafting appropriate air barrier details that account for the characteristics
of a specific window product.
■
Richard Keleher is a consultant specializing
in reviewing architectural designs and documentation, with an emphasis on design of
building enclosures. He has been a senior architect in charge of technical quality reviews for
design and construction documents on over a
billion dollars worth of heavy construction, office
buildings, libraries, museums, hospitals, and
laboratories. He is also founder and current
chair of the Boston Society of Architects’ Building Enclosure Council. He can be contacted at
kel@rkeleher.com.
Laverne Dalgleish is a principal in the bpc
Building Professionals Consortium, which designs, develops and delivers site quality assurance programs for the construction industry
and has been actively involved in the construction industry for over 32 years. He is a frequent
presenter across North America on a variety of
topics relating to building envelopes, energy efficiency, green building practices, standards and
quality of construction. Laverne is currently the
Executive Director of the Air Barrier Association
of America.
Lance Robson is a principal of Building Envelope Technologies, Inc., (BET). He works
closely as a consultant and technical expert for
new and retrofit building enclosures. Through
his 25 years of experience in building enclosure design, restoration and investigation, he
has developed areas of expertise in roofing,
wall cladding, curtain walls, fenestration,
masonry and concrete repair, waterproofing
and air barriers. Robson is also a founding
director of the Air Barrier Association of
America (ABAA).
Vince Cammalleri, AIA is an Associate
Principal in the Boston area office of Simpson
Gumpertz & Heger Inc. He has extensive experience investigating and designing repairs
for walls, roofs, glass curtain walls and windows. Cammalleri has lectured as an adjunct
professor at the School of Architecture,
McGill University and as a visiting lecturer at
the Department of Architecture and Urban
Planning, Massachusetts Institute of Technology. He has published numerous papers and
is an active member of the Boston Society of
Architects and ASTM International.
Feature
A Critical Review of the Use of
Double Façades for Office Buildings in
Cool Humid Climates
By Dr. John Straube, Department of Civil Engineering and the School of Architecture at the University of Waterloo
SO-CALLED DOUBLE FAÇADES (DF) or
ventilated façades, environmental second
skins, etc have attracted great interest as
modern building enclosures. Numerous examples have been built in Europe but only a
few have been completed in North America.
The DF label actually covers a wide range of
different enclosure types. In most cases, a
DF has three layers of glazing with ventilation
and solar control devices between the outer
two glazing layers, although some ventilate
the space between the inner glazings. In
most cases, the airflow through the glazing
cavity is driven by natural buoyancy (hot air
rises) aided by wind pressure differences, although some systems use small fans (often
driven by photovoltaics). In hybrid systems,
HVAC supply or exhaust air streams are directed through a glazing cavity before connecting with the outside.
The ventilated cavity shown schematically in Figure 1 (Page 50) may be extended
over the height of several stories, the whole
height of the building, the height of a single
story, or some combination of the above.
The most common solution is the singlestory height ventilation space. A single-story
space offers the advantages of separating fire,
smoke, odor and noise between floors as
well as the construction simplicity (and economic advantages) of a repeating unit.
The current interest in double façades in
temperate climates (i.e., Continental Europe
and the UK) appears to stem from several
beliefs and desires. Double façades are believed to reduce cooling loads, allow for
more or better natural ventilation, facilitate
daylighting, increase noise control and reduce heating energy consumption.
This paper aims to provide a critical review, at a general level, of the technical merit
of each of these beliefs. The scope of this
work is for new commercial buildings that
are entirely or mostly glazed in Canada and
the Northern tier of the United States.
48 Journal of Building Enclosure Design
COOLING LOAD REDUCTION.
Reducing cooling loads can best be
achieved, in approximate order of effectiveness, by using opaque wall elements, exterior shading, solar-control coatings on glazing,
and interior shades. Many analyses of DFs
begin with the assumption that close to 100
per cent of the vertical enclosure must be
transparent. This eliminates the possibility of
using the most effective and lowest cost
means of reducing cooling load. Shading can
also be very powerful, but requires exterior
BELOW AND RIGHT: Examples of double façades for office buildings.
shading elements to be truly effective. Reflective glazing is often not seen as an acceptable
means of reducing cooling loads since the reflected light can cause glare and overheating of
adjoining buildings. Psychologically, reflective
coatings also create a sense of separation between the building and its surroundings when
viewed from the exterior during the day. Perhaps most importantly, reflective glazing with
a low solar heat gain coefficient (SHGC) does
not admit as much natural light as clear glazing, with visible light transmittances of below
20 per cent common for reflective windows.
This lower light transmittance is not a problem in climates with bright sunshine all year
(e.g. Arizona, Florida) but, for Continental Europe and Northern parts of North America,
significant portions of the year are dull and
overcast. A high natural light transmittance is
desirable for psychological and daylighting reasons, and reflective glass usually cannot provide this characteristic.
Hence, the solution proposed by a DF is
to use clear glass to allow light in, but to absorb and reflect most of the solar radiation
that passes through the outermost pane of
glass on shading devices. If the cavity in which
the shading device is placed were a sealed
glazing unit, the heat absorbed by the shades
would raise the temperature of the air space
and this heat would then be partially transmitted into the building. Some ventilated façades
uses air flow—induced by wind pressures and
thermal buoyancy—through the glazing space
to remove this heat. For this reason DFs are
also often called ventilated façades. However,
shades with a DF do result in a higher temperature in the space, and exterior glazing
slows the rejection of this heat significantly.
Shading devices of less than 12” (300 mm)
projection that are fully retractable so as not
to influence cleaning and to reduce
snow/ice/wind loads are both feasible and desirable. The architectural design of these devices is of course critical. In some parts of the
world, notably south-east Asia, large horizontal shading devices at the floor line are used
that allow foot traffic for cleaning (this load is
not a problem since the strength is controlled
by wind and snow loads).
Consider Figure 1 (Page 50), which compares the total percentage of glazing to the effective solar gain into the building (Solar Heat
Gain Coefficient = SHGC) for three types of
glazing. If a building has a large percentage of
transparent glass, the glazing system must have
a low SHGC to reduce solar loads. In fact, this
is the reason most all-glass buildings in the past
used dark body tints or reflective coating—it is
economically prohibitive (for all but big budget
buildings) to use clear glass because of the high
capital cost of the large cooling system required. Unfortunately, the choice of body tints
and reflective coatings reduces visible light
transmission. Ideally, one would like to have
low SHGC for those times and orientations
that receive high solar radiation but maximize
visibility and useful winter solar gains (note,
however, that very few winter solar gains are
needed in well insulated office buildings because of the large internal gains, however, so
this is a relatively unimportant issue). Doublefaçades, by using ventilated movable solar shading devices behind glass are one way to achieve
this ideal. Spectrally-selective glazing with fixed
or movable exterior shading is another way to
achieve the same goal. Similar low-solar gain
performance can also be achieved by reducing
the percentage of wall area that is glazed, and
this has the advantage of reducing winter heat
loss, glare and uneven daylighting as well. Reduced glazing area also almost always results in
reduced construction and maintenance costs,
as well as reduced embodied energy.
The sizing of the plant to control the cooling load will be considered later in more
depth. Note: this assumes a SHGC of 0.03 for
an opaque wall.
DFs have also often incorporated openings
for natural ventilation. Issues of natural ventilation are not, of course, tightly connected to
the design of a double façade. While natural
ventilation and DFs can be designed in an integrated manner, there is no compelling technical argument to do so. In fact, the differences
in climates and comfort expectation between
continental Europe and North-eastern North
America are significant enough that natural
ventilation is rarely of assistance in cooling
deep-plan office buildings. Natural ventilation
might be used in conjunction with artificial
cooling by the careful design of certain building
types and occupancies.
The space between the two layers of glazing in a DF does buffer wind gusts and thereby
helps to control comfort and utility problems
with the space inside. Natural ventilation air
flow need not flow through windows however. In fact allowing ventilation flow through
windows requires means to deal with the simultaneous entry of noise, dust, insects, rain
and snow. Protected, operable, screened and
sound baffled openings can, and have, been incorporated into buildings. It is also important
to realize that many very tall buildings in the
past, notably the Empire State Building,
Chrysler Building, and the RCA building, used
operable windows in conjunction with air conditioning systems without any serious difficulty.
Therefore, DFs are not required, and may
even be a handicap (in that their summer
gains are high), for natural building ventilation.
DAYLIGHTING
Façades that use large expanses of clear
glass obviously increase the amount of light
entering a building. Daylighting can save energy (although only when combined with controls that can dim and turn artificial lights off)
and is generally preferred by occupants.
Daylighting and DF are also not tightly
connected issues. Most types of façades can
(even should) be designed to provide an appropriate amount of daylighting. The amount
of window area required to provide daylighting depends on a number of factors, but DFs
are certainly not the only or best way to
achieve excellent daylighting in commercial
buildings. Properly placed windows (e.g., light
shelves and similar) have long been successfully used for daylighting.
Double façades have advantages (they can
allow lots of light in when it is dull and overcast) and disadvantages (they allow too much
light and glare in most of the time, and too
much heat out during all cold nights). A façade
with 40 or 50 per cent of its area covered in
high visual transmission glazing can usually provide plenty of daylight deep into a building. In
general, high glazing ratios (over 50 per cent)
require special measures to avoid glare and visual discomfort, especially in modern offices
that contain computer screens.
Winter 2007 49
In some of the scenarios discussed below,
it has been assumed that the floor and service
distribution system is 2’10” (0.85 m) deep and
that a wall projects 3’ (0.9 m) above the finished floor level. This leaves a 6’6” (2.0 m)
high glazed band around a building with 12’4”
(3.75 m) story heights. The extra daylighting
and view provided by adding transparency to
this 3’ (0.9 m) parapet is negligible, whereas
the additional cooling and heating loads and
glare problems imposed by a transparent skin
are significant.
relative to typical double-glazed sealed units.
The sound transmission of sealed triple-glazed
glazing units with asymmetrical airspace sizes is
almost always superior to a DF, since there is
no direct air connection of the exterior air cavity to the outside air. The DF can provide better sound control if the windows are the primary ventilation opening. Dedicated
ventilation openings, recommended above,
provide the best in sound performance, and
airtight triple or quadruple glazed punched
windows also provide excellent sound control.
SOUND CONTROL
The addition of a third pane of glass to a
façade, along with asymmetrically sized air
spaces results in reduced sound transmission
HEATING LOAD REDUCTION
Claims of the superior thermal resistance
of DF systems are generally only true when
the comparison is made to a standard doubleglazed curtainwall. The thermal bridges
caused by floor penetrations and outer pane
glazing supports used in most DFs makes
even this claim dubious. However, there are
several curtainwall systems available in North
America that use triple-glazing in thermallybroken curtainwalls. This type of system can
have a heat loss coefficient (U-value) as low as
0.8 W/m2C (over R6, e.g., Visionwall‰ or
Kawneer 7550) when used in conjunction
with gas filling and low-E coatings. Other
commercially available systems suspend thin
plastic films between two sheets of glass, driving the overall U-value even lower, (R-values
of nearly 10 are practical). Hence, there is offthe-shelf technology available that can reduce
the thermal transmission well below that of a
DF with much less cost and complexity.
Heating loads in an office building should
be relatively unimportant in cool and cold climates if the typically high levels of internal
heat generation from the occupants and the
extensive use of computers, copiers, printers,
etc. are kept inside by an airtight and well-insulated building enclosure. A properly designed quality curtainwall can often reduce
and usually eliminate the need for perimeter
heating, and thereby largely offset the capital
cost penalty of highly insulating glazing units.
Figure 2 shows how very good quality curtainwalls (U=1.3 W/m2C or 0.30 Btu/ft2F) can
almost eliminate heating requirements if the
percentage of wall area is kept below 50-70
per cent. In practical terms, heating the minimum level of ventilation air is all that is required for heating in such a building. Unfortunately, most curtainwalls in common use have
much higher heat flow, greater than 0.35
Btu/ft2F (U= 2 W/m2) and in many cases, 0.5
Btu/ft2F (U=3 W/m C)!
Figure 1 – Two (of many) Generic Types of Double
Façades.
Figure 2 – Effective SHGC as a Function of Glazing
Area and Glazing SHGC Natural Ventilation.
Figure 3 – A closer look at Space Heating Load Requirements as a Function of Glazing U-value and Area Heating and Cooling. Design Heating Load based on outdoor
temperature of -4F (-20C) and an average of 32.8 ft (10
m) distance from enclosure to center of building.
50 Journal of Building Enclosure Design
This figure assumes that no heat is released by occupants and equipment, nor is
any stored in thermal mass. If one quarter of
the lighting is left on for safety reasons, the
heat given off would be sufficient to maintain
the interior temperature during a cold -4F (20C) night, even with a 100 per cent glazed
façade, if a carefully designed high performance curtainwall (e.g., U<0.8 W/m2C or 0.15
Btu/ft2F), were used. During occupancy, ventilation loads are the most significant, not conductive losses through a well-insulated façade,
and hence heat recovery of the ventilation air
is an important energy saving strategy.
Design Heating Load based on outdoor
temperature of -4F (-20C) and an average of
32.8 ft (10 m) distance from enclosure to center of building.
The claim that double façades are energy
efficient is somewhat difficult to substantiate.
We conducted a simple peak load analysis of
one zone of an office building to compare the
performance of different façades, and assess
the capital cost implication for cooling plant.
Almost all technical comparisons in the literature use standard double-glazing as the
benchmark. This is outdated technology that
is inappropriate for a quality building and is actually uneconomical on a first-cost basis in
many parts of the world. Any building design
concerned with energy consumption and occupant comfort should use low -E, argon-filled
double-glazed units with super spacers in
properly thermally broken frames as a minimum baseline. Table 1 lists a broad range of
generic glazing product types that might be
chosen for a commercial or institutional building for which a DF is being considered. All of
the options assume that the glazing is installed
in a thermally broken metal curtainwall, with
high performance spacers in the glazing.
When comparing the values in Table 1
the performance of a typical efficient
opaque wall system should be considered –
i.e., Solar Heat Gain Coefficient SHGC
<0.02, U<0.35 W/m 2 C, R’ w >45 dB.
Hence, no glazed system that is presently
available can come close to the level of
performance delivered by a simple and relatively inexpensive opaque wall system.
CURTAINWALLS
• Solar Gain Heat Gain measured with best
performance, shades at optimum angle for
design conditions.
• Visual transmittance (VT) measured—
without shades drawn or tilted.
• Heat Loss Coefficient-measured for winter conditions with a gas fill in sealed units,
no impact of shading devices.
• Assumes that exhaust air would otherwise
be vented directly outdoors. Heat recovery of the exhaust air will usually save
much more energy than venting through a
DF.
The SHGC for the Helicon DF in London
(designed by Sheppard Robson), one of the
better-designed DF for which performance
values are available, is about 0.13, but only
when the shades are closed to 70 degrees. As
discussed above, a typical double-glazed unit
with reflective coatings can achieve this level
of solar control, but at the cost of much lower
natural light transmission during all hours, not
just when the sun is shining directly on the
wall. The Helicon can modulate the visual
transmittance and solar control of the façades
on a continuous basis by controlling the shading device.
The use of clear (e.g., Visual Transmittance,
VT >0.50), unshaded spectrally selective double-glazing would result in a SHGC much higher than a DF (e.g. typically about 0.35, but as
low as 0.28) and hence a higher cooling load.
However, the addition of light-colored shading
to the exterior of any clear double-glazed unit
would allow for very low SHGC values, under
0.1 if required. The shading can of course be
controlled (by the building control system or
the occupant) to admit as much natural light as
desired. Under design cooling conditions, the
solar radiation striking a west-facing wall will
often be very high—only a small fraction of this
light needs to be admitted to the interior to
provide sufficient daylighting. The use of perforated horizontal or vertical shading elements
will allow some view during hot sunny weather,
the same conditions during which a DF must
have the blinds closed. In fact, any shading device exposed on the exterior will be able to
allow more light to pass through to the interior
than an equivalent DF, since the heat generated
by the solar energy absorbed by the shade is
rejected to the exterior far more efficiently
than in a DF. This is so because some of the absorbed heat is retained within the glazing cavity
of a DF despite ventilation.
A simple analysis of peak cooling loads for
a Toronto, Canada office building is summarized in Table 2 (Page 53) below. We considered a single perimeter zone of offices, with a
12.3 ft (3.75 m) floor to floor height and a
depth of 26 ft (8 m) to the core zones. The
peak load analysis considers an energy-efficient office with the following characteristics:
• Energy-efficient lighting 0.9 W/ft2 (10
W/m2);
• Very high quality (1.4 W/m2C) or exceptional (0.8 W/m2C) curtainwall;
• High ventilation rates at 10 lps/person (20
cfm/person);
• Occupant density of 1 person per 140 sf
(13 m2);
• 10 W/m2 for plug loads such as computers and copiers; and
• Spectrally selective glass with a SHGC=
0.35 and VT>0.55.
Peak cooling loads are typically generated
in the climate of North-eastern North America by afternoon sun. In this case we chose a
solar load of 700 W/m2 at outdoor conditions
of 86F (30C) and 60 per cent RH and indoor
conditions of 75F (24C) and 60 per cent RH.
Although thermal mass could play an important role in improving comfort and reducing
peak loads, it has not been considered in the
analysis since it would require a detailed analysis and would benefit (in a slightly different
way) all of the systems.
Several possible enclosure/service system
scenarios are considered in the analysis:
A 100 per cent double-glazed clear glass
curtainwall. The waste of this solution can be
seen by the peak load predicted—high enough
to require one ton of cooling for every 133 sf in
this zone! Many studies by the proponents of
DFs use this type of building as their comparison, but very few buildings are actually built this
way for obvious reasons. Solar control in the
form of body tints and reflective coatings are
generally employed for all-glass buildings, (typically at the expense of visual transmittance).
A 100 per cent glass curtainwall with spectrally selective coatings to reduce the solar
heat gain while providing excellent visible
transmittance. This solution drops the solar
load to about one-half of the total load, but it
still requires 226 sf/ton cooling. There is an increase in cost for glazing but a significant savings in plant (chiller, fans and ducts) costs versus the previous scenario.
The double-façade specifications of the
Helicon building in London have been used
since this is one of the best documented projects the authors have been able to find. The
predicted performance is average—about
405 sf/ton—as expected given the quality design. Many DF are not as well designed as the
Helicon. Note that a common cooling capacity design value for speculative office buildings
(which have lower glazing areas and solar control glazing) in North America is 400 sf/ton.
The most sensible technical comparison to
a DF would be spectrally selective glazing in a
curtainwall with exterior shading, preferably
but not necessarily operable, like that in a DF.
This enclosure would of course be expected
to out-perform a DF by the mere virtue that
any heat absorbed by the shades is rejected
directly to the exterior and not trapped by the
outer pane of glass used in a DF. Hence this
type of wall is predicted to result in a lower
peak cooling load (444 sf/ton) than a DF. The
capital costs would likely be less than a DF, but
the capital and maintenance costs of exterior
blinds are still high.
Winter 2007 51
The lighting loads are reduced (by 25 per
cent, to 75 W/m2) for all of the subsequent
scenarios, since daylight-dimmed lights are
usually a cost-effective option that would likely
be used for all high-performance systems (including the DF).
The Double-Glazed Spectrally Selective
curtainwall (Scenario 4) could be limited to a
transparent band 2m (6 ft 7”) high around the
entire floor. The glazing band solution significantly reduces the solar gain versus a completely clear wall by reducing the area of glazing. The performance is somewhat inferior (at
344 sf/ton) to a well-designed double-façade,
but would be significantly less expensive to
build (perhaps half as much), clean, and maintain. Its energy performance could reach that
of the DF considered by using an Enthalpy Recovery Ventilator for the ventilation air or by
reducing the band height a further 10 per cent
to 20 per cent.
The concept of the previous scenario can
be extended to punched windows. Even at
the generous size of 2 m by 2 m (6’7” by 6’7”)
located at 3 m (9’10”) centers (e.g., 1 m or
3’3” wide columns between windows and 1.5
m or 4’11” tall spandrels), the use of doubleglazed spectrally selective glass with NO shading results in lower energy consumption than
a DF. With an ERV, the loads could be reduced
to about 25 per cent below that of the topquality DF building. This solution would be
cost competitive with a mid-range all-curtainwall building.
The glazed band concept of Scenario 5
can be improved by adding interior shading
(likely Venetian blinds) and reducing the glazing band to 6’ (1.75 m). This would commonly be done of course, but the blinds considered here would have very high reflectivity
and some small amount of perforation for
daylighting and view. The performance is
near the practical limit of what can be done
to reduce cooling loads by demand control
but the solar load still contributes 40 per cent
of the total peak load in this scenario.
Finally, triple-glazed punched windows will
further reduce summer loads and can also
practically eliminate winter heating requirements. This scenario will also be affordable
relative to the DF and exterior shaded scenarios. This scenario still provides generous views
and daylighting, while allowing for improved
control of glare, thermal comfort, and a cooling load of as low as 600 sf/ton with an ERV.
Several well-developed technologies,
proven cost effective in many applications,
have been included in the analysis of some of
the scenarios. For example, in humid climates
the high summer humidity and high occupant
density generates a significant latent cooling
load. An Enthalpy (or Total Energy) Recovery
Ventilator can be used to reduce this cooling
load penalty in the summer and the humidification/heating load requirement in the winter.
The bottom line of Table 2 above shows the
predicted impact of an ERV.
Ideally, the lighting system of the building,
or at least the exterior 20 to 25 ft (6 to 8 m),
could be designed (and even operated) in
connection with operable shading systems.
This ensures that the maximum depth of natural daylighting is achieved and the lighting
power reduced with dimmable ballasts. Such
an approach maximizes natural lighting while
minimizing cooling loads and allowing view to
the outside.
The combination of high performance features assumed in Scenario 8: triple glazed
solar control glazing, high thermal resistance
enclosure, daylighting design with control, and
ERV demand controlled ventilation have been
incorporated in some buildings, such as the
Green on the Grand (Canada’s first C2000
building) near the University of Waterloo,
(Figure 3). Enermodal designed the mechanical system of this building, completed 10 years
ago, which consumed less than 40 kBtu/ft2
(125 kWhe/m2) in 2005.
Many DFs built to date have a ventilation
space of at 18” to 2 ft (0.4 to 0.6 m). A space
of this size is needed to allow human access to
TABLE 1: PERFORMANCE CHARACTERISTICS OF A DOUBLE FAÇADES AND BEST AVAILABLE GLASS
SHGC1
VT2
U3
Sound
(W/m2C)
(dB)
Opaque Wall
<0.02
0.0
<0.35
>45
Double SS (Spectrally Selective)
0.28 – 0.40
0.55 - 0.68
1.2-1.5
30-35
Double SS w/ exterior shades
0.05 - 0.10
0.55 - 0.68
1.2-1.5
30-35
Double w/ reflective coating
0.07 - 0.20
0.15 - 0.40
1.4-1.6
30-35
Triple SS Argon filled
0.25 - 0.35
0.52 - 0.62
0.8-1.2
35-45
DF vented outer w/ shades
0.10 - 0.30
0.65 - 0.75
1.0-1.5
35-40
DF exhaust vented w/shades
0.07 - 0.15
0.70 – 0.75
<0.74
35-42
52 Journal of Building Enclosure Design
the ventilation space to allow for cleaning. The
costs of adding a large ventilated cavity in
terms of both construction cost and lost buildable area are significant (the additional cleaning
costs of a DF are also not insignificant and
worth considering). The cost of projecting the
outer glass pane outward 1.64 ft (0.5 m) is
also relatively high, although this cost could
likely be reduced through clever value engineering.
CONCLUSIONS
This general review suggests to these authors that DF’s are merely one approach to
overcoming the large energy consumption
and comfort problems that are created by
the use of excessive glazing areas of inferior
performance. Other technically valid and
less expensive solutions to solve the same
problems have been proposed above. At
this stage of research and experience, it appears that the most environmentally sound
and least expensive (construction and operating cost) solution for new buildings avoids
the problems that DFs are intended to solve
by reducing glazing area and increasing the
quality of the glazing product. The only cost
of the proposed approach is the loss of an
all-transparent-glass aesthetic. There are no
technical disadvantages.
The application of DF technology to
special use buildings, and retrofit of buildings may generate different conclusions.
There are some cases where DF technology will result in energy savings relative to
other available approaches.
ACKNOWLEDGEMENTS
This work has been initiated and partially funded by a grant from the Buildings
Group, CANMET Energy Technology
Centre (CETC), of Natural Resources
Canada as part of their HOT3000 Research Network Initiative. This important
support is gratefully acknowledged.
■
Dr. John Straube holds a joint appointment as Associate Professor in both the Department of Civil Engineering and the School
of Architecture at the University of Waterloo, in Waterloo Canada. His research and
practice have focused on the design of energy-efficient, healthy and durable buildings,
and the development of new building systems and products. He is a principal of
Building Science Consulting LLC, a building
science consultancy.
TABLE 2: PEAK COOLING LOAD ANALYSIS OF VARIOUS GLAZING STRATEGIES FOR AN OFFICE BUILDING
Scenario #
1
2
3
4
5
DG-clear
DG-SS
DF-1 based on DG-SS exterior DG-SS w/glazed
air filled
(spectrally
Helicon data shades
band lighting
selective)
control
Glazing ht (eff)
Glazing area (% of façade)
Glazing area (% of floor)
SHGC (effective)
Curtainwall U-value
Opaque U-value
Calc Solar load
Calc Solar load
Calc Conductive
Plug Loads
Lighting
Occupants-Sensible
Occupants-Latent
Ventilation-Sensible
Ventilation-Latent
Total Load
Square ft per ton of AC
Using 65% ERV
m
—
W/m2K
W/m2K
W/m
W/m2
W/m2
W/m2
W/m2
W/m2
W/m2
W/m2
W/m2
W/m?
Ft2/ton
W/m?
Ft2/ton
3.75
100%
47%
0.70
2
0.3
1838
230 (81%)
6.58 (2%)
10 (4%)
10 (4%)
5.8 (2%)
4.2 (1%)
5.6 (2%)
11.6 (4%)
283
133
272
138
3.75
100%
47%
0.35
1.4
0.3
919
115 (69%)
4.89 (3%)
10 (6%)
10 (6%)
5.8 (3%)
4.2 (3%)
5.6 (3%)
11.6 (7%)
167
226
156
242
3.75
100%
47%
0.125
1.4
0.3
328
41 (44%)
4.89 (6%)
10 (11%)
10 (11%)
5.8 (6%)
4.2 (5%)
5.6 (6%)
11.6 (12%)
93
405
82
460
3.75
100%
47%
0.1
1.4
0.3
263
33 (39%)
4.89 (6%)
10 (12%)
10 (12%)
5.8 (7%)
4.2 (5%)
5.6 (7%)
11.6 (14%)
85
444
74
511
2
53%
25%
0.35
1.4
0.3
490
61 (56%)
3.45 (3%)
10 (9%)
7.5 (7%)
5.8 (5%)
4.2 (4%)
5.6 (5%)
11.6 (11%)
109
344
98
384
6
DG-SS punched
windows +
lighting control
1.33
36%
17%
0.35
1.4
0.3
327
41 (46%)
2.90 (3%)
10 (11%)
7.5 (8%)
5.8 (7%)
4.2 (5%)
5.6 (6%)
11.6 (13%)
88
426
77
488
7
DG-SS w/
spandrel +
inner shading
+ lighting
control
1.75 m
47%
22%
0.21
1.4
0.3
257
32 (40%)
3.24 (4%)
10 (12%)
7.5 (9%)
5.8 (7%)
4.2 (5%)
5.6 (7%)
11.6 (14%)
80
470
69
547
8
TG-SS punched
+ inner shading
+ lighting
control
1.33
36%
17%
0.231
0.8
0.3
216
27 (36%)
2.30 (3%)
10 (14%)
7.5 (10%)
5.8 (8%)
4.2 (6%)
5.6 (8%)
11.6 (16%)
74
510
63
600
Winter 2007 53
Industry Update
BEC Corner
BOSTON-BEC
By Richard Keleher, AIA, CSI, LEED AP
The Boston-BEC continues to meet
monthly (except for August and December)
for 1-1/2 to 2 hours at the BSA headquarters
in Boston’s financial district. Recent presentations have included Moisture Migration
Through Existing Masonry Walls by Ann Coleman of Wiss Janney Elstner Associates, Curtainwall Design by Tammy Forner of CDC,
Inc., FM Roof Ratings by Keith Roemer,
Charles Olivier, and Richard Davis from Factory Mutual, and Radiance Daylight Simulation
by Paul LaBerge of Advanced Glazings. We
typically get 20-30 attendees at our meetings, and there’s always spirited discussion
with the presenters.
Our outreach efforts continue both in terms
of education of architects and contacts with related organizations. Our traveling “roadshow”
of 3 building science classes ended its 2006 season at Build Boston in November 2006 with attendance of up to 250 persons at each session.
We continue to reach out to other organizations including CSI and AGC to keep up the diversity of our membership beyond just architects. A membership subcommittee is starting
to spread word of our meetings at local firms
and studying ways to broaden our membership.
We have formed a subcommittee to develop an
awards program for excellence in building enclosure design. The subcommittee is currently
developing criteria and a schedule, hoping aiming to make an award in late 2007. The subcommittee includes architects, consultants, and
manufacturers representatives, and is reaching
out to other industry experts for input.
Upcoming meetings will focus on the
building enclosure aspects of the Advanced
Buildings program, which is being used as a
rebate mechanism by local utilities, and Autoclaved Aerated Concrete as a construction
material.
More information about our current initiatives and past meetings can be found at
our website: www.bec-boston.org
www.bec-boston.org.
CHARLESTON-BEC
By Nina M. Fair, AIA, CCS, LEED AP,
BEC-Charleston Chair
Charleston-BEC is roaring into its second
year! We had our Board Planning Retreat in
early November, 2006. At that meeting, we
54 Journal of Building Enclosure Design
clarified leadership succession, discussed organizational improvements, identified membership areas for further development and
brainstormed programs for 2007. We have
many more suggested topics than there are
months in the year. Our board consists of
four officers and board members working on
three committees: Membership, Sponsorship and Programs. They are doing a stellar
job! We hope to add some board members
for professional diversity.
Our membership consists of over 130 architects, engineers, builders, manufacturer’s
reps and consultants. We hope to add more
contractors and building officials in 2007. We
typically meet on the 4th Thursday of the
month with the exception of July and December. Our board meets monthly yearround. In addition to regular meetings, we
also have joint meetings with other professional organizations (AIA, CSI, ASHRAE,
AGC, etc.) and special events, such as our
popular Air Barrier University.
We have chosen to support our activities
by voluntary member sponsorships ($100
per year) and revenue-generating events
such as WUFI and air barrier classes. This approach avoids paperwork associated with
tracking membership dues.
Our recent and planned programs are:
• February 2007 Meeting: Thursday,
February 15, 6:00 – 7:30 PM
• Topic: “A Wall in Charleston: WUFI Analysis of a Brick Veneer / Metal Stud Wall”
• Presenter: Larry Elkin, PE
CHARLOTTE-BEC
By Phil Kabza, FC SI CCS AIA, Chair,
BEC-Charlotte
Our brand-new BEC-Charlotte held an
Education Day kickoff event in cooperation
with the University of North Carolina/Charlotte College of Architecture’s Center for
Architectural Technology. Over 70 local architects and contractors attended the event,
as well as over a dozen students from the
University. Several building product manufacturers held tabletop, demonstrations, and
slide presentations. The feature presentation
by Bob Kennerly of Sutton Kennerly and Associates gave attendees an in-depth look at a
complex building forensics project featuring
the reconstruction of a troubled UNCC
building located nearby. Catering for the
event was handled by volunteers from the
UNCC Student Affiliate of the Construction
Specifications Institute.
For the November 2006 meeting I presented on Specifying Mold and Moisture Control in New Construction. In January we enjoyed a presentation on thermographic
analysis of building envelopes. Upcoming
topics will include an introduction to WUFI
and an examination of regional envelope
construction practices.
Regular BEC-CLT attendees include local
architects, several roofing consultants, contractors, and representatives of two large facility owners. We meet the third Thursday of
most months at the AIA-Charlotte offices,
whose Executive Director Erica Rohrbacher
has provided the administrative leadership
we’ve needed to get our organization going.
Our website address is www.beccharlotte.org.
BEC-DALLAS
By George M. Blackburn, III,
AIA + NCARB + CSI
The Building Enclosure Council chapter
BEC-Dallas began its third year of operation
in October 2006 with myself assuming the
chair leadership position. BEC-Dallas functions as a sub-committee of the AIA-Dallas
Education Committee. The regular meetings
were moved to the second Monday of each
month at 5:00 pm in the offices of AIA-Dallas, at 1444 Oak Lawn, Suite 600, Dallas,
Texas 75207. Meetings will also be held at
other venues at various time of the year.
A dues structure of $50 for industry
members and $10 for students has been instituted to help cover a chapter expenses that
includes purchasing the copyright to the BEC
logo, purchasing stationary, covering AIA-Dallas administrative expenses for BEC-Dallas,
and paying for the BEC-Dallas Chair to travel
to Washington, DC for the two annual BEC
Chairs meetings. Work has also begun on establishing the BEC-Dallas Executive Leadership Committee that will be involved with
writing the new chapter by-laws, membership recruiting, and developing and organizing
regular educational seminars and workshops
relative to building enclosure design, construction, and maintenance. BEC-Dallas will
also be establishing a relationship with the
University of Texas at Arlington’s (UTA)
School of Architecture, the UTA Construction Research Center in the school of Engineering, and the Building and Energy Advisory Committee of the North Central Texas
Council of Governments during 2007.
During 2006 BEC-Dallas sponsored its
first open seminar Air Barriers: Increasing
Building Performance, Decreasing Energy Costs
presented by Maria Spinu of Tyvek. We had
quite a few contractor field personnel present in addition to architects. BEC-Dallas
cosponsored the Preventing Moisture, Air, and
Vapor in the Building Envelope workshop with
AIA-Dallas. BEC-Dallas is also one of the
sponsors for the next WUFI Workshop being
held in Dallas during the first week of next
February.
BEC-HOUSTON
Andy MacPhillimy, AIA, LEED AP
AIA Houston is joining the national initiative by AIA National and the National Institute for Building Sciences by establishing
BEC-Houston to establish an open forum to
promote discussion, education, and transfer
of information and technology among all
stakeholders in buildings enclosures—owners, architects, engineers, consultants, manufacturers, installers, contractors and others.
We are excited about this opportunity to
raise regional expertise, skill, and understanding of building exterior enclosure construction resulting in the improvement of the
quality of design, the installation, and the
maintenance. A kick-off meeting was held on
May 24th and was attended by a diverse
group of those interested in the mission of
BEC Houston.
In the coming weeks we will be establishing the Steering Committee to set the Vision
and Mission of BEC Houston and the Program committee to develop the series of
speakers, panels and work shops needed to
accomplish the vision and mission established
by the steering committee.
MINNESOTA-BEC
By Judd Peterson, Chair, Beverly
Hauschild-Baron, Co-Chair
From our inception on February 14,
2006, the BEC–Minnesota has scheduled
monthly meetings involving both lectures by
experts about specific aspects of the building
envelope, and informal round table discussions about preferred section detailing of the
building envelope. Speakers have included
Kim Bartz of WR Grace Company and Brent
Anderson of BA Associates about
air/water/vapor barriers on backup construction and sheathing; Dan Braun and Dan Johnson of Architectural Testing, Inc. about the
range of possible field tests for exterior
building envelopes; Craig Hall of WL Hall and
Wausau Windows about critical detailing of
window and curtainwall openings and primary seals.
Upcoming lectures include Bob Moran,
Northeast Regional Technical Representative
of BASF Polyurethane Foam Enterprises,
talking on spray polyurethane foam insulating
air barriers in the exterior envelope; Chemrex Technical Representatives will discuss all
aspects of sealant application, including
chemical compositions, compatibilities, incompatibilities, proper uses depending on
the type of sealant, primers, application conditions; and Craig Thompson, Technical Representative of the Copper Development Association, talking on copper sheet metal
enclosures and detailing, with examples
formed and fabricated at the seminar by McGrath Sheet Metal.
Our BEC participants have voiced appreciation for the access to critical building enclosure expertise, and the extended resources and advice from other BEC peers.
PORTLAND-BEC
By Rob Kistler, The Facade Group, Inc
In our rookie year, the Portland-BEC has
been hugely successful, attracting between
40-50 people per event. Monthly topics have
ranged from Membrane and Sealant Compatibility to a Construction Claims Task Force Update (a task force created by the Oregon
Legislature to study the relationship between
construction liability claims and construction
industry practices, construction defects, consumer protections, and state-mandated liability insurance requirements for contractors) to panel discussions on Eco-roofs and
how to maximize for sustainability.
In addition to the monthly meetings hosted at various firms, the most exciting event
was a two-day Symposium on Building Enclosures: Function, Sustainability, and Innovation.
The seminar, with attendees from throughout the west, called upon seven industry experts to explain the following topics: Why we
Need to Manage Rain and Moisture; Selecting
Proper “Barriers” for Your Project; Using Computer Simulation to Design More Moisture Tolerant Envelopes; Off the Shelf to off The Wall—
Green Mainstream To Innovative; Designing
One of the Worlds Largest Glass Walls; Comparing The Sustainability of Architectural Materials; and Integrating Water With the Urban
Fabric—Eco-Roofs.
The coming year offers more promise as
we continue our exploration of Eco-roofs,
delve into envelope acoustics, review more
compatibility issues, and take a look at the
marketing of sustainability.
Please visit our website at www.portlandbec.org for updates on our monthly presentations and PDF copies of past presentations including six of the seven presenters at
the November Symposium.
SEATTLE-BEC
By David K. Bates, AIA, Olympic Associates Company
SeaBEC survived the aberrant November 2006 snows and rain with membership
intact at about 120. After a summer hiatus of
two months during which we limited activity
to board meetings, we resumed monthly
programs in September with a program on
LEED and its relationship to building enclosure and sustainability. October brought an
update from the Washington State University/Oak Ridge Laboratories Natural Exposure
Test Facility in Puyallup Washington. We
rounded out November with a presentation
on in-wall moisture detection and monitoring systems. Programs planned for 2007 include Green Roofs, Building Design with Future
Repairs in Mind and a discussion of the Washington State Condominium Act; What’s Working,
What’s
Not.
We continue to have the generous support
of firms who provide light refreshments for
our meetings. This welcome enhancement
keeps growley stomach noises from interfering with the programs.
In September 2006, the National Building
Science Corporation held WUFI training at
the Natural Exposure Test Facility. For helping sponsor the training, Barry Hardman
generously donated a share of the registration fee to SeaBEC and Portland BEC.
Our “Task Force on Inspector Qualifications,” committee set out to address some
of the gray areas in what is known as the
“Washington State Condominium Act.” He
committee members have produced a document which will be posted on our website to
help people choose third party inspectors
and understand the scope of the condo act.
SeaBEC is collaborating with BEC Portland and BETEC for a spring symposia on
Winter 2007 55
membranes, a one-day event to be run in
both Portland and Seattle.
We are upgrading our website at
www.seabec.org to make it more useful and
informative to our members. As we launch
into the New Year, we have made a fair
amount of progress regarding the internal
structure our organization. As soon as all that
paperwork is put away, we can focus our energy on awareness and education in the construction/design community.
WESTERN PA-BEC
By Jeff Light, AIA
On January 30, 2007 we held the Western Pennsylvania Building Enclosure Council
Seminar called Double-Skin Facades: Integrated design solution. The purpose of this presentation was to describe the concept of
Double-Skin Facades (DSF) based on different sources of literature and examples. Although the concept is not new and it is already a common feature of architectural
competitions in Europe; there are still few
buildings in which DSFs have actually been
realized, and there is still too little experience
of their behavior and performance. With the
increasing concern about the energy consumption and the indoor environmental
quality in buildings, architects are now eager
to explore innovative and new facades systems. It is the opinion of the speakers that
DSF can provide both improved indoor climate and energy savings if designed properly.
The complexity of the DSF systems increases the need of careful design and collaborative effort between architects, engineers and
manufactures in the early design stage. The
intention of this presentation is to stimulate
an open discussion between the attendees
from different background and experience
on the feasibility of using this type of Façade
construction in the United States with special
focus on the environmental and economical
aspects.
Hosam Habib with Astorino the Architecture, Engineering, and Construction Management Company located in Pittsburgh presented on Double-Skin Façades design
principals.
Mark Bonczak with TRESPA the laminated panel manufacture based in the Netherlands presented on Trespa air barrier systems (www.trespa.com).
The following 2007 BEC meetings will
be:
• January 30 - Seminar Meeting - DOUBLE SKIN FACADES
• February 28 - Membership Mixer
Meeting in Cranberry,PA.
• March 29 - Seminar Meeting - Topic
and location needed.
• April 30 - Membership Mixer Meeting
in Pittsburgh,PA.
• May 29-31 - Seminar Meeting - Topic
and location needed.
• June 25-29 - Membership Mixer Meeting in Mt. Lebanon,PA.
• July 30-31 - Seminar Meeting -Topic
and location needed
• August 27-31 - Membership Mixer
Meeting in ?
• September 24-28 - Seminar Meeting Topic and location needed
• October 29-30 - Membership Mixer
Meeting in ?
• November 26-30 - Seminar Meeting Topic and location needed
Any suggestions on locations,
dates, times, and programs is appreciated.
■
CONCRETE ROOFING TILES
MODIFIERS & SEALERS
ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .37
METAL ROOF COATINGS
ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .37
Buyer’s Guide
AIR BARRIERS
Henry Company . . . . . . . . . . . . . . . . . . . . . .25
ARCHITECTURAL GLASS
Oldcastle Glass . . . . . . . . . . . . . . . . . . . .30-31
ARCHITECTURAL WINDOWS
Oldcastle Glass . . . . . . . . . . . . . . . . . . . .30-31
ASSOCIATIONS
NAIMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
National Fenestration Rating Council . . . . . .36
ASHRAE . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Indoor Air Quality Association . . . . . . . . . . .58
AUTOMATED STRUCTURE
MONITORING/MOISTURE DETECTION
Dectec Systems . . . . . . . . . . . . . . . . . . . . . .51
BUILDING DESIGN SERVICES
Wauters Design Group LLC . . . . . . . . . . . . .28
BUILDING ENVELOPE ARCHITECTS
CONSULTANTS
Conley Design Group Inc. . . . . . . . . . . . . . .24
Construction Consulting Intl. . . . . . . . . . . . .24
CONSULTANTS
Patenaude Trempe Inc. . . . . . . . . . . . . . . . . .43
ELASTOMETRIC ROOF COATINGS
ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .37
ENGINEERED CURTAIN WALL &
WINDOW WALL
Oldcastle Glass . . . . . . . . . . . . . . . . . . . .30-31
ENGINEERS
Sutton-Kennerly & Associates Inc. . . . . . . . .28
ENTRANCE SYSTEMS & STOREFRONT
Oldcastle Glass . . . . . . . . . . . . . . . . . . . .30-31
EXTERIOR INSULATING FINISH SYSTEMS
ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .37
MULTI-DIRECTIONAL DRAINAGE BARRIER
Valeron Strength Films . . . . . . . . . . . . . . . . .47
RAINSCREEN STUCCO ASSEMBLY
Stuc-O-Flex International . . . . . . . . . . . . . . .41
ROOF DECKS
Global Dec-King . . . . . . . . . . . . . . . . . . . . . .14
ROOFING MANUFACTURER
GAF Materials . . . . . . . . . . . . . . . . . . . . . . . . .4
SEALANTS, WATERPROOFING &
RESTORATION
SWR Insitute . . . . . . . . . . . . . . . . . . . . . . . . .34
SIDING, WOOD, VINYL FIBRE CEMENT
ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .37
GLASS MANUFACTURING
AFG Glass . . . . . . . . . . . . . . . . . . . . . . . . . . .18
STRUCTURAL ENGINEERING DESIGN
& CONSULTANTS
Simpson Gumpertz & Heger . . . . . . . . . . . .40
BUILDING PRODUCTS
Georgia Pacific . . . . . . . . . . . . . . . . . . . . . .IFC
INSULATION MANUFACTURERS
Johns Manville . . . . . . . . . . . . . . . . . . . . . . . . .9
Knauf Insulation . . . . . . . . . . . . . . . . . . . . . . .3
VAPOR BARRIERS
El DuPont Building . . . . . . . . . . . . . . . . . . . . .7
BUILDING SCIENCE &
RESTORATION CONSULTANTS
Read Jones Christofferson . . . . . . . . . . . . . .35
MANUFACTURER REFLECTIVE ROOF
COATING, LEAD COMPLIANT
Karnak Corporation . . . . . . . . . . . . . . . . . . .11
CERAMIC TILE ADHESIVES
ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .37
MASONRY
Mortar Net USA Ltd. . . . . . . . . . . . . . . . . . .15
WATERPROOFING / ROOFING
UNDERLAMENTS / RESTORATION
CETCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Carlisle Coatings & Waterproofing . . . . . .OBC
STO Corp. . . . . . . . . . . . . . . . . . . . . . . . . .IBC
The Waterproofing Company . . . . . . . . . . . .28
CONCRETE MODIFIERS & SEALERS
ROHM & HAAS . . . . . . . . . . . . . . . . . . . . . .37
MEMBRANE / VAPOUR BARRIER
Certainteed . . . . . . . . . . . . . . . . . . . . . . . . . .10
WEATHER BARRIER
Cosella Dorken . . . . . . . . . . . . . . . . . . . . . . .29
56 Journal of Building Enclosure Design
Applications
JOIN BETEC
Building Environment and Thermal Envelope Council
1090 Vermont Avenue, NW, Suite 700 | Washington, DC 20005-4905
Tel: (202) 289-7800 | Fax: (202) 289-1092 | www.nibs.org/BETEC
To become a member of the Building Environment and Thermal Envelope Council, please complete and return the following application form:
Name: ______________________________________________ Title: ___________________________________________________
Company: ______________________________________________ Address: _____________________________________________
City: ______________________________________________ State: _________________ ZIP Code: _________________________
Telephone: ______________________________________________ Fax: ________________________________________________
E-Mail Address: __________________________________________
MEMBERSHIP CATEGORY:
❑ Individual Member - $100
❑ Corporate Member - $250
(optional alternate member)
GROUP CLASSIFICATION:
❑ Material Supplier
❑ Trade Association
❑ Builders/Building Contractors
❑ Code & Standards Organization
❑ Academic Institution
❑ Product Manufacturer
❑
❑
❑
❑
❑
Labor Organization
Professional Society
Federal, State, Local Government
Consumer/Public Interest Group
Other (describe)
__________________________
JOIN BETEC RESEARCH
COORDINATING COMMITTEES:
I will participate on the following Research
Coordinating Committees (RCC’s):
❑ Building Thermal Envelope Materials
DUES PAYMENT:
❑ Check or Money Order enclosed payable to BETEC
❑
❑
❑
❑
❑
Fenestration
Moisture
Acoustics
EIFS
Sustainable Building Envelope
Materials & Systems
❑ Mold
❑ Walls
❑ Membranes
OPERATIONAL COMMITTEES:
I will participate on the following
Operational Committees (OC’s):
❑ Technology Transfer
❑ National Program Plan
ALTERNATE MEMBER
INFORMATION
(corporate members only):
❑ Name
❑ Title
❑ RCC’s and OC’s
❑ Please bill my Credit Card: ❑ AMEX ❑ MC ❑ VISA
Account No. ___________________________________________________ Exp. Date _________________________
Cardholder’s Name _____________________________________________ Billing Address ________________________________________________
City __________________________________________ State… _____________ ZIP ___________________________
Signature ______________________________________________________ Date _____________________________
JOIN NIBS
National Institute of Building Sciences
1090 Vermont Avenue, NW, Suite 700 | Washington, DC 20005-4905
Tel: (202) 289-7800 | Fax: (202) 289-1092 | www.nibs.org
Membership Application
Membership in the National Institute of Building Sciences is open to all interested parties as provided in the enabling legislation. Individuals are eligible to become either public interest or industry sector members. Organizations that wish to support the Institute in achieving
its objectives may become sustaining or contributing organization.
Name: ______________________________________________ Title: ___________________________________________________
Company: ______________________________________________ Address: _____________________________________________
City: ______________________________________________ State _________________ ZIP Code: _________________________
Telephone: ______________________________________________ Fax: ________________________________________________
Nature of Business/interest areas: _________________________________________________________________________________
❑ INDUSTRY SECTOR MEMBER:
Open to any individual in the following categories: Building construction;
labor organizations; home builders;
building or construction contractors;
producers, distributors or manufacturers of building products; trade
and professional associations; organizations engaged in real estate,
insurance or finance; research and
testing of building products; and
code and standard organizations.
ANNUAL CONTRIBUTION: $150
❑ PUBLIC INTEREST SECTOR
MEMBER: Open to any individual
in the following categories: Federal, state and local government,
consumer organizations, nonprofit
research and educational organizations, the media, architects, professional engineers or other design
professionals, and retirees.
ANNUAL CONTRIBUTION: $75
❑ SUSTAINING ORGANIZATION: Open to organizations in
the public interest or industry sectors desiring to provide additional
support for and participation with
the Institute to achieve the goals
and objectives. Sustaining organizations may designate up to five
individuals from their organization
to be Institute Members. ANNUAL CONTRIBUTION: $1000
❑ CONTRIBUTING ORGANIZATION: Organizations making
contributions to the Institute in
an amount substantially exceeding
$1000. Contributing organizations are accorded the same
rights and privileges as sustaining
organizations and such other
rights and privileges as authorized
by NIBS’ Board of Directors.
ANNUAL CONTRIBUTION:
$______________________
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