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Evaluating The Field Performance Of Large Buildings: Windows And Curtain Walls

May 15, 2007

EVALUATING THE FIELD PERFORMANCE OF WINDOWS
AND CURTAIN WALLS OF LARGE BUILDINGS
MARIO D. GONÇALVES
PATENAUDETREMPE,
MONTREAL, PQ
ROBERT JUTRAS
AIRINS
INC., MONTREAL, PQ
MICHAEL VELJI
VP ENGINEERING, BOSTON, MA
S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 0 7 GO N Ç A LV E S , J U T R A S A N D V E L J I • 5 7
ABSTRACT
The most common and costliest problems associated with the inservice
performance of
the vertical building envelope of large buildings are attributed primarily to excessive air
leakage and water intrusion. In particular, windows and curtain walls, as well as their interface
with the adjacent wall construction, are determining elements in the performance of
the vertical building envelope. Improved standards and design principles have contributed
significantly to improving the performance of window and curtain wall systems, whether
with respect to resistance to water penetration, air leakage resistance, wind load resistance,
or condensation resistance. The reality, however, is that many buildings of recent construction
are still experiencing problems with the inservice
performance of installed window
and curtain wall systems. Typically, these problems are the result of poor installation,
poor fabrication, or lack of adequate quality control.
This paper will evaluate the field performance of windows and curtain walls of large
buildings 1) during the early stages of construction to validate asbuilt
design and 2) during
later construction stages as a qualitycontrol
measure. Largescale
field testing to assess
building envelope performance in large buildings will be demonstrated through several practical
casestudy
examples.
The primary objective of this paper is to provide an increased level of knowledge to the
building community for an improved awareness of the benefits and limitations of the use of
field testing in evaluating the field performance of the vertical building envelope of large
buildings.
SPEAKERS
MARIO D. GONÇALVES — PATENAUDETREMPE,
MONTREAL, PQ
ROBERT JUTRAS — AIRINS
INC., MONTREAL, PQ
MICHAEL VELJI — VP ENGINEERING, BOSTON, MA
MARIO D. GONÇALVES is a senior engineer and building envelope consultant. He is the
president of PatenaudeTrempe,
a Montreal,
Quebec City,
and Bostonbased
building
envelope consulting firm with projects across eastern Canada and the northeastern United
States. He is the lead author and presenter of this paper and can be reached at
m.goncalves@patenaudetrempe.
com.
ROBERT JUTRAS is a senior engineer specializing in the laboratory evaluation of building
envelope components. He is the president of AirIns
Inc., a fullservice
building envelope
testing laboratory located in Montreal, Quebec.
MICHAEL VELJI is a senior engineer and building envelope consultant. He is the principal
of VP Engineering, a Bostonbased
building envelope consulting firm with projects
across the United States.
5 8 • GO N Ç A LV E S , J U T R A S A N D V E L J I S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 0 7
EVALUATING THE FIELD PERFORMANCE OF WINDOWS
AND CURTAIN WALLS OF LARGE BUILDINGS
INTRODUCTION
Windows and metal and glass curtain
walls generally represent as much as 50 to
100 percent of the exterior cladding of large
buildings and are determining elements in
the performance of the vertical building
envelope. They are often an important
architectural feature of a structure and represent
a significant portion of the overall
cost of a construction or renovation project.
As a determining element in the performance
of the vertical building envelope,
they must be airand
watertight,
prevent
condensation from occurring on the interior
surfaces, and resist wind load and other
Figure 1 – Metal and glass
curtain wall – new construction
(New York, NY).
Figure 3 – Aluminum
punch windows and
precast concrete (Montreal,
Quebec).
exterior forces from acting on the building
envelope. Given the evergrowing
complexity
and variety of modern building
envelopes, evaluation of their performance
in the preconstruction
and construction
phases is essential in order to avoid undesirable
and costly problems during the service
life of the building.
PERFORMANCE REQUIREMENTS
Any form of water infiltration to the interior
of a building or excessive air leakage
resulting in 1) discomfort to building occupants,
2) the formation of excessive condensation
on the interior side of the building, or
3) the formation of icicles
on the exterior side
of the building would be
unacceptable to any
building owner or occupant.
This being said,
one of the primary performance
criterium for
any window or curtain
wall system is that it
provides an appropriate
level of resistance to
water penetration and
air leakage.
Resistance to water
penetration and air
leakage resistance are
obviously not the only
performance criteria
that need to be considered;
however, the majority
of problems associated
with the inservice
performance of
building envelopes are
due to either water infiltration
or air leakage
issues. Other performance
considerations
include thermal performance,
condensation
resistance, and windload
resistance.
Performance requirements
need to be
established for each
project on a casebyFigure
2 – Metal and glass
curtain wall – building
reclad (Montreal, Quebec).
Figure 4 – Aluminum
punch windows and brick
cladding (New York, NY).
S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 0 7
Figure 5 – Example of water
infiltration within a curtain wall
assembly.
Figure 6 – Example of water
infiltration at a punch window
assembly.
case basis, based on building height and
geographic location, exterior and interior
design parameters, and type of building occupancy.
The primary performance requirements
that need to be established at
the design phase of each project are as follows:
• Wind load resistance: The design
pressures are typically established
by the project’s structural engineer
and are based on the building’s
exposure classification, height, type,
and configuration. The window and
curtain wall components need to be
designed to resist deflection and failure
at the specified design pressure.
• Resistance to water penetration:
Resistance to water penetration performance
requirements will vary
depending on the building’s height,
geographic location, and exposure
classification. In the United States,
the resistance to water penetration
rating is typically established as a
GO N Ç A LV E S , J U T R A S A N D V E L J I • 5 9
Figure 7 – Example of exterior
icicle formation due to excessive
air exfiltration within a curtain
wall assembly.
Figure 8 – Example of excessive
interior frost formation due to
excessive air infiltration at a
window/wall interface.
function of the design wind pressure.
In Canada, the CAN/CSAA440
Standard includes a user’s
guide, which recommends minimal
performance levels for each major
Canadian city, based on geographic
location and installation height.
• Airleakage
resistance: Airleakage
resistance performance requirements
are often established by local
building and energy codes and will
vary for fixed and operable sections.
• Condensation resistance: Condensationresistance
performance requirements
will depend on the
building’s geographic location and
climate conditions, as well as the
interior hygrothermal design conditions
and type of building occupancy.
INDUSTRY STANDARDS
Both the United States and Canada
have industry standards that establish
stringent performance requirements and
testing methods for windows and curtain
walls. In the United States, the American
Architectural Manufacturers Association
(AAMA) and the National Fenestration
6 0 • GO N Ç A LV E S , J U T R A S A N D V E L J I
Rating Council (NFRC)
are the primary bodies
that regulate the window
and curtain wall
industry. In Canada,
standards for the performance
of windows
are established by the
Canadian Standards
Association (CSA).
There is no industry
standard for the performance
of curtain
walls in Canada.
Testing methods to
evaluate both laboratory
and field perforFigure
9 – Exterior mockup
test (AAMA 501), AirIns
laboratory.
Figure 10 – Interior mockup
test (CAN/CSAA440),
AirIns
laboratory.
mance are established
by the American Society for Testing and
Materials (ASTM) for both the United States
and Canada.
Following is a list of the principal industry
standards commonly used to establish
the laboratory performance criteria for windows
and curtain walls in North America.
• AAMA/NWWDA101:
Voluntary
Specifications for Windows and
Glass Doors. Primarily outlines laboratory
performance requirements
with regards to resistance to water
penetration, air leakage resistance,
and wind load resistance for windows
and glass doors (United
States).
• CAN/CSAA440:
Windows. Primarily
outlines
laboratory perf
o r m a n c e
r e qu i r eme n t s
with regards to
resistance to water
penetration,
airleakage
resistance,
and
windload
resistance
for windows
(Canada).
• AAMA 501:
Methods of Test for Metal Curtain
Walls. Primarily outlines laboratory
performance requirements with
regards to resistance to water penetration,
air leakage resistance, and
wind load resistance for metal curtain
walls (United States).
• NFRC 102: SteadyState
Thermal
Transmittance of Fenestration Systems.
Primarily outlines laboratory
Figure 11 – Environmental test
chamber, AirIns
laboratory.
performance requirements with regards
to thermal performance of
fenestration products (United
States).
• AAMA 1503: Voluntary Test Method
for Thermal Transmittance and Condensation
Resistance of Windows,
Doors, and Glazed Wall Sections.
Primarily outlines laboratory performance
requirements with regards to
thermal performance and condensation
resistance of windows, doors,
and glazed wall sections (United
States).
• CSA/A440.2: Energy Performance of
Windows and other Fenestration
Products. Primarily outlines laboratory
performance
requirements with
regards to thermal
performance and
condensation resistance
of windows and
other fenestration
products (Canada).
The following is a
list of the principal
industry standards
that are commonly
used to establish the
field performance criteria for installed windows
and curtain walls in North America.
• AAMA 502: Voluntary Specification
for Field Testing of Windows and
Sliding Glass Doors. Primarily outlines
field performance requirements
with regards to resistance to
water penetration and airleakage
resistance for windows and glass
doors (United States).
• AAMA 503: Voluntary Specification
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for Field Testing of Storefronts,
Curtain Walls and SlopedGlazing
Systems. Primarily outlines field
performance requirements with
regards to resistance to water penetration
and airleakage
resistance
for storefronts, curtain walls, and
sloped glazing systems (United
States).
• CAN/CSAA440.4
(Appendix D):
Field Testing of Window and Door
Installations. Primarily outlines field
performance requirements with
regards to resistance to water penetration
and airleakage
resistance
for windows and doors (Canada).
FIELD PERFORMANCE EVALUATION
The previous section of this paper highlighted
the primary performance requirements
and industry standards related to
windows and curtain walls and is intended
to provide the reader with some basic background
on the subject; however, the main
focus of this paper is the evaluation of the
field performance of installed
windows and curtain walls. Given
the evergrowing
complexity
and variety of modern building
envelopes, the evaluation of the
performance of installed windows
and curtain walls in the
preconstruction
and construction
phases is essential in order
to avoid undesirable and costly
problems during the service life
of the building.
In most projects of any significance,
the performance of the
window and curtain wall systems
that are to form part of the building
envelope are evaluated in an
accredited testing laboratory prior to construction.
It is equally important, however,
that the field performance of the installed
products be evaluated as a quality control
measure at different phases of construction.
Site conditions, variations in the manufacturing
process, and the quality and
experience of the field installation team are
all factors that will impact the performance
of the installed products or systems.
The first step when considering field
testing is to identify test areas that are representative
of the most common elements of
the building envelope. Fieldtesting
is usually
limited to three to six test areas due to
budgetary and scheduling constraints. It is
therefore very important that the test areas
be carefully selected in order to ensure good
samples. The test areas should be selected
based on the complexity of any given detail
or condition, as well as the frequency at
which a given detail or condition is repeated
throughout the project. Fieldtesting
Figure 12 – Field testing
for resistance to water
penetration.
Figure 13 – Field testing
for resistance to water
penetration.
Figure 14, 15, and 16 –
Identification of
representative areas for
fieldtesting
(precast
concrete/punch window
wall assembly).
Figure 17 – Identification of representative area
for field testing (metal and glass curtain wall).
Figure 18 – Identification of
representative area for field testing
(metal and glass curtain wall and
adjacent masonry assembly).
S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 0 7 GO N Ç A LV E S , J U T R A S A N D V E L J I • 6 1
Figure 19 – Vertical
section illustrating
location of test
chamber and elements
included in typical
curtain field test.
should always
include the interface
between
the window
and/or curtain
wall and the
adjacent wall
assembly, in
order to be representative
of
the entire installation.
This
interface is often
the most
critical element
of any installation
and may
not have otherwise
been validated
by any
form of laboratory
testing prior
to construction.
The test
area for metal
and glass curtain
walls must
incorporate all the essential components in
order to be representative. The test area
should be at least three glass bays wide so
as to incorporate a central bay that includes
all the junction details. In the case of a unitized
curtain wall system, a vertical module
joint should also be included within the test
area. The height of the test area should
include at least one expansion or stack
joint, at least one spandrel section, and one
vision section. Typically, the height of the
test area should be at least one full story
high. If the curtain wall is installed adjacent
to another type of wall assembly, the interface
detail should also be included within
the test area.
TEST METHODS
The two primary criteria evaluated in
the field are air leakage resistance and
resistance to water penetration. The following
are the principal standardized test
methods used to evaluate these criteria in
the field.
• ASTM E783: Field Measurement of
Air Leakage through Installed Exterior
Windows and Doors. Outlines
the test method for field measuring
air leakage through installed exterior
windows and doors. This test
method is also used for measuring
air leakage through curtain wall systems
(quantitative test method).
• ASTM E1186: Standard Practice for
Air Leakage Site Detection in
Building Envelope and Air Barrier
Systems (chamber pressurization in
conjunction with white smoke tracers
method). Outlines the test
method to qualitatively assess air
leakage through exterior building
envelope and air barrier systems in
the field (qualitative test method).
• ASTM E1105: Field Determination of
Water Penetration of Installed
Exterior Windows, Curtain Walls,
and Doors by Uniform Static Air
Pressure Difference. Outlines the
test method for the field determination
of water penetration of installed
exterior windows, curtain walls, and
doors.
Regardless of the three test methods
noted above, a pressure differential must be
created across the test specimen in order to
simulate wind pressure. In order to create
the required pressure differential, a test
chamber is typically erected on the interior
side of the test specimen. When exterior
access is difficult, such as in the case of
skylights, the test chamber can be erected
on the exterior side of the test specimen. In
certain cases, it may be possible to use
Figure 20 – Interior test chamber
used to test a portion of curtain
wall section.
Figure 22 – Exterior test chamber
used to test a skylight section.
highpower
blower doors installed within a
confined space. This method, however, is
typically only used for forensic testing in
occupied buildings. For new construction or
major renovation projects, a minimum of
three test sequences should be foreseen as
a quality control measure: at the very beginning
of the project, midway through the
project, and near the end of the project.
The test pressures are typically specified
by the project architect and are different
for the airinfiltration/
exfiltration test
and the waterpenetration
test. The air infiltration/
exfiltration test is typically undertaken
at a pressure differential of 1.57 psf
(75 Pa) or 6.24 psf (300 Pa). The waterpenetration
test is undertaken at pressure differentials
varying between 6 psf (290 Pa)
and 14.6 psf (700 Pa). Figure 24 provides
the wind speed equivalences for different
pressure differentials.
AIR INFILTRATION/
EXFILTRATION TEST
As previously noted, airleakage
testing
is typically undertaken at a pressure differential
of 1.57 psf (75 Pa) or 6.24 psf (300
Pa). In the United States, the AAMA 502
standard provides guidelines for allowable
airleakage
rates of installed windows and
sliding glass doors. In accordance with
Figure 21 – Interior test chamber
used to test a punch window
assembly.
Figure 23 – Highpower
blower
door installed within a confined
space adjacent to an exterior
wall.
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Pa kph psf in. H2O mph
75 Pa 40 kph 1.57 psf 0.30 in. H20 25 mph
137 Pa 54 kph 2.86 psf 0.55 in. H20 34 mph
144 Pa 56 kph 3.00 psf 0.58 in. H20 35 mph
150 Pa 57 kph 3.13 psf 0.60 in. H20 35 mph
180 Pa 62 kph 3.75 psf 0.72 in. H20 39 mph
200 Pa 66 kph 4.17 psf 0.80 in. H20 41 mph
216 Pa 68 kph 4.50 psf 0.87 in. H20 42 mph
252 Pa 74 kph 5.25 psf 1.01 in. H20 46 mph
288 Pa 79 kph 6.00 psf 1.15 in. H20 49 mph
299 Pa 80 kph 6.24 psf 1.20 in. H20 50 mph
300 Pa 80 kph 6.26 psf 1.20 in. H20 50 mph
324 Pa 83 kph 6.75 psf 1.30 in. H20 52 mph
360 Pa 88 kph 7.50 psf 1.44 in. H20 55 mph
383 Pa 90 kph 8.00 psf 1.53 in. H20 56 mph
384 Pa 91 kph 8.00 psf 1.54 in. H20 56 mph
396 Pa 92 kph 8.25 psf 1.59 in. H20 57 mph
400 Pa 93 kph 8.34 psf 1.61 in. H20 58 mph
431 Pa 96 kph 9.00 psf 1.73 in. H20 60 mph
467 Pa 100 kph 9.75 psf 1.88 in. H20 62 mph
500 Pa 104 kph 10.43 psf 2.01 in. H20 64 mph
503 Pa 104 kph 10.50 psf 2.02 in. H20 65 mph
539 Pa 108 kph 11.25 psf 2.17 in. H20 67 mph
575 Pa 111 kph 12.00 psf 2.31 in. H20 69 mph
600 Pa 114 kph 12.51 psf 2.41 in. H20 71 mph
700 Pa 123 kph 14.60 psf 2.81 in. H20 76 mph
750 Pa 127 kph 15.64 psf 3.01 in. H20 79 mph
Figure 24 – Table of wind speed equivalences.
Figure 25 – Example of allowable airleakage
rates depending on window
classification (source: AAMA 50202).
AAMA 502, allowable rates of air leakage for
field testing should be 1.5 times the applicable
laboratory test rating, unless otherwise
specified (see Figure 25).
In Canada, the CSA A440.4 standard
provides guidelines for allowable air leakage
rates of installed windows, tested at a pressure
differential of 1.57 psf (75 Pa), as outlined
in Figure 26.
When it comes to metal and glass curtain
walls, the allowable air leakage rates
are typically indicated in the architectural
specifications and will vary depending on
local building and energy codes and will
also vary for fixed and operable sections.
The field air leakage resistance test consists
of sealing a chamber to cover the interior
or exterior face of the specimen to be
tested, supplying air to or exhausting air
from the chamber at a rate required to
maintain the specified test pressure difference
across the specimen, and measuring
the resultant air flow through the specimen.
It is important to note that obtaining
accurate air leakage results in the field is
often difficult, particularly with curtain wall
assemblies. Test results should be questioned
when extraneous air leakage from
either the test chamber and/or the confines
of the test specimen significantly exceeds
the allowable air leakage for the test specimen.
Where it is not practical or possible to
quantify air leakage, smokeexfiltration
testing is an excellent alternative that can
be used to qualify an air leakage problem.
The smokeexfiltration
test is undertaken
by applying a uniform positive staticpressure
differential of 1.57 psf (75 Pa) across
the test specimen and filling the test chamber
with white smoke, using a portable
smoke generator. The test
consists of checking for
any visible excessive
smoke exfiltration from
the exterior side of the test
specimen.
WATERPENETRATION
TEST
The field waterpenetration
resistance test
consists of sealing a
chamber to the interior or
Figure 26 – Allowable
airleakage
rates
depending on window
classification (source:
CSA A440.407).
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exterior face of the test specimen to be tested,
supplying or exhausting air to the
chamber at the rate required to maintain
the desired air pressure difference across
the test specimen. Simultaneous to the
application of airpressure
difference, water
shall be applied to the exterior face of the
test specimen at the required rate (5 gal
US/h/ft2) while observing for any water
penetration at the interior.
In the United
States, the AAMA
502 standard provides
guidelines for allowable water penetration
resistance ratings of installed windows
and sliding glass doors. In accordance
with the AAMA 502 standard, water penetration
resistance tests shall be conducted
at a static test pressure equal to 2/3 of the
applicable laboratory test rating, unless
o t h e r w i s e
specified. In
Canada, there
is no provision
in the CSA
A440.4 standard
for reduction
in the fieldtesting
pressure.
For the waterpenetrationresistance
field test, a
calibrated sprinkler rack is
hung on the exterior side of
the test specimen in order
to apply a continuous and
uniform water spray. It is
important that sufficient
water pressure is available
on site in order to ensure
that the required amount of
water is sprayed on the
entire specimen. When sufficient
water pressure is not
available on site, the use of
a portable water reservoir
and pump system may be
necessary.
It is also important that
the exterior temperatures
be above freezing in order
to run a water test. When
undertaking a water test in
winter conditions, a temporary
heated enclosure
should be installed on the
exterior side of the test specimen.
OTHER DIAGNOSTIC TOOLS
Depending on specific applications, a
variety of other diagnostic tools can be used
to assess the performance of the vertical
building envelope, whether as a quality control
measure or for forensic purposes. For
example, when attempting to pinpoint a
specific water infiltration problem, AAMA
501.2, titled, “Quality Assurance and
Diagnostic Water Leakage Field Check of
Installed Storefronts, Curtain Walls, and
Sloped Glazing Systems,” can be used.
Figure 28 – Portable smoke
generator used to fill test
chamber with white smoke.
Figure 29 – Excessive smoke
exfiltration visible on exterior side
of curtain wall test specimen.
Figure 27 – Typical setup for field airleakageresistance
test (source: CSA A440.4).
Figure 30 – Typical setup for field waterpenetration
test (source:
AAMA 503).
Figure 31 – Calibrated
sprinkler rack hung from
suspended scaffolding.
Figure 32 – Calibrated
sprinkler rack hung from
motorized man lift.
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Infrared thermography is also used
extensively in the buildingconstruction
industry as a quality control and forensic
tool to assess airleakage
performance and
the presence of moisture in exterior wall
assemblies, in accordance with the
CAN/CGSB 149GP2MP
standard, titled
,“Manual for Thermographic Analysis of
Building Enclosures.”
SUMMARY AND CONCLUSION
Any form of water infiltration to the interior
side of a building or excessive air leakage
resulting in 1) discomfort to building
occupants, 2) the formation of excessive
condensation on the interior side of the
building, or 3) the formation of icicles on the
exterior side of the building would be unacceptable
to any building owner or occupant.
This being said, one of the primary performance
criterium for any window or curtain
wall system is that it provides an appropriate
level of resistance to water penetration
and air leakage resistance.
In most projects of any significance, the
performance of the window and curtain wall
systems that are to form part of the building
envelope are evaluated in an accredited
testing laboratory prior to construction. It is
equally important, however, that the field
performance of the installed products be
evaluated as a quality control measure at
different phases of construction. Site conditions,
variations in the manufacturing
process, and the quality and experience of
the field installation team are all factors
that will impact on the performance of the
installed products or
systems.
The first step
when considering
fieldtesting
is to
identify test areas
that are representative
of the most common
elements of the
building envelope.
The test areas
should be selected
based on the complexity
of any given
detail or condition
as well as the frequency
at which a
given detail or condition
is repeated
throughout the project.
Fieldtesting
should always include
the interface
between the window and/or curtain wall
and the adjacent wall assembly in order to
be representative of the entire installation.
This interface is often the most critical element
of any installation and may not have
been validated otherwise by any form of laboratory
testing prior to construction.
For new construction or major renovation
projects, a minimum of three test
sequences should be foreseen as a quality
control measure: at the very beginning of
the project, midway through the project,
and near the end of the project.
REFERENCES AND
ADDITIONAL READING
Canada Mortgage and Housing
Corporation, Best Practice Guide –
Glass and Metal Curtain Walls,
2004.
Quirouette, R.L., ‘‘Building Envelope
Design Using Metal and Glass
Curtain Wall Systems,’’ Building
Practice Note, Division of Building
Research, National Research Council
Canada, September 1982.
Gonçalves, M., P. Gendron, T. Colantionio,
‘‘Commissioning of Exterior
Building Envelopes of Large
Buildings for Air Leakage and
Resultant Moisture Accumulation
Using Infrared Thermography and
Other Diagnostic Tools,’’ Thermal
Solutions, Sarasota, Florida, 2007.
Figure 33 – Portable water
reservoir and pump system.
Figure 34 – Temporary exterior
heating via test specimen.
Figure 36 – Diagnostic hose
testing of window/wall interface.
Figures 38 and 39 – Thermographic
image of excessive air leakage at the
perimeter of the fenestration system.
Figure 37 –
Thermographic
image of
excessive air
leakage at the
interface of the
curtain wall with
the adjacent wall
assembly.
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Figure 35 – Diagnostic hose
testing of curtain wall section.