Heading Off Problems at the Pass
Shortstopping Window Leakage
by Dean Lewis
Given the possible liability consequences of water leaks,
ranging from physical damage to mold infestation, manufacturers and contractors
are well-advised to verify the actual installed performance of fenestration
products during construction and prior to building occupancy.
their high-profile role as potential sources of leaks, fenestration systems
are not always likely to be the source of wall leakage problems."
Despite their high-profile role as potential sources of
leaks, fenestration systems are not always likely to be the source of
wall leakage problems. Products that meet the code-mandated standard AAMA/WDMA/CSA
101/I.S.2/ A440, Standard/Specification for windows, doors, and skylights
(a.k.a. the North American Fenestration Standard (NAFS)) must pass water
leakage tests of increasing stringency depending on their Performance
Class and Performance Grade.
Yet, there are limitations on the extent to which even this rigorous laboratory
testing can predict performance in the field. Water leakage may occur
during a heavy rainstorm because the wind velocity pressure exceeds that
for which the water penetration resistance of the door or window was designed.
In addition, such standards and laboratory tests do not account for water
penetration at or near an installed fenestration product that may actually
originate from the surrounding wall or from poor installation.
Field Testing is Crucial
Field testing soon after installation begins and before building occupancy
is a recommended option to reveal design, fabrication and installation
weaknesses at a time when corrections can be relatively simple and inexpensive
for the installer.
AAMA provides four field test methods and two of those are higlighted
• AAMA 502, Voluntary Specification for Field Testing of Newly
Installed Fenestration Products, intended for use with fenestration products
defined within the scope of NAFS.
• AAMA 511, Voluntary Guideline for Forensic Water Penetration
Testing of Fenestration Products, intended for performing a systematic
forensic investigation of observed leaks.
The recognized field test method for determining whether newly-installed
operable windows and doors permit water leakage when subjected simultaneously
to high winds and heavy rainfall is the freshly updated AAMA 502-12, Voluntary
Specification for Field Testing of Newly Installed Fenestration Products.
It is based on ASTM E783, Standard Test Method for Field Measurement of
Air Leakage Through Installed Exterior Windows and Doors, and ASTM E1105,
Standard Test Method for Field Determination of Water Penetration of Installed
Exterior Windows, Skylights, Doors, and Curtainwalls by Uniform or Cyclic
Air Pressure Difference.
Air and Water Testing
AAMA 502 specifically calls for air leakage and water resistance field
testing subject to a minimum of three units, as indicated in the short
form specification. On large projects, tighter construction monitoring
may be performed by testing at approximate intervals of 5-, 50- and 90-percent
completion of the installation.
For water testing, air is supplied to, or evacuated from, a temporary
sealed test chamber at the rate necessary to establish and maintain the
desired air pressure difference across the specimen as water is sprayed
against the window exterior at a specified rate. To pass the test, there
can be no penetration of uncontrolled water beyond a plane parallel to
the innermost edges of the product.
AAMA 502 also provides for an air leakage resistance test. It is conducted
per ASTM E783 and limits the acceptable air infiltration rate to 0.45
cfm/ft2 (0.15 cfm/ft2 for AW class products). Note that air leakage should
actually be tested before the wall is wetted for water leakage testing.
The recommended Short Form allows the specifier to prescribe the test
pressure for both air infiltration and water resistance, depending on
the location and wind exposure of the specific project (as determined
using the principles of ASCE/SEI 7, Minimum Design Loads for Buildings
and Other Structures).
Dean Lewis serves as chief engineer, certification programs, for
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