Volume 13, Issue 5 - June 2012

AAMA Analysis

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.

"Despite 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 below:
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 Static
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 AAMA.








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