| |
Field Testing Dampens Leak Problems
By: John Lewis
Water penetration through exterior walls is a serious concern of architects,
product manufacturers, contractors and building owners. Fenestration products
typically receive the greatest scrutiny.
However, product design is not so likely to be the cause of leakage problems.
Fenestration products that meet the code-mandated standard AAMA/WDMA/CSA
101/I.S.2/A440-05, Standard/Specification for Windows, Doors, and Unit Skylights
and its predecessors must pass ASTM E547 and/or E331 water leakage tests of
increasing stringency depending on their Performance Grade (PG) and Performance
Class. Laboratory water penetration spray tests simulate wind-driven rain by
simultaneously applying air pressure at 15 percent of Design Pressure (DP) for
all window performance classes except AW, for which it is 20 percent of the DP.
The AAMA Certification label verifies conformance with this standard and is the
foundation for water penetration resistance.
Unfortunately, meeting such standards and testing of factory-made window, door
and unit skylight products does not account for leakage due to poor
installation, the more likely culprit when leaks occur. In addition, water
penetration at or near a fenestration product opening may actually originate
from the surrounding construction.
Contractors are well advised to verify the actual installed performance of
fenestration products during construction and prior to occupancy of a building.
Situations can also arise where a forensic investigation of an actual leakage
problem is useful to pinpoint a leakage path. Properly applied field testing
serves both purposes.
Newly-Installed Fenestration
The recognized field test method for verifying water penetration resistance
and air infiltration of newly installed operable windows and doors is the
updated AAMA 502-08, Voluntary Specification for Field Testing of Newly
Installed Fenestration Products. A sister standard, AAMA 503-08 offers the same
protocols for testing of newly installed storefronts, curtain walls and sloped
glazing systems. Both are 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 Curtain Walls by Uniform or
Cyclic Static Air Pressure Difference, and both require that the testing be
performed during construction and prior to occupancy of a building, but in no
case later than six months after installation.
Per AAMA 502-08, a temporary sealed test chamber is applied to the interior side
of at least three of a project’s installed windows or doors, then sealed and
pressurized to establish a specified pressure differential across the product
and the rough opening that simulates wind pressure. Installation of the test
chamber to the exterior is also provided as an alternative method. Tests are
conducted at a static test pressure equal to two-thirds of the water test
pressure (WTP) prescribed in AAMA/WDMA/CSA 101/I.S.2/A440, but not less than 91
Pa (1.9 psf). Water is then sprayed against the outside surface from a
calibrated spray rack. The entire installed fenestration product is tested,
including the frame, corners, panning, subframe/receptor system, etc. and the
adjacent substrate including the perimeter seals. To pass the test, there can be
no penetration of uncontrolled water beyond a plane parallel to the innermost
edges of the product.
Performing the tests as soon as practical on the job site can help determine if
manufacturing, installation and/or perimeter sealing problems are present and
aid in implementing corrective action before a substantial portion of the
project is completed. Access to the windows for proper testing must be provided
before the openings are finished with drywall, trim, stools, etc.
A recommended Short Form Field Testing specification allows the architect/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 7–05, Minimum Design Loads for
Buildings and Other Structures).
Forensic Investigation
If the source of the water leakage cannot be determined per AAMA 502 or 503, or
if leakage becomes evident after occupancy or more than six months after
installation, a forensic evaluation of the complete wall system can be performed
using the procedures of AAMA 511-08, Voluntary Guideline for Forensic Water
Penetration Testing of Fenestration Products. The objective of this testing is
to identify the leak paths by recreating the known water leaks through
simulation of the weather events that produced the reported water penetration.
AAMA 511 expands on the investigative steps set forth in ASTM E2128, Standard
Guide for Evaluating Water Leakage of Building Walls, which recommends a total
of seven steps prior to actual testing, as well as post-testing steps. Pretest
inspection and data gathering include a review of project documents, evaluation
of the design concept, a review of service history and inspections – all aimed
at developing a hypothesis for the source of the water intrusion. If necessary,
an optional sill dam test can be used to further investigate the leak path.
The test methods are similar to those referenced in AAMA 502 for newly installed
products, but have specific differences in preparation and data interpretation.
For example, the process begins by calculating the differential air pressures
that the suspect units experienced, based on actual weather data for the
wind-driven rain conditions coinciding with observance of the original leak.
This calculated pressure defines the test pressure to which the fenestration
product is to be subjected during the actual investigative testing. If this
calculated wind speed is greater than two-thirds of the rated WTP for the
product, it may be that the product was not the most appropriate selection for
the project.
Note that AAMA 502-08, AAMA 503-08 and AAMA 511-08 all require that the
indicated field testing must be performed by an AAMA-accredited testing
laboratory, i.e., one recognized as meeting the requirements of AAMA 204-98,
Guidelines for AAMA Accreditation of Independent Laboratories Performing On-Site
Testing of Fenestration Products.
AAMA documents may be obtained online from the AAMA Publications Store at
www.aamanet.org.
About the Author: John Lewis is Technical Director of the American
Architectural Manufacturers Association (AAMA).
|
