by Dean Lewis
Water penetration through the building envelope is a serious concern, involving issues ranging from what constitutes reasonable performance during a hurricane to resolving liability for interior water damage and possible toxic reactions to moisture-induced mold. Fenestration is the prime candidate for being the weakest link in the weather-resistant barrier, and thus typically receives the greatest scrutiny.
However, faulty fenestration design is not likely to be the cause of leakage problems. Products that meet the appropriate Performance Class and Grade defined by the code-mandated American Architectural Manufacturers Association/Window and Door Manufacturers Association/Canadian Standards Association (AAMA/WDMA/CSA) 101/I.S.2/A440, North American Fenestration Standard/Specification for Windows, Doors, and Skylights (NAFS), must pass laboratory water leakage spray tests of increasing stringency, depending on the applicable onsite Design Pressure (DP) as based on the wind speed contour maps of American Society of Civil Engineers/Structural Engineering Institute (ASCE/SEI) 7-10, Minimum Design Loads for Buildings and Other Structures.
These laboratory tests simulate wind-driven rain according to ASTM E547, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Cyclic Static Air Pressure Difference, and ASTM E331, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference, by simultaneously applying air pressure at 15 percent of DP for all window classes, except the AW Class, for which it is 20 percent. (For more, see “Performance Classes.”)
These are not trivial conditions. For example, a 290-Pa (6.0-psf) water test pressure (WTP) is equal to that exerted by an 80-km/h (50-mph) wind. Such pressure develops an equivalent hydrostatic water head of 30 mm (1.2 in.), which may be enough to force water over a windowsill and into a building.
Yet, there are limitations on the extent to which even this rigorous 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 window or door was designed and tested.
Additionally, laboratory tests cannot account for water penetration that actually may originate from the surrounding wall or roofing construction, causing water to run down the wall’s inside surface. Most importantly, lab tests do not account for window leakage due to improper installation, which—because building construction is rarely perfect—is the more likely culprit.
Product samples tested in the laboratory are positioned perfectly plumb, level, square, and true within a precision test fixture opening. In the field, although installed within acceptable industry tolerances, products are unlikely to find such exacting conditions. Shipping, handling, acts of subsequent trades, aging, and other environmental conditions all may have an adverse effect on product performance as installed when compared to the test results.
Specifiers are advised to require verification of the actual installed performance of fenestration products by insisting on field testing during or immediately after construction and before occupancy.
AAMA provides four field testing methods:1
- AAMA 501.2, Quality Assurance and Diagnostic Water Leakage Field Check of Installed Storefronts, Curtain Walls, and Sloped Glazing Systems, which should be used as a spot-check during construction of a curtain wall or storefront system;
- AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products, which is the proper test method for verifying field air leakage and water penetration resistance of newly installed operable windows and doors;
- AAMA 503, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems, which is the proper test method for field testing of new storefronts, curtain walls and sloped glazing for air leakage resistance and water penetration resistance; and
- AAMA 511, Voluntary Guideline for Forensic Water Penetration Testing of Fenestration Products, which is intended for performing a systematic forensic investigation of observed, known leaks.
Intended to be used during the construction process, AAMA 501.2 is inappropriate for testing operable windows and doors. It neither simulates the effects of wind-driven rain nor provides quantitative performance information. Rather, it is a simple, economical water spray quality check to reveal leaks in non-operable glazing, including gaskets, sealant, perimeter caulking, splices, and frame intersections.
The designated test area is divided into 1.52-m (5-ft) sections of the framing and joint. The area selected must include typical, representative samples of each part of the construction—usually a minimum of 9.3 m2 (100 sf), with no outstanding punch list items or other visible defects.
The test is conducted using a hose (19-mm [¾-in.] diameter suggested) and a special nozzle as specified in the standard. The water pressure to the nozzle must be 205 to 240 kPa (30 to 35 psi), unless a lower pressure is unavoidable, such as at a multistory building, but not lower than 172 Pa (25 psi). The nozzle is held at a distance of 305 mm (12 in.) from the location under test. Each section is evaluated for five minutes by slowly moving the nozzle back and forth over the test section. If leakage occurs, modifications are made and the test is repeated.
The correct field test for air leakage and water penetration of newly installed fenestration units is AAMA 502. Testing is to be conducted before issuance of the building occupancy permit, but in no case later than six months after installation. It is based on ASTM E783, Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors, and ASTM E1105, Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Curtain Walls, and Doors by Uniform or Cyclic Static Air Pressure Difference.
To implement AAMA 502, a temporary test chamber is sealed to the interior (or, optionally, the exterior) side of representative fenestration products at appropriate stages of the product installation, subject to a minimum of three units. The test chamber is to be in such a manner as to apply the pressure differential to all joinery conditions with the wall. The number of products tested, and the frequency of testing, should be clearly specified by contract. (On large projects, tighter construction monitoring may be performed by testing at approximate intervals of five, 50, and 90 percent completion of the installation.)
Depending on whether installed on the interior or exterior, air is supplied to, or evacuated from, the test chamber at the rate necessary to establish and maintain the desired air pressure difference across the specimen. The maximum pressure needed is equal to two-thirds of the lab-tested and rated water test pressure as prescribed for the applicable product performance grade designation in NAFS, but not less than 91 Pa (1.9 psf).
For example, a product tested or rated as H-CW50 is field tested for water penetration resistance at a pressure differential of two-thirds of 360 Pa (7.5 psf), which equals 240 Pa (5 psf). This one-third reduction of the test pressure for field testing is considered to be a reasonable adjustment to account for the variables inherent in a field test environment.
Once the test pressure is established, a calibrated spray-rack applies water against the outside surface—with all operable portions of the specimen closed and locked—while technicians observe for any water penetration at the interior. ASTM E1105 Procedure A (uniform static air pressure difference; used for AW performance class windows) requires a 15-minute test with continuous pressure and water application. Procedure B (cyclic static air pressure difference; for all but the AW class) applies four water spray cycles of five minutes each under pressure, interspersed by one minute with the pressure released. To pass the test, there can be no penetration of uncontrolled water beyond a plane parallel to the product’s innermost edges.
AAMA 502 also provides for an air leakage resistance test, conducted per ASTM E783 at a minimum uniform static test pressure of 75 Pa (1.6 psf) except 300 Pa (6.2 psf) for the AW class; or as specified for the project, but not to exceed 300 Pa (6.2 psf). The acceptable air infiltration rate is limited to 2.3 L/s•m2 (0.45 cfm/sf) or 0.8 L/s•m2 (0.15 cfm/sf) for AW Class products. It is important to remember that air leakage is to be tested before the wall is wetted for water leakage testing—otherwise, water trapped within the wall components will tend to reduce air leakage.
Similar to AAMA 502 but applicable to storefronts, curtain walls, and sloped glazing systems, AAMA 503 is also applied soon after the specimen is installed and sealants are cured, but before installation of gypsum wall board, insulation, or other finish materials, and no later than six months after issuance of the occupancy permit. Like AAMA 502, AAMA 503 bases its testing protocols on ASTM E1105 and E783.
AAMA 503 calls for testing to be conducted on at least a single 9.3-m2 (100-sf) area of installed product that is representative of the project.
Under AAMA 503, as with 502, the water penetration resistance test is performed per ASTM E1105’s Procedure A (uniform static air pressure difference), with the test pressure set at two-thirds of the specified project water penetration test pressure, but not less than 200 Pa (4.18 psf). In the event the project does not have a specified water penetration test pressure, the default value is 20 percent of the positive design wind load times 0.667. Water leakage is defined as any water not contained in an area with provisions to drain it to the exterior or the collection on an interior horizontal framing member surface of more than 14 g (0.5 oz) of water in the 15-minute test.
While ASTM E783 is referenced by AAMA 503 for field air infiltration testing, and may be used to evaluate the installed air leakage of ‘punched opening’ curtain walls, storefronts, and sloped glazing, it is not recommended for a portion of continuous systems due to the complexity of compartmentalizing air chambers and cavities. It is impractical to install a chamber on a segment of a continuous horizontal or vertical member.
If conducted, the air infiltration test proceeds at the same pressures called for in AAMA 502. However, the maximum allowable rates of measured air leakage must not exceed 1.5 times the project specification rate, or 0.45 L/s•m2 (0.09 cfm/sf)—whichever is greater. Or, the specifier may require project-specific air leakage.
Importance of early testing
Once it is installed, changes needed to repair a wall can be difficult and expensive. Thus, defining the acceptance criteria and field testing requirements in the project specification and performing the tests as soon as practical before a substantial portion of the project is completed (but no later than six months after installation) can help determine whether problems are present.
The advantage of testing prior to closing up interior walls and before building occupancy is design, fabrication, and installation problems can be revealed early enough that remedial work will be easier and less expensive.
AAMA 502 and 503 each provides a recommended short-form model specification that allows the specifier to prescribe the test pressures 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. These are used by merely inserting the following paragraph(s), completed with the indicated information, into the project specifications.
AAMA 502 Short Form Field Testing Specification
- Newly installed fenestration product(s) shall be field tested in accordance with AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products.
- Test three (unless otherwise specified) of the fenestration product specimens after the products have been completely installed for air leakage resistance and water penetration resistance as specified.
- Air leakage resistance tests shall be conducted at a uniform static test pressure of ___ Pa (___ psf). The maximum allowable rate of air leakage shall not exceed ___ L/s•m2 (___ cfm/sf).
- Water penetration resistance tests shall be conducted at a static test pressure of ___Pa (____ psf). No water penetration shall occur as defined in AAMA 502.
AAMA 503 Short Form Field Testing Specification
The newly installed (storefront, curtain wall, and/or sloped glazing system) shall be field tested by an AAMA accredited independent laboratory, in accordance with AAMA 503, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls and Sloped Glazing Systems. The area(s) to be tested is (are) as follows: [(exact description of the area(s) to be tested by referencing an architectural drawing that clearly shows the intent of the area to be field tested.)]
Any of the following optional paragraphs may be added to modify the standard AAMA 503 specification:
- Optional air leakage resistance tests shall be conducted at a uniform static test pressure of ___ Pa (___ psf). The maximum allowable rate of air leakage shall not exceed ___ L/s•m2 (___ cfm/sf).
- Water penetration tests shall be conducted at a static test pressure of Pa (psf).
The specifier may increase the field water test pressure to the value specified for the project. In the event the project does not have a specified water penetration test pressure, the value would be equal to 20 percent of the positive design wind load times 0.667.
Forensic investigation of existing fenestration
In addition to field testing before occupancy, situations may arise where a forensic investigation of an actual problem in an occupied building can pinpoint the leakage path by recreating the known water leaks. This is done by researching the actual weather events that produced the reported water penetration, using the procedures of AAMA 511. Unlike quality assurance (QA) field testing during or shortly after installation, forensic investigators are required to provide more information than pass/fail criteria.
AAMA 511 expands on the investigative process set forth in ASTM E2128, Standard Guide for Evaluating Water Leakage of Building Walls, which recommends a total of seven investigative, review, and preparatory steps prior to actual testing, as well as post-testing steps. Pretest inspection and data gathering include a review of project documents, design concept evaluation, and a review of service history and inspections—all aimed at developing a hypothesis for the water intrusion’s source.
The process begins by calculating the differential air pressures the suspect specimens experienced during the actual wind-driven rain conditions coinciding with the original leak. This calculated pressure defines the test pressure to which the fenestration product is subjected during the actual field testing. If this calculated wind pressure is greater than two-thirds of the rated WTP for the product, it may be the product was not the most appropriate selection for the project.
The investigative process then moves to actual testing—the protocol for which is similar to that of AAMA 502 or 503. An optional sill dam test, also described in AAMA 511, can be used as necessary to further investigate the leak path.
Generally, field testing accounts for the unavoidable fact that performance of installed exterior wall systems likely will be somewhat less than laboratory performance, due to accumulated manufacturing and installation tolerances. Built-in allowances accommodate this, as well as the difficulty that may be encountered in conducting field tests with the same precision as laboratory tests.
In many cases, investigators have used inappropriate field testing adaptations to AAMA 502 and AAMA 503 to investigate the reported water penetration. A common, incorrect adaptation involves performing water testing at a differential pressure higher than the pressure the fenestration product experienced during the wind-driven rain events that produced the water penetration. Field testing at these high pressures may result in new leaks and the false conclusion the fenestration product is the cause of all the reported water penetration. Field testing at elevated pressures also may conceal defects that would have produced leakage at lower pressures.
Determining which units to test is an important step when planning field testing. It is important the units chosen as the test specimens include typical perimeter and joint conditions that occur throughout the wall system between fixed glass, fixed panels, and the framing members.
However, the quantity and location of the specimen(s) selected for AAMA 503 testing can markedly affect the cost of testing. ASTM E122-09e1, Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process, provides guidance on how to establish the number of test specimens required to measure the quality of a production lot with prescribed precision. Obviously, a situation where the cost of testing and building remediation approaches the cost of the glazing system should be avoided. Selecting as few as one specimen (or surface area as small as 9.3 m2 [100 sf] of glazing) may be sufficient to provide the information needed. On larger projects, a formal cost-benefit analysis is appropriate.
It is important to note AAMA 502, AAMA 503, and AAMA 511 all require the indicated testing to be performed by an AAMA-accredited testing laboratory—that is, one recognized as meeting the current requirements of AAMA 204, Guidelines for AAMA Accreditation of Independent Laboratories Performing On-site Testing of Fenestration Products. This ensures the laboratory has the qualified staff and calibrated equipment to properly perform field testing. One should be wary of any self-proclaimed window-tester, and ask to see the AAMA certificate of accreditation.
Finally, AAMA 501, Methods of Tests for Exterior Walls, is a good general reference that provides an overview of field testing. It places the individual protocols in context with one another, and also provides a comprehensive guide specification to cover all field testing protocols and options.
Dean Lewis is the educational and technical information manager for the American Architectural Manufacturers Association (AAMA). He began his career in the fenestration industry at PPG Industries with positions in project engineering, product design, and sales and customer technical support, and has served on committees of American National Standards Institute (ANSI), ASTM, and the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE). Further experience includes teaching in the industrial and military sectors, and 35 years of managing technical training, publishing, and certification. Lewis has served on standards and certification committees of a dozen national and international organizations. He can be reached at firstname.lastname@example.org.