Testing Insures Delivery of Today's Tougher Performance Requirements
Impact resistance, water penetration, thermal performance mandates– even bomb blast resistance – are among the headline issues that have raised the bar on building performance in recent times. Building codes, industry standards development and both government and non-government rating programs have taken up the drumbeat for performance requirements that weren’t even thought about when window standards were first introduced more than 60 years ago. This evolving stringency of criteria, hand-in-hand with advances in technology, has produced products that perform much better than their predecessors, to the benefit of end users and arguably of society in general.
Still, not many folks outside the technical cognoscenti of this industry realize what goes into ensuring that these ever-tougher criteria are met by the products intended for markets that impose conditions ranging from sub-zero temperatures to hurricane-impelled flying debris. This challenge is met by third-party product certification programs, based upon continuously updated consensus standards, mandated by model codes and backed by rigorous third-party laboratory testing.
The AAMA certification program, based as it is on AAMA/WDMA/CSA 101/I.S.2/A440-08, NAFS — North American Fenestration Standard/Specification for windows, doors, and skylights or that standard's applicable predecessors, offers a uniform, material neutral, performance-based platform from which all materials and products can be tested and compared on a level playing field. Fenestration products that purport to meet this standard must pass laboratory tests of increasing rigor depending on their performance class.
State of the Art Test Methods
Most of the test methods that the laboratory must follow are independently developed and continually updated by ASTM International (formerly the American Society for Testing and Materials), and are accepted and used around the globe as the basis for R&D, manufacturing, product testing and quality systems, procurement and regulatory activities. While conducted under controlled parameters that can only simulate “real world” conditions, the tests hardly treat fenestration products delicately.
For example, the test methods for determining water penetration resistance (ASTM E547 and E331) require the exterior surfaces of fenestration products to be subject to a deluge of 5 gal/ft2/hr–roughly equivalent to 8 inches of rain per hour–driven by a static pressure equivalent to a wind speed of up to more than 70 mph for a total of 15 minutes.
This is quite extreme compared to typical real-world conditions. For example, ASCE/SEI 7-02 cites the design rainfall intensity for a 100-year, 1-hour rainfall in Birmingham, Ala., as 3.75 inches per hour, and 1.5 inches per hour in Los Angeles. A 15-minute duration 100-year design event typically ranges from 2 to 4 inches per hour for areas within the 90 mph basic wind speed contour. Therefore, for most applications, the required ASTM E331 water penetration test is the most stringent of the various tests that can be applied and gives reasonable assurance that the design as tested will perform satisfactorily.
In terms of impact resistance, optional tests can be conducted according to the protocols set forth in AAMA 506 Voluntary Specifications for Impact and Cycle Testing of Fenestration Products or the more severe tests of Florida’s Miami-Dade and Broward Counties, located in the defined high velocity hurricane zone. The latter require windows to withstand impacts simulated by impelling a 2 x 4 stud into the product at 34 mph.
Verification that the tests are reliable as performance indicators is built into the requirements of the AAMA certification program. It begins with the fact that a laboratory must be qualified and accredited by AAMA for its ability to accurately perform the required specific tests per the specified ASTM or AAMA protocols and have no business relationship to the manufacturer(s) whose products it may test. The lab must apply to participate in the program and contract that it will properly and responsibly maintain the accreditation. Then, the lab is subjected to initial and periodic repeat inspections that include confirmation of the calibration status of its testing apparatus by the program’s independent third-party validator organization. Finally, each and every test report from the laboratory is reviewed and approved by the validator before the results can be used as evidence in support of certification.
Testing at the Component Level
Any effective definition of window quality must encompass the performance of its components as well as the way they interact to make a completed window unit. Separate standards and test methods therefore apply to components such as reinforcing members, glass, coatings, weatherstrip, gaskets, glazing beads and hardware as well as sealants, flashing and other installation products. As a prerequisite for their use in fenestration products that bear the AAMA Certification Gold Label, such components must be qualified through separate, independent testing per the cited standards.
In addition, to be eligible for the AAMA certification program, polymer-framed windows must be made from profiles that comply with the appropriate AAMA specifications which typically include requirements for factors such as dimensional stability, impact resistance, weatherability, heat resistance, weight tolerance, heat build-up and lead content. Compliance is verified by independent laboratory testing of samples randomly-selected at the extruder’s plant by the validator’s inspector. The first of the standards for polymer extrusions was for rigid PVC. Profiles made of other materials–including ASA or PVC-capped ABS, fiberglass pultrusions, glass-reinforced extrusions, cellular PVC and cellulosic composites–can also be certified now, as industry-consensus performance standards continue to be developed along with new material technologies.
Testing in Context
As stringent as the testing is, it is still the buyer’s or specifier’s task to first determine the tradeoff between performance level and cost that is acceptable for the job at hand. Given equal performance as verified by laboratory testing, the choice of product basically reduces to one of preference with regard to operating features, appearance, brand name or manufacturer’s reputation and other factors for the specific application.
Laboratory test parameters have indeed become more and more draconian to keep pace with the ratcheting of performance requirements, but laboratory testing, however artfully contrived, is conducted under ideal conditions. Try as we might, we simply cannot duplicate all the vagaries of nature and conditions at all ultimate job sites. And, for obvious economic reasons, product testing must be done on a sampling basis rather than as 100 percent screening.
Also remember that despite robust laboratory testing, installation remains the potential weakest link. Following recognized installation standards such as ASTM E 2112, Standard Practice for Installation of Exterior Windows, Doors and Skylights; using contractors qualified through the AAMA-founded InstallationMasters program or testing after installation and before building occupancy per field testing protocols such as those of AAMA 502 Voluntary Specification for Field Testing of Newly Installed Fenestration Products will help ensure that the care taken in product design and laboratory testing translates to intended performance in the field.