Bad IG: Certification Testing Is the Best Assurance We Have to Give

By Dave Cooper

We have all seen it—that door or window that is fogged over, or water stained. It stands out like the proverbial sore thumb. Our industry does much to help consumers avoid this issue. The most important is certification of insulating glass (IG).

For a window to be certified by the National Fenestration Rating Council (NFRC) and Energy Starrated, the IG must be certified. This process normally involves an auditor visiting the IG fabrication plant. The fabricator then produces a series of IG samples that are 14 inches by 20 inches in size on their production line, using normal production methods and materials or components. These units are labeled on the spot by the auditor and are carefully set aside for shipment to an accredited third-party lab. The auditor also checks the plant’s quality management system to ensure they are following a set protocol.

Where does the 14-inch by 20-inch size come from? It was determined long ago as a size that imparts great stiffness of the glass relative to overall size. This stiffness acts to stress the edge seal system of an IG during the durability testing for certification.

The IG, and presently vacuum insulating glass (VIG) units, are subjected to a durability test in the lab that is prescribed by the ASTM E2190 Standard Specification and E2188 Durability Standard. In this test, six IG units are first placed into a chamber known as the high temp high humidity (HTHH) chamber for 14 days. The condition inside is a hot (140° F) environment that’s saturated with moisture to drive moisture into the unit. Next, the units are placed on the weathering chamber wall. Here, one side is at room temperature while the other is cycled between a cold -20° F and hot 140° F over a six-hour period, repeatedly, for 63 days or 252 of these cycles. The test cycle includes both ultraviolet (UV) irradiation and high humidity segments. The idea is to replicate what happens to a window installed in a building during extreme weather conditions. The stiff IG is actually stressed by the temperature cycle, ballooning out while hot and compressing in when cold. Following this, units are again moved into the HTHH chamber for 28 days, to drive moisture into the IG air space.

If the units meet a minimum requirement, as measured by residual moisture within the unit, then the test is considered a pass and, if all else is in order, the fabricator is certified for another year.

Testing Every Recipe

Each type of IG unit (IGU) that is manufactured must be tested. That means if a fabricator uses two different sealant systems or two different spacer types, for instance, separate tests on each type of unit must be conducted, which leads to separate certifications. There is also a volatile fog test, according to ASTM E2189, in which the units must not exhibit a chemical fog after exposure to heat on one side and a cool plate on the other. This test is designed to condense volatile vapors should they exist. It is highly subjective, since the lab inspector holds the unit out and in front of
themselves in a dark room, with a single light source, looking for a fog “spot.”

The test standard isn’t necessarily designed to fail IGUs, but to ensure that they meet a minimum requirement. As we say in IG circles, “A well-made IG unit will pass the test.”

Dave Cooper is a consultant and president of Fenestration Consulting Services LLC.
dcooper@fenconsultant.com

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