Glossary of Related Terms
This is a sidebar to the article A Manufacturer's Guide to IG Certification.
Accelerated Aging: Laboratory conditions designed to recreate the normal aging process of IG units in a short period of time.
ASTM E 2188: North American harmonized ASTM standard test method for IG unit durability performance testing.
ASTM E 2189: North American harmonized ASTM standard test method for testing IG unit resistance to volatile fogging.
ASTM E 2190: North American harmonized ASTM standard specification for IG unit performance and evaluation.
ASTM E 773, E 774, E 1887: Previous U.S. standards for IG unit, testing performance and evaluation (replaced by harmonized E 2188, E 2189, E 2190).
CGSB 12.8: Canadian standard specification for IG unit testing, performance and evaluation (replaced by harmonized E 2188, E 2189, E 2190). CGSB 12.8 remains an active standard in Canada and is the reference standard for IG certification under the IGMAC certification program.
Condensation: Formation of moisture on an IG unit surface when surface temperature is lower than the localized air dewpoint. Condensation occurs first around the window's edge where the glass insulates least effectively and where surface temperatures are the coldest. If a standard "cold edge" spacer exists and outside temperatures fall to 0¡F/-17.78¡C, condensation will form on the glass edge-even in homes with as little as 15 percent relative humidity.
Dual seal units: Insulating glass utilizing two separate sealants for the edge seal system. Based on material characteristics, one sealant is used principally for the resistance of moisture into the IG unit and to prevent leakage of insulating gases (argon, krypton) out of the unit. The second sealant primarily acts as a structural sealant/adhesive to maintain the integrity of the IG unit.
Frost point: Temperature within an IG unit at which moisture condenses and/or freezes on the interior glazing surface(s). To pass the requirements of ASTM E 2190 an IG unit must have a frost point equal to or less than -40¡F. Dry ice with thermocouples and digital indicators are used to determine the frost point in an IG unit.
P-1 test: Method under which IG units are tested and evaluated under extreme temperatures, humidity and ultraviolet light exposure. Test specimens are fully and continuously exposed to conditions of 140¡F, 95 percent RH and 100 percent UV. Many engineers consider P-1 the world's toughest accelerated aging and durability test. One week spent in a P-1 chamber is considered by industry experts to be equivalent to approximately one year in the field.
Single seal units: Insulating glass utilizing a single sealant for the edge seal system. Based on material characteristics, the single sealant is used for the resistance of moisture into the IG unit, to prevent the leakage of insulating gases (argon, krypton) out of the unit and as a structural sealant/adhesive to maintain the integrity of the IG unit.
Spark emission spectrograph: Equipment used to measure argon gas concentration in an IG unit through non-destructive emission of an electrical spark within the IG unit.
U value or U factor: The air-to-air thermal transmittance of a fenestration system. A measure of the rate of heat loss from the warm side of the unit to the cold side. The lower the U Factor, the greater the insulating value.
Volatile fog: The condensation of chemicals or other impurities within an IG unit on the interior glazing surface(s). Volatile formation is typically due to contaminates left within the IG unit when sealed. These materials become a vapor when exposed to heat and/or UV radiation and condense on the glazing surface to create a permanent haze or "fog."