Things about ASTM-E774-97: Standard specification for the classification of the durability of sealed insulating glass units.
1.1 Thisspecificationisapplicabletothosesealedinsulating glass units, with one or two airspaces.
1.2 The classification of test specimens is based on frost or chemical dew point after the specified test duration(s).
1.3 Qualification under this specification is intended to provide a basis for the classification of the durability of sealed insulating glass units. SIGMA field correlation studies started in 1980 show that units that have achieved a Level A classification have less than 1 % field failure rate in ten years provided the glazing system weeps water away from contact with the unit edge seal. Class C and CB tested units have significantly higher field failure rates in ten years. SIGMA continues to gather correlation data.2
1.4 This specification is not applicable to units that are constructed from vision materials other than glass.
1.5 This specification does not cover other physical requirements such as appearance, thermophysical properties, heat and light transmission, and glass displacement.