Environmental Stress as a Factor in IG Durability, Phase I

Gerald L. Hendrickson

Environmental stress from local climatic conditions is believed to be a major element in insulated glass (IG) durability. Severity of climatic stress was examined for 262 locations in the United States. Equivalent atmospheric pressures were calculated to give a stress related severity factor. The same weather data was checked for vapor pressure severity. Severity of the applied stress is the first step in analyzing IG durability. Response of a given IG construction to that stress is the second step. Stress severity was found to vary over a range of 6 to 1 in the six years (1990 to 1995) of data examined.

Separation of the applied environmental stress from response to those conditions is a key element to accurately create appropriate accelerated durability tests. Assumptions and methods for analyzing the data are presented. Test development considerations will be discussed in a Phase II report. A similar range of stress conditions was found for locations in the former USSR. The methods described will allow this analysis to be made for Europe and other areas. The data results will lead to better understanding of regional variations in IG durability.

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