Measurement of the frost point of air in sealed insulating glass

Abstract

This paper describes the aims and results of recent cooperative research by the National Bureau of Standards (NBS) and the American Society of Testing and Materials (ASTM). The research programme concerned the development of methods of testing, and standards to be adopted, for factory-produced sealed double glazing units. These must comprise an air-tight space between two (or more) sheets of glass in order to reduce the flow of heat through the window, while at the same time there must be provision for avoiding condensation of water on the inner surfaces of the glass, during construction and use. In addition to the reduction of visibility, repeated condensation of liquid water or of ice, and subsequent evaporation, tends to leave a residue on the glass surfaces, which are not accessible for cleaning. An apparatus is described for non-destructive testing of the air space inside hermetically sealed assemblies (US Patent 3. 89. 658); the test is repeatable from at least 273.8K to the dew or frost point. The references and standards established by the ASTM are given and described (ASTM designations: E546-75, E576-76, E6P, E6P2, and E6P3).