General performance requirements for sealed double-glazed windows and the need for performance tests are discussed. The possibility of condensation of moisture and clouding or scumming on the inside glass surfaces is emphasized. The results of some exploratory studies on the degree of sealing achieved in a number of units and on condensation on the interior surface are given. These results are based on measurements of the dew point of the air between the panes and on surface temperature measurements taken with various temperature differences across the windows. Factors involved in determining the adequacy of the sealing of the space between the panes are considered and lines of study suggested. General requirements of a test procedure for determining the degree of sealing achieved and the relative life of seals are discussed and accelerated aging apparatus proposed for this purpose is described.
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