Description: A survey of glazing materials is presented and initial (nondegraded) properties are compared. Weathering characteristics are discussed in terms of mechanisms and their effects upon candidate glazings. Examples of failure modes are given for various commercially available materials. A specific process, optical degradation, was studied in detail to determine how loss of solar transmission affects the thermal performance of flat-plate solar energy collection systems. Computer simulations of singly and doubly glazed collectors having cover plates of various commercially available transparent materials were made for one-week time periods using Phoenix, Ariz., insolation and meteorological data. Optical degradation was modeled by systematically decreasing the specified values of solar transmittances of the plastic cover plates under consideration. Energy collection efficiencies corresponding to each decrement of transmittance were normalized to that of nondegraded glass to allow comparisons both with a standard and among the different plastics. This provides a measure of the relative usefulness of various candidate polymeric glazing materials when realistic rates of optical degradation are known.
Date: January 1, 1979
Creator: Jorgensen, G.J.
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