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This study was undertaken to compare methods of calculating the transmittance of cover plate materials and the reflectance of absorber materials. The study was limited to evaluation of factors which influence the results with method A of ASTM E 424, Optical data were obtained for both aged and unaged test specimens using an integrating sphere spectrophotometer. The data were integrated using: (1) the weighted and selected ordinate methods in ASTM E 424, Method A, at air mass 2.0, and (2) the selected ordinate method at air mass 1.5 and 1.0. The solar reflectance and solar transmittance values calculated using the various methods are presented in this report along with discussions of the impact of the data in terms of possible revisions to ASTM E 424.

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