Procedure for measuring simultaneously the solar and visible properties of glazing with complex internal or external structures.
Accurate solar and visual transmittances of materials in which surfaces or internal structures are complex are often not easily amenable to standard procedures with laboratory-based spectrophotometers and integrating spheres. Localized "hot spots" of intensity are common in such materials, so data on small samples is unreliable. A novel device and simple protocols have been developed and undergone validation testing. Simultaneous solar and visible transmittance and reflectance data have been acquired for skylight components and multilayer polycarbonate roof panels. The pyranometer and lux sensor setups also directly yield "light coolness" in lumens/watt. Sample areas must be large, and, although mainly in sheet form, some testing has been done on curved panels. The instrument, its operation, and the simple calculations used are described. Results on a subset of diffuse and partially diffuse materials with no hot spots have been cross checked using 150 mm integrating spheres with a spectrophotometer and the Air Mass 1.5 spectrum. Indications are that results are as good or better than with such spheres for transmittance, but reflectance techniques need refinement for some sample types.
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Smith