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ASHRAE STD 74

1988 Edition, January 31, 1988

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Method of Measuring Solar-Optical Properties of Materials



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Description / Abstract:

Procedure Aof this method covers the measurment of spectral absorptance, reflectance, and transmittance of materials using spectrophotometers equipped with integrating spheres. Procedure C of this method covers the measurement of solar transmittance (terrestrial) of materials using a pyranometer, and enclosure, and the sun and sky as the source of radiation.

Methods of computing solar-weighted radiant and luminous properties from the measured spectral values are specified in procedures Aand B, which are applicable to materials having both specular and diffuse optical properties. Except for transmitting sheet materials that are inhomogeneous, patterned, or corrugated, proceduresAand B of this method are preferred over procedures C, D, andE.

Procedure B describes the calculation of luminous (photometric) transmittance and reflectance of materials from spectral radiant transmittance and reflectance data, or both, obtained from the performance ofProcedureAof this method.

Procedure C of this method allows measurement of solar transmittance of materials in sheet form at normal incidence and at angles other than normal incidence and is applicable to transparent, translucent, textured, or patterned sheet materials.

ProcedureD ofthis method covers the measurement of solar photometric transmittance of materials in sheet form. Solar photometric transmittance is measured using a photometer (illuminance meter) in an enclosure with the sun and sky as the source of radiation, the enclosure and method of test being specified in ProcedureC. The purpose ofProcedureDis to specify a photometric sensor to beused with Procedure C for measuring the solar photometric transmittance of sheet materials containing inhomogeneities in their optical properties.

ProcedureEcovers the measurement of the solar radiant and luminous reflectances at normal incidence, and at other angles, of sheet materials that are opaque and which may also be textured or patterned.

PURPOSE

To develop astandard method for measuring and reporting the following solar optical properties of materials: spectral transmittance, reflectance, and absorptance between 320nm and 3000 nm in wavelength, and total radiant and luminous transmittance and reflectance.

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