Glazing solar parameters evaluated by ISO, CEN and ASTM Standard procedures

Abstract

The solar behaviour of glazing for architectural or automotive applications is generally characterized by (near) normal incidence spectrophotometry The spectral transmittance and reflectance curves are integrated in the solar range using a global or direct solar irradiance curve at sea level as a weighting function. These solar curves can be obtained taking into account the effects of the atmosphere on the extraterrestrial solar radiation and comparing the computed spectra with the measured spectral irradiance values on the earth surface. However, the theoretical global and direct solar curves depend on the model used to simulate the atmospheric behaviour (type of model and values assumed for the atmospheric parameters). Moreover, solar irradiance measurements made at ground level were limited in accuracy, at least in the past. For these reasons different solar curves were standardized by ISO, CEN and ASTM. Glass samples representative of commercial production are considered in this paper and a comparison is performed among t he values obtained for the solar parameters following international. European and American Standards .