Solar-optical and thermal behavior of photochromic glazing: Small-scale testing under real sky conditions

Abstract

The poor performance of conventional building glazing, which is usually responsible for large climatization needs and glare problems, has been promoting the development of innovative smart glazing technologies with an improved performance. Photochromic glazing, a type of smart glazing, exhibits a dynamic behavior by darkening/bleaching in reaction to the presence/absence of solar radiation. The aim of this study is to evaluate the thermal and solar-optical behavior of a photochromic filmed clear glazing, against the same glazing without film, through experimental tests. The transmittance and reflectance spectra of the glazing solutions were initially measured with a spectrophotometer. Then two small-scale models were used to assess the behavior of the glazing solutions under real sky conditions (clear and overcast). The thermal behavior was assessed through air and surface temperature measurements. The solar-optical behavior was investigated through solar radiation and illuminance measurements, which were also used to compute the solar and visible transmittance of the glazing systems, respectively. The dynamic behavior of the photochromic film resulted on a reduction of 14 % of the interior temperature. Interior illuminance and irradiance levels were significantly reduced with the film, corresponding to 10–50 % and 15–35 % visible and solar transmittance values of the photochromic glazing, respectively.