Optical scatter measurement and analysis of innovative daylight scattering materials

Abstract

Bidirectional reflection and transmission distribution (BRTD) measurements are an important tool in understanding the transmission of light across complex fenestration systems. Facade designers usually control the daylighting, glare, shading and to some extent heating or cooling with the choice of glazing used in fenestration systems. Light redirection and diffusion is of immense interest because of the potential to save operation costs with daylight use in office buildings and other commercial buildings while providing a comfortable working environment. In this paper, we have presented the detailed BRTD measurements for five different light scattering samples, which are developed for integration into building facades. The samples scatter a large portion of the incident light into non-specular directions. The samples vary from a double glazing unit with embedded diffusing structure, redirecting films, a laser cut panel and a semitransparent photovoltaic panel. The properties of these samples were studied with a goniophotometer to observe the angular resolved reflection and transmission. The percentage of light contributing to the non-regular transmission is also estimated. The results emphasize that reflection and transmission of such complex fenestration samples should be assessed at various angles of incidence or sun position in order to assess the potential of these systems reliably. © 2011 Elsevier Ltd.