Optical models of complex fenestration systems

The need for energy conservation in buildings has spurred innovations in window technologies. These products include windows combined with shading devices, and windows featuring complex glazing such as switchable glazing, diffuse glazing, translucent and transparent insulation, patterned or decorative glass, etc. Current fenestration simulation tools for energy performance product ratings do not cover complex fenestration products. This paper addresses the development of detailed calculation models to compute the optical characteristics of complex fenestration products made up of a mixture of clear and scattering glazing layers. The models take into account not only the optical properties of the individual glazing layers making up the window product, but also the haze and gloss properties of the glazing layers. Specific optical models are developed to compute the optics of a clear substrate with applied or laminated scattering film, and composite film made up of a number of homogeneous materials with known optical properties. A general optical model was also developed for screen-like glazing panes such as insect/shading screens, roller blinds, drapery sheets, honeycomb transparent insulation and fibreglass translucent glazing.