The radiation transfer through coated and tinted glazing

The incidence angle dependent transmittance and absorptance of special glazing containing coated or tinted glass are conventionally modelled using a simple application of the Fresnel equations, treating the glazing as if it were clear glass. This simplified approach leads to only a rough approximation of the true transmission and can result in an inaccurate assessment of the solar energy gains in highly glazed spaces such as atria and in commercial buildings where special glazing is popular. An improved calculation technique has been developed which is based on the fundamental optical behaviour of radiation in thin films and in substrates. It considers the physical effects of coherent and incoherent layers, interference, and absorption. The main feature of the model is its applicability to any combination of coating and glass, with no limitation on the number or sequence of the layers. This paper shows the theoretical basis of the calculation technique and demonstrates its ability to produce wavelength and incidence angle dependent properties of special glazing. The validity of the predictions is illustrated by comparison with measurements.