Spectrophotometric characterisation of homogeneous and inhomogeneous thin films for architectural glazing applications

Thin solid films deposited on glazings for buildings reduce the intensity and modify the spectral curve of solar radiation in order to obtain better comfort in the indoor environmento The daylight and energy behaviour of a fenestration with a coated glass sheet can be characterised even in nonmeasurable conditions provided that the coating structure (number of layers and thicknesses) and the material optical parameters (refractive index and absorption coefficient) are known. Suitable computer programs then allow natural illuminance and solar irradiance in the room to be predicted. The required optical parameters of the film can be determined by spectrophotometric measurements and data processing. This characterisation is not straightforward when the film deposited on the glass substrate shows a refractive index variation through its thickness. In this paper an approach for inhomogeneous thin films is presented together with some examples of the application of the coated glasses in architectural glazings.