The basic optical properties for the calculation of solar energy transmittance and daylight properties of glazing according to ISO 9050 and EN 410, are the reflectance and transmittance spectra of the individual glass panes. The spectra of the coated and uncoated glass panes are combined to obtain the reflectance and transmittance spectra for double or triple glazing units. the standards also prescribe the calculations which result in the glazing factors. These factors are single numbers representing the total solar energy transmittance, visible light transmittance and other glazing specifications at normal incidence. In the first of a two-part article, the author gives an update on current techniques for the optical characterisation of architectural and automotive glazing products.
