An empirical model for angle-dependent g-values of glazings

An empirical relation, to determine g-values of glazings at oblique angles of incidence, has been determined. The requirements of the model are: g(o), g-value at normal incidence and number of panes in the glazing. The effect of glazing type (clear, tinted or coated), thickness of glass and the number of panes, appear in g(o). At off-normal incidence, g-value is determined by number of panes in the glazing. Fresnel equations are used to calculate g-values at different angles of incidence and these values are treated as ‘exact’. These calculations involve optical constants of each glazing (spectral refractive indices and spectral extinction coefficients) and then an empirical fit is found. The present model is compared to other three models, namely Monolithic model, Montecchi model and Karlsson model. The study includes nine types of glazings like clear, tinted and coated glazings.