Correlations for glazing properties and representation of glazing types with continuous variables for daylight and energy simulations

In daylight and energy simulations, fenestration products are characterized by their visible transmittance (VT) and solar heat gain coefficient (SHGC) that are both dependant on the angle of incidence, as well as by their U-value. In this work, 18 typical fenestration products suitable for the Canadian context were chosen and correlations between their actual properties were developed. First, it is shown that variations from a “standard” angular dependency curve for VT and SHGC are relatively small in such a way that the angular dependency can be approximated either by an average relation for all fenestration types, or by more precise correlations involving a linear combination of solutions with the use of a weigh coefficients. Then, relationships between values of normal VT, U-value and normal SHGC are established. In the end, it was possible to deduce the detailed behavior of all insulated glazing units (IGU) from only one continuous variable. A more precise approach with three continuous variables was also developed. A test case is presented to illustrate how to use the correlations to generate different types of IGUs in simulations.