## A Simple-to-Use Calculator for determining the Total Solar Heat Gain of a Glazing System

Authors: Luther, Mark Brandt; Horan, Peter; van Kan, David Jack

This project is to develop a simple-to-use calculator for the total solar heat gain of a glazing sys¬tem exposed to various angles of incidence. Given the date and time, global solar (horizontal) radiation and the global diffuse component, the incident beam angle for the surface orientation under consideration is calculated. The calculation incorporates the results of the Solar Heat Gain Coefficients predicted for the glazing system by the well-known program WINDOW 6.0.

We address the factors to be considered such as solar position and the incident angles to the hor¬izontal and the window surface, and the fact that the solar heat gain coefficient is a function of the angle of incidence. We also discuss the effect of the diffuse components of radiation from the sky and from ground surface reflection, which require refinement to the calculation methods.

The calculator is implemented in an Excel spreadsheet allowing the user to input multiple datasets and immediately produce the resulting solar gain. We consider comparing this calculated total solar heat gain with measurements of a test facility described elsewhere in this conference.