Summary and comparison of methods to calculate solar heat gain

Abstract

Methods used to calculate the solar gain of windows (including center-glass, edge-glass, and frame) are examined and compared Particular attention is devoted to the public-domain computer programs VISION3 and WINDOW 4.1. Calculated results are presented to quantify the sensitivity of solar heat gain with respect to a wide range of glazing system design parameters and operating conditions. Details concerning solar optical properties and heat transfer mechanisms are examined and discussed When possible, comments are made concerning the development of solar gain measurement procedures. Solar gain is most sensitive to the solar optical properties of the glazings--the most important property being the transmittance of the outdoor glazing. Variables that directly affect heat transfer rates (e.g., fill gas type, convective heat transfer coefficients) have a significantly smaller effect.