The DOE-1 building energy analysis computer program is being modified to include analysis of passive solar and large thermal mass heating and cooling systems. SUNSPOT is a detailed thermal network computer program developed for direct gain systems as a reference analysis tool to compare with DOE-1. It was validated by comparison of calculated results with experimental test cell data. A series of runs was then made to determine the sensitivity of solar fraction to type of glazing, location and quantity of mass, and method of computing infrared radiant interchange among inside surfaces. Simulations using DOE-1 in its present form indicate that the weighting factors used in the program are not satisfactory for large-mass/direct-gain systems. However, it does appear that the weighting factor approach can be retained if an efficient method of determining weighting factors appropriate to passive systems can be developed. Future work will proceed in that direction
