ASHRAE Technical Committee 4.7 developed the modified bin method to fill the need of a simple yet comprehensive method of calculating the energy requirements of buildings. The method is widely used, but the solar calculations are not accurate. This causes the results to be erroneous if the solar gains contribute extensively to the building load. A new method to calculate the solar gains based on analyses of real solar data was developed. This method has many advantages over the one used in the original modified bin method. When compared to actual temperature and insolation bin data, the new method gives considerably better results than the original. This is not achieved by a complicated process or a very computationally intensive method but by a simple equation that uses only one parameter, the standard deviation of the temperature distribution. The original method not only gives inaccurate values for the solar gains but uses six parameters per orientation. The present work is limited to solar flux calculations only, solar-related cooling loads are not addressed.

KEYWORDS: calculating, buildings, solar heat gain, comparing, insolation, temperature, temperature distribution, heat load