Comparison of ASHRAE peak cooling load calculation methods

The building peak cooling load calculation is one of the fundamental steps to develop a proper whole-building HVAC system design. The accuracy of the calculation not only impacts the system size but also influences the building’s performance over the long run since oversized or undersized HVAC systems can exhibit less than optimal operation. Therefore, an accurate, easy-to-use method has been a goal for more than 60 years in the United States. To date, ASHRAE has published five methods for determining building peak cooling loads, including the total equivalent temperature difference/time averaging (TETD/TA) method, the transfer function method (TFM), the cooling load temperature difference/solar cooling load/cooling load factor (CLTD/SCL/CLF) method, the heat balance method (HBM), and the radiant time series method (RTSM). This article presents the results of a comprehensive comparison of these building peak cooling load calculation methods with a focus on the sensible building envelope cooling loads. The results show that the HBM is the most accurate method, followed by the RTSM, the TFM, the TETD/TA method, and the CLTD/SCL/CLF method.