Introduction This manual focuses on two methods for calculating cooling loads in nonresidential buildings??the heat balance method (HBM) and the radiant time series method (RTSM). The two methods presented are based on fundamental heat balance principles@ directly so in the case of the HBM@ and less directly so in the case of the RTSM. Both methods were first fully presented for use in design load calculations in the predecessor to this volume@ Cooling and Heating Load Calculation Principles (Pedersen et al. 1998). Since that time@ there have been a number of developments in the RTSM. This publication attempts to bring the previous volume up to date@ incorporate new developments@ and provide a more in-depth treatment of the method.