Building energy analysis programs are useful for identifying energy saving opportunities in air-conditioned buildings. In this book, mathematical models are presented for developing such programs. Models are developed for calculating thermal response factors for multilayer building envelope and for rapid computing of weighting factors. A chilled water coil model is described for obtaining latent heat transfer correlation for simulation of three centralized air distribution systems: constant volume, dual-duct multizone and variable air volume. Merkel''s theory is used to simulate forced draught air/water counter flow and cross flow cooling towers to obtain correlation between tower leaving water temperature and two variables: tower inlet water temperature and ambient air wet bulb temperature. The correlation is used in chiller algorithms for accurate prediction of compressor power usage. Simplified models are also presented for simulating generic cool thermal energy storage (CTES) systems. A case study is presented to compare the energy performance and economics of CTES and conventional systems. The book is of interest to ventilating and air-conditioning professionals.