BSIMAC’s three main functions are: (a) calculation of the cooling/heating loads and the required capacities of HVAC equipment, (b) annual energy simulation of the building and HVAC equipment, and (c) calculation of the expected room (space) temperatures with no cooling or heating on summer and winter design days. These three functions require virtually the same input data. The computations are carried out on an hour-by-hour basis. Heat transfer through walls is calculated using a conduction transfer function, with its coefficients determined for each wall/roof construction using the ‘State-Space’ method. Computations of the heat gains through glazing are based on the principles of radiant heat transfer using the solar-optical properties of the glazing element, solar radiation intensities and angles, and the effects of shading. BSIMAC has been successfully tested in accordance with ANSI/ASHRAE 140-2007. These tests have been independently verified by Agrément South Africa. BSIMAC has been certified by Agrément South Africa as “Tested and approved fit for modelling or calculation purposes” for all classes of buildings. Full Certificate available upon request.