<p> The general purpose of this work is to study the feasibility of using McMaster University's PACER and MACSIM Executive Computer Programmes to simulate the environmental control system in a large building by means of elementary modules. </p> <p> The operation of PACER is described together with some general instructions as to its use. </p> <p> A number of module subroutines are developed, covering a wide cross-section of the type of equipment used in the air conditioning, heating and ventilation of a building. They are used in various combinations within the main programme to demonstrate their use. The programmes developed are not sufficient to simulate a complex system; however, they would act as a guide to the user for developing the necessary programmes to enable him to represent almost any type of equipment. </p> / Thesis / Master of Engineering (ME)