In this paper, the mathematical model of a HVAC (Heating, Ventilation and Air-Conditioning) equipment is described. This system is inserted into a computer code developed in Matlab/Simulink platform which is devoted to the analysis of building thermal behavior and HVAC closed-loop control performance. The model is presented in terms of non-linear state-space equations that represent the energy and mass balances for each HVAC component. Two control loop structures are described and analyzed. The IMC structure is used for the PID controllers tuning procedure. Finally, comparative results are provided in terms of energy efficiency and indoor air temperature and humidity control performance by using data of two Brazilian cities.