Faulty operation of HVAC systems can lead to discomfort for the occupants, energy wastage, unreliability and shorter equipment life. Cost-effective Fault Detection and Diagnosis (FDD) methods can therefore ensure an increase in the system uptime, reliability, and overall efficiency. In this paper, in order to evaluate and compare FDD methods for HVAC systems, we resort to a particular case of Variable Air Volume models, that are capable of describing the response of the control system in both normal and fault operating conditions. The system is tested by performing extensive simulations using Matlab/Simulink™tools in order to allow the description of the most common and relevant fault affecting this kind of systems.