Buildings Indoor air quality (IAQ) is a problem that affects both well-being of occupants and energy consumption relative to the structure. Controlled mechanical ventilation system (CMV) allow to control the air exchange rate. When using CMV systems is interesting to investigate the relationship between the useful thermal energy requirements for ventilation and the energy consumption of these systems. Is there a correlation between these two parameters? This paper will address this question. The methodology used in this work involves the application of equations of technical regulations UNI/TS 11300 in a case study. The case study is represented by a 54 m³ room where it is assumed to be present three CMV systems (extraction, insertion, insertion/extraction) for 20 different devices available on the market. Simulations of useful thermal energy requirements QH,ve and primary energy EP,V were performed according to the electrical power of fan (W) and the ventilation flow. The results show that the two values are not linearly correlated: it’s not possible to associate the operating cost for CMV systems according to building requirement. The study also shows that CMV systems are especially efficient for high performance buildings, where there is not leakage that can be ascribed to windows infiltrations.