According to recent regulations on energy saving in buildings, all new structures should guarantee high-energy performance. To this aim, the building envelope should be equipped with insulated walls and high-efficiency windows. This approach leads to considerable thermal insulation, but at the same time, in the absence of a suitable ventilation system, it results in a worsening of indoor air quality. A healthy quality of life requires good indoor air quality; especially in places where people spend most of their time, adequate air exchanges should be guaranteed and indoor pollution reduced to "acceptable" levels. In the present work, we performed a dynamic simulation of a ventilation system for an apartment using a mathematical model, i.e., the Trnsys commercial code. The model has been applied to an apartment of 66 m2 inside a condominium located in Bologna (Italy), but can also be used for other types of buildings as well. The variation of energy request due to different measurements of volume flow rate was evaluated