Heat Recovery Ventilation (or HRV) is a system designed for the continuous and constant exchange of air inside buildings in order to improve air quality. Ventilation units are equipped with two fans to supply and extract air at the same time. A cross-flow counterflow heat exchanger recovers the energy contained in the extracted air and transfers it to the supplied air, guaranteeing efficiencies of over 90%. This reduces the building energy consumption, while at the same time purifying the air from pollutants and moisture. This system allows improving the energy characteristics of the buildings, complying with current regulations, while maintaining a high level of living comfort.