Heat recovery ventilation system not only provides us with extra energy that would otherwise go wasted, it also helps us maintain home temperature and renew air content. In order to make it efficient, we must have it installed in a thickly-insulated house of zero thermal bridges and with a perfect airtightness, i.e. a passive house. At residences that work that thermos containers and maintains a stable temperature, ventilation enables us to renew inbound air with fresh air while not wasting its energy. The ventilation system absorbs air and moisture out of auxiliary uses’ rooms such as the bathroom and the kitchen, and imports fresh pre-heated air to the main compartments, living-room and bedrooms. Outgoing polluted air is coming in thermal contact to the ingoing fresh air and exchanges its energy.