Image source: nrcan.gc.ca
Heat Recovery Process
At the core of an HRV is the heat transfer unit. Both the exhaust and outdoor air streams pass through the unit, and the heat from the exhaust air is used to pre-heat the outdoor air. Only the heat is transferred; the two air streams remain physically separate. Typically, an HRV is able to recover 70 to 80% of the heat from the exhaust air and transfer it to the incoming air. This dramatically reduces the energy needed to heat outdoor air to a comfortable temperature.
Air Exchange Process
The HRV system installed in a home can change all the air in the house over a three-hour period. Most HRV units are also equipped with automatic humidity sensors that increase the ventilation rate when needed – for instance, when you use the shower. Exhaust air is normally collected from the kitchen and bathroom areas, where most moisture and odours are created.