Heat recovery is a ventilation system that reduces energy usage.
The air that is extracted from a bathroom or kitchen contains heat; this heat can be reused to preheat fresh air being delivered to habitable rooms rather than being wasted.
It is normally referred to as MVHR (Mechanical Ventilation with Heat Recovery). These systems comprise two independent ducts each with its own fan as follows:
- Extract fan extracts warm/humid air from wet areas such as bathrooms, kitchens, utility rooms; this air passes through a heat exchanger where heat is recovered before it is exhausted from the building.
- Fresh air is delivered from outside to habitable rooms, it passes through the heat exchanger to recover the heat from the extracted air.
This arrangement ensures there is no cross contamination of the different air flows; the fresh air in, and extracted air out, are completely separate.
Heat recovery systems can be single room or whole house. Whole house systems are more suited to new builds where the supply and extract ducts can be incorporated within the structure.