A heat recovery ventilator works by drawing in stale air from inside the building and replacing it with fresh air from outside. To maintain comfortable temperatures and air quality, the amount of stale air being removed is equal to the amount of fresh air being supplied. When the air from inside and outside your building are exchanged within the system, a heat transfer process occurs so that the clean air supplied to your home is not only fresh but also maintains the temperature within your building. Without this transfer process, the heat from the internal air would be lost, hence the term ‘heat recovery’. The process of removing air from your home or commercial building and replacing it with the fresh outside air happens simultaneously, but the two air streams never mix, therefore avoiding contamination.