Balanced pressure / Heat recovery systems

Balanced pressure / Heat recovery systems

Balanced pressure / Heat recovery ventilation systems are particularly suitable for homes in colder areas of the country, if they are already well heated and if they are reasonably airtight.

These systems have two fans: an intake fan which supplies fresh outdoor air into the house through several ceiling vents; and an exhaust fan which takes stale air from inside the house and discharges it to the outside. An air-to-air heat exchanger (usually in the roof space) transfers heat from the inside air to the incoming fresh air from outside. In this way, most of the heat is recovered.

Some products include additional features to utilise heat in the roof space when it is available on sunny winter days, or to avoid warming incoming fresh air in summer when it is hot.

To ventilate effectively, these systems need gaps or vents in internal doors so that air can flow through all areas of the house between the intake and exhaust.

In winter, the heat exchanger transfers a portion of the heat in the warm exhaust air to the colder outdoor air, thus reducing the heat loss associated with the ventilation. To be effective, the house should be airtight so that almost all ventilation air passes through the heat exchanger, rather than being leaked out through draughts.
Heat recovery systems provide good fresh air ventilation but they are not a heating system.  However, they can recover between 67–95% of the heat from the inside air which means that the fresh air coming in will be warmer. This means you will need less heating to warm your home.