This guide covers the fundamental questions that people ask when looking at purchasing a Mechanical Ventilation with Heat Recovery unit for their property.
What is MVHR?
Mechanical Ventilation with Heat Recovery (MVHR) is a whole house ventilation system that both supplies and extracts air throughout a property. A heat recovery system is designed to extract moist stale contaminated air and supply fresh filtered air to the occupied space to continue the desired level of comfort. The heat recovery system keeps the house fully ventilated by recovering the heat which being extract from the inside environment. Heat recovery systems typically recover in excess of 85% of the heat being extracted and have significantly improved the energy efficiency of buildings. MVHR is generally the most efficient ventilation system.
- Habitable rooms are provided with fresh air while stale moist air is extracted from wet rooms and kitchens on a continual basis.
- Before the extracted air is exhausted out of the building, the heat in the air is transferred by means of a heat exchanger into the fresh filtered air, which is introduced into the building.
- The pre-warmed fresh air is introduced into all habitable rooms on a continual basis. Thereby the need to completely heat the fresh air as it enters the building is eliminated. Efficient systems typically heat cold outside air from 0ºC to 18ºC through the heat transfer, when the extract air is 20 ºC.
- No extract air is re-introduced or re-cycled, thus extracted germs and pathogens will not spread through the system.
- A gentle cooling effect in the warm season is achieved by a potential summer bypass. The cooling effect is limited and needs to be supplemented by cross-ventilation if there are excessive solar gains. However, some systems can be combined with active cooling (Zehnder ComfoAirQ cool).
All new-build properties require sufficient ventilation: that is, a system which works to remove any excess moisture by creating airflow. Typically, ventilation systems work by removing some of the air from a property and replacing it with air from outside., traditional ventilation systems remove heat, severely reducing the property’s energy efficiency and increasing the cost of heating.
Mechanical Heat Recovery Ventilation addresses that shortcoming by recovering the heat from any air extracted from a property. A typical MVHR system comprises a heat recovery unit, ideally installed in a central location, which is connected to every room in the property via a network of ducts, which open into the rooms via ceiling or wall vents.