An MVHR system will extract the warm, moist air from rooms such as kitchens and bathrooms. This is done through a concealed duct system. The air is passed through a heat exchanger then ducted outside. Fresh air from outside is drawn in and passed through the heat exchanger, which warms it, and it’s then ducted to the living rooms and bedrooms. Some systems have a feature so that when it’s warm outside, the air can bypass the heat exchanger to help keep the house cool.
The systems should be run continuously 24 hours a day, and should be only disconnected by a competent trained person during service or maintenance.
This is how it works, the system draws stale air from ‘wet rooms’ such as bathrooms, WC’s, kitchens, etc. recovering up to 93% of the heat from the air using a high efficient heat exchanger, before ejecting waste air from the rooms out to atmosphere.
Simultaneously, fresh air is drawn into the home, filtered and warmed by the recovered heat and then supplied into the habitable rooms, such as living rooms, bedrooms, hallways, etc. The systems often have two speeds, so when the kitchen and bathrooms are being used – and producing lots of moisture – the extraction rate can be boosted.
MVHR system can significantly reduce the space heating bill of a domestic dwelling, whilst also delivering a healthier and more comfortable environment for the occupier. MVHR systems eliminate many issues caused by poor indoor air quality within the home such as condensation and the resultant formation of ‘black mould’. Additionally, the advanced air filtration system ensures the home environment is much more conducive to allergy and asthma sufferers alike.
If you’ve built an energy efficient house, then the system can meet part of the heating needs of your home, as well as helping to distribute the heat. If you are building to Passivent standard, MVHR will contribute to satisfying the requirements. Many systems come with air filters, so they’re helpful in preventing potential allergens entering the house.
An MVHR system will need regular maintenance. The system needs to be kept in balance in terms of the supply and extraction of air. Filters, grilles, fans and heat exchangers need to be maintained on a regular basis.