If you wondered what MVHR is, it stands for Mechanical Ventilation with Heat Recovery. You can also call it Heat Recovery Ventilation. It is a form of controlled ventilation and the only one which cuts out almost all ventilation heat losses, which can make up to 30% of the general heat demand of a new dwelling.
Please see the following slides for more information. Click on the right hand side of the image to forward.
- Almost all new built dwellings are built to good air tightness standards - and that for a reason: to conserve heating energy. Without a proper ventilation strategy it is very likely that pollutants build up and the air quality is below the required standards.
- The build-up of humidity can cause serious harm to the occupants and structure. This especially the case for older buildings that are being renovated as through the home improvements the chance of black mould triples. But also new build properties have often humidity issues which give cause to rising house dust mite infestation.
- The solution is simple: Keep your bedroom windows open all night and cross-ventilate regularly during the day. However the resulting heat loss is considerable, especially in the colder climates.... and thus it defeats the drive for more energy efficient homes.
- Another solution is a controlled ventilation system that eliminates the need for trickle vents and constant window opening. MVHR was born in the 1980s to avoid the upcoming health risks of more energy efficient and air tight dwellings. It was refined ever since to be inaudible, easily controlled and hygienic.
- Such system is based on delivering fresh air into all habitable rooms on a constant basis. In most cases air ducts are installed in the service zone to deliver the air where it is needed.
- At the same time air is extracted from room where there is moisture or pollution, thus replacing all normal extractor fans in kitchens, bathrooms, utilities and toilets.
- The extracted stale, humid and polluted air is exhausted out of the dwelling. However beforehand it passes through a heat exchanger, which transfers the heat energy into the fresh air that comes into the house. Modern systems are 90% or more efficient.
- Thus in winter the incoming air is pre-heated to almost ambient levels, e.g. from minus 2 to 18 degrees just passive, without active heat input. Only at frost below minus 2 a small heating element is being used in good systems to allow peak performance when you need it most.
- This way the fresh air is introduced into the habitable rooms is in balance with the stale air extracted from the wet rooms. The air moves slowly through all parts of the dwelling, avoiding zones of stale or polluted air. The air movement can be slowed down or speeded up when necessary.
- So, for very little expenditure of typically 25W-60W energy use, up to 30% heating costs can be saved. But what's more important is that you live in a healthy and comfortable environment. Because it uses little energy, you can open your windows when you want, but if you don't, you will still have fresh air inside.