What is MVHR?
All homes need fresh air for the people who live in them to be comfortable and healthy. When you’re building your own home, you need to make sure it’s properly ventilated to avoid issues with damp, condensation and mould.
In this post, we’re going to talk specifically about a method of ventilation called MVHR – mechanical ventilation with heat recovery. This type of system removes warm, damp air from bathrooms, kitchens and utility rooms, and replaces it by bringing fresh, usually filtered air from outside into living rooms and bedrooms. As it does so, it collects heat from the outgoing air and transfers it to the incoming air, reducing your heating costs.
What are the benefits of MVHR?
It reduces the humidity in your home, which should reduce any issues with condensation, damp, mould and dust mites. It should also reduce cold spots and make temperatures throughout the home more even – though that may not be what you want.
MVHR can be helpful if anyone in your household suffers from allergies or lung conditions like bronchitis, as the filters remove some pollutants and airborne allergens like pollen.
The Centre for Sustainable Energy says an MVHR system could save you up to 25 per cent on your heating bills, though this will depend on your home. However, MVHR isn’t a heating system in itself, just a type of heat recovery system.
How does MVHR work? Heat recovery systems explained
MVHR works by passing the outgoing air and the incoming air through a heat exchanger, via which the outgoing air transfers its heat to the incoming air. The unit is usually around the size of a boiler, and placed somewhere like a loft or utility room. Concealed ducts, usually between 10cm and 25cm wide, transport the air through your home.
Some systems have a boost setting which you can switch on while you’re using a lot of water, for example when you’re cooking, and a summer bypass mode so that the air doesn’t pass through the heat exchanger in summer. Other good features to have are frost protection and an alert that tells you when the filters need to be replaced.
MVHR works best in a reasonably airtight, energy-efficient home – it’s used in many Passivhaus homes. The more airtight your home, the better the system will work. You’ll also need to change the filters regularly – www.greenbuildingstore.co.uk recommends every three to six months.
How much does an MVHR system cost?
The cost will depend on your home, but as a guide, you can expect to pay between £3,000 and £6,000 for an MVHR system. Quality varies, so it’s important to choose a good quality, well designed system and have it properly installed.
Can I retrofit an MVHR system?
You can, but it’s expensive, and especially in older homes, which tend to be less airtight than newer homes, and where installing ducting can be difficult, the cost may outweigh the benefits. MVHR is generally best installed in new builds.
South east London architects Bluelime Home Design has been designing new homes, extensions, conversions and renovations for 13 years – and now has offices in Dartford, Bromley, Erith, Bexley and Croydon. Call us on 01322 517632 to chat about the architectural services we offer or to arrange a free architect consultation.