MVHR Explained: The Complete Guide to Heat Recovery Ventilation
Modern airtight buildings can't breathe on their own. MVHR delivers continuous fresh, filtered air while recovering up to 90% of the heat you'd otherwise throw away — here's how to get it right.
The better we insulate and seal our buildings, the more deliberately we must ventilate them. MVHR — Mechanical Ventilation with Heat Recovery — is the technology that squares that circle: continuous fresh air without throwing away the heat you've paid for.
How MVHR works
Stale, moist air is continuously extracted from kitchens, bathrooms and utility rooms. Fresh filtered air is supplied to bedrooms and living spaces. In between, both airstreams pass through a heat exchanger — without mixing — where up to 90% of the outgoing heat transfers to the incoming air. In summer, a bypass lets cool night air in without warming it.
Do the Building Regulations require it?
Approved Document Part F requires every new and substantially refurbished dwelling to have a designed ventilation strategy. MVHR (System 4) isn't the only compliant route — but for airtight buildings (below ~3 m³/h.m²), it is usually the only one that delivers both compliance and comfort. Part L's energy targets push the same direction.
Why some MVHR installations disappoint
Noise complaints, stuffy rooms and units switched off by frustrated owners almost always trace back to the same errors: undersized units running at full speed; ductwork designed for cost rather than airflow; no attenuation; poor filter access; and no commissioning. An MVHR system should be inaudible in bedrooms — that is a design outcome, not luck.
MVHR in luxury refurbishments
Retrofit is where experience shows. Routing rigid duct through a Victorian terrace or a listed building without losing ceiling height — or period features — demands early coordination with the architect and structural engineer. We model duct routes in 3D before anyone lifts a floorboard, which is precisely the BIM-first approach we bring from commercial projects.
Frequently asked questions
- Does MVHR replace heating? +
- No. MVHR recovers heat that ventilation would otherwise lose, but it is not a heating system. It pairs beautifully with underfloor heating and heat pumps in low-energy homes.
- How often do MVHR filters need changing? +
- Typically every 6–12 months depending on location — more often near busy London roads. Good design puts filters somewhere genuinely accessible.
- Can MVHR cool my house in summer? +
- MVHR provides summer bypass and useful night purging, but it moves modest air volumes — it is not air conditioning. For real cooling, pair it with a properly designed AC system.
- Is MVHR worth it in a refurbishment? +
- If you're improving airtightness substantially — new windows, insulation, membranes — yes, and it's far easier to install during works than after. Below-average airtightness makes the case weaker.
Planning a project? We're happy to talk it through.
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