TL;DR:

  • MVHR recovers 70–95% of heat from outgoing stale air and uses it to warm incoming fresh air — cutting ventilation heat loss dramatically without sacrificing air quality.
  • It’s most cost-effective in well-insulated, airtight homes (new builds, Passivhaus, deep retrofits); less worthwhile in draughty older properties where the system loses efficiency through uncontrolled infiltration.
  • Installed cost is typically £4,000–£8,000 for a whole-house system in the UK; the technology is eligible for VAT at 0% on installations in existing homes since the 2023 VAT changes.

As UK homes get better insulated, a problem emerges: a tightly sealed house needs mechanical ventilation or it accumulates moisture, CO₂, cooking odours, and volatile organic compounds. Open a window and you lose the heat you paid for. Mechanical Ventilation with Heat Recovery (MVHR) solves this by ventilating continuously while recovering the energy in the outgoing air.

It’s become a standard specification for Passivhaus buildings and is increasingly specified in new builds meeting the Future Homes Standard. For retrofits, the calculus is more nuanced.

How MVHR Works

An MVHR unit sits in a loft, utility room, or airing cupboard and manages four separate duct runs:

  1. Extract from wet rooms — bathrooms, kitchen, en-suites pull stale, humid air out of the house
  2. Supply to living rooms — fresh filtered air is delivered to bedrooms and living spaces
  3. Exhaust to outside — the stale air is expelled, but not before passing through the heat exchanger
  4. Fresh air intake from outside — incoming cold air passes through the same exchanger

In the heat exchanger, the two airstreams pass each other without mixing. Heat transfers from the warm outgoing air to the cold incoming air. A good unit recovers 85–93% of that heat. In winter, this means you’re delivering air to your living room at 18–20°C that came in at 2°C outside.

The result: continuous fresh air with minimal heat loss, no condensation issues, and no draughts.

What MVHR Is Not

MVHR is not a heating system. It recovers heat that would otherwise be wasted — it doesn’t generate heat. You still need a boiler, heat pump, or other heating system. MVHR reduces your heating demand by cutting ventilation losses, but it doesn’t eliminate the need for a heat source.

It also requires a reasonably airtight building to work well. In a house with an air permeability above roughly 3 m³/(h·m²) at 50Pa — which is most pre-2000 UK homes in their existing state — significant amounts of uncontrolled infiltration bypass the system entirely. You’re spending money on MVHR but much of the ventilation is still happening through gaps you haven’t sealed.

When MVHR Makes Sense

New builds: MVHR is almost always specified for new builds targeting high efficiency. The ductwork is designed in from the start, installation is straightforward, and the building’s airtightness targets make it effective.

Passivhaus and EnerPHit retrofits: Both certification standards require the building to meet strict airtightness criteria. At this level of airtightness (0.6 ACH at 50Pa for Passivhaus), MVHR isn’t optional — you need mechanical ventilation, and recovering the heat is the obvious step.

Deep energy retrofits: If you’re doing external wall insulation, replacing all windows, and achieving significant airtightness improvement as part of a whole-house retrofit, adding MVHR makes sense. The airtightness work creates the conditions where MVHR performs well.

Problem rooms: Even in a less airtight house, MVHR in a specific problem area — a persistent damp bathroom, a poorly ventilated kitchen — can address specific issues, though you won’t see whole-house efficiency benefits.

When to Wait or Consider Alternatives

Draughty older houses: If your home has an air permeability above 5–7 m³/(h·m²), the MVHR system will be less effective. The priority should be airtightness improvement first — draught-proofing, window upgrades, filling penetrations — and MVHR second. Spending £6,000 on MVHR in a leaky Victorian terrace will underdeliver.

Limited ducting routes: MVHR requires a full duct network to every habitable room. In a house with limited loft space, solid floors, or complex layouts, routing ducts can be expensive and disruptive. Single-room heat recovery ventilation (SRHV) units are an alternative — they’re less efficient but require only a single wall penetration per room.

Budget constraints: If you’re choosing between MVHR and other energy improvements, insulation and draught-proofing typically deliver better returns in most UK homes. MVHR adds value once those fundamentals are in place.

Costs

Installed cost for a whole-house MVHR system in a 3–4 bedroom UK home typically runs £4,000–£8,000 including supply, installation, commissioning, and ductwork. Larger or more complex houses with more duct runs cost more. Brand matters — Zehnder, Paul, STIEBEL ELTRON, and Brink are commonly specified by AECB-certified installers.

Running costs are modest: fan electricity use is typically 40–80W for a whole-house unit, equating to roughly £60–£130/year at current UK electricity prices. Filter replacement (typically twice yearly) runs £20–£50 depending on the unit.

The heat recovered reduces your heating demand. In a well-sealed house, MVHR can account for a meaningful fraction of heating energy savings — estimates vary, but 15–25% reduction in heating demand in new build performance is commonly cited. In monetary terms at current gas prices, the energy saving is roughly £100–£250/year for a typical house, depending on size and how cold the winters are.

Payback purely on energy savings is long — 15–25 years. The value case is better understood as: you need ventilation anyway (a sealed house requires it), and MVHR is the energy-efficient way to provide it while maintaining air quality.

VAT and Grants

Since April 2022, MVHR installation in existing residential buildings qualifies for 0% VAT as an energy-saving material. This represents a worthwhile saving on what would otherwise be a 20% addition to installed cost.

MVHR is not currently included in the Boiler Upgrade Scheme or the UK government’s Warm Homes Plan directly, though local authority retrofit programmes under the Social Housing Decarbonisation Fund have included MVHR as part of whole-house retrofits in social housing.

Finding a Good Installer

MVHR installation quality matters enormously. A poorly commissioned system with leaky duct joints, unbalanced flows, or incorrect filter specifications will underperform significantly. Look for:

  • Membership of the Passive House Institute (PHI) or AECB
  • Experience with MVHR specifically (not just HVAC generally)
  • Willingness to carry out commissioning and measure achieved flows against design
  • Access to the manufacturer’s balancing guide for your specific unit

The Passivhaus Trust maintains a database of certified tradespeople; the AECB (Association for Environment Conscious Building) also lists experienced retrofitters.

Maintenance

Filters need changing 2–4 times per year depending on location and air quality. Most modern units have filter change indicators. The heat exchanger itself is low-maintenance — an annual clean is sufficient. Summer bypass mode (most units have one) allows the exchanger to be bypassed on warm nights, bringing in cool air without pre-warming it.

For the typical UK homeowner, MVHR is not a set-and-forget system — it rewards a small amount of regular maintenance. But for homes built or retrofitted to modern energy standards, it’s increasingly the default choice for healthy, efficient ventilation.