MVHR Systems Explained: How Heat Recovery Ventilation Works

What Is MVHR?

Mechanical Ventilation with Heat Recovery (MVHR) continuously extracts stale air from wet rooms (kitchens, bathrooms) and supplies fresh, filtered air to living rooms and bedrooms. A counter-flow heat exchanger recovers 90-95% of the heat from the outgoing air, warming the incoming fresh air without mixing the two streams. Running costs are just £40-£160/year in electricity while saving £300-£500/year in recovered heat.

Costs and Leading Brands

New-build MVHR installation costs £3,000-£7,000. Retrofit installation is more complex at £8,000-£20,000 due to ductwork routing through existing walls and ceilings. Leading brands include Vent-Axia Sentinel Kinetic (up to 95% heat recovery), Nuaire MRXBOX-ECO (95% recovery), and Zehnder ComfoAir Q (app-controlled with enthalpy option for humidity recovery). Building Regulations Part F classifies MVHR as System 4, required for new homes with air permeability at or below 5 m³/m²·h.

MVHR and Heat Pumps: The Perfect Pairing

MVHR works synergistically with heat pumps by recovering heat that would otherwise increase the heat pump's workload. In a well-insulated home, ventilation heat loss can account for 30-40% of total heat demand. By recovering 90-95% of this through MVHR, the heat pump needs to produce less heat, improving overall system efficiency and reducing running costs. For Passivhaus builds and whole-house retrofits in East Anglia, MVHR is effectively essential.

What actually drives the cost of an MVHR installation

The unit itself is the smallest part of the bill. A whole-house MVHR unit runs roughly £600–£2,500, or £1,500–£3,500 ex VAT for a premium Passivhaus-accredited Brink or Zehnder, and on most jobs that is only a quarter to a third of the finished project. Installed, most UK whole-house systems land somewhere between £3,000 and £7,000, with published averages clustering around £5,500–£6,500 and Checkatrade's estimators putting a typical domestic installation at £6,450. Itemised 2025 specialist pricing for design, supply and commissioning — with installation labour quoted separately — is around £5,270 ex VAT at 150m², £6,770 at 250m² and £8,290 at 350m². Simpler whole-house systems are quoted from about £2,500–£5,000, and a retrofit will always sit above the equivalent new build.

Size and terminal count come from the design, not the brochure. Approved Document F (2021 edition) sets the minimum whole-dwelling ventilation rate as the greater of two figures: 0.3 litres per second per m² of internal floor area, counting every floor, and a rate fixed by bedroom count — 19 l/s for one bedroom rising in 6 l/s steps to 43 l/s for five, plus 6 l/s for each bedroom beyond that. Separately, every wet room needs a minimum high extract rate — 13 l/s kitchen, 8 l/s bathroom and utility, 6 l/s WC — and the dwelling's total extract at its continuous rate must at least equal that whole-dwelling figure. The 2026 edition, which applies to work from 24 March 2027, carries all of those numbers over unchanged. Supply air goes to every habitable room and extract comes from every wet room, so a four-bedroom house with two en-suites needs more terminals, more duct runs and a larger unit than a three-bed with one bathroom, and the price follows.

Ducting is where quotes diverge, and where a retrofit gets expensive. Rigid galvanised spiral has the lowest resistance and the most predictable pressure loss, so it earns its place on main runs and in the steel drum silencers that keep the system quiet; semi-rigid 75mm or 90mm radial takes one continuous, smooth-bore run from manifold to terminal; flexible duct, if it appears at all, belongs only in short final connections, and several specialists refuse both flexible and PVC outright on acoustic and air-quality grounds. Budget £1,500–£3,000 for ducting on a typical house, or £2,310 ex VAT at 150m² rising to £4,060 at 350m² including valves, manifolds, silencers and insulation. Installation labour is priced on top of the supply package at roughly £2,730 ex VAT at 150m² to £4,290 at 350m², with headline figures from the same supplier reaching £6,600 on the largest homes: two to five days in a new build, considerably longer threading ducts through finished floors and ceilings.

Commissioning is not optional and not a formality. Approved Document F requires every mechanical ventilation system to be commissioned to its design flow rates, with a commissioning notice given to building control — due by the date the completion certificate is required, or within 30 days of completion where that does not apply. In a new dwelling there is a second duty on top: the air flow rate at every terminal must be measured using a flow device with a proprietary hood, accurate to ±5% and UKAS-calibrated within the last 12 months, with the results notified to the local authority no later than five days after the final test. Standalone commissioning runs £400–£800; inside a full package expect roughly £460–£640 ex VAT. Skip it and you get a system that is noisy, unbalanced and short on air. An NHBC Foundation study of ten MVHR homes at Greenwatt Way in Slough found nine units needed recommissioning and one needed replacing after around a year of occupation.

Running costs are modest but real. Fans draw roughly 20–70W continuously, which at the July–September 2026 price cap rate of 26.11p per kWh works out at about £45–£160 a year; a well-designed, low-resistance system sits well below that, with one commissioned unit measured at 16W — under 0.5 kWh a day — and specialists quoting £15–£40 a year on that basis. Filters are the recurring item: £20–£60 a set for the familiar G4 coarse and F7 fine grades, now classified under ISO 16890. Manufacturers such as Zehnder recommend changing them every six months, with the fine supply-side filter usually going sooner than the coarse extract one, so budget roughly £25–£120 a year. A professional service — heat exchanger clean, fan clean, flow check — is typically £150–£300 and most specialists advise every 12 to 18 months. MVHR is not on HMRC's zero-rated energy-saving materials list; the guidance states plainly that MVHR systems do not qualify because they are not air source heat pumps, so expect 20% VAT outside new build, where it is zero-rated as part of the construction, or a qualifying long-empty property at 5%.

• Design: a room-by-room airflow schedule and duct layout, not just a unit model number — around £500 ex VAT on a 150m² house if bought separately, and £450–£700 by other published guides.
• Kit: unit, manifolds, valves and terminals, silencers, insulated duct on cold runs, roof or wall cowls, condensate traps and boost controls.
• Commissioning record: measured supply and extract at every terminal against the design figures, recorded on the commissioning sheet and notified to building control — flow-rate measurement is a statutory duty in new dwellings.
• Noise: Approved Document F's guidance figures are 30dB LAeq,T in noise-sensitive rooms such as bedrooms and living rooms at the minimum low rate, and 45dB LAeq,T in kitchens and bathrooms at the high rate. There is no requirement to noise-test, but silencers, duct sizing and low air velocity are what get you there.
• Commonly excluded: scaffolding, builder's work openings, making good and decoration, the fused spur and electrical supply, and plasterwork around ceiling valves — installers normally expect ceilings open and core holes cut before they arrive.
• Also usually excluded: VAT, and any airtightness improvements — MVHR only delivers its rated efficiency in a reasonably airtight house.