MVHR Explained: Do You Need Mechanical Ventilation in Your Home?

What is MVHR?

MVHR stands for mechanical ventilation with heat recovery. It is a whole-house ventilation system that extracts stale air from wet rooms (bathrooms, kitchens, utility rooms), recovers heat from it through a heat exchanger, and supplies warmed fresh air to living spaces (bedrooms, living rooms).¹

The system runs continuously at low speed, providing constant background ventilation as required by UK Building Regulations Part F.² Unlike conventional extract fans that dump warm air outside, MVHR transfers heat from outgoing stale air to incoming fresh air, recovering between 85% and 95% of heat that would otherwise be lost.³

MVHR is most common in Passivhaus and low-energy new builds, where airtight construction prevents uncontrolled air leakage. The system maintains indoor air quality while minimising heating energy lost through ventilation.

How does MVHR work?

An MVHR system consists of a central unit (typically mounted in a loft, cupboard, or utility room), ductwork to every room, and wall or ceiling vents for supply and extract terminals.¹

Inside the central unit is a heat exchanger core, usually made of thin plastic or aluminium sheets arranged to create two separate airflow paths. Stale air from wet rooms passes through one side of the core, warming the metal or plastic surfaces. Fresh outdoor air passes through the other side, absorbing heat from those surfaces without the two air streams ever mixing.³

Two fans drive the process. One extracts stale air from bathrooms and kitchens. The other supplies warmed fresh air to bedrooms and living rooms. The fans run continuously at low speed (typically 15-35 watts combined), ramping up to boost mode when bathroom humidity sensors detect moisture or when manually triggered via a switch or timer.⁴

The system requires ductwork throughout the house. Installers typically run 2-3 ducts per room: supply ducts to living areas and bedrooms, extract ducts from wet rooms. Ducts are usually 75-125mm diameter rigid or semi-rigid pipe, routed through ceiling voids, floor spaces, or internal walls. Retrofit installations can be challenging if ceiling voids are shallow or already full of services.

Do I need MVHR in my home?

MVHR works best in airtight homes. UK Building Regulations do not mandate MVHR, but systems are increasingly fitted in new builds meeting higher energy standards. The key test is air permeability.

For MVHR to recover meaningful heat, your home must achieve air permeability below 3 m³/h/m² at 50 Pascals pressure, as measured by a blower door test.² New Build standard in England is currently 8 m³/h/m², but Passivhaus and many low-energy self-builds target 0.6-1.5 m³/h/m². Older homes typically measure 10-15 m³/h/m² or worse.

If your home is draughty, air will leak in and out through gaps around windows, doors, and service penetrations. This uncontrolled ventilation bypasses the MVHR system, wasting heat and reducing efficiency. In such cases, a simpler extract-only ventilation system or positive input ventilation (PIV) may be more cost-effective.

MVHR makes sense if you are:

• Building a new low-energy home to Passivhaus or similar standards
• Undertaking a deep energy retrofit with external wall insulation and airtightness improvements
• Extending a property and can run ductwork through new ceiling voids or floor spaces
• Suffering from condensation and poor air quality in an already airtight home

MVHR is not recommended if:

• Your home has original single-glazed sash windows with visible gaps
• You have no ceiling voids or floor spaces to route ducts
• Air permeability is above 5 m³/h/m² and improving airtightness is not planned
• You want a ventilation system you can fit yourself (MVHR requires professional duct design and commissioning)

What does an MVHR system cost?

MVHR installation costs vary widely depending on home size, duct complexity, and unit specification. Typical UK prices:

Unit cost

£1,200-£3,500

Installation cost

£2,500-£5,000

Total (3-bed home)

£4,000-£8,000

Lifespan

20-25 years

Heat recovery efficiency

85-95%

Unit prices depend on flow rate and features. A basic 2-bedroom system handling 100-150 m³/h costs around £1,200-£1,800. A 4-5 bedroom system with humidity sensors, summer bypass (to avoid overheating), and high-efficiency motor costs £2,500-£3,500.⁴

Installation in a new build is cheaper than retrofit because ductwork can be routed before plasterboard goes up. New build installation typically costs £2,500-£4,000 including commissioning. Retrofit installation costs £3,500-£5,000+ if ceiling voids are tight or duct runs are complex.

DIY installation is possible if you are competent with ductwork and electrical connections, but commissioning and air balancing require specialist equipment. Most suppliers only provide design support and warranty coverage if installation is carried out by an approved installer.

MVHR running costs

MVHR systems draw 15-35 watts continuously at normal speed (equivalent to a broadband router running 24/7), rising to 60-120 watts in boost mode when bathroom extraction is required.⁴

Annual electricity cost at continuous low speed:

• 20W continuous = 175 kWh/year = £50/year at 28.6p/kWh (April 2026 price cap)
• 30W continuous = 263 kWh/year = £75/year
• 40W including occasional boost = 350 kWh/year = £90/year

Filters must be replaced every 6-12 months, costing £30-£60 per year depending on filter grade (G4 or F7 specification).⁵ Some systems use washable filters, reducing ongoing costs.

Heat recovery savings depend on home heat loss and occupancy. In a well-insulated airtight home, MVHR can save £150-£300/year compared to extract-only ventilation by recovering heat that would otherwise be lost. Payback period is typically 15-25 years for the full installation cost, meaning MVHR is more about air quality and comfort than pure financial return.

Pros and cons of MVHR

Advantages

• Continuous fresh air supply without opening windows (useful in noisy urban areas or near busy roads)
• Recovers 85-95% of heat that would be lost through extract-only ventilation
• Filters incoming air, reducing pollen and outdoor pollution
• Prevents condensation and mould by maintaining controlled airflow
• Low running costs (similar to leaving a light bulb on)
• Silent when correctly installed and balanced

Disadvantages

• High upfront cost (£4,000-£8,000 installed)
• Only effective in airtight homes (below 3 m³/h/m² permeability)
• Requires ductwork throughout the house (difficult in retrofits)
• Filters need regular replacement (£30-£60/year)
• Poor installation or lack of maintenance can cause noise, draughts, or reduced efficiency
• Long payback period (15-25 years) means financial benefit is marginal compared to comfort benefit