Home Ventilation Installation: Extractor Fans, PIV, MVHR

Home ventilation installation covers three main jobs: extractor fans that pull wet air out of kitchens and bathrooms, positive input ventilation (PIV) that pushes filtered air in from the loft, and mechanical ventilation with heat recovery (MVHR) that swaps stale air for fresh air through ducts while keeping most of the heat. The right one depends on how airtight your home is and where the moisture comes from.

We don’t install ventilation ourselves. Tell us about your home and the problem, and we pass your request to ventilation installers and electricians who cover your postcode.

Signs your home needs better ventilation

windows streaming with water every winter morning, especially in bedrooms
black mould in ceiling corners, behind wardrobes or around window reveals
a bathroom mirror that stays fogged long after a shower
a musty smell, or cooking smells that linger into the next day
condensation that got worse after new double glazing went in

That last one catches many people out. Approved Document F says replacing windows is likely to make a home more airtight, which can cut useful ventilation. Wet air that used to leak out through draughty frames now stays in and settles on the coldest surfaces. Our guide on how to stop window condensation covers the day-to-day fixes.

Extractor fans, PIV and MVHR compared

System	How it works	Best for	Disruption
Extractor fan	Pulls wet air out of one room to outside	Bathrooms, kitchens, utility rooms	Low: a core hole or a duct through the ceiling
PIV	Fan in the loft blows filtered air into the house, pushing damp air out through gaps	Older, leaky houses with condensation	Low: one unit in the loft and a ceiling diffuser
MVHR	Extracts from wet rooms, supplies fresh air to living rooms, swaps heat between the two	New builds, airtight homes, deep retrofits	High: ducts to most rooms, boxing-in

Extractor fans

A working extractor fan is the first fix for a damp bathroom or kitchen. Approved Document F sets minimum intermittent extract rates: 15 litres per second for a bathroom, 30 l/s for a kitchen with a cooker hood that vents outside, 60 l/s for a kitchen without one, and 30 l/s for a utility room. Many cheap fans fall short once you add a long or crushed duct.

MyJobQuote puts a like-for-like bathroom fan swap at £80 to £150 and a new ceiling fan ducted through the loft at £350 to £600, with an average new install of around £300 in 2026.

Common faults an installer will look for:

a fan ducted into the loft instead of outside, or no duct attached at all
a long flexible duct with sags that collect water and cut airflow
no overrun timer or humidistat, so the fan stops as soon as the light goes off
a fan too small for the room, or sitting far from the shower

Swapping an old fan for a new one on the same cabling doesn’t need to be notified to building control, according to Approved Document F. GOV.UK lists any new circuit from the fuse box as notifiable work, so a new fan on its own circuit needs a registered electrician or a building control application. Ask for a certificate.

Positive input ventilation (PIV)

A PIV unit sits in the loft and runs all the time, drawing air from the roof space, filtering it and blowing it gently into the house through a ceiling diffuser, usually on the landing. The slight positive pressure pushes stale, damp air out through the gaps in the building. MyBuilder puts the unit at about £250 to £850 and a typical installed system at £400 to £1,200.

PIV is popular with landlords and owners of older houses because it goes in quickly with little mess. The usual complaint is a cool draught near the diffuser in winter, which a model with a small heater or temperature control can reduce. Flats without a loft can use wall-mounted versions.

MVHR

MVHR extracts air from kitchens and bathrooms and supplies fresh, filtered air to bedrooms and living rooms. The two streams pass through a heat exchanger, so incoming air is warmed by the outgoing air. MyJobQuote puts the average installed cost at £6,900, with a typical range of £3,500 to £12,000 depending on house size and how hard it is to run ducts.

Before you commit, know what MVHR is not:

It is not air conditioning. A summer bypass lets cooler night air in, but it won’t cool a hot room the way a split system does. For that, see air conditioning installation.
It doesn’t work well with windows open. The heat recovery is lost.
It needs upkeep. Filters need changing every six to twelve months, and MyJobQuote puts an annual service at £100 to £300.

MVHR pays back best in an airtight home. In a draughty older house, much of the air bypasses the unit through gaps, so PIV or good extract fans may do the job for far less.

How a ventilation install works

Survey. The installer looks at where the moisture comes from, checks existing fans and ducts, and looks in the loft.
Design. For MVHR, someone should size the system and plan duct runs to each room. Expect design to be a separate line.
Fitting. An extractor fan or PIV unit is usually a few hours. MVHR in an existing home can take several days.
Commissioning. The installer measures the airflow at each fan or valve and records it. Approved Document F expects air flow rates to be recorded in litres per second.

Rules and who to use

Most fan and PIV work involves electrics, so use an electrician registered with a competent person scheme such as NICEIC or NAPIT, who can self-certify. For MVHR, ask whether the installer has fitted and commissioned similar systems and will hand over the airflow readings. When you replace windows, Approved Document F says new windows should keep any existing trickle vents and the overall ventilation should be no worse than before.

Landlords have a duty to keep homes free of serious damp and mould hazards. Since 27 October 2025, social landlords in England must investigate significant damp and mould within 10 working days under Awaab’s Law. See our damp and mould removal page for more on landlord duties.

Comparing ventilation quotes

Does the quote name the make, model and the extract or supply rate the unit will deliver?
Is the duct route and length stated, and does it vent outside?
Are controls included: humidistat, overrun timer, boost switch?
For MVHR, are design, commissioning and the first set of filters listed?
Is making good, such as boxing-in and decorating, included or excluded?

A quote that offers MVHR to fix one damp bathroom is probably oversold. A quote that offers only a dehumidifier for a whole-house problem is probably undersold.

Typical ventilation prices

Job	Typical UK price	Notes
Bathroom extractor fan, like-for-like replacement	£80 to £150	One to two hours on the existing cabling and duct
New window extractor fan	£150 to £300	Two to six hours
New wall or ceiling fan ducted through an outside wall	£250 to £450	Four to eight hours
New ceiling fan ducted through the loft	£350 to £600	About a day
PIV unit, supplied and fitted	£400 to £1,200	Unit alone £250 to £850; heaters and smart controls cost more
MVHR, one or two bed flat	£2,500 to £5,000	Supply and fit
MVHR, three bed house	£4,000 to £8,000	Higher for retrofit with awkward duct runs
MVHR, four or five bed detached	£8,000 to £12,000	Difficult retrofits can go higher
MVHR design	£300 to £700	Often a separate line on the quote
MVHR commissioning	£300 to £800	Airflow balancing at each valve
MVHR annual service	£100 to £300	Replacement filters £15 to £120

Sources: MyJobQuote extractor fan cost guide (September 2026) and heat recovery cost guide (October 2026), MyBuilder PIV price guide and Trade2Base MVHR installation costs (2026). Prices vary by region and access, and London and the South East are usually dearer.

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Common questions

Is PIV or MVHR better for condensation?

PIV is cheaper and quicker to fit, often in a few hours in the loft, and suits an older, leaky house with a condensation problem. MVHR recovers heat and gives better control, but it needs ducts to every room and works best in an airtight home. In a small semi with streaming windows, PIV is usually the first thing to try.

How much does MVHR cost to run?

Golding Homes, a housing association, tells its tenants an MVHR system costs around £35 to £75 a year in electricity to run constantly. Your figure depends on the unit, fan speed and tariff. Replacement filters cost about £15 to £120 and are changed every six to twelve months.

What size extractor fan does a bathroom need?

Approved Document F sets a minimum intermittent extract rate of 15 litres per second for a bathroom, 30 l/s for a kitchen with a cooker hood that vents outside, 60 l/s for a kitchen without one, and 30 l/s for a utility room. The fan has to achieve that rate once ducted, not just on the box.

Do I need building regulations approval for an extractor fan?

Replacing an extractor fan or cooker hood that uses the existing cabling does not need to be notified to building control, according to Approved Document F. A new fan on a new circuit, or ventilation as part of a bigger job, may need to be. Your installer should tell you which applies.

Does PIV blow cold air?

Some people notice a cool draught near the diffuser in winter. Many units have a small heater or temperature control to temper the incoming air. Placing the diffuser on a landing rather than above a seat also helps.

Will new windows make condensation worse?

They can. Approved Document F says replacing windows is likely to make a home more airtight, so the new windows should keep any existing trickle vents and the overall ventilation should be no worse than before. Ask your window fitter about background ventilators before the order goes in.