Ventilation Bristol: Extractor Fans, PIV and MVHR

Bristol's converted houses create some of the hardest ventilation problems around. Basement and lower-ground flats sit partly below ground, kitchens and bathrooms are often internal rooms, and many buildings are in conservation areas where new vents on the front are frowned upon.

Bristol at a glance

Converted flats: 35.1% of Bristol households lived in a flat in 2021. 10.2% were in a converted or shared house, about one household in ten, and 21.9% in purpose-built blocks. Source
Conservation areas: A Bristol City Council appraisal from 2008 records 33 conservation areas covering about 30% of the city. Source

Basement and lower-ground flats

These flats are prone to condensation because outside walls are cold and partly buried. A good extract fan in the kitchen and bathroom is essential, and a wall-mounted PIV unit can keep air moving through the flat.

Check that air bricks and light wells are clear. Blocked ones trap moisture.

Extract fans

Approved Document F sets minimum extract rates. In internal bathrooms, ducts often run through ceiling voids to the back of the building. Make sure the duct is insulated and slopes away from the fan so condensate does not drip back.

Conservation areas

New vent grilles on the front of a building in a conservation area may need permission. Route ducts to the rear or roof where possible.

MVHR

Heat recovery ventilation suits new builds and deep retrofits. In a typical Bristol conversion, good fans and PIV are usually more practical.

If you are planning a major refurbishment of a whole house, with new windows, insulation and airtightness work, MVHR can be designed in at that stage. Ducts are far easier to route while ceilings and floors are open.

Bristol homes and what they need

Victorian terraces on the city's hills

Rear extension bathrooms often lack windows. A humidity-controlled fan with an overrun timer is the minimum.

Flats in converted Georgian and Victorian houses

Internal rooms need ducted fans. Lower-ground flats benefit from wall PIV.

Interwar and post-war semis on the outskirts

Replacement windows have reduced natural ventilation. Trickle vents and a loft PIV unit are common fixes.

Areas covered

Engineers who cover Bristol work across areas including Clifton, Bedminster, Southville, Bishopston, Redland, Easton, Fishponds, Horfield, Kingswood and Keynsham.

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Questions people in Bristol ask

Can my landlord be asked to fit fans?

Yes. Landlords must address damp and mould hazards, and effective extraction is usually part of the fix.

Is PIV noisy?

Modern units are quiet. Most people do not notice them once fitted.

Do I need permission for a new extractor fan?

Not usually inside, but a new grille on the front of a listed building, or on a building in a conservation area, may need consent. Bathroom fan wiring must be done or certified by a registered electrician.

Sources

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