Condensation and mould are among the most common problems we see in homes and rental properties, and a weak or broken extractor fan is often the cause. A properly sized, correctly installed fan removes moisture at the source before it settles on cold walls and ceilings.
How powerful should the fan be?
Building Regulations (Approved Document F) set minimum extract rates for intermittent extractor fans in homes:
| Room | Minimum intermittent extract rate |
|---|---|
| Kitchen (cooker hood extracting outside) | 30 litres/second |
| Kitchen (fan elsewhere in the room) | 60 litres/second |
| Utility room | 30 litres/second |
| Bathroom | 15 litres/second |
| WC | 6 litres/second |
These are minimums. Long or bendy duct runs reduce performance, so the fan has to be chosen with the ducting in mind. A cheap fan pushing through a long flexible duct may move a fraction of its rated airflow.
Timers, humidistats and quiet fans
- Overrun timers keep the fan running for a set time after the light goes off, clearing steam after a shower.
- Humidistats switch the fan on automatically when humidity rises, which is ideal for rental properties where tenants may not use the fan.
- Continuous low-level fans run quietly all the time and boost when needed, often the best answer for persistent mould.
- Quiet fans get used. If a fan is noisy, people switch it off.
Electrical safety in bathrooms
Bathrooms are a special location in the wiring regulations:
- fans in the zones around the bath or shower need a suitable IP rating, and in some positions must run on a safety extra-low voltage (SELV) supply
- circuits serving the bathroom need RCD protection
- an isolator, usually a fan isolator switch outside the room, allows safe maintenance
Ducting: get it outside
A fan should always duct to the outside, through a wall, roof tile or soffit vent, never just into the loft. Venting into a loft simply moves the moisture somewhere you can’t see it, where it can cause condensation and rot.
For landlords
Damp and mould are now a major focus under housing standards, and inadequate ventilation is one of the first things looked at. Making sure every bathroom and kitchen has a working, correctly sized fan, ideally on a humidistat, is one of the cheapest ways to prevent complaints and protect the property. Read our damp and mould guide for landlords, or for whole-house ventilation see our MVHR guide.
Get fans fitted properly
We fit and upgrade extractor fans for homeowners, landlords and agents, including ducting, isolators and humidistat controls. We cover London and Essex, with our own engineers working every day across Chigwell, Loughton, Buckhurst Hill, Woodford, Ilford, Romford, Brentwood and Epping. Call 020 8227 0035 or request a quote.