Process and cost factors
Ventilation requirements in a modern bathroom
How it works in practice
Rooms without an opening window generally need mechanical extraction ducted to the outside air, not just recirculated internally.
Fan sizing is based on room volume, so a larger bathroom or one with a bath and separate shower may need a higher-rated unit than a small cloakroom.
A run-on timer or humidity sensor keeps the fan working after the room is vacated, clearing residual moisture rather than switching off immediately.
Ducting length and the number of bends affect how well a fan actually performs, regardless of its rated output.
Questions to ask any fitter
A run-on timer or humidity sensor keeps the fan working after the room is vacated, clearing residual moisture rather than switching off immediately.
Your questions answered
Is an extractor fan legally required?
In a room without adequate natural ventilation, mechanical extraction is generally required as part of building regulations.
Why does my new fan seem quieter but less effective?
Longer duct runs or extra bends reduce airflow, so the fan's rated performance needs matching to the actual installation, not just the room size.
Planning ventilation requirements?
Tell us the town or postcode and roughly what stage you are at. We'll tell you honestly whether it is a job we can take on.