Bathroom and Kitchen Extraction: Is Your Fan Doing Its Job?

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What you are seeing

Streaming windows after a shower, a bathroom ceiling that never quite dries, speckled mould around a bath or window frame, or a kitchen where the cupboards and the tops of the walls feel clammy after cooking. If the moisture is worst in or beside the room that makes the steam, extraction is the first thing to check, before blaming the rest of the house.

Cooking and boiling kettles put a lot of water into the air, and so does bathing. Shelter points out that closing the kitchen door while cooking stops wet air moving into other parts of the home. A fan that is off, weak or venting into a loft leaves that moisture to settle on the nearest cold surface.

Rule these out first, cheapest first

Work down the list and stop when the symptom stops.

1. Step 1, free: use what you have. Switch the fan on whenever you cook, bath or shower, and shut the door so steam does not travel to colder rooms. Shelter advises using a fan every time, and Kensington and Chelsea guidance suggests leaving it running for 20 minutes afterwards.
2. Step 2, free: check it moves air. Hold a sheet of tissue to the grille with the fan on. If it does not cling, the fan is weak, blocked or failing. Make sure curtains and blinds are not covering it and that vents are not blocked.
3. Step 3, free: lids and doors. Cover pans while cooking, close the kitchen door and keep windows shut while a fan is running. GOV.UK guidance lists closing internal doors and covering pans as simple habits.
4. Step 4, low cost: clean it, add a timer. Dust clogs grilles and impellers. Switch off at the isolator before cleaning. A run-on timer or humidity-controlled fan removes the need to remember. GOV.UK guidance lists humidity-controlled fans and fans wired to the light with an overrun as options.
5. Step 5, trades: fix the fan or the duct. An electrician or ventilation installer can replace an under-powered fan, check that the duct runs to the outside and is not kinked, and fit a hood close to the hob. GOV.UK guidance notes kitchen extractors work best close to the hob and that fans should be serviced by qualified people.
6. Step 6, system: only then think about dehumidifying. If steam is controlled at source and the home still shows condensation, the moisture may be coming from the home as a whole, and a survey can measure it.

The Ashford factor

We have not gathered local measurements for this guide, so the advice here is general. If your Ashford home is an older property where a bathroom was added later, check whether the fan has an outside wall to duct to. If it is a newer home with a tight, well-insulated shell, steam has fewer ways to leak out on its own, which makes a working fan more important. In a rented home, a broken fan is usually the landlord's job to fix, according to Shelter.

When a dehumidifier is not the answer

A dehumidifier does not replace a working fan, and it does not fix a leaking pipe, a failed seal around a bath or shower, or damp coming through a wall. If the mould sits around a leak, fix the leak first. A Dryzen unit needs a loft to mount in, is for owner-occupied homes, and is not suitable for rentals unless the landlord authorises the changes. Existing mould must be cleaned off; GOV.UK guidance recommends a mould and mildew cleaner in preference to bleach for small areas, and a professional for larger ones.

Where Dryzen fits

A Dryzen system is a loft-mounted dehumidifier with insulated ductwork to the central area or stairway of the home. Each unit is rated for 150 square metres and has an extraction rate of 12 litres a day, and it uses about 20 pounds a year in energy. It helps stop the conditions mould and dust mites need by keeping humidity near the 50 to 55 percent default target. It does not replace a bathroom or kitchen fan. If fans, habits and repairs are sorted and condensation continues, a free survey can measure humidity through the day and say honestly whether a system would help.

Quick questions

How long should I leave the extractor fan on after a shower?

Royal Borough of Kensington and Chelsea guidance suggests leaving a fan on for 20 minutes after cooking, showering or bathing. A fan with a timer or humidity sensor does this for you.

Should I open the window while the fan is running?

The same council guidance advises keeping the windows in the room closed while an extractor fan runs, so the fan pulls moist air out instead of letting it drift into the house.

Is a recirculating cooker hood enough?

A hood that recirculates air through a filter does not send steam outside. Cooking with lids on pans, closing the kitchen door and using a fan that vents outdoors do more for moisture.

Sources: GOV.UK: Understanding and addressing the health risks of damp and mould in the home; Royal Borough of Kensington and Chelsea: Preventing condensation in your home; Shelter England: How to deal with condensation

Last reviewed 2026-10-08. General guidance only; this is not a survey of your home.