Condensation and ventilation fixes
Condensation is the most common cause of mould in English homes. Moist air from cooking, washing and breathing settles on cold surfaces and stays there. The lasting fix is a mix of moving that air out and keeping surfaces warm enough that it doesn't settle.
We don't fit fans or ventilation. We pass your enquiry to one independent specialist near you, who works out what's needed and quotes you. Free to ask.
Signs it's condensation
- Windows streaming with water first thing, especially in bedrooms.
- Black spotty mould in the corners of rooms, around window reveals and on the bathroom ceiling.
- Mould behind wardrobes, beds and sofas pushed against outside walls.
- Worse in winter, better in summer.
- Clothes, shoes or bags in cupboards going mouldy.
If you're not sure, our guide to damp or condensation goes through the differences.
What a specialist can fit or fix
- Extractor fans. Replacing weak or broken fans in bathrooms and kitchens with ones that move enough air, with a humidity sensor or an overrun timer so they keep going after the light's off. Ducting matters as much as the fan: a long, kinked flexible duct can halve what reaches outside.
- Continuous running fans. Quiet fans that run all the time at a low speed and boost when the room gets humid.
- Positive input ventilation (PIV). A unit, usually in the loft, that gently pushes filtered air into the home so damp air is pushed out through gaps and vents. Common in houses with condensation spread across several rooms. Flats can use wall-mounted versions.
- Trickle vents and air bricks. Adding vents to windows that have none, and clearing or adding air bricks.
- Heat recovery units. Single-room units that swap stale air for fresh while keeping most of the heat.
- Cold spots. Pointing you to insulation where a wall or ceiling is so cold it attracts condensation however well ventilated the room is.
What you can do now
- Run the extractor fan during and for 15 to 20 minutes after a shower or cooking, with the door shut.
- Put lids on pans. Dry washing outside, in a tumble dryer that vents outside, or in a room with the window ajar and the door closed.
- Keep trickle vents open. Leave a small gap between furniture and outside walls.
- Keep some heat on in every room in cold weather, rather than heating one room hard and leaving others cold.
- Wipe condensation off windows and sills each morning and wring the cloth out down the sink.
What it usually costs
| Job | Typical range | Source |
|---|---|---|
| Replacing an extractor fan like for like | £80–£150 | MyJobQuote |
| New wall or ceiling fan ducted through an outside wall | £250–£450 | MyJobQuote |
| New ceiling fan ducted through the loft | £350–£600 | MyJobQuote |
| Positive input ventilation (PIV) unit, installed | £400–£1,200 | MyBuilder |
Sources: MyJobQuote extractor fan costs (updated 15 September 2026), labour and materials; and MyBuilder PIV installation cost guide (updated 21 August 2026), including the unit and fitting.
What changes the price: how far the duct has to run, whether a new hole has to be cored through a wall, whether an electrician needs to add a circuit, and access to the loft. Mould treatment on top is priced separately; see mould removal.
Facts, dates and prices on this page were last checked on 29 October 2026.
Common questions
Isn't condensation just a lifestyle problem?
Daily habits play a part, but they're rarely the whole story. Cold walls, poor insulation, fans that don't work and windows with no trickle vents all make condensation more likely however careful you are. Landlords in particular shouldn't treat it as the tenant's fault without checking the building.
Do I need a PIV unit?
Not always. If the problem is mainly in the bathroom and kitchen, a decent extractor fan in each may be enough. A PIV unit helps where condensation is spread through the home. A specialist should check fans and vents before suggesting one.
Will opening windows in winter make my home cold?
A short burst of fresh air, ten minutes or so after a shower or cooking, swaps damp air for drier air without losing much heat. Leaving windows open all day in winter costs more in heating and can make walls colder.
Does a dehumidifier help?
Yes, for condensation. It pulls water out of the air and is especially useful for drying washing indoors. It won't fix a building problem such as a broken fan or a cold, uninsulated wall.
Why do I get condensation after new windows were fitted?
New windows are much more airtight than old ones, so less damp air escapes. If they came without trickle vents, or the vents are kept shut, moisture has nowhere to go. Better ventilation elsewhere usually sorts it.
Ask for a local damp and mould specialist
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We're a matching service, not the firm that does the work. The specialist contacts you, looks at the problem and quotes you directly. Whether you go ahead is up to you.