Home & Cleaning

How to stop condensation in a bedroom: 10 fixes for wet windows and walls overnight

Bedrooms get the worst condensation in many UK homes: warm breath, a closed door and a cold night. Here are 10 fixes, in the order to try them, plus what a quiet dehumidifier costs to run overnight.

Ad Contains affiliate links · Updated 29 October 2026 · 5 handy products · By James Mackie

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If you wake up to streaming windows, a wet window sill or damp patches in the corner of the ceiling, you're not alone. Bedrooms are where condensation is often worst: we breathe and sweat moisture into the air all night, the door's usually shut, and the heating goes off just as the walls and glass get coldest.

That moisture lands on the coldest surfaces first: the glass, the window reveal, the outside wall behind the bed or wardrobe, and the ceiling under a poorly insulated loft. Left there night after night, it turns into black mould. GOV.UK says condensation is the most common form of damp in UK homes.

Below are 10 fixes in the order we'd try them, most of which cost nothing. If you've already got mould, start with our guide to getting rid of black mould safely, then come back here to stop it returning.

Why bedrooms get so much condensation overnight

Condensation forms when warm, moist air touches a surface that's colder than its dew point. In a bedroom overnight, three things combine: moisture goes up (from breathing and sweating, plus any washing drying in the room), air movement goes down (door shut, window closed, vents blocked by curtains) and surfaces get colder as the heating goes off and the temperature outside drops.

That's why the glass, the window reveal, the corner where the outside wall meets the ceiling and the wall behind the bed or wardrobe are where you'll see water, and then mould, first. It's rarely one cause, so the fixes below work best together.

10 ways to stop condensation in a bedroom

1. Open the trickle vents and leave them open. They're the slots in the top of most modern window frames. GOV.UK's guidance notes that all replacement windows must have them. They let a little moist air out all night without a draught.
2. Open the window for 10–15 minutes in the morning, or crack it on the latch overnight if it's safe and not too cold. Short bursts of fresh air lose less heat than leaving it open all day.
3. Keep a low, steady background heat. Warmer walls are drier walls. A room that drops right down overnight gets far more condensation than one held at a modest temperature. Notting Hill Genesis suggests a thermostat setting of 18–21°C in its tenant advice.
4. Leave the bedroom door open (if you can) so moisture spreads into a bigger volume of air, or run a dehumidifier if it has to stay shut.
5. Don't dry washing in the bedroom. A wash load holds a lot of water, and in a closed bedroom most of it ends up on the windows. See our guide to the cheapest way to dry clothes indoors for better options.
6. Pull furniture away from outside walls by a few centimetres. GOV.UK recommends leaving a gap between furniture and external walls so air can circulate.
7. Keep the bathroom and kitchen doors shut when cooking or showering and use the extractor fans, so steam doesn't drift into the bedrooms.
8. Wipe or vacuum the glass every morning. Clearing the water stops it soaking into frames and sills. A window vac makes this quick, and you pour the water away rather than leaving it to evaporate back into the room.
9. Pull curtains back during the day and don't let thick curtains or blinds sit against wet glass overnight; tuck them behind the radiator or leave a gap.
10. Run a dehumidifier overnight if the room still runs wet. This is the most reliable fix when you can't ventilate or heat enough, and quiet models cost about 29–31p a night (see below).

For condensation through the rest of the house, including the window-specific fixes, see our main guide to stopping condensation on windows.

Is it OK to run a dehumidifier in the bedroom overnight?

Yes, if it's designed for it. Look for three things: a night or sleep mode that dims the lights and turns the fan down, a humidistat so it isn't working flat out all night, and an auto shut-off when the tank is full. Place it away from the bed with space around it, on a hard, level floor, and empty the tank each morning.

Noise is subjective. Meaco quotes 35dB for the Arete Two on its low fan and from 36dB for the ABC 12L, roughly a quiet library, but compressor models also make a low hum. If you're a light sleeper, run it on its normal setting in the evening with the door shut, then switch to night mode or turn it off at bedtime. See our full roundup of the best dehumidifiers for a bedroom for more options.

What it costs to run a dehumidifier or heater overnight

We used Ofgem's October to December 2026 cap of 26.32p per kWh and each maker's stated wattage. The working is kWh = watts ÷ 1,000 × hours, then kWh × 26.32p. Real costs are usually lower, because a humidistat or thermostat switches the machine down once the room reaches its target.

So a compressor dehumidifier is far cheaper to run all night than an electric heater, though it doesn't replace heating in a genuinely cold room. If your bedroom is cold, see our guides to oil-filled radiators and electric blankets for cheaper ways to stay warm.

Condensation on bedroom walls and ceilings

Water on the walls, rather than just the glass, usually means the wall itself is cold: a solid outside wall, a corner where insulation is missing, or a ceiling under a patchy loft. GOV.UK suggests at least 270mm of loft insulation and points to cold spots caused by gaps in insulation.

Check behind the bed and wardrobe; that's where air doesn't move. If you see a dark tide mark low on a wall, or damp that gets worse after rain rather than overnight, it may be penetrating or rising damp, which needs a surveyor, not a dehumidifier.

A musty smell in the bedroom or wardrobe is often the first sign. Our guide to a damp smell in the house shows where to look, room by room.

If you rent: what to ask your landlord

GOV.UK's guidance for landlords in England says it's "totally unreasonable" to blame damp and mould on everyday activities like cooking, bathing and drying laundry, and that landlords are responsible for addressing damp whatever the type. Things to ask for include working extractor fans, trickle vents that open, adequate heating and insulation, and repairs to any leaks.

Report it in writing with dated photos. Shelter's damp and mould pages explain the next steps if nothing happens, and social housing tenants in England are covered by Awaab's Law timescales.

Handy products for bedroom condensation

Bedroom condensation kit compared

Specs are from manufacturer listings as of 29 October 2026; claimed figures (running costs, runtimes) are the maker’s, not ours. Check the retailer’s page for the current price and exact variant before you buy.

FAQs

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