The quick answer
- Will a dehumidifier stop condensation? Yes. By pulling excess moisture out of the air, a dehumidifier lowers indoor humidity, so far less water ends up streaming down your windows.
- Will it get rid of mould? It helps prevent mould and stops it coming back by keeping the air dry. Clean off any existing mould first.
- Aim for 30–50% humidity (30–40% in winter), close doors, and place the dehumidifier near the worst windows.
- Pick the right size: up to 12 m² → OmniDry 10L; up to 20 m² → OmniDry 12L; up to 30 m² → OmniDry 20L; up to 50 m² → OmniDry 40L.
- See the room-by-room plan.
Wet windows every morning, black spots creeping along the sealant, a musty smell in the bedroom: condensation and mould are the classic signs of a damp UK winter. The good news is that a dehumidifier for condensation and mould is one of the simplest, cheapest ways to take control. This guide explains what really works, where to put your dehumidifier, the humidity level to aim for and exactly which size suits each room in your home.
1Will a dehumidifier stop condensation?
In winter, when windows stay shut and glass is cold, the moisture from cooking, showers and breathing has nowhere to go. A compressor dehumidifier draws in the damp air, condenses the water onto cold coils and collects it in a tank. Set a target humidity and it switches itself on and off to hold it, so you wake up to clearer windows instead of puddles on the sill.
Our OmniDry range removes 10–40 litres of moisture a day at maximum rating, depending on the model, so it tackles condensation at the source rather than just mopping up after it.
2Does a dehumidifier get rid of mould?
A dehumidifier is your best long-term defence against mould. Mould needs damp to grow, and a dehumidifier takes that damp away. Black mould can start to grow from around 50% humidity, so keep your home in the healthy 30–50% range and mould struggles to get a foothold, so it is far less likely to come back after you’ve cleaned it.
What a dehumidifier won’t do is remove mould that’s already there, so start with a clean slate:
- Clean existing mould from sealant, window frames and walls with a suitable mould remover, following the product instructions.
- Fix the source if there’s a leak, rising damp or a broken extractor fan. A dehumidifier deals with moisture in the air, not water coming through the walls.
- Then keep it dry with a dehumidifier running on its humidity setting, so the problem doesn’t return.
Many of our customers with asthma, allergies or eczema tell us they notice the difference once their home is drier and fresher. Damp and mould primarily affect the airways and lungs, according to UK government guidance, which lists people with asthma, children and older people among those most at risk. Keeping humidity under control is one of the easiest steps you can take.
3What causes condensation and mould in UK homes?
Condensation is the most common form of damp in UK homes. It happens when moisture generated indoors cools and condenses onto the coldest parts of the building: single glazing, window frames, the corners of external walls and the backs of wardrobes pushed against them.
- Drying washing indoors. A single load can release litres of water into the air. Read our guide to drying clothes indoors with a dehumidifier.
- Cooking and kettles, especially without lids or an extractor.
- Showers and baths in bathrooms without a working fan.
- Breathing overnight in closed bedrooms, which is why bedroom windows are often the wettest.
- Cold walls and rooms that are heated on and off, so surfaces never warm through.
4What humidity should I set my dehumidifier to?
The ideal indoor humidity is 30–50% in summer and 30–40% in winter. Black mould can start to grow from around 50% humidity, so this is the number to watch. Our dehumidifiers with automatic humidity control hold your room at the level you set. Use this as a quick guide to what your readings mean:
| Room humidity | What it means | What to do |
|---|---|---|
| Below 30% | Too dry | Turn the dehumidifier off or raise its target. Very dry air can irritate skin and sinuses; see the benefits of a humidifier. |
| 30–50% | Ideal | Set your dehumidifier to hold it here: 30–40% in winter, up to 50% in summer. |
| 50–60% | Mould can start to take hold | Switch your dehumidifier on and set it to 50% or below. |
| 60–70% | High condensation risk | Run the dehumidifier daily, especially overnight in bedrooms, and ventilate when cooking and showering. |
| Above 70% | High mould risk | Run it continuously, ideally with continuous drainage, until readings fall. Check for leaks or rising damp too. |
Cold windows and walls can still get wet below these levels, so keep the dehumidifier near them. The OmniDry 10L, 12L, 20L and 40L and the 10L Desiccant all show the room’s current humidity on their display, so check it at the same time each day for a week to see the difference.
5Where to put a dehumidifier for condensation
- Start in the worst room, usually the bedroom or wherever washing dries.
- Place it near the wettest window, but leave space around it so air flows freely in and out.
- Keep it out of curtains and away from furniture pressed against walls.
- Don’t block radiators under windows. Warm glass attracts less condensation.
- Close the right doors. For one problem room, close its door. For connected rooms, keep the internal doors between them open and keep external windows and doors closed while dehumidifying; keep background ventilation such as trickle vents open.
- Use continuous drainage if the tank fills too often. Every Pro Breeze plug-in dehumidifier in this guide has a continuous-drainage outlet.
6How much water should a dehumidifier collect?
The amount collected changes with the weather and how damp your home is; the litres-per-day rating is the maximum. In the first few days a dehumidifier often fills its tank faster than you expect, because it’s pulling moisture out of the walls, carpets and soft furnishings as well as the air. That is a good sign: it shows how much damp was there. Once the room reaches your target humidity the machine cycles off more often and collection slows down.
Extraction figures are maximum ratings from Pro Breeze product specifications. Hourly cost at full power (rated power from Pro Breeze product specifications: rating label, at 27°C/60% RH where stated) and 26.32p per kWh, the Ofgem price cap electricity unit rate for Direct Debit customers from 1 October 2026. Want the full picture? See how much a dehumidifier costs to run.
7Room-by-room plan
Match the dehumidifier to the space. If a room is very damp, or you also dry washing there, go one size up.
Bedrooms
Overnight breathing makes bedrooms the most common place for streaming windows and black mould behind wardrobes. You want something quiet. The OmniDry 10L suits rooms up to 12 m² at 38 dB, and the OmniDry 12L covers up to 20 m² at just 36 dB. See all dehumidifiers for bedrooms.
Bathrooms
Showers create bursts of steam that fog mirrors and leave mould in the grout and sealant. Run your extractor fan, then let a compact dehumidifier finish the job. The 12L Compact handles up to 20 m² in a small footprint. Browse bathroom dehumidifiers.
Living rooms, flats and whole homes
For open-plan living spaces, a flat or the main floor of a house, choose more capacity. The OmniDry 20L covers up to 30 m² and doubles as a laundry dryer, while the OmniDry 40L handles up to 50 m² for the dampest homes.
Conservatories and cold rooms
Standard compressor dehumidifiers slow down in the cold. For a conservatory, unheated spare room or garage, choose the 10L Desiccant Dehumidifier, which works down to 1°C. Read more in our guide to the best dehumidifier for cold rooms and garages.
Wardrobes, cupboards and caravans
Small enclosed spaces where air doesn’t circulate need a small solution: the 1500ml Mini Dehumidifier or an electricity-free Osmo® moisture absorber. For caravans and motorhomes, see caravan dehumidifiers.
| Space | Room size | Our pick |
|---|---|---|
| Small bedroom, box room | Up to 12 m² | OmniDry 10L |
| Double bedroom, bathroom | Up to 20 m² | OmniDry 12L or 12L Compact |
| Living room, flat, laundry | Up to 30 m² | OmniDry 20L |
| Large or very damp home | Up to 50 m² | OmniDry 40L or 30L Max Extraction |
| Conservatory, cold room | Cold spaces | 10L Desiccant |
| Wardrobe, cupboard, caravan | Small spaces | Mini range or Osmo® |
Room sizes from Pro Breeze product specifications. Still unsure? Our 13-step guide to buying a dehumidifier walks you through every choice.
8Condensation absorbers, damp traps and tablets vs a dehumidifier
Condensation absorbers, damp traps, tablets and bags all use moisture-hungry salts to draw water from the air, with no plug and no noise. They are brilliant for wardrobes, cupboards, under sinks and caravans in storage. For a whole room with wet windows or mould on the walls, though, an electric dehumidifier removes far more water and can hold a set humidity. Many homes use both: a dehumidifier in the main living space and absorbers in the tight spots. Compare them in detail in moisture absorbers vs dehumidifiers.
9Other quick fixes that help
- Run extractor fans while cooking and showering, and for a while afterwards.
- Open trickle vents or a window briefly each morning to swap out humid air.
- Put lids on pans and close the kitchen and bathroom doors.
- Wipe windows first thing, before the water soaks into frames and sealant.
- Keep heating steady at a low level rather than big on-off swings, so walls don’t get cold.
- Leave a gap between furniture and external walls so air can circulate.
For more on tackling damp, read our guide to treating and preventing damp.
10Best Pro Breeze dehumidifiers for condensation and mould
OmniDry 12L
Which? Great Value winner, Good Housekeeping Institute approved and Quiet Mark certified. Removes up to 12 L a day at 36 dB with automatic humidity control.
View OmniDry 12L
OmniDry 20L
Which? Best Buy and Quiet Mark certified. Up to 20 L a day at 36 dB, with laundry mode, a 4 L tank and smart app and voice control.
View OmniDry 20L
10L Desiccant
Works down to 1°C, removes up to 10 L a day and switches off once it reaches your set humidity. Covers up to 35 m².
View 10L Desiccant
1500ml Mini
Ideal Home Approved. Quiet Peltier technology removes up to 0.5 L a day for about 1p an hour.
View MiniCompare every model, with a size guide, on our dehumidifiers page.
11Frequently asked questions
How long does a dehumidifier take to stop condensation?
You’ll usually see a difference within the first few days, once the machine has pulled the built-up moisture out of the room and its furnishings. After that, running it on its humidity setting keeps windows clearer day to day.
Should I run a dehumidifier overnight?
Yes, if condensation forms overnight. Bedrooms are where most moisture builds up while you sleep, which is why quiet models like the OmniDry 12L at 36 dB are popular. Set a target humidity and it will only run when needed.
What size dehumidifier do I need for a 3-bed house?
Choose by the area you need to treat, not bedroom count alone. The OmniDry 20L is rated up to 30 m² and the OmniDry 40L up to 50 m². For separate damp rooms or floors, treat each problem area rather than assuming one unit covers the whole house.
Will a dehumidifier help with damp walls?
It helps walls dry out when the damp comes from condensation, which is the most common cause in UK homes. If damp comes from a leak, rising damp or penetrating rain, fix the source first; the dehumidifier then helps the room dry out.
I rent. What can I do about condensation and mould?
Ventilate when cooking and bathing, dry washing with a dehumidifier rather than on radiators, and keep humidity at 30–50%. Report damp, mould or leaks to your landlord in writing as soon as you notice them. Government guidance for housing providers in England asks landlords to tackle the underlying causes.
With the right size dehumidifier in the right spot, set to 30–50%, you can keep windows clearer, walls drier and your home fresher all winter. Explore our full range of dehumidifiers, and find more advice on the Pro Breeze blog.
