Dehumidifiers for mould: a helper, not a cure
A dehumidifier can help stop mould by pulling water out of the air, which is useful for drying washing indoors or getting a damp room through the winter. It won't remove mould that's already there, and it won't fix a leak, rain getting in or rising damp. If you find yourself emptying a full tank every day and the mould is still spreading, it's probably covering a bigger problem.
When a dehumidifier helps
Most mould in Scottish homes comes from condensation: moisture from everyday life settling on cold walls and windows. A dehumidifier reduces the amount of moisture in the air, so less of it ends up on those surfaces. It's most useful when:
- you have to dry washing indoors and there's no other option
- a room has no extractor fan, or a window you can't easily open
- a room is drying out after a leak has been fixed, or after a damp wall has been repaired
- you're keeping things under control while you wait for a repair or a visit
Used like that, alongside better ventilation and steady heating, it can make a real difference. Our page on condensation and ventilation fixes covers the other changes that matter.
When it just masks the problem
A dehumidifier treats the air. It can't stop water that's coming into the walls from somewhere else. If the damp is from:
- rain getting in through a blocked gutter, cracked render or a leaking roof
- a plumbing leak, or water getting behind shower tiles
- ground moisture rising up an old wall
then a dehumidifier may make the room feel drier while the wall stays wet. Signs it's more than condensation include a tide mark low down, a stain that grows after rain, damp patches with clear edges near pipes, and plaster that's soft or crumbling. Those need finding and fixing, and a damp and mould survey is the usual first step.
Desiccant or compressor: the difference in plain words
Compressor dehumidifiers work a bit like a fridge. They pull air over a cold coil, the water condenses on it and drips into the tank. They tend to be the more economical choice in a room kept at normal living temperature, but they lose a lot of their effect in a cold room, because the coil struggles to pull water out of cold air.
Desiccant dehumidifiers pass air over a material that soaks up water, then use a heater to dry that material out again. They keep working in cold rooms, so they suit unheated bedrooms, conservatories and garages, and they give off a little warmth while they run. They usually use more electricity than a compressor model to do the same job.
Whichever type you look at, check the size of room it's designed for, how big the tank is, whether it can drain continuously through a hose, and how loud it is if it's going in a bedroom.
Running costs, without the guesswork
We're not going to quote a figure, because it depends on the model, how long you run it and what you pay for electricity. You can work it out yourself in a minute:
- Find the power rating in watts (W) on the label or in the manual.
- Divide by 1,000 to turn it into kilowatts (kW).
- Multiply by the number of hours you'll run it.
- Multiply by the unit price per kWh shown on your electricity bill.
Many dehumidifiers have a humidity setting that switches them off once the room reaches it, which cuts the hours they actually run. Running one in a room with the door shut, rather than trying to dry the whole house, also helps.
Getting the most out of one
- Put it in the dampest room, with the door and windows shut while it runs.
- Keep it away from walls and curtains so the air can flow in and out.
- When drying washing, put the dehumidifier in the same room as the clothes horse.
- Empty the tank and clean the filter as the manual says.
- Keep using the extractor fans and keep trickle vents open. The dehumidifier is extra, not a replacement.
Your health
The NHS asthma causes page lists mould among the allergy triggers that can bring on asthma. Government guidance for rented housing in England, Damp and mould: understanding and addressing the health risks for rented housing providers (MHCLG, DHSC and UKHSA), says damp and mould can affect anyone. A dehumidifier can help keep a room drier, but it doesn't replace dealing with the cause, and if anyone's breathing gets worse, speak to your GP.
When to get a specialist
Get help if the mould keeps spreading even with a dehumidifier running, if the tank fills fast every day and you can't work out why, or if you see signs of water coming in. A specialist can find where the damp is coming from and deal with it, so you're not relying on a machine to keep it at bay. Tell us what's happening and we'll pass it to one independent local specialist to quote. It's free to ask.
If you rent: a dehumidifier can help while you wait, but you shouldn't have to run one forever to keep mould away. Report the damp to your landlord in writing, with photos. Our tenants' guide explains what they must do and by when.
If you're a landlord: supplying a dehumidifier can help limit damp while you arrange repairs, but it doesn't take the place of the investigation Awaab's Law requires in Scotland. Our landlord checklist sets out the steps, and the deadline calculator works out the dates.
Last checked 26 October 2026. This is general guidance, not legal or building advice. We don't recommend particular products and we don't earn anything from them.
Common questions
Will a dehumidifier get rid of mould?
No. It takes water out of the air, which helps stop new mould growing, but it doesn't remove mould that's already there. You still need to clean it off and deal with whatever is making the room damp.
Should I get a desiccant or a compressor dehumidifier?
For a cold room, such as an unheated bedroom or a garage, a desiccant model usually copes better. For a room kept at normal living temperature, a compressor model is usually the more economical choice. The guide above explains why.
How do I work out what one costs to run?
Find the power rating in watts on the label or in the manual, divide by 1,000, multiply by the hours you run it, then multiply by the price per unit (kWh) on your electricity bill. That gives you the cost for that many hours.
Get a free quote
This is a free matching service, not the firm doing the work. We pass your details to one independent damp and mould specialist who covers your postcode. They contact you, arrange a visit and quote you directly. You don't pay us anything.