Dehumidifiers can be a game-changer for reducing damp, mould and condensation in your home – but what do you do if nothing is changing, despite having invested in one?
There are lots of reasons why your home's humidity levels might not be dropping while using one of the best dehumidifiers, but according to our air quality experts, it's not always because your device is broken or faulty.
Below, we explain five potential reasons why your dehumidifier isn't working as you had expected – from buying the wrong-sized unit for your room to using it on the incorrect setting.
1. The humidity sensor isn't reliable
Modern dehumidifiers will usually feature a built-in sensor that displays the humidity levels of your room. While this is great for getting a rough idea, Martyn Fowler, founder of Elite Renewables, says you shouldn't necessarily take it as gospel.
He explains, "It's measuring the air around the unit and that’s not always representative of the whole room. So the conditions next to a radiator will be very different to near a cold window."
Instead, he recommends placing a separate hygrometer in a location that's away from direct heat and windows to give to a better sense of the humidity levels.
Keep an eye on your humidity levels with this four-pack of hygrometers – one for every room.
Founder of Elite Renewables, Martyn Fowler is one of the UK's leading renewable technology experts, working with heat pumps for the last two decades. His passion for decarbonisation matched with a deep technical experience of the technology make him one of the industry's go-to experts for all things renewable.
2. You've chosen the wrong size
"Dehumidifiers have a limit to how much moisture they can remove in an hour," says Martyn Fowler. "If you've got one running in a hallway with five rooms open around it, it might be dealing with far more moisture than it can actually extract."
To find out whether it's you or your dehumidifier to blame, he says to test the unit in one room and monitor how well it reduces the humidity. If it's only not working when your home is opened up, then it's probably not strong enough to take on all the work you're putting on it.
You'll also need to check whether your machine has a suitable extraction rate for the size of your room and the amount of moisture your household produces, adds Chris Michael, founder of Meaco.
Chris and his partner Michelle started Meaco in 1991. Meaco is now regarded internationally as a major player in the dehumidifier industry selling to 20+ countries throughout Europe, North America and South Africa. Meaco sets the benchmark for quality and development in its sector, leading by example and reducing the energy consumption of its appliances.
3. The settings are wrong
Dehumidifier settings are often overlooked, but if your humidity level is set too high, then your machine isn't going to get a chance to tackle the excess moisture, according to Simon Trenerry CSDV, Technical Manager at Safeguard Europe.
As a guide, Chris Michael recommends aiming for a relative humidity of 55%, but you may want to set it to 45% RH when the outdoor temperature drops if you specifically want to beat condensation. Again, a budget-friendly hygrometer (like this one from Amazon) can help you keep track of this.
Simon is a Certified Specialist in Dwelling Ventilation (CSDV) and since joining Safeguard in 2022, he has built a strong reputation among building and renovation contractors for his expertise in diagnosing damp and mould issues and advising both professionals and homeowners on effective solutions to create safer, healthier homes.
4. The compressor is spending too much time defrosting
Not all dehumidifiers will be suitable for cold rooms, such as conservatories, garages and utility rooms. If your space rarely exceeds 10°C, then you'll need to use a desiccant model, as opposed to a compressor model – otherwise, your dehumidifier could freeze up.
"The temperature in the room can make a big difference to the performance of a compressor dehumidifier," Martyn explains. "If the air is too cold, the moisture can freeze around the cooling coil. The machine then has to stop extracting water while it defrosts. Most units have an operating range in the instructions."
Extracting up to nine litres per day, this desiccant dehumidifier is ideal for cold spaces and features an antibacterial charcoal filter as a bonus.
5. The placement is wrong
If your dehumidifier is pushed into a corner, behind furniture or against a wall, it might not draw in as much air as it needs to, according to Simon Trenerry. With this in mind, you'll need to ensure it's at least 20 to 30cm away from other objects.
However, some dehumidifiers, such as the Meaco Arete range (available on Meaco), are fine to be placed near surfaces, so you'll need to check the guidance for your individual unit.
"Close the windows and external doors in the room while it’s running, otherwise you’re effectively trying to dry the outdoors. Air the room separately, with short bursts of ventilation," Simon adds.
These are just some of the reasons why your dehumidifier isn't working. It goes without saying, but ongoing moisture issues are a sign of an underlying problem – something that a dehumidifier can't (and shouldn't) be used to fix.
For more advice, read our guide on how dehumidifiers work or see how we rated the ProBreeze 20L Premium Dehumidifier after testing it.
