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Top 3 things you need to know about dehumidifiers

Which? helps you find the best dehumidifier


Condensation on windows can be a precursor to damp.  

With all this wet weather we’ve been having, you might be tempted to close your windows and turn on the heat to keep yourself nice and cosy. But beware, as this creates the perfect environment for damp and mould.

Spending more time indoors, drying laundry inside, and keeping windows shut can dramatically increase the water content and humidity found inside your home. To keep your winter lifestyle from turning into a mouldy problem, you could buy a dehumidifier.

But before you spend your money on this somewhat pricey appliance, here are three things you need to know about dehumidifiers.

Need to sort your damp, fast? Our tough lab tests reveal the best dehumidifiers.

1 Not all dehumidifiers are the same

Do you need a dehumidifier for your whole home, or just a single room? Is that room your slightly chilly conservatory or your warmer bathroom? Are you better off with a desiccant dehumidifier or a refrigerant dehumidifier?  

Choosing the right dehumidifier for the job is important to ensure that you are spending your money on a product that will work for you. Spending more won’t necessary guarantee you a better dehumidifier, as our lab tests have found there’s no direct link between price and quality.

To learn more about the different types of dehumidifiers, find out how to buy the best dehumidifier for you.

2 Dehumidifiers can help prevent mould and damp

Mould Infestation

A dehumidifier can help with unsightly and unhealthy mould. 

Dehumidifiers aim to reduce the relative humidity in a home or indoor space, such as a boat, caravan or garage.

The relative humidity in the UK is between 70% in the summer and up to 92% in the winter. While the relative humidity inside your home will be much lower, many properties experience the effects of moisture and damp due to high humidity.

A healthy relative humidity for indoors is between 40-50%, and a dehumidifier can help maintain this level in your home. It can also help prevent damp or mould, as well as blistering paint in your bathroom or condensation on your windows. 

However, a dehumidifier cannot reverse the effects of mould once it’s taken hold. If you want to know more about how to prevent and fix damp or mould, see our expert advice on the best ways to deal with damp and mould.

3 Your dehumidifier’s size matters

Each dehumidifier has a specific capacity.  This refers to the amount of water the manufacturer claims the machine can pull from the air in a day, rather than the tank size. But beware, as we’ve discovered that manufacturers’ water extraction claims are often based on conditions you’re unlikely to experience in a UK home.

We tested a machine with a manufacturer’s claimed capacity of 10 litres. That means that, in 24 hours, this machine should remove a volume of moisture from the air in your home that’s the equivalent of 30 cans of fizzy drink. However, our tests discovered it would take more than 60 hours – two and a half days – for this dehumidifier to extract 10 litres of water from air at 21°C with 59% relative humidity. 

To find out which dehumidifiers are best at pulling water from the air, check out our dehumidifier reviews.

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