FAQ

Damp, condensation and dry air

Do I need a humidifier or a dehumidifier?

It depends on whether your air is too damp or too dry. Wet windows, mould and musty smells mean it's too damp: you need moisture absorbers or a dehumidifier. Dry skin, a scratchy throat and static shocks mean it's too dry: you need a humidifier. A hygrometer tells you for certain. See our Find Your Fix guide.

What humidity should my home be?

Between 40% and 60% relative humidity. A hygrometer tells you where each room sits.

Will a dehumidifier get rid of mould?

It stops the damp conditions mould needs, but it won't remove mould that's already there. Clean existing mould off first, then keep humidity down so it doesn't come back.

Do moisture absorbers actually work?

Yes, in small enclosed spaces like wardrobes, cupboards and cars. They won't dry out a whole room; that's a job for a dehumidifier.

Can I use a humidifier in a room with condensation?

No. A humidifier adds moisture, so it will make condensation worse. Only use one when a hygrometer shows the air is below about 40%.

How do I look after a humidifier?

Empty the tank daily and clean it weekly, following the instructions supplied. In hard-water areas, filtered or distilled water helps avoid a fine white dust.

Can I dry washing with a dehumidifier?

Yes. Put it in a small room with the door shut and the washing spread out. A dehumidifier uses far less power than a tumble dryer.

How much does a dehumidifier cost to run?

Check its wattage, then: watts ÷ 1,000 × hours used × your price per kWh. For example, a 200W model running for 8 hours uses 1.6kWh.

Which type of dehumidifier is best for a cold room or garage?

A desiccant dehumidifier. Compressor models lose efficiency in cold rooms.

Why are my windows wet every morning?

Breathing overnight in a closed bedroom puts moisture into the air, which condenses on the cold glass. Moisture absorbers, opening a trickle vent and wiping the windows each morning all help.

Car air conditioning and misted windscreens

Why does my car windscreen keep misting up?

Moisture from your breath, wet coats and wet shoes builds up inside the car. When it meets cold glass, it turns into a film of water. It's worst on cold, wet mornings and with more people in the car.

How does air conditioning clear a misted windscreen?

Your car's air-con absorbs moisture as well as cooling. Air passes over a very cold part inside the system, the water in it condenses and drains out under the car. That dry air clears the glass quickly. For the fastest result, turn the air-con on with the heat up and the airflow on the windscreen.

How do I know if my car air-con is low on refrigerant?

Common signs are air that isn't as cold as it used to be, a windscreen that takes much longer to clear, or air-con that only works some of the time. Car air-con systems can slowly lose refrigerant over time, and once it's low, the system can't cool or dry the air properly.

My car air-con isn't working at all. What should I do?

If it blows warm air, makes unusual noises or smells musty, have it checked by a qualified air-con technician rather than just topping it up. Refrigerant should only be handled by a certified technician, and a proper check finds the cause, such as a leak or a faulty part, before regassing.

Who can regas or repair my car air-con?

We recommend Cool My Car AC for car air-con regas, diagnostics and repairs, with mobile and workshop options across South East and East London and parts of Kent and Essex.

Do I still need a car dehumidifier if my air-con works?

It helps. Air-con only works while the engine is running, but a reusable car dehumidifier bag soaks up moisture overnight while the car is parked, so the windscreen is clearer when you get in.

Home air conditioning

Does air conditioning reduce humidity at home?

Yes. Air-con takes moisture out of the air as it cools, which is why a room with air-con feels less sticky in summer. Many wall-mounted units also have a "dry" mode for muggy days. For condensation and damp in winter, a dehumidifier or moisture absorbers are usually the better choice.