When moist air hits a cold surface such as a wall or window, water droplets are formed. This is known as condensation.

Condensation can occur in any property, regardless of its age. The effect of condensation includes a black mould which carries a musty smell (example pictured below).

Black mould created by condensation

Ensuring a home is ventilated and has good air circulation helps prevent condensation, as it enables the air to release moisture outside instead of in your home.

Did you know?

● A family of four can add the equivalent of 40 litres of water into the air a week just by breathing.

● Showering, cooking and washing can add 15 to 20 litres a week.

● Drying clothes indoors can add 10 to 15 litres a week.

● Condensation is more likely to form on walls in rooms below 15°C.

● Condensation occurs less where there is good ventilation.

Using your hygrometer to reduce condensation

A hygrometer measures room temperature (the big dial) and relative humidity (the small dial, pictured). The relative humidity dial tells you how much moisture is in the air in that room.

 The front of a hygrometer

The ideal relative humidity for health and comfort is between 40–50%. In the winter months, when the temperature is low outside, it should be lower than 40% to help prevent condensation forming.

Here are some steps you could take to reduce relative humidity

• In colder weather, reduce condensation forming by keeping temperatures between 18-21°C in main living areas when you are home.

• Take care not to obstruct airbricks or air vents.

• Dry washing outside when possible.

• If drying clothing indoors, place clothes on a drying rack in a room where a window can be opened slightly and keep the door closed. Putting clothes directly on a radiator releases moisture into the air faster and is more expensive, as your boiler needs to work harder to heat your home.

• Open windows whilst bathing/washing and aim to leave them open for 20 minutes after if safe to do.

• Use an extractor fan in your bathroom if you have one.

• When running a bath put the cold water in first as this creates less condensation.

• Wipe down windows/mirrors/tiles/shower doors with a super absorbent cloth which can be wrung out in the sink.

• Aim to open windows for 10 minutes a day whenever possible.