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Condensation and mould - Prevention and Cure

Condensation forms when warm moist air hits a cold surface and condenses on it. If there is a lot of moisture in the air it will condense on the coldest surfaces in your home and mould may start to grow. Follow our advice about heating and ventilation to try and reduce moisture in your home.

What is condensation?

• It is caused when warm moist air - produced by ordinary household activities such as cooking and bathing - hits a cold surface, such as a cold wall or window.
• If the moist air does not escape to the outside through an open window, air vent or extractor fan, it stays in your home moving around until it finds a cold spot where it can condense.
• There is always some moisture in the air, even if you cannot see it. If the air gets colder, it cannot hold all the moisture and tiny drops of water appear. This is condensation. You notice it when you see your breath on a cold day, or when the mirror mists over when you have a bath.
• Condensation occurs mainly during cold weather, whether it is raining or dry. It does not leave a “tidemark”. It appears on cold surfaces and in places where there is little movement of air and can often lead to mould forming in corners, on or near windows, in or behind wardrobes and cupboards. It often forms on north-facing walls, as these are often colder.

Our Damp and Condensation fact sheet has more information on pevention and cure.

HFI has been working with a group of residents who have been having problems controlling condensation. We hope to be able to repeat the project next year. Read more about our resident project.

We have sent each recipient a hygrometer factsheet with tips on using the hygrometer.