Condensation is caused when warm, moist air hits a cold surface (like a window or external wall) and condenses, running down the cold surface as water droplets. If it's left where it is, it can develop into a black mould which looks and smells unpleasant.

Condensation is not due to building failure, or damp from the outside.  It is internal air dampness that comes from breath, cooking, and drying clothes. Thankfully there are some steps you can take to manage condensation before it becomes a problem.  

If it's not managed, condensation can cause black mould growth on walls, ceilings, furniture, clothing and even in or behind wardrobes and cupboards. Any damage to belongings caused by condensation is your responsibility.

How to prevent condensation

The best way to avoid mould is to minimise condensation, and properly heat and ventilate your home where possible.

Manage and prevent condensation by:
•    ventilating your home. Fresh air clears the moisture
•    wiping down surfaces where moisture settles such as windows and sills every morning in cold weather
•    covering boiling pans when cooking and using an extractor fan
•    drying clothes outside where possible. If you have to dry clothes inside, try and do so in a small room with the doors closed and windows open
•    making sure tumble dryers are vented to the outside
•    switching on kitchen and bathroom fans, if these are fitted in your home.

When cooking, bathing or washing, close kitchen and bathroom doors to prevent steam going into colder rooms. Increase ventilation by opening windows and using the extractor fan, even after you have finished.

Maintain a low constant heat in your home when the weather is cold or wet.  This is more effective than short bursts of high heat and needn’t mean increased heating costs.  Your room heating thermostat should ideally be set between 18°C and 21°C.

How to treat condensation mould

If mould appears:
•    use a mild bleach solution to remove light mould staining on hard surfaces
•    to kill mould, wipe down walls and window frames with a fungicidal wash. Follow the manufacturer's instructions carefully
•    dry-clean mildewed clothes and shampoo carpets
•    improve ventilation to reduce moisture in the air 

After treating mould, redecorate using a good quality fungicidal paint to help prevent mould recurring. Please note, this paint is not effective if painted over with ordinary paints and wallpaper.

Download and print this handy leaflet:

Managing and Preventing Condensation

Or check out this video on damp and condensation: