Condensation and mould

What is condensation?

Condensation occurs mainly during cold weather. There’s always some moisture in the air, even if you cannot see it, and when moist air hits a cold surface tiny drops of water appear. You can see this when the mirror mists up when you have a bath.

It appears on cold surfaces and in places where there is little movement of air, such as in corners, on or near windows, in or behind wardrobes and cupboards and in rarely used rooms. It often forms on colder, north facing walls.

Condensation can lead to mould which can contribute to asthma and other respiratory problems.

How can I produce less condensation?

1 Produce less moisture

  • Cover boiling pans when cooking and turn off kettles after use.
  • Dry washing outdoors, whenever possible, or over the bath with the door closed and the window open.
  • Vent any tumble dryers outside, or buy a self-condensing type.
  • Keep bathroom and kitchen doors closed. This will help reduce the amount of moisture-laden air affecting other rooms.
  • Avoid large uncovered fish tanks, especially tropical fish.
  • Avoid the use of liquid gas or paraffin type heaters as these produce large quantities of moist air.


2 Ventilate

  • Keep a small window ajar or trickle ventilator open in all rooms
  • If you have an extractor fan, make sure you use it to clear moisture from the air. If your fan has a boost function, make sure you activate this when needed.
  • Always ventilate kitchens and bathrooms when in use, by opening windows or use an extractor fan. Some fans come on automatically when the air becomes humid and are cheap to run.
  • Open curtains for at least four or five hours each day to let moisture through any window vents.
  • When cooking or having a bath or shower, keep doors closed.
  • Let air circulate in cupboards and wardrobes by not over-filling. Where possible position wardrobes and furniture against internal walls.



3 Insulate and protect from draughts

Insulated roof spaces and the installation of cavity wall insulation will reduce cold spots. Take care not to compress the insulation in your loft (which reduces its efficiency) and avoid boarding your loft or storing items on top of the insulation.


4 Heat more efficiently

It is better to heat your whole home to a lower temperature rather than heat one room to a high temperature. Condensation often affects the rooms you are not heating, for example, a colder spare bedroom, rather than where you are making the moisture.

Use the heating system we have provided as efficiently as possible. Refer to the operating instructions for the boiler, the heating programmer and the room thermostats.

Contact us if you need information about the best value energy tariffs.


Treating mould

If you deal with the basic problem of condensation, then mould should not appear.

To kill and remove mould on washable surfaces, wipe down walls and window frames with a fungicidal wash readily available from shops. Follow the manufacturer’s instructions precisely. Disturbing mould by brushing or vacuum cleaning can increase the risk of respiratory problems.

Other items such as fabric materials can often be washed, although this may not always remove the mould staining.

After treatment, redecorate using a good quality fungicidal paint to help prevent mould recurring. Note that this paint is not effective if it is overlaid with wallpaper. The only lasting way of avoiding severe mould is to follow these steps to eliminate condensation.


  • To prevent condensation on mirrors or windows rub a cloth with a small spot of washing up liquid over the surface. Try this at home or in the car – taxi drivers have been doing this for years!
  • To prevent condensation on windows, cut a potato in half and rub across the surface then buff with a cloth.
  • Protect yourself from mould spores by wearing rubber gloves when cleaning affected areas. Open windows, but keep doors closed to prevent the spores from circulating around the house.
  • Have a plastic bag ready to take away any soft furnishings, clothes and soft toys that are mouldy.
  • Soft furnishings should be shampooed and clothes machine washed on the highest setting the clothes label will allow. If there is extensive mould you may need professional help to remove it.
  • Fill a bucket with water and some mild detergent, such as washing up liquid or a soap used for handwashing clothes. Use a rag or a cloth, dip it in the soapy water and carefully wipe the mould off the wall. When you have finished, use a dry rag to remove the moisture from the wall. Afterwards, put the rags in a plastic bag and throw them away.

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