It is well known nationally that in recent years some houses and flats have suffered from condensation. Walls and ceilings, and sometimes floors, become damp and sometimes discoloured and unpleasant as a result of mould growing on the surfaces.
Why condensation occurs
Condensation occurs when warm moist air meets a cold surface. The risk of condensation therefore depends upon how moist the air is and how cold the surfaces are. Both of these depend to some extent on how a building is used.
When condensation occurs
Condensation occurs most commonly in winter, because the building is colder and because windows are opened less and moist air cannot escape.
Where condensation occurs
Condensation which you can see, occurs often, for short periods, in bathrooms and kitchens because of the steamy atmosphere, and quite frequently for long periods in unheated bedrooms; also sometimes in cupboards or corners of rooms where ventilation and movement of air are restricted. Besides condensation on visible surfaces, damage can occur to materials out of sight, for example from condensation in roofs.
What is important
Three things are particularly important:
- To prevent very moist air spreading to other rooms from kitchens and bathrooms
- To provide some ventilation to all rooms so that moist air can escape
- To use the heating reasonably
The following notes give advice on how you can help to prevent serious condensation in your home:
Reduce moisture content
- Good ventilation of kitchens when washing or drying clothes or cooking is essential. If there is an electric extractor fan, use it when cooking, or washing clothes, and particularly whenever windows show any sign of misting. Leave the fan on until the misting has cleared.
- If there is not an extractor fan, open kitchen windows but keep the door closed as much as possible.
- After bathing/showering, keep the bathroom window open, and shut the door for long enough to dry off the room.
- In other rooms provide some ventilation. In modern flats and houses sufficient ventilation does not occur unless a window or ventilator is open for a reasonable time each day and for nearly all the time a room is in use. Too much ventilation in cold weather is uncomfortable and wastes heat. All that is needed is a very slightly opened window.
- Where there is a choice, open the upper part of window, about a 10mm opening will usually be sufficient.
- If condensation occurs in a room which has a gas heating appliance with a flue, the heating installation should be checked, as the condensation may have appeared because the appliance flue has become blocked. Report this immediately if you suspect a problem to the Co-op 0131 657 3379.
- Do not use unventilated airing cupboards for clothes drying.
- Avoid drying washing indoors.
Provide Reasonable Heating
- Try to make sure that all rooms are at least partially heated
- Condensation most often occurs in unheated bedrooms
- To prevent condensation the heat has to keep room surfaces reasonably warm. It takes a long time for a cold building to warm up, so it is better to have a small amount of heat for a long period than a lot of heat for a short time
- Houses and flats left unoccupied and unheated during the day get very cold. Whenever possible, it is best to keep heating on, even if at a low level.
- In houses, the rooms above a heated living room benefit to some extent from the heat rising through the floor. Some rooms are especially cold because they have a lot of outside walls or lose heat through a roof as well as walls. Such rooms are most likely to have condensation and some heating is therefore necessary. Even in a well-insulated house with reasonable ventilation it is likely to be necessary during cold weather to maintain all rooms at not less than 10oC in order to avoid condensation.
- When living rooms are in use, their temperature should be raised to about 20oC