Condensation occurs when warm moist air meets a cold surface. The risk of condensation depends upon how moist the air is, and how cold the surfaces in the rooms are. Both of these depend to some extent on how the building is used.
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Condensation usually occurs in winter because the building structure is cold and because windows are opened less often and moist air cannot escape. Condensation often also occurs for short periods in bathrooms and kitchens because of the steamy atmosphere, and quite frequently for long periods in unheated bedrooms and in cupboards or corners of the room or behind large items of furniture where movement of air is restricted. Besides condensation on visible surfaces, damage can occur to materials that are out of sight, for example under suspended timber floors and in roofs. For the reduction of condensation three things are particularly important: |
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- Prevent very moist air spreading to other rooms from kitchens and bathrooms or from where clothes have been left to dry.
- Provide some ventilation to all rooms so moist air is able to escape.
- Use heating wisely.
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Good ventilation of kitchens when washing or drying clothes or when cooking, is essential. Too much ventilation in cold weather is uncomfortable and wastes heat. All that is needed is a slightly opened window or ventilator. Where there is a choice, open the upper part of a window - a 10mm gap will be sufficient. If condensation occurs in a room that has a heating appliance with a flue, the heating installation should be checked as the condensation may have appeared because the appliance flue has become blocked. |
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Any sign of mould growth is an indication of the presence of moisture, and if caused by condensation gives warning that heating, structural insulation or ventilation may require improvement.
