Dampness in your home may not always be caused by condensation. It could be caused by leaking pipes, a leaking roof or rising damp.
Leaks often result in patches of damp coming through the plaster and wallpaper near where the leak is. Rising damp can be identified by a damp 'tidemark' low down on the walls indoors.
Condensation is the dampness formed when air containing water vapour is cooled by contact with a cold surface, such as a window or external wall. On contact this air-borne moisture turns into droplets of water and collects on the cold surface. It mainly occurs on cold walls indoors and other cold surfaces such as tiles and cold water supply pipes under sinks and hand basins. It is usually at its worst during the winter and often results in black mould growing on walls and other surfaces.
To deal with a condensation problem effectively, you will need to keep your home ventilated, keep it warm and reduce moisture.
Here are some guides to help prevent condensation:
Let wet air out! The best way to remove water vapour is by providing adequate ventilation. Nobody likes draughts, but some ventilation is vital.
If you open windows, make sure you shut them again when you go out.
If you leave small windows open for background ventilation, make sure they're not accessible from the outside, for example, from a garage or shed roof. Most new windows are fitted with a night latch so that the window can be left ajar and locked.
Heating your home can help solve a condensation problem, but only if it is used in addition to the other three steps already described.
However, it needs to be 'dry heat', such as central heating or gas fires, not paraffin or portable gas heaters as they put a lot of water vapour into the air.
Also, simply heating your home will tend to warm the air. Warmer air holds more water vapour, so the air in your home could become even wetter. There will be more water to condense out onto any cold surfaces.
This is more likely to be a problem if you only put the heating on for an hour in the morning and an hour at night. In this case only the air is warmed, and building fabric itself stays cold, so there's more chance of warm wet air being in contact with cold surfaces.
The best approach to heating in order to reduce condensation, assuming you have completed the other three steps, is to heat your home at a low level for a long time.
Keep the heating on, but set it to provide just a minimum of background heating. This will warm the whole building up, and keep it warm, so there are no cold surfaces to create condensation.
The amount of condensation depends on how much water vapour is in the air. Many everyday activities add to the water vapour level in your home, but their effect can be kept to a minimum. An average family will produce up to 17 litres in a 24 hour period.
Heat recovery fans are expensive, but they are a very good investment. They cost about £250 to buy and install.
They are very effective as they:
Heat recovery fans are designed to be left running continuously on a low speed setting.
De-humidifiers are expensive to buy (£200 to £300) and must be emptied every day. However, they are useful to dry out damp buildings, for example after leak damage, or for specific rooms.
De-humidifiers are no substitute for the vital, no-cost measures of reducing the amount of water vapour put into the air and keeping rooms well ventilated.
If you already have mould growth in your home, you can purchase fungicidal solutions to wash down surfaces where the growth is apparent. Redecorating with fungicidal paint can also help prevent mould growth.