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Condensation

Be sure it is condensation!

Dampness in your home may not be caused by condensation at all. 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, on the other hand, is surface dampness. 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.

What is condensation?
Condensation is formed when air laden with water vapour is cooled by contact with a cold surface.

Why do you get condensation?

The air we breathe can hold varying amounts of water vapour, depending on its temperature. If warm moist air is cooled by a cold surface, such as a window or external wall, it is then no longer able to hold the same amount of water vapour. The air-borne moisture turns into droplets of water and collects on the cold surface. This is called condensation.

When is it a problem?
Every home gets condensation at some time – usually when lots of moisture and steam are being produced – for example, at bath times, when a main meal is being cooked or when clothes are being washed. It is quite normal to find your bedroom windows misted up in the morning after a cold night. There is nothing much you can do to stop this.

How can I reduce condensation?
There are four key approaches. To deal with a condensation problem effectively, you will probably need to do all four, though the first three are the most important and can be done at no cost.

1: Produce less water vapour or steam in your home. 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.

  • Cooking: Cover pans when you’re cooking. Don’t leave kettles and pans boiling longer than necessary.
  • Drying clothes: Hang washing outside to dry whenever you can. If you have to use a tumble dryer make sure it’s vented to the outside. If you have to dry washing indoors use the bathroom and keep the door shut and the room well ventilated. Do not hang wet washing on radiators all round your home – doing so is very likely to cause condensation problems.
  • Bathing: Keep the bathroom door shut and the room well ventilated.
  • Heaters: Paraffin heaters, portable bottled gas heaters and fixed flueless gas heaters all produce heat, but at the same time they also put a lot of water vapour into the air. One gallon of water is produced by one gallon of gas or paraffin burning. Paraffin and portable bottled gas heaters can also be dangerous and very expensive to run. They can cost as much as, or even more than, heating using peak rate electricity.

2: Restrict the spread of the water vapour and steam around the house. Confine wet air to just a few rooms. Your bathroom and kitchen are ‘wet rooms’ – keep these doors shut so the wet air can’t spread to the rest of your home. Especially when you’re washing, cooking or taking a shower or bath, keep the door shut to stop the moist air spreading into the rest of your home.  At the same time make sure your bathroom and kitchen are well ventilated so the water vapour can escape outside.  This is even more important if some of the other rooms are very cold. If rooms are not being used and are unheated it’s a good idea to keep their doors shut. Don’t completely draught-proof kitchens, bathrooms and other rooms where condensation is already a problem – you could make it far worse.

3: Ventilate your home. The best way to remove water vapour is by providing adequate ventilation to let the wet air out. Nobody likes draughts, but some ventilation is vital. Keep a small window ajar, or a trickle ventilator open, in each occupied room to give background ventilation, (but make sure your home is still secure). Open the windows to let the water vapour out, especially when you’re doing the washing or cooking. Windows near the ceiling are more effective at letting water vapour out than ones lower down. Heat recovery fans are very good for ventilating ‘wet rooms’ such as bathrooms and kitchens. They are more effective than ordinary fans, since they get rid of the moisture from the air and let fresh air in, and also recycle the heat back into your home.

BUT DON’T FORGET – keep your home secure! 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.

4: Warm your home. Heating your home can help solve a condensation problem, but only if it’s used in addition to the other three steps already described. The heat used to warm your home needs to be ‘dry heat’, such as central heating or gas fires, not paraffin or portable gas heaters. The best approach to heating in order to reduce condensation, assuming you have taken 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.