Condensation in Houses

This is occurs when the amount of moisture generated by activities in the house exceeds the ventilation flow that gets rid of it, and there are surfaces in the house which are cooler than the air.

Moisture held in the (warm, damp) air will condense out when it reaches a cooler surface. This is very obvious on the outside of a glass will an iced drink in it, but also happens on outside walls and windows. Double-glazing makes the inner surface of glass less cold, but it also usually reduces the amount of ventilation so that there is more moisture in the air.

Common causes of excessive moisture are: Wet washing lying about the house or draped over radiators (this is a dreadful source of damp) Using a tumble-drier without venting it outside (this includes condenser driers which release quite a lot of steam) Using baths and showers without running the extractor long enough to dry out the room during and after Cooking and washing up without running extractor. Damp towels Wet outdoor coats hanging inside

To combat excessive moisture and condensation: improve ventilation - if you have replacement windows, open the trickle vents. Open bedroom windows in morning Open upstairs windows during the day unless it is very cold. Verify you have plenty of air bricks to ventilate the under-floor void, and they are not blocked with dust, rubble or cobwebs.

If you want to experiment, tape a piece of clear polythene tightly to one of the damp walls, see if you get more water forming on the wall side or the room side of the polythene.

There are other sources of moisture. Look for any signs of water getting in, especially small roofs over bay windows, or leaking radiators, downpipes or other plumbing. Sometimes it is caused by wet under the floors, perhaps due to waterlogged ground in low-lying areas or near a river, sometimes by a leaking watermain.

JohnD 20070124