Condensation is one of the most common forms of dampness in residential buildings. It is largely caused by modern living standards and building design. Moist, warm air from activities such as cooking, washing, bathing or even just breathing will ultimately condense on (and sometimes in) colder surfaces in the house, the temperature at which this happens is called the DEWPOINT. On average each person produces about 4 pints of water vapour each day just from breathing, washing, cooking etc. Therefore a family of five will produce about 20 pints a day; this equates to 140 pints of water vapour a week!

This figure will be much higher with activities such as using: -

1. unvented tumble dryers

2. using portable gas heaters

3. drying clothing indoors or on radiators


Condensation can occur at any time, but is more likely to occur at night because the air temperature drops (when your heating switches off) causing humidity to rise. Also many surfaces in the home (particularly the external walls and windows) become colder and this lowers the dewpoint temperature to these areas. The most commonly affected areas are moisture to windows, mould growth to walls/ceilings particularly behind curtains, corners of rooms behind beds/pieces of furniture


1. Improving heating/insulation all help to increase surface temperatures, however this generally does nothing to remove the problem and can be very costly.

2. Reduce the input of moisture! This would be fine if everybody in the house could hold their breath for long periods of time!

More practical measures would be to close bathroom/kitchen doors when bathing/cooking and not to use portable gas heaters.

3. The use of a dehumidifier will help to control A SYMPTOM of the problem, but they can be noisy and cost around 2.7 pence per hour to run.

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