Condensation has become a major problem in recent years, brought about by higher occupancy rates, better draught exclusion and double glazing. It is a problem that occurs mostly during the winter months.

Condensation happens when warm, moist air comes into contact with cold surfaces, such as uninsulated external walls, solid floors, lintels or window panes. The warmer the air, the more moisture it can hold in the form of vapour. However, when moist air comes in contact with a cold surface the air temperature drops. It then loses the ability to hold the moisture in vapour form, which then condenses into water upon the cold surface. This is known as the dewpoint.

If ignored, condensation can lead to mould growth, stained decorations, curtains and even books. It can appear behind furniture and in cupboards, and where it occurs under suspended floors can increase the chance of fungal decay in floor timbers.


Cold winters and human lifestyles are the main causes of condensation. A family of 4, through cooking, drying laundry or taking showers, can generate as much as 14 litres of water a day.

  • As cold air enters the property it heats up, takes up this moisture and is unable to exit the building. On contact with cold surfaces, the dewpoint is reached and condensation occurs.
  • The walls of kitchens and bathrooms are particularly susceptible, the problem aggravated by the intermittent cooling and heating of the property as warm, damp air cools, reducing its ability to hold water.

In all cases, should you find condensation in your property it is imperative to act fast and not ignore the problem.


In many cases, condensation problems can be rectified by simple changes in lifestyle.

Opening windows when cooking or showering, having a constant background heat to raise the ambient temperature, avoiding drying clothes inside or installing extractor fans in kitchens and bathrooms will all help.

In more severe cases it may be necessary to install thermally efficient wall linings or wall plasters, insulating the outside of the building or installing cavity wall insulation. Sub-floor condensation can be solved by inserting air bricks to increase air circulation or spreading a membrane over the soil oversite.

Another solution could be the installation of a Positive Pressure Ventilation System. These units take dry air from a roof or loft space and mix this with moist air in the property, lowering total moisture content and forcing moist air from the dwelling.

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