Condensation and damp are caused by excess moisture in the air settling on cool surfaces, and is most often seen as water on the coldest surfaces in the house, such as window sills, walls or ceilings. It can cause musty smells, crumbling plaster, rotten window frames, peeling wallpaper, mould spots on walls and paintwork and mildew on furnishings. Housemites thrive in damp conditions. Along with the millions of spores produced by mould, they can aggravate chest conditions such as asthma, as well as cause allergic reactions. Cooking, washing, drying clothes and even breathing can create up to 10 litres of moisture a day within the average home. Reduced ventilation in most modern houses keeps moisture inside, increasing the likelihood of condensation and damp. Double glazing reduces condensation on windows but increases its likelihood on other cool surfaces in the home.
One in four homes in the UK (5 million) is affected by condensation and damp.