What is condensation?
Moisture is always in the air, even when you can't see it. If the air gets colder, it can't hold all the moisture and tiny drops of water appear on cold surfaces. You will have noticed it when you can see your breath on a cold day or if your mirror mists over in the bathroom or when condensation appears on windows.
It occurs normally during cold weather and unlike other forms of dampness, it does not leave a tidemark, but it will leave patches of mould. Look for it in corners, on or near windows, in or behind furniture, cupboards and anything that may be resting or hanging on walls such as pictures. It often forms on walls and/or in unheated spaces.