Condensation is the technical term used to describe the change of water in vapour (gas) form into water droplets (liquid form), when the water vapour comes into contact with a cold internal surface. Typically the cold internal surface will be a cold external wall or a single glazed window. The droplets will cause damp staining to surfaces which can then allow the growth of a black coloured fungus. To remedy this defect, it will be necessary to increase ventilation and heating. The increase in ventilation will reduce the amount of water vapour in the air, while the increased heating will result in warmer surface temperatures, thereby reducing the risk of the water vapour condensing into a liquid form. Condensation is more of a problem in older, poorly insulated buildings and is most prevalent in the colder winter months, when occupants keep the windows closed to prevent heat loss. The prevention of condensation will usually result in a compromise between ventilation and heat loss.