The commonest form of dampness in properties today, especially during the colder months, is condensation. Air can hold X amount of water vapour depending on the temperature of the air. The colder the air the less water vapour it can hold. Condensation will start to form when the Relative Humidity drops below the dew point (Dewpoint is the temperature at which the air is 100% saturated).
The more moisture and the colder the air = the more condensation will form. Condensation can often spoil decorations and can cause the formation of mould. Mould in properties has been reported to cause breathing difficulties and other health related problems. Condensation can form in all rooms including sub-floor level and roof voids.
Mould growth will often grow where there there is dampness and is also largely associated with condensation. Mould growth can have adverse effects on the health. Condensation and mould will often form where there is a lack of ventilation, heating and moisture control.