Condensation control in dwellings

Date Published

20 August 2022

Document Type





Condensation in dwellings occurs when warm moist internal air comes into contact with cold inside surfaces, or with cold air or surfaces within the structure.

With improved thermal performance and air tightness in new and existing buildings, the risk of damage from condensation has increased. Most surface condensation is largely caused by the behaviour of occupants, such as breathing, cooking and bathing – all emitting moisture. However, the designer can influence these effects by specifying suitable controls (such as mechanical ventilators) and reducing thermal bridging to enable the occupant to limit the incidence of surface condensation.

This Wood Information Sheet (WIS) explains the difference between surface and interstitial condensation and describes design measures to reduce the incidence of condensation.

Surface condensation
Interstitial condensation
Factors that affect condensation
Control of condensation
Design measures to reduce condensation
Properties, units and definitions related to water vapour in air and in materials

Key Information

The dew point is the temperature below which the water vapour in the air will condense into liquid water.

Sensible design and detailing with good supervision of construction can reduce or eliminate these risks. Factors such as building use, occupancy levels, temperature and the type of heating/ventilation system all need to be considered.

Ensure that vapour transmission into the structure is controlled and that vapour can escape to the outside.

Case studies

The new Performing Arts Centre for Sevenoaks School sits on a beautiful sloping site overlooking Knole Park. It contains a concert hall large enough for a symphony orchestra, choir and an audience of 450, a recital room for 100, and a music school with 23 teaching spaces of various sizes, plus a new drama studio, with drama teaching and technical spaces.

This £7.3 million scheme has transformed a town centre football ground into a new public park and a swimming pool, fitness suite
and cafe, giving the town and community a new focus and forming a civic presence in the High Street.