Condensation control in dwellings

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. The first of these is called surface condensation (Figure 1) and the second, interstitial condensation (Figure 2).

Warm air has a greater capacity for carrying water vapour than cold air and so will readily take up vapour from various household activities such as cooking or washing. This warm moist air then has a high vapour pressure which can drive vapour through most building materials and as the vapour reaches colder conditions within the structure interstitial condensation can occur.

Figure 1 Surface condensation

Figure 2 Interstitial condensation