Where the winters are cold and severe, resulting in problems of condensation and mould growth in houses and flats. Condensation and mould can occur in any type of construction including weatherboard, brick veneer, solid brick, masonry veneer and monocrete dwellings.

Atmosphere heavily laden with water vapour is referred to as being of a high humidity. When highly humidified air comes in contact with any cold surface such as a wall or ceiling, it cools down, water vapour is extracted from the air and remains in the form of condensation on the cold surface.