Condensation in insulated domestic roofs.

Describes the types of damage that condensation can cause in a domestic pitched roof with insulation, and outlines the design options available to reduce the risk of condensation. Most of the water vapour comes from within the house, both by movement of air through gaps in the ceiling and by diffusion through the plasterboard. The type of damage depends on the structure of the roof. If there is a non-absorbent lining, water can condense on it and subsequently run or drip on to the timbers and ceilings. Absorbent linings are then wetted and may rot. The importance of adequate ventilation of the roof is emphasised. Openings in the eaves on opposite sides of the roofare recommended where possible, other methods of ventilating are discussed.