Condensation in insulated domestic roofs
Authors
Citation
Asian Architect & Contractor, v.13, no.5, 1983, pp. 30-34
Abstract
Thermal insulation laid on top of the ceiling in the roof space is one of the most cost-effective methods of energy conservation. But increasing the amount of insulation in a domestic pitched roof increases the risk of condensation in the roof. This digest describes the types of damage that condensation can cause 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, to a much lesser extent, by diffusion through the plasterboard. The type of damage depends on the structure of the roof. If there is a non-absorbent lining, such as sarking felt or plastics sheet, water can condense on the lining and subsequently run or drip on to the timbers and ceiling. Absorbent linings, such as sarking boards, 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 roof are recommended where possible; other methods of ventilating are discussed.
(1) Roofs with a non-absorbent lining
(2) Roofs with an absorbent lining
(3) Sources of water vapour
(a) Within the roof space
(b) From within the house
(4) Routes of water vapour transfer
(5) Reducing moisture transfer into the roof
(6) Ventilation of the roof space
(7) Effect of ventilation on fibrous insulation
(8) Checklist
Description
Subject
Type
Article
Format
Date
1983
Language
en