condensation

Discusses the possible effects of wind, stack effect, vents and fans on air leakage, and the influence of air leakage openings and the location on the pattern of air flow through buildings. Considers the possible extent and location of condensation in relation to these patterns, as well as methods of controlling moisture entry and removal of accumulated moisture.

Describes large-scale field studies to investigate the effectiveness of measures to prevent condensation in some 4-storey blocks of walk-up flats in Stirling. The remedial measures in the blocks of flats are improvement of thermal insulation

Common assumption is that tight houses cause mould. Questions this attitude and suggests that low-energy and very well insulated housing causes mould as a result of condensation. Discusses factors which cause mould and possible countermeasures.

Reports on conference arranged by AIC where main topic was different building standards in different countries. Discusses condensation problems in UK housing and frequency of toxic gases in Scandinavian housing. Notes research into more efficient ventilation and future expectations.

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.

Treats the relation between transmission heat loss and ventilation heat loss of buildings. Notes normal methods of fresh air ventilation of dwellings and problems arising with buildings being made increasingly airtight so that air infiltration is greatly reduced with consequent condensation and lack of maintenance of minimum hygiene standards. Illustrates and discusses possible future ventilation systems including mechanical supply and extract ventilation systems incorporating heat recovery systems. Illustrates several alternatives diagramatically.

Gives answers to practical problems encountered when retrofitting older Canadian houses. The first section gives an overview of a typical house both before and after retrofitting. The second section gives detailed answers togeneral questions covering ventilation, moisture and condensation, air barriers (sealing a house), vapour barriers, insulation, basements, walls, attics, roofs, windows, doors, weatherstripping, caulking, air quality, heat recovery and heat loss testing.

Notes the high heat loss in Canadian houses due to air leakage and condensation problems caused by uncontrolled moisture movement into the exterior wall structure. Recommends the installation of an air-vapour barrier to form a completely sealed envelope around the house structure except at doors, windows, vents and other obstacles. The recommended thickness for the polyethylene sheet of the air vapour barrier is 6mm, which is continually sealed at all joints. Details the recommended installation procedures for realising an air-vapour barrier.

Detailed studies of public sector modernisation programmes show that the principal problem resulting from lack of thermal insulation and inappropriate methods of heating and ventilation is condensation and mould growth. Gives the optimum air change rate (for dwellings with particular heat loss characteristics) at which the heat input necessary to prevent the RH rising is at a minimum. The resulting temperatures are too low to be considered comfortable, so air change rates need to be less than the optimum.

Describes the extent of the problem of condensation in roof spaces of well-insulated dwellings, discusses the mechanisms resulting in condensation, and evaluates possible solutions. Factors considered in condensation occurrence include air movement to the roof space, and roof space ventilation rates. Control measures discussed include direct extract ventilation to the kitchen and bathroom to control water vapour, and the provision of adequate roof ventilation according to British Standard BS 5250.