Notes field evidence of increased condensation in houses with reduced ventilation and increased thermal insulation installed to conserve energy. Treats the possible long term effects. Gives advice on taking into account the whole package of heating and ventilation of the property when energy conservation measures are being contemplated.
Starting from the premise that condensation in the building envelope is a prime cause of its deterioration, the mechanisms that cause condensation are discussed and control measures explained. The conflicts that arise between some of these measures, the probability of achieving them under realistic construction conditions, and the possible need for fail-safe provisions should complete success not be achieved, are described.
The need for reduced energy consumption has led to an overall decrease of air infiltration rates in buildings. particularly in dwellings. Unfortunately. this has given rise to a significant number of problems involving condensation. with resulting damage to the structure and contents of affected buildings. Various means of condensation control are available. The use of a passive ventilation system to achieve this aim has several attractions. not the least of which is that the occupants of houses fitted with such a system need little. if any, knowledge of the principles involved.
After years of intensive studies on indoor air pollution sources, pollution levels, condensation effects, building airtightness, and air change rates, we are now at the point to discover that no solution whatsoever to the ventilation problem is possible if compatibility with user comfort and user habits are not properly taken into account. User compatibility of aventilation strategy under todays conditions in dwellings must in fact be understood as a requirement equivalent to the purely functional ones of pollutant removal and of economy.
One of a series of articles focussing on problem areas in buildings. 1) Examines condensation risks in buildings. Treats condensation processes, water vapour input and movement, conditions for surface and interstitial condensation in walls and roofs. 2) Treats condensation avoidance in general, humidity control, controlling vapour flow, adding insulation, heating, mould. Illustrates numerous examples diagrammatically from various building types.