A number of cases of water and frost damage in masonry and non loadbearing walls have been examined. This damage could not have resulted from vapour diffusion or rain penetration and is primarily caused by condensation due to exfiltration of air. Air exfiltrates through the many cracks and joints and in this connection the result of chimney action and wind is explained in some detail, including the pattern and magnitude of building pressure differences that induce ex-filtration together with a discussion regarding the moisture that is transferred.
Presents calculations of mean temperatures and relative humidities , shown graphically for three typical housing types assuming different heat and moisture inputs: 1) whole house uniformly heated with moisture from household activities uniformly distributed; 2) kitchen at constant temperature with high moisture emission rate; 3) unheated bedroom with two occupants assumed to be in thermalequilibrium with a room below at 15 c. Concludes that there is a certain critical amount of heat needed to give a relative humidity of less than 70% and thus avoid the danger of mould growth .
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