Discusses basic physical features of combined energy and moisture flow in porous building material. Discusses mathematical and physical structure of these dynamic processes in terms of local thermodynamic equilibrium, flows induced by gradients in intensive state variables and conservation of energy, moisture and other components. Gives conditions for thermodynamic equilibrium, discusses peculiarities of pore-water tension, and problems concerning energy flow. Deals with the causes of hysteresis and the complications due to hysteresis.
Gives equations and charts for the calculation of heat and moisture flow due to natural convection through openings in vertical partitions separating spaces at different air conditions. Finds that heat and moisture transfer coefficients depend on the Grashof number and to some extent on the ratio of opening height to thickness. Also gives chart and equations for flow across an opening in a horizontal partition when the higher density air is above the opening.
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.
Discusses oxygen requirements and moisture emission of individuals and generation of CO2, odours, and aerosols in inhabited rooms. Treats calculation of hygienically necessary air flow rates. Notes characteristics of continuous andintermittent ventilation, whereby additional outside air is discharged into a room at set intervals when continuous airflow rate falls below hygiene requirements. Compares hygienically adequate, continuous ventilation with intermittent ventilation by calculating hygienically-necessary outside air flowrate using a mathematical mode.
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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