A standard method for investigating the air leakiness of a building or component involves the use of fans to generate pressure differences across building cracks. It is often found that the air flow characteristics of such cracks vary depending upon whether the pressure differences are positive or negative with respect to a reference pressure. This note suggests one possible mechanism for explaining these flow differences, based on laboratory measurements using L-shaped cracks.
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References
1.
1 Ward, I. C. and Sharples, S., ‘An investigation of the infiltration characteristics of windows and doors in a tall building using pressurisation techniques’, Department of Building Science Report BS68, University of Sheffield (1982).
2.
2 Etheridge, D. W., ‘Crack flow equations and scale effect’, Building and Environment, 12, pp 181–189 (1977).
