A study of mean pressure gradients, mean cavity pressures, and resulting residual mean pressures across a rainscreen for a representative building
Skerlj, P.S. and D. Surry
1994
Prepared for Housing Innovation Division, Canada Mortgage and Housing Corporation. Ottawa
Skerlj, P.S. and D. Surry, (1994), A study of mean pressure gradients, mean cavity pressures, and resulting residual mean pressures across a rainscreen for a representative building, Prepared for Housing Innovation Division, Canada Mortgage and Housing Corporation. Ottawa.
| Abstract: |
| Experiments were conducted in the Boundary Layer Wind Tunnel at the University of Western Ontario to examine the mean pressure gradients on the external surface of a representative building and to investigate the resulting net rainscreen pressures. A module comprising a variable number of vented compartments was used to determine external mean pressure distributions, mean cavity pressures and resulting mean pressures across the outer wall of a rectangular building model at six locations on the long face. At each location, wind angles ranging from normal to parallel to the long building face were examined. The bulk of experiments were performed using a compartment width (the dimension parallel to the array of external pressure taps) of 2 m in full scale. A limited number of experiments were also performed which considered 1-m, 2-m, 4-m and 8-m compartment widths.
External pressure results show steep horizontal and vertical external mean pressure gradients near side and top edges respectively. For a typical 10 -year dynamic pressure of 300 Pa (hourly mean speed of 78 km/hr), pressure gradients as large as 260 Pa/m were measured near the top corner. The gradients over interior regions of the building face were generally found to be smaller. Measurements of mean internal cavity pressures verify that compartments do not pressure-equalize when exposed to large external gradients. In this situation, significant residual mean pressure differences result across the rainscreen. As expected, net mean rainscreen pressures were found to decrease with decreasing compartment size and with decreasing mean pressure gradient. Hence, regions near edges, which generally contain large external pressure gradients, require frequent compartmentalization to reduce residual pressures. |
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