Date of Award

2011

Degree Type

Thesis

Degree Name

Master of Engineering Science

Department

Civil and Environmental Engineering

First Advisor

Dr. Craig Miller

Abstract

The pressure equalized rainscreen wall, considered as the most effective building envelope against wind induced rain penetration, requires continuous investigations to reach better performance. This research seeks the optimum pressure equalization process under external pressure conditions and wall parameters that have not previously been studied in detail. For this purpose, a single compartment full-scale wall model was built in a controlled facility at the University of Western Ontario. The cavity pressure response to external fluctuations was experimentally examined with respect to the rainscreen venting area ratio, under two types of real wind pressure distributions generated mechanically at zero degree incidence: 1) single pressure and, 2) pressure gradient caused by the application of three different signals varying horizontally across the rainscreen.

As the rainscreen venting area ratio increases, the pressure equalization performance improves, irrespective of the nature of the applied pressure, implying an increase in the critical damping frequency. However, an applied pressure gradient leads to a lower degree of pressure equalization at a constant venting area. Moreover, the change of the vent openings layout has an impact on the wall performance, mainly at low venting areas. Locating the vent openings at the bottom of the rainscreen gives better pressure equalization rather than distributing them between top and bottom.

Using a numerical model, the cavity pressure measurements were underestimated under a uniform pressure and overestimated when subject to a pressure gradient. The agreement in the frequency domain between experimental and predicted signals was satisfactory in the high frequency regions at high venting area ratios. However, transfer functions and phase angles were overpredicted at low venting rates. Based on numerical simulations, the cavity volume change does not significantly affect the performance of the model under an external pressure gradient. When a single pressure is applied, the pressure equalization is reduced at a larger cavity depth, which is only apparent at low venting areas.

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