Field Testing of Pressure-Equalized Rain Screen Walls

Abstract

One approach to controlling rain penetration into walls is to design them using the pressure-equalized rain screen principle. This design minimizes the wind pressure difference across the exterior cladding (rain screen), thus reducing the predominant force that drives rain into the wall. A pressure-equalized rain screen wall is essentially a cavity wall with sufficient venting in the cladding to enable the cavity pressure to equalize to the exterior pressure. Additional design requirements include an effective air barrier system on the inside of the cavity and horizontal and vertical baffles to form compartments within the cavity. Two buildings with vented cladding were monitored for pressure equalization. Successful pressure equalization was confirmed with a well-vented precast concrete wall system. On the other hand, the cavity pressure of a poorly vented masonry wall system did not equalize with the exterior pressure, with the result that much of the wind pressure was taken by the cladding. While the initial cost of a pressure-equalized rain screen design may be higher, it can be recovered through lower maintenance costs and a modest reduction in the design wind load for the cladding.