OSB Sheathing with Integral Water-Resistive Barriers

Elimination of polyethylene film for most of the North American climate zones changes thepattern of moisture control in wood frame walls and leads to re-examination of the performance of water resistive membranes (WRB). WRB products contribute to the following aspects of environmental control: (1) water penetration, (2) drainage, (3) air flow resistance, (4) water vapor diffusion to and from the wall and if the rain-screen principle is used, than (5) WRBs affect the pressure in the air cavity.

WRB membrane installation practice, being so different from the laboratory testing conditions, gives a reason for the development of a new technology, namely that of integral WRB that is applied directly to OSB boards. In this work the air control performance of integral WRB was found superior to plastic films, which combined with easier adjustment of water vapor permeance to the required level for a given climate zone and with the ease of installation makes them a winning technology. This paper shows also the significance of details in the installation of WRB materials.