Comparison of experimental and numerical results of wood-frame wall assemblies wetted by simulated wind-driven rain infiltration

A large-scale building envelope experiment was conducted to study the effect of three sheathing materials and two vapor retarders on the drying performance of walls exposed to simulated rain infiltration in springtime in Montreal. The moisture source was a pre-wetted component within the wall called the bottom plate insert. Its moisture content was monitored on a daily basis through the course of the 35-day experiment. The experimental set-up was simulated using a two-dimensional hygrothermal model, WUFI-2D, and the moisture content within the bottom plate inserts was used to study the ability of the model to predict the wall response to the initial liquid water load. The differences between the experimental results are mainly attributed to: air convection loops within the insulated space, which are not accounted for in the simulation; estimation of the initial moisture content distribution within the bottom plate inserts in the simulation; isotropic material properties for an orthotropic material like wood material properties that were taken from a variety of sources and did not cover the entire moisture content range and use of a two-dimensional domain to simulate three-dimensional wall systems.