A numerical model to evaluate the performance of pressure equalized rainscreen walls

Abstract

Advancements in Computational Fluid Dynamics (CFD) and numerical modeling techniques provide new approaches to quantify air flow around buildings and wind induced pressures on the building envelope. This paper describes the progress made on developing a numerical model to predict the performance of Pressure Equalized Rainscreen (PER) wall assemblies. The model is three dimensional and time dependent. The Navier Stokes Equations (NSE) are discretized using a control volume method. External wall boundaries are treated with cyclic pressure differentials, the onlyfluid property available as a boundary condition from the experiment. This paper presents the steps involved in the numerical model development and the effect of static and dynamic parameters on the model predictions. Two types of wall assemblies, one representing an airtight air barrier system and another with a leaky air barrier system, are modeled. Predicted performances of both wall types are analyzed with respect to time and space. Preliminary model validation is performed by comparing computed results with limited experimental data. The paper also includes some of these comparisons for various geometrical configurations of the PER wall assembly.