Wind-driven rain as a boundary condition for HAM simulations: analysis of simplified modelling approaches

While the numerical simulation of moisture transfer inside building components is currently undergoing standardisation, the modelling of the atmospheric boundary conditions has received far less attention. This article analyses the modelling of the wind-driven-rain load on building facades by partial simplification of a complex CFD-based method along the lines of the European Standard method. The results indicate that the directional dependence of the wind-driven-rain coefficient is not of substantial importance. A constant wind-driven-rain coefficient appears to be an oversimplification though: the full variability with the perpendicular wind speed and horizontal rain intensity should be preserved, where feasible, for improved estimations of the moisture transfer in building components. In the concluding section, it is moreover shown that the dependence of the surface moisture transfer coefficient on wind speed has an equally important influence on the moisture transfer in building components.