Improvement alternatives for determining the watertightness performance of building facades

The accurate determination of a facade's watertightness performance is important for optimizing design. Different micro-climatic conditions can affect water penetration. The recently developed Bayesian method allows this performance to be estimated for any operating condition and location, based on the results of standardized watertightness tests. This performance-based method uses semi-empirical calculations for wind-driven rain, estimates of wind velocity based on the wind profile power law and analyses of the annual maximum climatic data. This method determines the return period of climatic conditions that each facade system can withstand. Alternative approximations are studied that may be implemented using the Bayesian method to obtain more precise or functional estimations: improved friction coefficients, peaks-over-threshold analyses or catch ratios from computational fluid dynamics (CFD), among others. The effects of these alternatives on the results of the Bayesian method were evaluated by analysing different case studies in two cities in Spain. This analysis suggests that the original formulation of the method underestimates watertightness performance and highlights the fundamental importance of wind velocity to estimate the performance of any facade accurately. This will provide greater precision for estimating facade performance and provides potential for introducing performance-based codes for watertightness.