A uniform methodology to establish test parameters for watertightness testing part II: Pareto front analysis on co-occurring rain and wind

A critical review on boundary conditions for watertightness testing was presented in a related paper forming Part I of “A uniform methodology to establish test parameters for watertightness testing”. Existing methodologies to establish test conditions only partially consider co-occurrence of rain and wind, which yields large uncertainties when determining return periods for extreme wind-driven rain events. This paper presents a new approach based on a Pareto fronts method for which wind driven rain intensities and wind pressures are derived. Straight lines can be fitted to consecutive fronts, and a generalized Pareto distribution describes the corresponding probabilities of occurrence of wind-driven rain events. Assumptions in the use of the methods are given and constraints to its use provided by means of case-studies. Advantages over existing methods for estimating watertightness test parameters are highlighted. Test conditions can be calculated for various configurations and different averaging periods depending on the failure behavior of specific building envelop components. Subsequently it is shown that the conversion of case-based test conditions to generic test protocols and performance levels requires careful consideration. Finally, the paper provides practical guidelines on defining realistic watertightness performance levels for building envelop components.