Review of rainwater infiltration rates in wall assemblies

Detailed knowledge on expected infiltration percentages through various exterior cladding surfaces is of importance when conducting hygrothermal simulations to evaluate the long-term performance of wall assemblies. Due to the stochastic nature of rainwater infiltration through wall assemblies, it is not possible to precisely predict the amount of rainwater that will infiltrate. However, laboratory and field tests may provide insight into the range of infiltration rates that can be expected for a given cladding and insight into the impact of deficiencies and the parameters affecting infiltration. Therefore, quantitative studies concerning infiltration rates, which were mostly laboratory studies, were reviewed. Based on the reviewed studies, the driving forces for infiltration were determined and the impact of the applied test method, pressure difference and water deposition rate on the infiltration rates was analysed. A methodology to obtain information on infiltration percentages without performing additional laboratory tests was proposed and a categorization of cladding materials was developed.