Hygrothermal Modelling of one-dimensional Wall Assemblies: inter-model Validation between WUFI and DELPHIN

Abstract

Various Heat-Air-and-Moisture models may give divergent results for the same case, due to differences in assumptions, simplifications, or approximations. Inter-model comparisons have been used as ‘peer review’, but common limitations and/or mistakes may remain concealed. Recent validation efforts, confronting simulations with measured datasets, use limited materials, configurations, and boundary conditions. A thorough and stepwise assessment is still lacking. In this study, dedicated hygrothermal experiments on four wall assemblies (comprising calcium silicate board, mineral wool, wood fiber board and vapor barrier in different configurations) are conducted in a hot box-cold box at KU Leuven, Belgium as a benchmark. Temperatures, relative humidity, heat fluxes and moisture mass are monitored while the thermal and hygric properties of the materials from the same batch are measured. One dimensional simulations in WUFI and DELPHIN are employed to reproduce the experiments in three stages: (1) “similar” materials (with the closest properties) from respective databases provide realistic trends but also significant deviations; (2) “same” materials (attained by mathematical translation) give better agreement but uncertainties in material properties and simplifications still have great influence; (3) monitored datasets are employed to compare with simulated results using measured material properties, based on which a collaborative inter-model blind-box validation has been initiated.