Modelling Cavity Ventilation Behind Brick Veneer Cladding: How Reliable are the Common Assumptions?

Abstract

Throughout the years, different numerical HAM-simulation tools have been developed to assess and predict the heat, air and moisture response of building components. But, though commercially available and commonly applied in building practice, still, several simplifications and shortcomings exist in the common models. Probably the most important one, is the fact that most tools neglect or strongly simplify air transport, focusing only on heat and moisture transport. Especially for the analysis of wood frame constructions, these simplified models may cause a large discrepancy between simulation results and real performance. This study aims at a comparison of the outcomes of numerical HAM-simulations for wood frame constructions with experimental data of real test cases. In particular, the focus of this paper is on cavity ventilation behind brick veneer. Therefore, a simplified version of a wood frame wall with brick veneer cladding is studied in this paper. Different common modelling assumptions are compared. Furthermore, a detailed measuring campaign has been conducted at the VLIET test building of the KU Leuven to validate the different modelling approaches. By verifying the results of the numerical simulations by the data of real test cases, the reliability of the modelling assumptions can be analysed. The results of this study clearly show that simplified assumptions on cavity ventilation in HAM-models might cause large discrepancies between simulation results and in-situ measurements.