Hygrothermal simulation and risk evaluation - The impact of discretization on numerical results and performance

Regulations for modelling when deducting thermal simulations are represented in the standards [1]. However, the level of model detail regarding discretization in hygrothermal simulations and especially for evaluating the mould risk on surfaces of organic vapour barriers is almost never discussed. The presented approach shows that the chosen discretization of the simulation model is one of the most influencing factors for the risk analysis of surfaces of very fine layers, such as paper vapour barriers, in walls with interior insulation via hygrothermal simulations. To reduce the computational performance issues caused by very fine finite volume meshes [2], the hygrothermal properties of the connecting surfaces of the finite volumes can be calculated instead. For the risk analysis the VTT-Model was implemented in the hygrothermal simulation program HAM4D_VIE, followed by a comparison of the effect of discretization on the results of the surfaces of the vapour barrier. The results of the comparison are discussed with regard to numerical results and their qualitative impact on computational performance. The presented numerical model will be proposed as an alternative for risk analysis on surfaces of vapour barriers, where mould growth would either stay undetected or the necessary discretization with elements comes at the cost of computational performance.