ABSTRACT
This paper presents computational modelling of the impact on the thermal performance due to cracks and gaps in multi-layered building envelopes. Light constructions are to be analysed. The aim of the study is to simulate the interaction between cracks and gaps and the porous insulation material of a wooden frame construction. In particular the effect of joints of the wind protection and the vapour sealing is of interest. Cracks in airtight layers do not necessarily have to be a drawback concerning the heat demand. The interaction between cracks and a porous insulation material can work as a heat exchanger, i.e. dynamic insulation effects, and thus decrease the heat loss due to conduction. On the other hand if the total air exchange rate increases it will lead to an additional overall heat loss. In any case air infiltration and exfiltration may lead to inferior performance of the ventilation system. Results from two-dimensional CFD calculations of steady state conditions, together with simulations of air infiltration caused by wind pressure on the building envelope and an exhaust fan ventilation system, will be the basis for the analysis. Realistic outdoor and indoor climatic conditions, such as pressure and temperature differences across the building envelope, will be considered. The risk of moisture convection is not considered in this work.
