Practical application of an uncertainty approach for hygrothermal building simulations—drying of an AAC flat roof

In civil engineering, there is an increasing demand for calculation methods to assess the moisture behaviour of building components. Current tasks, such as preserving historical buildings or restoring and insulating existing buildings are closely related to the moisture conditions in a building structure. In this context, questions regarding moisture behaviour and the related transport processes occurring under natural climatic conditions as well as the risks thus involved always occur. These questions can either be answered with the help of experiments or by numerical simulations. In view of the fact that experiments are often time-consuming and, in some cases, meteorologically both problematic and expensive, intensive work has been done over the past few years on the development of mathematical approaches and procedures to evaluate real thermal and moisture transfer processes. Until now, the uncertainty of input data was explicitly left out of hygrothermal modelling. But the hygrothermal conditions within a construction and the building depend on the variation of a large number of factors such as outdoor and indoor climate and material properties. This may introduce significant uncertainties in the results. Today, an increasing demand exists for defining more realistic processes that also include the type and dimension of elements of uncertainty. Their influences on the results are considered in this paper. The necessary input data for hygrothermal calculations are therefore described with a specific uncertainty.