Do we need hygrothermal simulations to evaluate the design for durability?

The Danish Building regulations are function based and describe in broad terms which requirements must be fulfilled. The main message is that buildings and their structures must be built in such a way that they have a satisfactory functionality and durability i.e. that materials and constructions used can resist the stresses they are exposed to under use. However, there are no Danish guidelines on how to document fulfillment of the requirements. Durability largely depends on moisture related problems, and many failure modes/mechanisms are linked to moisture conditions. It is a prerequisite that the hygrothermal performance of a building component is satisfactory if a long service life shall be obtained. The paper will demonstrate how the risk of moisture problems is assessed in Denmark by using a stud wall as an example. However, simulations can be used for documenting the expected performance of wall assemblies, under in use conditions, however is not a conditional necessity. Even though an evaluation or simulation of moisture conditions show satisfactory results problems can occur e.g. if unsuited materials are used or if materials or building elements are used in another way than foreseen. A few examples are shown how simulations could and could not be used to determine whether a structure would have a long service life or not. Finally, a comparison of simulations, calculations and measurements are performed to illustrate the difference in results from moisture assessment that can be achieved based on assessment methodology.