EFFECT OF INTERIOR AND EXTERIOR INSULATION ON THE HYGROTHERMAL BEHAVIOR OF EXPOSED WALLS

Massive walls exposed to die natural climate without special rain prot ection show a dynamic moisture equilibrium governed by the alternating events of rain and sunshine. The moisture further reduces the rather low insulation level of the walls. Therefore, thermal insulation measu res have to be taken in order to improve the hygienic conditions and t he thermal performance of the building. The influence of interior and exterior insulations on the hygrothermal behaviour of such walls can b e determined with the aid of a recently developed computer program whi ch has been experimentally validated by comparison with field tests. T he results show that an exterior insulation leads to the drying of the wall, with the drying rate depending on the vapour permeability of th e insulation system. An interior insulation, however, results in a ris ing water content of the wall due to the decreasing masonry temperatur e. This effect is almost independent of the vapour permeability of the insulating material. While an exterior insulation also improves the t hermal resistance of the masonry, an interior insulation has the oppos ite effect and increases the frost damage risk. Therefore, the interio r insulation of exposed walls should be combined with rain protection measures at the facade.