Today it is widely recognized that the construction industry plays a key role in the rational use of resources and the realization of a more sustainable society. Concerning buildings and energy use, renovation of the existing building stock to the higher energy performance is crucial. Among the various existing buildings in Europe, school buildings are of importance among the publicly owned buildings. However, there has been little effort in Sweden to promote the school building renovation by prefabricated wooden modules, which should be highly advantageous due to the short refurbishment period and its light weight.The present study investigated the hygrothermal property of wooden refurbishment modules in combination with an existing brick wall under Gothernburg (Sweden) climate. The criterion for the moisture safety inside the wall after the refurbishment was at 75% relative humidity in order to comply with the Swedish building regulation while it was assumed that the surface of the wall was wet from the precipitation during the refurbishment period. Two-dimensional transient heat and moisture transfer simulation was applied to three different module configurations. It was shown it is important to design the module vapour permeable so the entire wall system after the refurbishment have sufficient drying potential.