Evy Vereecken¹, Wouter Van De Walle¹, and Staf Roels¹
1)  KU Leuven, Department of Civil Engineering, Building Physics Section
Kasteelpark Arenberg 40, B-3001 Leuven, Belgium
e-mail: {Evy.Vereecken, Wouter.Vandewalle, Staf.Roels}@kuleuven.be

Keywords: Masonry, vapour permeability, condensation test setup, hygric risk assessment, Glaser, building composite

Abstract. In many European countries, the exterior building walls are typically built with masonry. Although masonry is a brick-mortar composite, in numerical hygrothermal simulations usually a simplification to an isotropic brick layer is made. Vereecken and Roels [1] concluded that for most climatic conditions such a simplification is allowed. Their study however neglected a potentially higher vapour permeability of the masonry caused by e.g. air voids, while, for instance when dealing with – especially vapour open – interior insulation, a higher vapour permeability of the masonry might result in less moisture in the masonry, a lower risk on interstitial condensation, etc. Hence, a more realistic risk assessment asks for a more representative vapour permeability of the masonry.
In this study the vapour permeability of 1,5-stone thick masonry, the common configuration for most Belgian historic buildings, is measured. To this end, a test setup that engenders a vapour flow through the test sample is developed. By bringing one side of the test sample in contact with a vapour tight cooled plate, condensation in the test setup is created. The vapour permeability of the masonry is – via a Glaser calculation – derived from the condensation measured and is shown to be higher than found for the pure brick and mortar layers.