This European Standard specifies a method of determining the steady state water vapour permeability of autoclaved aerated concrete masonry units at the upper and lower part of the hygroscopic range. The test method is limited to products from which disc shaped specimens of uniform thickness can be made.
No requirements are given for conditioning of the specimens. However, it will take longer for the test arrangement to reach equilibrium if the specimens are not in an approximately air dry condition at the start of the test.