Measurements of air leakage through clamped joints

Laboratory measurements have been performed to investigate the airtightness of clamped joints in the wind- and vapour layers. Air leakage was measured immediately after mounting with moisture content of the wooden members at approximately 17 weight %, and after drying down to approx. 7 weight %. It was found that screws as fasteners provided better airtightness than nails. Center distance of 600 mm resulted in general higher air leakages than shorter center distances like 300 mm or 150 mm. These findings confirm and support practical recommendations previously made by SINTEF Building and Infrastructure for the Norwegian Building industry.