Sammendrag
Air leakages in buildings cause increased energy needs, a poor thermal indoor climate and a greater risk of moisture damages in the structure. Also, the insulation in the building envelope will be impaired by infiltration of cold outdoor air. To avoid this, the insulation should have two airtight layers on each side, where the wind barrier constitutes the exterior layer. The joints in the wind barrier are weak points that are more exposed to air leakages, which makes the execution of the joints particularly important. The traditional way to ensure airtight joints has been to clamp the joints between a stud and a batten. Solutions such as use of adhesive tape over the joints have become more common due to new and stricter requirements for airtightness. The wind barrier layer is exposed to large variations in humidity and temperature within a year. This causes moisture-related movements in the studs and battens, that leads to changes in the airtightness of the joints. The variations in humidity and temperature will also reduce the performance of the adhesive tape. More knowledge about the long term performance of the tape, as well as the impact of the humidity and temperature variations, is necessary to develop solutions that are airtight over time. In this thesis, it has been conducted a laboratory test with repeated measurements of the airtightness of test samples consisting of clamped wind barrier joints. The test samples were exposed to moisture cycles to investigate how the air leakages are affected by repeated drying and humidification. During the moisture cycles, the test samples were dried and humidified between moisture levels that are representative for a Norwegian climate. Additionally, the impact of center spacing between the fasteners and use of adhesive tape over the joints has been investigated. This is conducted through six air leakage measurements of a total of 36 test samples designed for six different combinations of parameters. The center spacings used in the test samples were 150, 300 and 450 mm, and half of the samples were equipped with tape between the joint and the batten. Results from the laboratory test show that moisture cycles have a significant effect on the airtightness of clamped wind barrier joints. The test samples without tape had a rising leakage development throughout the moisture cycles, where the largest leakages occurred after drying, and the smallest leakages occurred after humidification. For the test samples with tape, humidification led to the largest leakages. After the first humidification, the leakage development for test samples with tape was flat where the center spacing was 450 mm, and declining where the center spacing was 150 and 300 mm. The center spacing between the fasteners is directly related to the number of perforations in the clamped joint. In addition, the clamp effect of the battens is crucial for ensuring the airtightness, also with the use of tape. Results from the test show that reduced clamp effect caused by deformations in the battens has a larger impact on the long term airtightness than small center spacing and a high number of perforations. The most airtight solution is a center spacing that is small enough to ensure a sufficient clamp effect, and large enough to limit the number of perforations. In addition, the use of tape will provide a considerable reduction of air leakages. Results from the laboratory test show that the effect of tape is significant for all the different center spacings that were tested. In average, use of tape reduced the air leakages by 55 %. To maintain airtight joints over time, the durability of the tape has to be sufficient to withstand the variations in humidity and temperature. Even though the function of the tape was maintaned during the moisture cycles in the laboratory test, it is difficult to predict how the function is maintained in a larger time perspective.