Sammendrag
Due to the Corona pandemic, this master’s thesis is separated into two different parts. Part 1: The wind barrier is the first airtight layer to prevent outside air form penetrating the structure of a wood-frame wall. In the wind barrier, the joint is a naturally weak point. This joint is usually performed as a clamped joint where the joint is clamped between a wooden batten and a stud. To maintain the airtightness of this layer, it is very important that the clamped joints are as airtight as possible, while maintaining the airtightness over time. This is especially true for the joints where the wind barrier is made of a board material. In a board material, the number of joints will be greater than when using of a roll product. The wood in the clamped joint will experience shrinkage and swelling due to varying humidity in the surrounding air, which may cause a deterioration of the joint’s airtightness. The clamped joints can be used in different ways with a different combination of parameters. There seems to be little knowledge of which combinations of parameters provides the best airtightness for the clamped joints. In this thesis, laboratory experiments have been carried out with the intention of testing airtightness of clamped joints in the wind barrier layer. The study examines the effect of different center spacing between the fasteners on the stud, as well as the effect obtained by using adhesive tape. In the experiment, 18 different test samples were pressure tested to measure the air leaks that occurs through the joints. The test samples will undergo humidifying and drying to simulate the aging of the clamped joints. This is done to investigate how the air leakages in the joints will develop over time. Three humidifying/drying cycles are performed. The moisture content of the test samples varies between 9 % and 15 % by weight. This interval was found using simulations on a clamped board joint in the WUFI-2D program. The closure of SINTEF’s laboratories due to the Corona pandemic, made it impossible to carry out the laboratory experiment that was envisioned for this thesis. Therefore, this task is to be looked as a methodology thesis, where the experiment can be continued by others later. Part 2: When constructing structural floors in wood-frame houses, the ceiling is constructed with an airtight layer between heated rooms. This airtight layer is, among other things, intended to prevent air leakages that can carry damp air further into the structure, and then condensate. It is desirable that the airtight layer has a low vapour resistance. The floor-construction in the upper floor is usually vapour tight. Because of this, the airtight layer need to have a low vapour resistance so that the built-in moisture in the materials are not trapped between two vapour tight layers. When the airtight layer has a low vapour resistance, damp air from the internal rooms can diffuse into the structure at the transition between the structural floor and the outer wall. This only applies to constructions where there is not used a continuous vapour barrier passed the structural flooring. When the damp air meets greater vapour resistance, in the form of the edge beam, condensation may occur. This can further lead to problems with mould growth on the edge beam. Simulations have been performed in WUFI-2D and WUFI Mould Index VTT to investigate how high moisture content that can be expected in the edge beam by using different parameters in the transition between the structural floor and the outer wall. Furthermore, the risk of mould growth has been investigated. The parameter study shows that, regardless of parameters used, the edge beam will experience high levels of relative humidity, up to 97 %. This further leads to a very high risk of mould growth. Parameters that add moisture to the structure, such as climate and moisture from the internal air, should be limited to keep the risk of mould growth at low levels. Parameters that reduce the risk of mould growth in the edge beam are the use of a smart vapour barrier as airtight layer in the ceiling, use of wood fiber insulation as edge beam insulation and increased wall thickness. In addition, a study of two separate measures for reducing the risk of mould growth in the edge beam have been investigated. The measures are the use of a vertical vapour resistance layer between the edge beam insulation and the flooring insulation (both a vapour retarder and smart vapour barrier) and to move the edge beam further into the structure. The results shows that both measures have a very good effect on reducing the risk of mould growth in the edge beam. The measures must be further investigated regarding their practical applicability.