Prefabricerade passivhusväggar

Sammanfattning: Background: The most energy efficient houses today are so called passive houses. These houses achieve high energy-efficiency partly by having well insulated walls. U-value describes the amount of heat transfered through a building element, the more insulation, the smaller U-value. A typical passive house wall have a U-value of 0.10 W/m2,°C. The passive houses are primarily made as small family houses and not as a block of apartments. This is partly because the bigger houses often are made of prefabricated walls, which at present times are not made with enough insulation. One construction method common in prefabrication is a sandwich-construction with two layer of concrete surrounding a core of cellular plastic. Skanska is making this type of walls in a factory on Gotland. We wanted to combine the energy efficiency of passive housing with the efficiency of prefabricated sandwich-walls. Aims: To present a suggestion of a sandwich-construction made with concrete and cellular plastic with a U-value below 0.10 W/m2,°C, that could be implemented in the factory on Gotland. Methods: By analyzing systems of today we developed two different models that have a U-value below 0.10 W/m2,°C. The first system was developed from a system used in Skanska’s factory on Gotland and the second one was based on a system delivered by Halfen DEHA. This was made through empirical tests and theoretical calculations. We compared the developed systems in terms of the conditions in Skanska’s factory on Gotland. Result and discussion: The system based on Halfen DEHA needs a larger amount of shackles, than the system developed from Skanska’s present system. This leads to the need of thicker insulation to achieve the desired U-value. The reason is that the Skanska-based system uses a combination of shackles and cellular plastic to carry the loads of the coating layer while the Halfen DEHA depends on the shackles alone. We believe that the first of our two developed systems is the best in terms of the ease in adopting to the production method in Skanska’s factory. The second system is safer in terms of controlling the production and has the possibility to have an air gap. Conclusion: In the rapport we present a sandwich-construction system that has a U-value below 0.10 W/m2,°C, that we believe would work for prefabrication of wall structures and could be easily adopted in Skanska’s factory on Gotland.