Passivhus, detaljutformning och dess köldbryggor

Sammanfattning: Along with rising energy prices and increasing awareness of environmental issues, the criteria for buildings energy performance have been sharpened through the years. Today, “passive house” and “low energy house” are commonly used phrases in the construction industry and is expected to become increasingly common in the future. For houses with well-insulated building envelope the importance of well constructed details increases when minimizing the heat losses. Examples of these details are floor-wall junction and window openings in the wall. In such connections thermal bridges occur, which means that heat more easily is transported out of the building, compared to the rest of the building envelope. This report deals with detail solutions around windows and a comparison between a traditional slab and a foundation from Koljern consisting of foam glass. As reference building, a preschool in Umeå, designed by WSP as a low energy house has been used. An analysis is made of various solutions and how much difference this makes to the building's average heat transfer coefficient, Um. Furthermore, studies also have been made of how the window's placement in the wall affects the size of the thermal bridge. For the analysis of thermal bridges the simulation software Heat2 is used. The result shows that it differs quite a lot between different solutions and that it’s preferable to place the window a bit into the wall. Overall, a light beam yields a smaller thermal bridge than ordinary construction timber. Making use of standard values ​​for thermal bridges can be very misleading and can in the worst case lead to incorrect sizing of the heating system.