Energy effective houses
This thesis is produced in corporation with Älvsbyhus representative in Östergötland. Älvsbyhus is for the moment the largest manufacturer of prefabricated detached timber houses in Sweden.
A prognosis from the Swedish environmental protection agency and the Swedish energy agency suggests that the discharge of greenhouse gases will increase rapidly until 2020. The prognosis concludes that all energy use affects the environment to some extent and energy efficient buildings can contribute to a reduction of the greenhouse effect. The Swedish government are using economical and administrative instruments of control to guide the building companies and property owners. The Swedish building regulations concerning energy management has since 1 July 2006 been sharpened and the law of buildings energy performance will come into force in October 2006.
The National Board of Housing, Building and Planning (BBR) has in the report “Piska och morot” concluded that it is impossible to estimate the socio economic potential of energy efficient buildings. The private economic potential can on the other hand lead to a decreased sensitivity to fluctuating energy prices. BBR’s report also suggests that the measurements could lead to an increased awareness and make energy efficiency to an important argument in project planning and marketing of buildings. Scientists working with energy matters are recommending a line of thought that means an increased focus on a reduction of energy losses through the building envelope. The building envelope should in other words have sufficient thermal insulation and protection against air leakage. The last step in the process would be to dimension the heating system after the remaining heating demand.
The purpose with this study is to investigate how the building envelope on prefabricated houses of timber is constructed concerning rational use of energy. The results of the study are meant to lead to an increased knowledge about the technical level of our newly built houses and possible actions to decrease the energy use by changing the building envelope. The report begins with a theoretical section that explains the background and problems concerning energy effectiveness. The theoretical section is also meant to help the reader with an introduction in terminology, basic building physics and mechanisms that effects the heat requirements. The practical section of the report is a study of model houses from six of Sweden’s largest manufacturers of detached timber houses.
A simulation programme (ENORM 2004) has been used to calculate the thermal needs for the model houses. The results from the calculations are used to decide if the model houses are following present (BFS 2002:19) and future (BFS 2006:12) building regulations (BR). The present regulations concern the total heat transfer coefficient (F s = Um (W/m2K)) and future regulations concern the specific energy use (kWh/m 2 · year). The model houses will also be compared to identify differences in construction and calculation results that has an effect on the heat requirements. Houses that do not live up to the BR will be submitted to changes in the building envelope until they meet the regulations. To conclude the practical section of the report the model houses will be provided with qualities from low energy houses. The purpose is to determine how the heat requirement is effected with extreme changes in the building envelope.
The results from the calculations (see table’s below) show that all model houses meet up to present building regulations. Future building regulations prescribe that Sweden will be divided into two climate zones separated on a level with the city of Karlstad. All model houses met up with the demands for the southern climate zone and none of the model houses met up with the demands for the northern zone. In the calculations Stockholm represents the southern zone and Luleå represents the northern zone.
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