This bachelor essay is divided into two parts, the first being a construction of a single-family house and the second an in-depth study of five different isolation materials, analysed from an energy perspective. The first part, the construction of the single-family house, has been created from knowledge acquired during three years of studying at KTH Royal institute of Technology in Stockholm, in the program Architecture and the Built Environment. The constructed house is a one-floor house of 137m 2with façade plaster, situated in Borlänge, Sweden. The house has a wooden frame which is built on a on sight cast concrete foundation, on the ground. The house’s roof is a gable roof, which has an angle of 24 degrees. The roofing is tile. The house is heated by underfloor heating connected to a geothermal heating pump and the ventilation is controlled by a FTXsystem. A specific energy requirement was set up so secure that an energy efficient construction was chosen. The reason for the topic of the study (isolation materials), is due to the increase of demands put on the energy economizing and climate aware, both from the building industry and society at large. The purpose was to investigate whether there are better alternatives than the traditional mineral wool isolation, when looking at energy efficiency. The depth study was based on both literatures on the subject and product information. From this a comparison of the five materials was made. The premises considered where: energy efficiency; price i.e. investment costs; energy release from manufacturing the material, and energy consumption during 25 years of a mortar phase. The comparison is divided between energy comparison and a calculation of the costs. The comparison was further divided by first looking at a scenario where the wall structures U-value is constant and a varying isolation thickness; and then the isolation thickness was constant and the U-value was varied. From this conclusions about the suitability of the materials were drawn. Stone wool was the material found most suitable when calculations where finished, and therefore it was chosen to be the isolation in the constructed single-family house.