The construction and real estate sector accounts for a significant part of Sweden's climate impact. By 2045, Sweden must reach the goal of no net emissions of greenhouse gases into the atmosphere. This means that the construction sector needs to contribute to the adjustment for the climate goal to be achieved. Previous studies demonstrate through a life cycle analysis that the climate impact from the product stage accounts for a significant part of the building's climate impact over the life cycle. They also state that insulation materials account for a significant part of the climate impact in wood frame constructions. An increased amount of insulation leads to an increased climate impact in the product stage, but at the same time a reduced energy use and thereby a reduced climate impact in the use stage.  The purpose of the study was to contribute to climate-smart choices when designing detached houses with wood framed constructions. The aim of the study is to calculate the climate impact in the product stage and construction process stage as well as the use stage for the most common insulation materials and heating systems. Then, based on these calculations determine optimal insulation thicknesses for minimal climate impact in the various cases. To meet the study's objectives, a case study was conducted in which the climate impact in the product stage and construction process stage was compared with the use stage for different insulation materials and heating systems. The case study examined the insulation materials stone wool, glass wool, cellulose fiber and wood fiber in combination with the heating systems heat pump, biofuel and district heating. The energy consumption in the operational phase was calculated using the energy simulation program BIM Energy. With emission factors for the various forms of heating, the climate impact of the use stage was calculated. This was then compared with the climate impact of the insulation in the product stage and construction process stage to determine the optimal insulation thickness. The results of the study show that the optimal insulation thickness regarding the climate impact in the product stage and construction process stage as well as the operational phase varies depending on the insulation material and heating system. For newly produced detached houses different types of heat pumps are common heating systems and the most common insulation material is stone wool. For the simulation with stone wool insulation in combination with a heat pump, the optimal insulation thickness is relatively low. The results of the study showed that the optimal insulation thickness varies depending on the insulation material and heating system. When designing wooden framed detached houses where low energy consumption is sought, it is important to weigh the climate impact from the product and construction production phase as well as the operational phase to achieve an overall climate footprint that is as low as possible. In some cases, a large amount of insulation is not advantageous if the climate impact over the entire life cycle is considered. It may be necessary to consider other types of insulation materials than mineral wool to minimize climate impact.