To reduce the emissions from energy use, high demands are set on new buildings. Studies have shown big differences between predicted and actual energy performance. This gap makes it more difficult to reduce the energy use in buildings. The aim of this study is to discover if deviations occur before the building is put into use, and if it does, discuss the reasons for that. 

In this study, energy performance for 20 multi-family houses have been compared between the early design stage and the production stage. The result of this study is that there are no major differences in energy use between the different documents. On the other hand, there are big differences in some of the parameters that the energy use is dependent on. The reasons of this are discussed later in this thesis.

None of the investigated buildings had the same value of energy performance in the production stage as in the early stage. The parameter that has shown the greatest difference is space heating and hot water recirculation. The biggest correlation was found between the energy required by the fans and the buildings total energy use.