In this graduation research the life cycle energy (embodied and operational energy) of a refurbishment project is researched by means of a literature study and a case study design. A design approach is made to make the life cycle energy as low as possible for the case study, an existing post-war residential building in Utrecht. The focus of the research is on the facade of the building, but also the building services are assessed. By looking at different strategies, variations and materials, the best possible design is made concerning energy use. This way conclusions and recommendations can be made for designers, for other comparable post-war residential buildings.