This paper presents a study for the renovation of a 50 year old, 8 floors high apartment building, in Graz, Austria. In this project different measures, concerning energy performance, design and comfort for the user, are united in one concept. Several upgrading steps are tuned to each other, each to carry its part of the total energy reduction. Lowering the heat loss in general during the heating season and the use of local energy resources like solar radiation, it is nowadays possible to reduce the energy consumption of the entire building to passive-house standard. In this case the fossil energy reduction in the end is more than 80 % and the reduction of CO2-emissions proportional. In this approach the block of flats becomes more flexible to different situations of living, more space and comfort for the occupants is offered and the building is transformed with a new upto-date design. Compared with a new building, construction costs and primary energy use are reduced. This result means not only maintaining the value of the real estate for the owner, but also increasing it
