Twice as much living space with half the amount of carbon-dioxide emissions: This was achieved in an energy-refurbished residential district on Bebelallee in Hamburg. Another goal of the planners: The housing development from the 1950s should retain its look. To this end, Blauraum architects added stories using prefabricated wooden building elements that were attached in a short time with little construction noise. The advantage: During the construction work, residents could remain in the old lower part of the building. Following the modernization, they were happy to have more space in an energy-efficient building.