In the German city of Frankfurt on the Main, a political coalition of the conservative and the green party fosters green communal residential flats as a low carbon housing policy for its inhabitants. Right in the middle of the city centre- a former railway goods yard has been redeveloped into an residential inner city area with ìPassiv Housesî. This concept of houses has been developed to use very limited energy resources during the year. A highly sophisticated computer based model of energy consumption is being used during the whole design and construction process to evaluate energy consumption. A total of 15 KW per sqm per annum electrical energy may be consumed to be awarded ìPassiv Hausî. Following design decision has to be taken as such: - Up to 300 mm high quality thermal insulation on the walls, - Triple glazing with high performance windows, - Up to 600 mm high quality thermal insulation on the flat roofs, - Compulsory air ventilation of the flats with energy recuperation, - High performance energy saving ventilation systems with heat pumps, - High performance kitchen equipment such as stove, washing machine, dish washer, etc. The paper will show sustainable measures in the design process to reduce carbon consumption in the life cycle of the new Green Buildings.