The Minimum Impact House in Frankfurt am Main is a sustainable solution for low cost living within city centers - a prototype typology with minimal footprint, built on a leftover urban space. The planning process itself became part of a scientific study. The ecological advantages of building in the city where integrated in a real building project with new typology, ecological construction-technique and materialization. The goal was to minimize environmental impact through construction and operation of the building. In a comparative study we compared advantages and disadvantages of a single-family house in the centre versus new building zones. This included qualitative an quantitative comparison over a life cycle of 50 years with construction, running, maintenance, disassembly and location related mobility.