With the Binovabau concept Bien-Zenker offers the possibility to add roof annexes to existing appartment buildings. Those annexes show a high quality, functionality and ecology. The system construction elements used are manufactured in Bien-Zenker’s own prefabricated house facility and show a high precision in mounting. The system means that it is possible to efficiently combine the modernization of existing buildings with creating new housing, especially in urban agglomerations. At the same time, it takes account of ecological aspects, fulfilling the current EnEv-Standard.