Building owners and investors in the private and public sector realize that the design of sustainable buildings serves general public interest. Furthermore they recognize that life-cycle oriented planning yields additional value. This means optimized buildings exhibit economic planning reliability, a healthy working environment as well as an adaptability to changing conditions and terms of use. In consequence of the introduction of the certifica-tion systems for the sustainability of buildings e.g. BREEAM, LEED, BNB or DGNB sustainable construction has become measurable. Investors gain interest in buildings that comply to a certain rating of sustainability. This demand poses a challenge for Architects, Engineers and Planners. This interest in dedicated certificate degrees leads to new chal-lenges for these experts. With respect to a specific site they often lack experience for the interaction and possibilities of influence in these certification systems. Subject of the dissertation is the development of an instrument to optimize the sustainabil-ity of buildings in any stage of the planning and realisation process. Exemplarily the in-strument is developed for the DGNB-system, which was originally developed for the German market. The optimization considers the feasibility of enhancing building performance as well as the cost-effectiveness of procedures.