The Danish sustainable certification scheme (DGNB) provides the framework and criteria for the construction of buildings in a sustainable manner. The scheme is voluntarily, however more and more clients have requirements for sustainability and wants a certification. A conventional design process of today with large focus on energy use and indoor environment is already highly complex, where the use of DGNB undoubtedly will increase the complexity. This research project investigate design and decision-making processes when using a DGNB certification scheme. The aim is to acquire an understanding of the processes and thereby being able to develop new methodologies and tools to support the design and decision-making processes.