In 2008 the Deutsches Gütesiegel Nachhaltiges Bauen (German Sustainable Building Certificate) was created as an alternative to the internationally established certification systems LEED and BREEAM. Based on around 50 individual criteria, it rates the ecological and economic sustainability but also the socio-cultural and process quality of a building design. Just what is involved in managing a rating system of this complexity? And how are the required data collected? Christine Lemaitre and Peter Mösle of the issuing authority, the Deutsche Gesellschaft für Nachhaltiges Bauen (DGNB – German Sustainable Building Council), talked to GREEN about the accreditation system.