The DGNB system for new construction aims primarily to ensure a holistic sustainability assessment of a building. This article examines which obstacles can arise in the certification process for assessing the environmental quality from the perspective of DGNB auditors. Expert interviews with three auditors form the basis for a succeeding structured questionnaire sent to all DGNB auditors registered in 2020. The interviews serve the explorative identification and systematizati-on of confounding factors. Then, the questionnaire empirically tests the extent to which these obstacles affect the time course of certification and the likelihood of achieving the highest possible assessment score. Results show that predominantly me-dium to large barriers exist both causing delay and lower over-all scores. Interface cooperation and a late integration of the DGNB concept in planning emerge as the most crucial obsta-cles. The article suggests that an early involvement of DGNB auditors significantly influences the implementation of sustainable building in practice.