Analysing sustainability certification systems in the German housing sector from a theory of social institutions

Sustainable residential buildings and a sustainable housing development ('sustainable housing') are key factors in the sustainability strategy of the German government. Certification systems have been developed to assess sustainable housing and to better inform stakeholders and hence improve sustainability in the housing sector. Currently, however, a variety of different certification systems exists to assess sustainable housing using different sets of indicators. The supply of different certification systems to measure the same ('sustainability') raises questions of validity of the assessment instruments. Also, different stakeholders hold different interests with regard to sustainability certification systems, which leads to investigate the legitimacy of certification systems. In this study, we applied the theory of social institutions to investigate legitimacy of sustainability certification in the housing sector. To find out about the validity of sustainability measurement, this article presents a survey where real estate stakeholders were asked to evaluate indicators applied by different sustainability certification systems. Results showed high heterogeneity of tastes towards indicators of sustainable housing. Results also identified potential 'areas of conflicts' where stakeholders differed most widely in the evaluation of indicators.