“Sustainable Intelligent Refurbishment” (NaiS) stands for the development of a digital platform with open-source standards and interfaces for the sustainable refurbishment of buildings. The focus is on energy refurbishment measures for sustainable building operation for real estate owners. Based on NaiS, green digital twins can be created, refurbishment measures can be analyzed with regard to economic, ecological, socio-cultural and technical aspects, and recommendations for sustainable refurbishment can be developed after an objective comparison of implementation alternatives. Recommendations for sustainable remediation can be developed. With the help of AI technologies, information from the building stock that is difficult to capture is automatically digitized and supplemented. Efficient digitization methods, objective evaluation benchmarks and scalable, sustainable refurbishment measures are at the core of NaiS as a contribution to achieving German and European climate and environmental goals. A strong consortium with high expertise and access to data in a wide range of projects and buildings, a broad network with high projection of digital solutions, as well as the previous work results of an ongoing large-volume research project in the field of artificial intelligence (AI) for the construction industry are guarantees for a successful research project.