DS²BE is a joint doctoral seminar on sustainability research in the built environment, co-organized by research centres from eight Belgian universities. It is a platform for PhD students to present their work and discuss the content with a broad panel of experts for feed-back and furthering their research. The 2025 edition was organized by UCLouvain and KULenven and took place on the 22nd of May 2025 in Leuven. The book of abstracts includes 28 contributions from 7 universities.