Growing concerns about climate change have prompted the European Union to create a taxonomy to guide investments towards sustainable activities. This study examines how such a taxonomy is being implemented in the building and energy sectors, also considering its impact on sustainability certifications such as BREEAM-SE. Using a qualitative approach including document analysis and case studies, the technical criteria of the taxonomy and its coherence with current practices in these sectors are explored. The findings reveal that although the EU Taxonomy provides a robust framework for sustainability assessment, there are considerable challenges in its application, especially in terms of business adaptation and integration with already existing certification systems. This analysis provides a comprehensive perspective on the interaction between European regulation and sustainability practices, highlighting key areas where the practical application of the taxonomy needs to be improved.