The 2025 Reading Guide on Circularity in the Built Environment pulls together the most useful frameworks, standards, and tools for turning circular economy principles into real projects—across design, materials, policy, and procurement. It highlights where to start (sufficiency and reuse), how to measure (LCA, circularity indices, DPPs), and what to adopt next (ISO 590xx, BIM integrations), with links to handbooks, indices, and case studies.