The Athena Sustainable Materials Institute is the pioneer of whole-building life cycle assessment (LCA) in North America. This guide provides tips on how to incorporate LCA during the building design process and presents the Institute’s supplementary best-practice recommendations for performing whole building LCA. It also offers an introduction to the Athena Impact Estimator for Building, which makes LCA accessible for architects, engineers, and other non-LCA experts in design and construction professions.