Circular Economy (CE) can help reduce the building industry’s immense environmental impact. Life cycle assessment (LCA) can facilitate CE decision-making by identifying the largest environmental impact reduction opportunities throughout a building’s life cycle, but it does not suffice in a design situation. Thus, aggregated LCA knowledge is needed. However, existing building LCAs lack transparency, coherence and a closer coupling with the building context. Performing in-depth systematic LCA on four Danish case-study buildings (a school, an office, a residential building and a hospital), this study identifies where the largest embodied greenhouse gas emissions (EG) exist. The study also identifies which building design and construction strategies should be in focus in transitioning the building sector to a CE. The LCA generalisations found that all the buildings exhibited considerable EG originating from production and replacement of floors and ceilings, outer walls, inner walls and roofs. Thus, to come closer to meeting climate goals, a combination of different strategies going across and beyond the life cycles of buildings, components and materials is needed. These strategies include reusing existing buildings, components and materials; avoiding, substituting or reducing the use of EG-intensive and short-lived materials; and enabling future reuse, recycling and/or energy recovery options for materials. Differences between the buildings were also found. Thus, it is suggested to combine generalised learnings with LCA of buildings on a case-to-case basis, and to focus on optimising EG-intensive components and materials based on their different use-contexts and interconnectedness rather than on optimising the entire building.

循环经济（CE）可以帮助减少建筑行业对环境的巨大影响。生命周期评估（LCA）可以通过确定建筑物整个生命周期中最大的减少环境影响的机会来促进CE决策，但在设计情况下还不够。因此，需要汇总的LCA知识。但是，现有的建筑LCA缺乏透明度，连贯性，并且与建筑环境缺乏紧密联系。该研究在四个丹麦案例研究大楼（一所学校，一间办公室，一栋住宅大楼和一所医院）上进行了深入的系统LCA，从而确定了最大的温室气体排放量（EG）存在的地方。该研究还确定了在将建筑行业过渡到CE时应重点关注的建筑设计和施工策略。LCA概括发现，所有建筑物均表现出可观的EG，这源于地板和天花板，外墙，内墙和屋顶的生产和更换。因此，为了更接近实现气候目标，需要结合跨越建筑物，组件和材料生命周期的不同策略。这些策略包括重用现有建筑物，组件和材料；避免，替代或减少使用EG密集型和短寿命材料；并实现将来材料的重用，回收和/或能量回收选项。还发现了建筑物之间的差异。因此，建议根据具体情况将广义学习与建筑物的LCA相结合，