A BIM-Based Workflow for Early-Stage Embodied Carbon Assessment Using Reusable Assembly Templates and Rule-Based Mapping

Embodied-carbon accounting is increasingly required at the early design stage to guide material and construction choices during design iterations. However, many life-cycle assessment (LCA) workflows and centralized building information modeling (BIM)–LCA plugins still rely on fragmented data, non-transparent mapping rules, and limited cross-project reuse, which slows rapid iteration. This study develops an open and traceable embodied-carbon assessment workflow driven by BIM object geometry and semantic attributes and demonstrates it through a single case study, enabling automated accounting for the A1–A3 stages from model input to result reporting. The framework is implemented as a Revit add-in prototype connected to an open-data platform. It uses assemblies as standardized assessment units, applies configurable rule-based mapping, and performs unit normalization to link model quantities with carbon factors. A single three-story brick–concrete residential building in Wuhan with an LoD 300 model is used as the sole validation case to demonstrate workflow feasibility, report coverage, and time metrics. The case yields an A1–A3 embodied-carbon intensity of approximately 333 kgCO2 e/m2, dominated by the structural system. Rule mapping achieves 82% coverage within the defined accounting scope. Compared with manual workflows (290–380 min), first-time accounting is reduced to 83–98 min and further to within 30 min when assemblies and rules are reused. Contribution decomposition shows a concentrated pattern and supports traceability from assemblies to material types. Overall, within the tested scope, the Revit-based prototype provides efficient and verifiable embodied-carbon feedback for early-stage design.