Carbon–Cost Optimization of Construction Projects Using BIM, Life Cycle Assessment and Multi-Criteria Decision Making

This research developed an integrated BIM–LCA–LCC–MCDM framework for evaluating and optimizing the carbon and economic performance of construction projects. BIM-based material quantities provided a common data foundation for life-cycle carbon and cost assessment, while MCDM enabled alternative construction strategies to be evaluated using multiple environmental and economic criteria. Sensitivity analysis was subsequently used to examine the robustness of the final decision. This integrated approach directly addresses the research objective of connecting BIM-derived quantities, carbon emissions, life-cycle costs, construction alternatives, and decision-making within a unified assessment framework. The baseline case-study building recorded a whole-life carbon emission of 1,867.7 t CO₂e, with operational carbon accounting for 50.6% and embodied carbon for 32.8% of the total emissions. The baseline life-cycle cost was £9.496 million. These findings demonstrate the importance of considering both embodied and operational impacts and evaluating economic performance beyond initial construction cost. Among the evaluated construction alternatives, individual material interventions produced moderate improvements. The low-carbon concrete alternative A1 reduced whole-life carbon by 5.9%, while the recycled-steel alternative A2 achieved a 4.2% reduction. The enhanced building-envelope alternative A3 provided greater improvement, reducing whole-life carbon by 11.4% and life-cycle cost by 4.0%. The strongest performance was achieved by A4 – Integrated Low-Carbon Design. Whole-life carbon decreased from 1,867.7 to 1,482.6 t CO₂e, representing a 20.6% reduction and a saving of 385.1 t CO₂e. At the same time, life-cycle cost decreased from £9.496 million to £8.983 million, producing a 5.4% reduction and approximately £0.513 million in life-cycle cost savings. Although A4 required a higher initial investment, its long-term operational and economic benefits resulted in superior whole-life performance. The MCDM evaluation further confirmed this outcome, with A4 achieving the highest performance score of 0.914, followed by A3, A1, A2, and A0. The final ranking was: A4>A3>A1>A2>A0 Sensitivity analysis showed that A4 maintained Rank 1 across all evaluated criterion-weight variations, confirming that the preferred alternative remained stable under changing environmental and economic priorities. The principal research contribution is therefore the integration of BIM, LCA, LCC, MCDM, and sensitivity analysis into a single carbon–cost optimization process. Rather than selecting construction solutions solely on the basis of initial cost or carbon emissions, the framework supports decisions based on whole-life environmental and economic performance. This extends the BIM-based carbon and cost integration discussed in the existing literature [1], [2] by incorporating alternative evaluation, multi-criteria ranking, and decision robustness. From a practical perspective, the framework can support project managers, cost consultants, designers, contractors, and sustainability professionals in material selection, design comparison, life-cycle budgeting, value engineering, and sustainable procurement. The findings demonstrate that low-carbon construction does not necessarily require a long-term economic penalty; appropriately integrated design strategies can simultaneously achieve lower whole-life carbon and lower life-cycle cost. Overall, the research demonstrates that BIM-enabled life-cycle assessment combined with economic and multi-criteria evaluation provides a systematic basis for achieving low-carbon, cost-efficient, and sustainable construction decision-making.

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