Human-Centred Carbon Decision-Making in Early Design: A Systems Review of Lifecycle Carbon Leverage

Abstract

The built environment is central to global climate mitigation, with lifecycle carbon emissions increasingly shaped by early-stage design decisions. As operational standards improve, embodied carbon and whole-life performance have emerged as critical concerns. Although substantial research documents carbon reduction strategies across materials, structural systems, passive design, building services, and cost evaluation frameworks, existing studies remain largely intervention-specific. This study therefore examines which early design decisions exert the greatest lifecycle carbon leverage within an integrated project system and aims to address this gap through a qualitative Systematic Literature Review (SLR) of 44 academic and industry publications examining early-stage lifecycle carbon reduction in commercial buildings mainly between 2015 and 2025. Studies were included if they evaluated feasibility- or conceptual-stage design decisions affecting embodied or operational carbon performance. Thematic synthesis was used to identify recurring intervention domains and reported carbon reduction magnitudes across material, structural, passive, services, and evaluation-based approaches. Findings indicate that structural configuration and material selection are consistently associated with significant embodied carbon variation (20–40% reduction through low-carbon substitution; up to 28–51% variation across structural systems). Passive design strategies demonstrate 25–50% operational energy reductions when embedded during conceptual design. In contrast, building services and renewable integration, while important, are frequently constrained by earlier structural and spatial decisions. Lifecycle cost–carbon frameworks improve trade-off visibility but function primarily as enabling mechanisms rather than direct carbon reducers. The evidence suggests that lifecycle carbon performance is largely determined during feasibility and conceptual design, where early decisions establish trajectories that are difficult to reverse. Decarbonisation therefore depends on embedding carbon alongside cost and performance criteria within human-centred early design decision environments. Future research should empirically examine how interdisciplinary teams integrate carbon metrics during concept-stage evaluation and develop structured methodologies for comparing early-stage intervention leverage in live project contexts.

Keywords: Human-centered, Carbon Decision-making, Sustainability, Energy, Early-design

DOI: 10.54941/ahfe1007904