Towards net-zero carbon buildings: Investigating the impact of early-stage structure design on building embodied carbon

Abstract

Purpose

This study tries to fill a gap in early-stage design and incorporate LCA results in design from early concept formation. This research aims to find the most influential parameters in building embodied carbon (EC) in early-stage design and suggest a range of their impact so that the architects can navigate their design process towards low-carbon intensive solutions. As the structure is the main contributor to building EC, the impact of structural parameters on mitigating EC of residential buildings was studied.

Methods

This research introduces a novel design exploration method for concept-stage life cycle assessment (LCA) to analyze over 8200 design solutions. Parametric modeling was employed to explore structural design variations for a multi-unit residential building on Vancouver Island, Canada. The study focused on eight key structural design parameters, with a comprehensive analysis of the resulting EC for both the structure and foundation. The study encompasses the A1–A3 stages of the building life cycle, and the findings were presented through a design-oriented dashboard for comparative assessment.

Results and discussion

The results of this study reveal that material and structural system choices exert the most significant influence on EC. Furthermore, the number of stories and building footprint geometry play pivotal roles. In low-rise buildings, geometry holds a higher impact, while in taller structures, the number of stories assumes greater significance. For steel and wood structures, floor-to-floor height emerges as a crucial factor in designing low-carbon buildings while the impact in concrete structures tends to be lower. The study challenges a prevailing misconception. It demonstrates that the normalized EC of the structure slightly decreases with an increase in the number of stories, for a given area. This decrease is attributed to material consumption savings achieved by minimizing structural components. This insight facilitates achieving lower carbon thresholds in taller structures with compact forms. Additionally, the study underscores the advantages of symmetrical and compact footprints in achieving lower carbon emissions.

Conclusions and recommendations

This research provides a free web-based tool for estimating the carbon footprint of the structure for concept design decision-making. To achieve the lowest possible carbon footprint, the study strongly advocates for using wood as the structural system, coupled with minimization of floor-to-floor height and span length. As the results show compact and symmetrical footprint shape contributes to lowering building carbon footprint. While variations to compact and symmetrical footprints do impact structural EC, their influence may be outweighed by prioritizing other design goals. The study highlights the dominance of structure over substructure in total carbon footprint within the scope of studied buildings, suggesting similar research in other regions and for underground structures. Additionally, future investigations should explore carbon savings through recycling and biogenic carbon at the end-of-life stage, thereby further reducing building emissions. This research equips designers, architects, and engineers with essential insights to make informed decisions at the concept design stage, advancing sustainable building solutions from inception.