Leveraging design to build with less: Evaluating the embodied carbon reduction potential of architectural design across scales

Abstract

Reducing embodied carbon (EC) in structural systems -- the most significant contributor to EC in a building -- is urgent to address the simultaneous need to reduce global warming and increase urban density. Much of the policy and research to date to reduce EC has focused on material-scale interventions or substitutions. However, EC depends on both: 1) the carbon intensity of the processes used to manufacture construction materials, and 2) the volume of raw materials required. Architects have significant agency to reduce the volume of structural materials in a building (and the resulting emissions) since the required quantity depends on design decisions architects make, including column spacing, structural typology, massing, etc. To date, most methods used to estimate EC during early-stage design do not: 1) integrate with architects’ existing design workflows, 2) evaluate multiple material systems simultaneously, and/or 3) include structural analysis to estimate material quantities. This functionality is critical so that designers can understand which decisions EC is sensitive to and evaluate design and EC tradeoffs before significant carbon is locked in.

To address this problem, this dissertation presents a method towards transparent estimation of structural material quantities, intending to inform architectural design and policy, or other emerging EC standards. This method is used to contribute an analysis of the effectiveness of emerging U.S. EC policies, which focus on different scales of intervention, at the building scale. These policies are evaluated in isolation and in combination with strategic design levers that take advantage of structural mechanics to reduce material quantities for various building configurations and material systems. It finds that the most prominent policy approach, “Buy Clean” materials, only reduces EC by ~9% and ~16% for steel and concrete systems, respectively, compared to strategic design choices that have the potential to yield savings of up to ~79%. This dissertation also identifies building massing as a key lever in the EC outcomes of structural systems and proposes a method to quantify the impact of massing using automated structural design and analysis. It finds that in some situations, cantilevered massing typologies can be materialized for no carbon penalty if efficient configurations are used. Indeed, if inefficient configurations are used, they can incur a significant carbon penalty (2.4x) compared to normative massing. The presented results highlight the potential of design to reduce demand-side EC across scales.