Policy and design levers for minimizing embodied carbon in United States buildings: A quantitative comparison of current and proposed strategies
Kiley Feickert, Caitlin Mueller
Abstract
• Effective approaches to reduce building embodied carbon are not reflected in policy. • Efficiently designed buildings can result in low embodied carbon. • Performance based policies are recommended for achieving low embodied carbon. • Most current embodied carbon policies are material-scale regulations. • Building scale policies are better at reducing embodied carbon than Buy Clean policies. Building additional floor area while reducing the environmental impact of embodied carbon (EC) is urgent in the context of simultaneously increasing urban density and global warming. An intensified policy response is required, as EC is responsible for nearly 13 % of global greenhouse gas emissions annually [1]. In the United States, policies are beginning to regulate EC; However, their expected impact at the building scale is not well understood. Design can also play a significant role in reducing EC since the quantity of materials required to construct a building depends on the interrelated impacts of design and structural mechanics. Therefore, this paper contributes a landscape analysis of active EC policies in the U.S. and an estimate of the achievable EC savings at the building scale from utilizing policy and design (in isolation and combination) by parametrically linking both approaches to high-fidelity building models for various building configurations and material systems. It finds that most active and planned regulations focus on reducing the carbon intensity of select materials, specifically cement. At the building scale, these Buy Clean policies only reduce EC by ∼9 % and ∼16 % for steel and concrete systems, respectively. Alternatively, leveraging strategic design choices, such as reducing structural spans or shape-optimizing reinforced concrete floors, results in EC savings of up to ∼70 % and ∼79 %, respectively. Therefore, performance-based policies that set ambitious global warming potential (GWP) limits (in kg CO 2 e/m 2 ) and allow design teams to reach targets creatively are recommended to facilitate deeper EC decarbonization more quickly.