State and local governments are increasingly targeting the hidden climate impact of construction through policies aimed at reducing "embodied carbon"—the greenhouse gas emissions associated with manufacturing, transporting, and installing building materials. These emissions occur before a building is even occupied but constitute a significant portion of its total lifetime carbon footprint. To address this, policymakers are primarily adopting two distinct strategies: procurement standards, often known as "Buy Clean" policies, and direct amendments to building codes. While both aim to promote the use of low-carbon materials, they operate through different mechanisms and affect different sets of construction projects. Understanding these approaches is crucial for construction professionals and public officials navigating the evolving landscape of sustainable building.

Comparing Embodied Carbon Policy Mechanisms

The two main strategies for regulating embodied carbon in construction—procurement standards and building code amendments—differ significantly in their scope, mechanism, and application. Procurement policies leverage a government's purchasing power to create a market for low-carbon materials, primarily affecting public projects. In contrast, building codes set mandatory requirements for a much broader range of private and public construction projects within a jurisdiction. According to RMI, cities are leveraging these and other strategies to meet their climate commitments by integrating embodied carbon reduction goals into their overall policy frameworks. The fundamental distinction lies in whether the policy uses market incentives driven by public spending or direct regulatory mandates for the entire construction sector.

A Comparison of 'Buy Clean' Procurement and Building Code Policies
Feature 'Buy Clean' Procurement Standards Building Code Amendments
Policy Type Procurement policies that integrate low-carbon requirements into government purchasing for public projects. Direct regulatory changes to building codes that set limits on embodied carbon for construction within a jurisdiction.
Mechanism Uses the government's role as a major purchaser to create demand for materials with lower greenhouse gas emissions. Establishes mandatory, enforceable limits on the embodied carbon of materials or entire buildings.
Primary Target Materials purchased for publicly funded construction projects, such as infrastructure and government buildings. All new construction and major renovation projects that fall under the jurisdiction of the building code, including private developments.
Example Implementation A state requiring material suppliers for a public project to meet specific greenhouse gas reduction benchmarks. The City of Portland's requirement setting maximum Global Warming Potential (GWP) values for specific concrete mixes used in city-solicited projects.

'Buy Clean' Procurement Standards: Leveraging Public Purchasing Power

"Buy Clean" policies represent a market-based approach to reducing embodied carbon. These policies require that materials purchased for public construction projects meet certain environmental standards. Instead of imposing a blanket regulation on all construction, governments use their own procurement processes to drive change. According to guidance for government agencies, the core idea is to integrate greenhouse gas reduction requirements into the purchasing of common construction materials. This creates a powerful incentive for manufacturers to invest in cleaner production processes and to transparently report the environmental impact of their products through documentation like Environmental Product Declarations (EPDs).

By specifying a preference or requirement for lower-carbon steel, concrete, or other materials in public contracts, governments create a reliable demand-side pull for more sustainable products. This can help emerging low-carbon technologies gain a foothold in the market and encourage established producers to innovate. Organizations like the Carbon Leadership Forum provide resources and an "Embodied Carbon Policy Toolkit" to support state-level development and implementation of these policies. The ultimate goal is to use the significant purchasing power of public agencies to shift the entire materials market toward greater sustainability without initially placing a regulatory burden on the private sector.

Building Code Amendments: Direct Regulation for All Construction

A more direct and comprehensive regulatory approach involves amending municipal or state building codes to set explicit limits on embodied carbon. This strategy extends beyond public projects to cover most new construction and major renovations within a jurisdiction, affecting private developers and builders as well. According to the New Buildings Institute, incorporating embodied carbon requirements into building codes is a practical way to achieve significant reductions in climate impact. A report from the institute presents model language for U.S. base codes, aiming to clarify what such a regulation would look like and how it could be implemented to target the highest-emitting materials.

This method makes embodied carbon a standard consideration in building design and material selection for the entire industry, not just for those bidding on government contracts. RMI outlines several strategies that can be implemented through codes, including setting whole-building embodied carbon reduction targets, promoting building reuse and deconstruction to minimize waste, and establishing clean construction practices. By embedding these requirements into the legal framework for construction, building code amendments can systematically lower the carbon footprint of the built environment across the board, making it a powerful tool for jurisdictions with ambitious climate action plans.

Case Study: Portland's Concrete Embodied Carbon Thresholds

The City of Portland, Oregon, provides a clear example of how a municipality can implement embodied carbon regulations through a multi-faceted approach. The city's "Concrete Embodied Carbon Threshold Requirements" establish a maximum global warming potential (GWP) for various types of concrete used in construction projects that are either owned or solicited by the city. This policy directly targets one of the most carbon-intensive materials in the built environment. By setting specific GWP limits, Portland ensures that contractors select lower-carbon concrete mixes for public works, effectively using its procurement power to drive down emissions.

In addition to material-specific limits, Portland is also tackling embodied carbon from a design and planning perspective. The city's "Parking Compliance Amendments Project" eliminated minimum parking requirements citywide. This zoning change is intended to reduce the overall amount of concrete used in new developments, which the city anticipates will cause a "tremendous reduction in embodied carbon." This illustrates a sophisticated strategy that goes beyond simply swapping one material for another; it aims to reduce the total volume of high-impact materials needed in the first place. This dual approach—setting procurement standards for city projects while also amending citywide rules to encourage less material-intensive design—shows how different policy tools can be combined for greater impact.

Why Concrete is a Primary Target for Regulation

Policies aimed at reducing embodied carbon typically focus on a few key materials that contribute disproportionately to greenhouse gas emissions in the construction sector. Concrete is a primary target, as noted by the City of Portland, because of the high emissions associated with its production. The material is composed of sand, gravel, water, and cement, and it is the manufacturing of cement that is particularly energy-intensive and releases large amounts of carbon dioxide. Given concrete's widespread use in foundations, structures, and infrastructure, even small improvements in its carbon footprint can lead to significant overall emissions reductions. This is why jurisdictions like Portland have focused their initial efforts on setting GWP thresholds specifically for concrete.

Beyond the direct climate benefits, promoting low-embodied carbon materials can yield other positive outcomes. According to the City of Portland, increasing the use of these materials can create jobs for frontline workers, support new small businesses in the zero-carbon economy, and create healthier living spaces for residents. These policies can also support local economies and practices, such as sustainable forestry. By focusing on high-impact materials like concrete, policymakers aim not only to cut emissions but also to foster a more sustainable, equitable, and resilient local economy.

Navigating Embodied Carbon Policy for Sustainable Construction

For construction professionals, developers, and policymakers, the key is to evaluate local and state embodied carbon policies to identify whether they are procurement-based ('Buy Clean') or building code amendments, and understand their specific material targets and GWP limits. This understanding is essential for ensuring compliance on public projects, making informed material choices in private developments, and contributing to broader climate goals. As these regulations become more common, the ability to navigate them will be critical for successful project delivery. A clear signal that these policies are in effect is the presence of specific GWP thresholds for concrete or other materials in project specifications or local building codes.

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