Third-party rating systems like LEED have put pressure on building product manufacturers to disclose details about the environmental impacts of their products. In just the past 16 months alone, the environmental product declarations (EPDs) for concrete within the Embodied Carbon in Construction Calculator (EC3) database have doubled from 16,000 to over 32,000 (see note below). As more product information has become available about the carbon-intensive footprint of building materials (spanning from raw material extraction through manufacturing), consumer demand for better options is growing.
As buildings become more energy efficient, embodied carbon can account for nearly half of a building’s total carbon footprint over its lifetime. Voluntary efforts will only get us so far. The embodied carbon of construction materials must be addressed at the policy level to keep global warming within 1.5 degrees Celsius and meet the goals of the Paris Climate Accord. Recognizing the climate emergency, some jurisdictions are aligning their policies to reduce embodied carbon emissions.
Accounting for embodied carbon in policies
Embodied carbon is calculated by summing all carbon emitted from non-renewable energy sources resulting from sourcing raw materials, manufacturing, transporting, construction and installation activities, ongoing material/product energy use, maintenance, repair, and finally, disposal.
Policies typically account for low embodied carbon with two categories: material-specific embodied carbon or whole-building lifecycle analysis (WB LCA) evaluation. Both approaches require embodied carbon disclosure and set global warming potential (GWP) targets for specific materials or for building types. And they require GWP data obtained from manufacturer-specific or industry-average EPDs.
Buy Clean policy (also referred to as an embodied carbon procurement policy) is the most common policy applied to individual construction materials. It incorporates low-carbon construction purchasing requirements for any project receiving jurisdiction funds. Material-specific GWP maximums often target the materials with the highest embodied carbon (concrete, steel, and aluminum.) Policy components include disclosure (EPD reporting), incentives (bid bonus), and standards (GWP maximum limits per material.)
The production of cement, iron, and steel are responsible for the largest percentage of building material emissions. Low-carbon concrete policies have the greatest potential to significantly reduce carbon emissions resulting from the purchasing of new building materials, according to the Carbon Neutral Cities Alliance. With concrete often being a locally made product and cities purchasing more concrete than any other entity, jurisdictions that specify low-carbon concrete can capture multiple benefits: significant GHG reductions while also retaining jobs and supporting the local economy. While Buy Clean Washington and Minnesota were not passed, there is interest in re-introduce the bills. In Washington, funding was allocated for the Buy Clean Washington Study, paving the way for future passage. At the federal level, the Clean Future Act is shining more light on Buy Clean policies. If adopted, more states are likely to pass similar policies for state or city procurement.
Whole-building LCA policies
Whole-building LCA policies are seeing more interest as tools like Tally and One Click LCA have made it easier to compare analyses of design options. This allows projects to take credit for building material reuse or material efficiency. Whole-building embodied carbon policies either set an absolute value to restrict the lifecycle carbon emissions or provide allowable emissions per area (kgCO2/m2.) Alternatively, WB LCA policies can require a percent-better-than requirement for a building to achieve a specific GWP reduction, using lifecycle analysis modeling compared to a baseline building.
One concern with WB LCA is that baseline buildings can vary by the project team, making it difficult to compare one project to another. These policies must include rigorous guidelines for WB LCA modeling to ensure consistency in enforcement and compliance. Vancouver’s Green Buildings Policy for Rezoning is an example of WB LCA accounting. The policy requires all rezonings in Vancouver to conduct a WB LCA study and report the embodied carbon GWP, but doesn’t yet require a specific target.
With new insight into the lifecycle impacts of building materials, consumers—including government purchasers—are requesting product disclosure, asking manufacturers to step up and meet a growing market demand for low-embodied carbon solutions. Manufacturers are responding and providing insight into their products. Thanks to growing interest in building material transparency, policymakers have the information necessary to implement low-embodied carbon procurement policies for concrete, rebar, steel and more. With nearly 500 U.S. mayors committed to upholding the goals of the Paris Climate Accord, low-embodied carbon policies are excepted tp become more commonplace.
Visit the Getting to Zero Embodied Carbon Resource Hub to access the latest resources on embodied carbon policies. And, check out the Carbon Leadership Forum’s Carbon Policy Toolkit—a must-read for any jurisdiction thinking of addressing embodied carbon while creating good-paying jobs and economic development.
Beyond policy, the building codes offer another pathway to address embodied carbon. Our next blog on embodied carbon will explore the symbiotic relationship between codes and purchasing policies when it comes to reducing embodied carbon in building materials.
by Webly Bowles, Project Manager