Embodied Carbon 101: Building Materials
How to eliminate the emissions hidden in concrete, steel, insulation, and other building materials
Embodied carbon represents the millions of tons of carbon emissions released during the lifecycle of building materials, including extraction, manufacturing, transport, construction, and disposal. Concrete, steel, and insulation are all examples of materials that contribute to embodied carbon emissions. Because they account for 11 percent of global greenhouse gas (GHG) emissions, it is imperative for builders, manufacturers, and policymakers to prioritize this issue to meet climate goals. Furthermore, reducing embodied carbon emissions is an effective and immediate way to take climate action, as the majority of emissions occur before a building’s construction phase. As such, reducing embodied carbon has emerged as a vital new frontier in building decarbonization and is rapidly gaining global recognition among leaders in architecture & design, manufacturing, and construction.
How is embodied carbon calculated?
Embodied carbon is calculated as global warming potential (GWP) and expressed in carbon dioxide equivalent units (CO2e). To quantify a product’s embodied carbon, an analysis called life cycle assessment (LCA) is used to assess the environmental impacts associated with each stage of the product lifecycle. The disclosure of LCA results through Environmental Product Declarations (EPDs) provides valuable information to consumers about the environmental impact of building products. EPDs are essentially material “nutrition labels” that report a variety of life cycle impacts, including global warming potential, acidification, eutrophication, ozone depletion, and smog formation.
Decarbonizing construction
Several strategies can be employed to reduce embodied carbon, including using low-carbon, carbon-neutral, or even carbon-storing materials. Most carbon-storing materials are plants (wood, hemp, straw, bamboo, algae) that have sequestered carbon during their growth before being transformed into a building material. Additionally, using recycled materials or reclaimed materials can reduce the emissions associated with manufacturing new materials.
340+ Dixwell timber panel progress for high-quality affordable housing in New Haven, CT.
Projects developed by Spiritos Properties, part of the RMI-led Advanced Building Construction Collaborative, are utilizing 3D modeling, prefabrication, and CNC machining to create precise, low-carbon mass timber building materials. These materials imitate the properties of heavy timber logs from old-growth forests by laminating fast-growing materials sourced from sustainably managed forests.
Another collaborator, Mighty Buildings, a construction technology company that leverages 3D printing and robotic automation to build sustainable and high-quality homes, has joined forces with Fortera, a materials technology firm that has developed a new cement with CO2 emission reductions of over 60 percent for every ton of cement replaced. This partnership will accelerate Mighty Buildings’ mission of addressing the housing availability crisis while achieving carbon neutrality by 2028, outpacing the construction industry’s target by 22 years.
A new RMI report series presents evidence supporting the use of low-carbon and carbon-storing materials in deep energy retrofits and building new homes, which can decrease net emissions and transform buildings into climate assets. To reach our climate goals, it is necessary to leverage building materials as an opportunity to sequester and store carbon.
Other strategies for reducing embodied carbon
Embodied carbon reductions can also be achieved through material efficiency and optimized design. For example, the use of modular or prefabricated construction techniques can optimize the use of materials, resulting in minimal waste material (known as offcuts) that would otherwise end up in landfills. Designing buildings with a focus on durability and deconstructability reduces the need for frequent replacements, improves adaptability, extends the building’s useful life, and facilitates better end-of-useful-life management. Additionally, using passive design strategies, such as better insulation and orienting buildings to take advantage of natural light and ventilation, can reduce the need for energy-intensive mechanical systems that come with high embodied carbon footprints.
The policy picture
The US federal government is the largest single purchaser of building construction materials in the United States. RMI’s Federal Buildings Roadmap charts a path to achieving zero embodied carbon from projects by 2050 and quantifies the emissions reduction benefits of low-carbon building and material programs. Altogether, the impact of federal adoption of whole-project emissions standards could directly reduce GHG emissions by a cumulative 17 million tons of CO2 by 2050, which is equivalent to removing 3.6 million gas-powered cars from the road for a year.
Throughout the last year, the Biden administration has made several announcements that demonstrate the federal government’s commitment to reducing emissions from building material industries such as steel, aluminum, and concrete. Furthermore, the Inflation Reduction Act (IRA) includes almost $10 billion of funding focused on reducing embodied carbon impacts through low-carbon specification and decision-making. The IRA will also advance this market with a $250 million investment to set up an Environmental Product Declaration (EPD) Assistance Program.
States are also adopting Buy Clean laws to ensure products and materials used for public projects such as infrastructure improvements are the cleanest and most sustainable available. So far, states taking action include California, Colorado, New York, New Jersey, and Oregon. In 2022, RMI and C40 Cities hosted a series of advisory meetings for self-selected cities and released the Embodied Carbon Cities Policy Toolkit, which is a resource library for any US-based municipal policymaker to incorporate embodied carbon reductions into their city’s climate action plans and policies. Policy developments can also be tracked using the Carbon Leadership Forums tool.
Benefits for industry
Reducing embodied carbon can bring numerous benefits for industry stakeholders, including increased sales and a competitive advantage in manufacturing, policy, and ESG compliance, as well as health and wellness benefits such as improved air quality from cleaner manufacturing. A 2021 RMI report demonstrated that applying low-cost and no-cost embodied carbon solutions could result in 19 to 46 percent emissions reduction at cost premiums of less than 1 percent.
Who can play a role in decreasing embodied carbon?
Everyone involved in the production of building materials, as well as in the design and construction of buildings, has a role to play in decreasing embodied carbon. Policymakers can promote the shift toward low-embodied carbon buildings by implementing regulations or incentives that reduce embodied carbon in private-sector buildings as well as by setting standards for public building projects. Developers can establish clear environmental objectives and encourage project team designers to identify additional opportunities to decrease embodied carbon, thereby setting the tone for a low-embodied carbon project. Designers can significantly reduce a building’s embodied carbon by optimizing building design, designing for material efficiency, using reclaimed or recycled materials, and specifying low-carbon and carbon-storing materials.
By reducing the embodied carbon in building materials through circular and efficient design, improved material manufacturing, and preferential policy approaches that create market demand for low-embodied carbon materials, we can make a significant impact in reducing greenhouse gas emissions. Since most embodied carbon emissions occur at the beginning of a building’s lifecycle, it’s essential that we reduce embodied carbon emissions from today’s construction as soon as possible because these reductions will significantly impact our near-term 2030 and 2050 climate goals. We need innovative solutions to address embodied carbon, in addition to operational carbon emissions if we want to make meaningful progress in mitigating the impact of climate change.