Reducing this impact requires paying much more attention to how buildings are built and what they’re built from. But with thousands of different materials and manufacturers, it’s not so easy to know which has the lowest carbon footprint.

A new tool aims to fix that problem, and it’s already helping companies like Microsoft and construction giant Skanska to make huge reductions in the embodied carbon of new building projects. The Embodied Carbon in Construction Calculator, or EC3, is an online tool that collects the carbon emissions data of thousands of types of building materials, allowing building developers, designers, and contractors to see the potential impact of their projects, and to compare materials to find ways of reducing their embodied carbon.

The tool works by compiling a massive database of construction materials’ environmental product declarations, which quantify the carbon footprint of their production. The calculator enables users to plug in the construction material choices and quantities they plan to use in their building projects to get clear estimates of their embodied carbon emissions. With specific data on materials ranging from concrete and steel to carpet tiles and window panes, the calculator shows how material choices made from the very earliest stages of a building’s design can drastically reduce its embodied carbon.

“You’re setting targets during design, you’re using the supply chain data to understand the range of emissions that are possible per material category, you’re specifying based on trying to get the lower carbon option that meets your specs, then you’re procuring based on that,” says Stacy Smedley, executive director of Building Transparency, a nonprofit coalition of building industry partners that created the EC3. “At the end of the day you can say I selected these materials and it was this much lower than the average or the baseline, so I actually made progress.”

One version of the tool is free and already has more than 12,000 registered users. This free version can be used to calculate the embodied carbon of a few key material types—including structural materials like concrete and steel and exterior materials like aluminum and glass—that can account for upward of 70% of a building’s embodied carbon. “We are hitting the heavy emitters first,” Smedley says.

Smedley led the development of the EC3 in-house at Skanska, where she is also director of sustainability. The project got early support from industry partners including Microsoft, which has piloted the calculator on a major project at its headquarters in Redmond, Washington—a 17-building redevelopment that will see its first new structures completed in 2022. The goal was to build up the data set and for the calculator to be able to reduce the project’s embodied carbon as early in the design process as possible. In line with Microsoft’s 2020 pledge to become carbon negative by 2030, it’s targeting an embodied carbon reduction of 30% for this project.

“Zero carbon was something that was really important to us because we knew that we had to as a society get to zero carbon, but we really wanted to dig into how would that actually work on a project and particularly on a project of this scale,” says Katie Ross, senior sustainability program manager for Microsoft’s real estate and facilities team. “EC3 is a prime example for us of how we think about leveraging technology to create data-driven decisions and really support our mission to become carbon negative.”

She says the calculator has been critical in reducing the redevelopment project’s embodied carbon, especially during the very early stages of structural engineering on the new buildings. The engineers were able to compare different approaches and select a structural system that used less material, resulting in lower embodied carbon. “Right now we are on track to meet the 30% reduction target and it is fully enabled by the tool,” Ross says.

Skanska is also using the EC3 on a variety of building projects, including several large-scale office buildings in Los Angeles and Seattle. Sarah King, sustainability director for Skanska USA Commercial Development, says the tool has been particularly useful at the point when basic designs have been decided but before any materials have been purchased or contractors hired. “We can really put some language into the specs before we go out to the market, and basically send that signal to the market that says we’re not just considering price and schedule, but we’re also putting carbon intensity alongside that in our procurement process,” she says.

Key to bringing down the embodied carbon of building projects is better information about how much embodied carbon is associated with each material. King says this information is highly variable, especially by region, and that materials suppliers often don’t provide detailed environmental product declarations because they aren’t asked to. The EC3 tool can help make the case that this information will be a part of doing business going forward. “It’s going to be great as other owners and developers, other contractors, architects, and engineers start asking these same questions of this same universe of suppliers,” she says.

The more information that’s available, the better the embodied carbon calculator can work. Smedley says that embodied carbon values could become as common a measurement on products as their quantity of recycled material or volatile organic compounds. Knowing these values, she says, is essential for building projects to target embodied carbon reductions. “If you get the Microsofts and Googles and large residential developers and life sciences developers and all these folks together to start aligning on that ask,” she says, “it makes a pretty big signal to the market that this is something they need to respond to.”

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