Embodied Carbon Influencing Decision-Making at Earlier Stages

Real estate developers across the United States and around the world are under pressure to cut the amount of carbon their activities put into the atmosphere.

Multiple municipalities and potential investment partners demand that developers report—and, in many instances, also reduce—the amount of embodied carbon released in the process of developing a real estate project.

“Tackling embodied carbon is not easy,” said Sara Neff, head of sustainability for Lendlease Americas. Neff spoke at “From Finger-Pointing to Handshakes: Reducing Embodied Carbon in Real Estate Developments,” at a breakout session during the 2024 ULI Spring Meeting in New York City. Early plans for a building are often based on several unexamined assumptions. After the fact, it can be difficult to say exactly who decided that a planned building should be made of this kind of steel or that type of concrete. But decisions of this sort often have a giant effect.

The panelists recommended considering embodied carbon at the very beginning of the development process, long before any stakeholders require formal reports on how much carbon is likely to be emitted into the atmosphere to create a building.

More stakeholders demand reductions in embodied carbon

Lendlease pledged in October 2021 to reduce the amount of carbon emissions produced by its activities to “absolute zero” by 2040. A growing number of real estate companies has made similar public promises to investors and other stakeholders. To keep those promises, they will have to address their embodied carbon. Roughly 92 percent of all the carbon emissions produced by Lendlease’s activities have occurred in the process of constructing buildings, Neff said.

More and more jurisdictions, including New York City, also now have laws on the books that require developers to reduce the amount of embodied carbon in the buildings they create. Smaller towns are likewise regulating carbon emissions caused by development. Cambridge, Massachusetts, for example, plans to require developers to disclose the embodied carbon of any planned development that applies for a permit, said Ben Myers, senior vice president for sustainability for developer BXP.

“It’s inevitable that cities that have building performance standards are going to have an embodied carbon disclosure requirement,” Myers said. “That’s the first step towards requiring a 20 percent reduction in your embodied carbon.”

Developers to who need to cut the embodied carbon in their projects should start early. Many opportunities come long before it’s time to create detailed construction drawings or even hire a contractor. The choice of whether to build with concrete, steel, or mass timber often comes near the start of a project. That decision has a giant effect on carbon emissions.

“The embodied carbon footprint for a new construction project [stems] 85 percent from the materials,” said Myrrh Caplan, national vice president of sustainability for Skanska.

For example, the heat required to create concrete causes 8 percent of the world’s carbon emissions, according to the panel. Should the concrete be made in the Pacific Northwest or some other region, however, where much of the energy comes from hydroelectric power, carbon emissions caused by the making of concrete are significantly lower, according to Jordan Woodson, associate for Arup, a design firm.

Other technologies can manufacture concrete without emitting as much carbon—by including such ingredients as fly ash in the mix, for example. Woodson advised developers to work with sustainability experts at the beginning of the development process, long before it makes sense to do the full Life Cycle Assessment (LCA) required by a growing number of jurisdictions, sustainable development certifications, and investment partners.

“We have to find ways to do lighter LCAs to analyze system decisions early in the process,” Woodson said.

The panelists also urged developers to do a full carbon accounting of their projects, so that the whole industry can learn to get better at reducing carbon emissions. “You don’t know where you are if you don’t measure,” said Skanska’s Caplan.

Often the best way to reduce the carbon emissions caused by developing real estate is to redevelop old buildings, rather than to create new ones from the ground up.

“You can avoid 70 to 90 percent of the embodied carbon by redeveloping buildings,” Woodson said.

Even keeping the drafty windows on an old building might prove to be more sustainable than tearing out windows and replacing them. Arup worked on a building where the windows had what’s referred to as a low, low R-value of about 0.6 in terms of energy efficiency. In comparison, a new single-pane window might have an R-value of 1 or 2 and an energy-efficient, double-pane window might have an R-value of more than 5, according to energy experts. But replacing the windows also come with both a financial cost and an embodied carbon cost.

“Over the 50-year life of those windows, it actually made more sense to keep the windows in place and avoid the embodied carbon [that would accompany] replacing the windows,” Woodson said.

Learn more about the Materials Movement at Knowledgefinder.uli.org.