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Heating and cooking aren’t the only sources of building emissions



Massachusetts lawmakers and municipal leaders are increasingly pushing for measures that would lower the greenhouse gas emissions associated with building materials. 

“We’ve seen a lot of new interest and momentum,” said Rebecca Esau, manager of the carbon-free buildings practice at the clean energy think tank RMI. “At the local level especially there’s a lot going on.”

The state legislature is considering three bills that would address “embodied carbon,” a measure of the carbon dioxide emissions generated in extracting, manufacturing, transporting, maintaining, and eventually disposing of building materials. The communities of Cambridge, Brookline, Newton and Amherst have all taken up the question as well.

Much of the conversation around reducing the climate impact of buildings so far has focused on the greenhouse gas created by the day-to-day use of a building, generally called “operational emissions.” While embodied carbon has received little notice, it makes up an estimated 11% of global greenhouse gas emissions.

And it is a time-sensitive problem, advocates said. The amount of emissions going into the atmosphere matters, but so does when they are released: A ton of emissions that goes into the air today will cause compounding effects into the future. So avoiding a ton of carbon dioxide today by choosing less carbon-intensive building materials will have more impact than avoiding that same ton of emissions five years from now. And because buildings last for decades, each new structure offers only one chance to choose the right materials and lock in the impact of lower embodied carbon emissions. 

Concrete, steel, glass and insulation are among the materials that contribute the most to a building’s embodied carbon. Cost-effective, lower-carbon versions of some materials are already available — lower-embodied concrete can reduce emissions by 14% to 33% with little cost premium, for example, according to a 2021 report from RMI. And alternative materials such as mass timber, which is a renewable resource and can sequester carbon, are also becoming more common, albeit slowly. 

“Everyone knows that has to be addressed, but the focus really has not been there,” said Logan Malik, interim executive director of the Massachusetts Climate Action Network. “We know that there are solutions to addressing it; we know it has to be done, so let’s start moving things forward.”

Cities and towns taking the lead

In Massachusetts, a handful of cities and towns has been leading the charge.

The city of Cambridge, which has been working to curb building emissions since 2015, made the reduction of embodied carbon a part of its net-zero action plan in late 2021, with provisions going into effect this January. The plan, which applies to buildings larger than 50,000 square feet — with exceptions for laboratories and affordable housing —will start by collecting data to determine baseline embodied carbon emissions. In a few years, the city will begin requiring reductions relative to that baseline, ratcheting up the required reductions to 50% over the years. 

“It is our intention to move beyond requiring an accounting, to also push in the direction of reducing,” said Sussanne Rasmussen, Cambridge’s director of environmental and transportation planning.

Neighboring Brookline has been addressing embodied carbon for the past two years. In November 2021, the town passed a resolution calling for the use of concrete with 10% lower embodied emissions than conventional standards in the construction of any town building. The measure also requires the city to recycle concrete that is removed in the course of municipal projects, and to encourage private developers to use lower-embodied-carbon concrete in their designs as well. 

In April, the city of Newton added a provision to its special permitting process requiring buildings larger than 20,000 square feet to conduct an embodied carbon analysis as part of their building permit application. Eventually, the city could add limits on embodied carbon, but the focus for now is on education and data gathering. 

“Let’s learn about these impacts and how to measure them, and get developers and designers up to speed on the whole topic,” said Mark Webster, a structural engineer and member of the Green Newton Building Standards Committee. “Once we have a nice set of data from around the region, we can start to use that to set thresholds.”

State-level solutions

Municipal action has been necessary because there has been little done at the state level so far to address embodied carbon emissions. 

“We have been doing these things and pushing it along because there hasn’t been action at the state level,” Rasmussen said. “And it is so urgent that we don’t add emissions.”

At the same time, it can be difficult for municipalities to effectively take action because of conflicts between state and local authorities. Cities and towns cannot require the use of certain materials in private projects, because these requirements fall under the authority of the state building code. Municipalities, therefore, have to find other ways to push for lower embodied carbon, such as Brookline’s focus on public projects and Cambridge and Newton’s use of the special permit process for larger buildings. 

These varied strategies should lay the groundwork for further action by the state and by other cities and towns by demonstrating the feasibility of lower-embodied-carbon construction, said Lisa Cunningham, a Brookline resident and co-founder of climate advocacy group ZeroCarbonMA.

“When you get multiple communities moving forward to enact these resolutions, you can point to it [and] say, ‘We’ve done this; this is a great solution,’” she said. “The power of local action is very important.”

And broader interest is starting to pick up. The state legislature is now considering three bills addressing embodied carbon. One bill would require state building projects to use low-embodied-carbon concrete. The second would create a “buy clean” policy, which would require public projects to meet progressively tighter limits on embodied carbon. The final bill calls for the state to establish an embodied carbon advisory board and to incorporate plans to measure and reduce embodied carbon into stretch building codes — optional, more environmentally stringent codes used by most municipalities in the state. 

“That is a real indication of how much support there already is from folks in the legislature,” Esau said. 

Other states have already gotten out ahead on tracking and restricting embodied carbon. California, Colorado, Oregon, New Jersey and New York have all passed “buy clean” legislation of their own. But with growing local efforts and the bills pending in the legislature, advocates hope Massachusetts will soon be among those with the most aggressive policies. 

“We see it as creating an opportunity for Massachusetts to be a leader on the issue of embodied carbon,” Malik said.

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