There was no formal agenda on Feb. 12, 2018, when Bruce King and William Kelley met for lunch at the Lotus Cafe in San Rafael, Calif. But building regulation is a favorite topic of Kingâs, a structural engineer devoted to reducing carbon emissions related to buildings. So it was no surprise to Kelley, Marin Countyâs deputy director for building and safety, that King suggested it would âbe niceâ to craft a low-carbon concrete building code âto rein in the profligate overuseâ of carbon-intensive cement in concrete.
Kelley liked the idea of regulating concreteâs embodied carbon (EC)âthe greenhouse gases (GHGs) emitted during production. But funding was needed to support the writing of a code for low-EC concrete.
Two weeks later, King happened to be at a meeting of an ad hoc group trying to rebuild sustainably after Californiaâs devastating 2017 wine-country fires. There, he heard an announcement that the Bay Area Air Quality Management District would soon offer grants for novel methods of addressing GHGs. He alerted Kelley. Soon, Marin County applied for a BAAQMD grant, which it received on Oct. 4, 2018.
The funds, a maximum of $206,456, set the wheels in motion for developing the model Bay Area Low-Carbon Concrete Code. If approved by Marin Countyâs board of supervisors on Nov. 19, the code, unprecedented in the U.S. because it would limit EC in privateânot just publicâprojects, would be the first of its kind in the nation.
Kelley likes the Bay Area model code because it is simple to use for customers, plan checkers and enforcers. The document, only four pages long, has two sets of compliance pathways for plain and reinforced concrete: 1) limit cement in either the mix or the project; or 2) limit the global warming potential (GWP) either of a concrete mixâbased on an approved environmental product declaration (EPD)âor a project, taking into account all the mix designs.
If adopted, the code would apply only to unincorporated Marin County, population 60,000. That doesnât bother King. âWe hope it will be the code heard around the world,â says the founder of the 20-year-old Ecological Building Network (EBNet).
Kelley agrees, saying, âIf we can do this here, the code could serve as a template for other places.â Several other Bay Area counties are likely to follow suit if Marin County adopts it, he adds.
King is setting even wider sights on the regulation of ECâthe GHG emissions associated with raw material supply, manufacturing, transport, construction, maintenance, decommissioning and recycling of a material, a building or infrastructure. He wants the Bay Area code to serve as a model for other nations, especially India and China. He also wants EC codes for other high-EC products, such as most refrigerants.
EC, formerly called embodied energy, is not exactly a household term in construction. The main focus in green building codes and certification programsâsuch as LEED and the Living Building Challengeâhas been on reducing the operational carbon (OC) emitted by buildings.
EC plus OC make up the carbon footprint of a building. Initial or up-front EC, which accounts for most of a materialâs or a productâs carbon, refers to GHG emissions from the cradle to the site gate.
âMany construction materials can be made to very similar performance standards with 50% or more carbon savings,â because manufacturing process, mix composition, recycled content and electricity or energy source have a dramatic effect on carbon emitted during manufacture, according to the University of Washingtonâs Carbon Leadership Forum. CLF is a nonprofit coalition of 40 construction industry sponsors, founded in 2009 by its director, Kate Simonen, also a professor at the College of the Built Environments.
âCarbon-aware specification and procurement policies, backed by a contractual requirement to deliver verified EPDs for materials delivered to sites, can drive change,â asserts CLF.
Reducing initial EC is no easy task. It has been fraught with problemsâfrom a lack of product and material data to data too complex to evaluate. âItâs an incredibly daunting and new challenge to address in a design process,â says Victoria Burrows, director of Advancing Net Zero for the World Green Building Council.
A net-zero EC building is one that has minimal up-front carbon, with all remaining