The architecture community is abuzz with talk about reducing embodied carbon in buildings. We asked Jennifer O’Connor, president of the Athena Sustainable Materials Institute, to give us a primer.
by Jennifer O’Connor
“Embodied carbon” is an imperfect term. The word “embodied” sounds like we’re talking about carbon encapsulated in a material. Instead, it’s shorthand for all the lifetime indirect greenhouse gas (GHG) emissions due to a building—in other words, everything other than emissions from building operations. For example, the GHGs emitted from diesel combustion in transporting a product to the building site are part of the embodied carbon in the product.
Embodied carbon is also known as value chain emissions, upstream/downstream emissions, or Scope 3 emissions.1 The complete carbon footprint of a building includes all of these GHG emissions. A true zero-carbon building would account for and offset its operational carbon as well as its embodied carbon.
Most embodied carbon emissions are upstream or “upfront” of building occupancy—they are primarily related to the manufacturing of materials. This includes the extraction of raw resources, manufacturing of building products, and transportation of those products.
GHG emissions due to material manufacturing, use and disposal are more significant than many people realize. First, these emissions are a big upfront GHG pulse in the life of a building, which makes them a good near-term target for climate change mitigation. Second, as buildings approach net-zero carbon operation, embodied impacts will make up most of the carbon footprint in the built environment.
Embodied carbon has a lot of buzz lately, and that’s inspiring to some design professionals. Kevin Welsh, Senior Sustainability Advisor at Integral Group, is one of them: “It’s great to see the accelerating interest in embodied carbon. It’s the next evolution of our industry’s enthusiasm and dedication towards reducing the impacts of projects.”