The built environment—which includes the construction and operation of buildings, highways, bridges and other infrastructure—is responsible for close to 40% of the global greenhouse gas emissions contributing to climate change.

While many building codes and benchmarks have focused on constructing "greener," more energy-efficient new buildings, it is not enough to seek to reduce emissions in operations, said Ming Hu, the associate dean for research, scholarship and creative work in Notre Dame's School of Architecture. Rather, policymakers and industry leaders must take a broader view by examining the role of embodied carbon in existing buildings.

Embodied carbon represents the amount of greenhouse gas emissions associated with the entire life cycle of a product, including the extraction, production and transfer of materials; the manufacture of the product or building; and its eventual disposal or demolition. In the construction field, materials such as asphalt, concrete and steel, in particular, have dire consequences for the environment.

The impact of embodied carbon in the built environment has been difficult to assess, however, due to a lack of data. To address that knowledge gap, Hu and Siavash Ghorbany, a Notre Dame graduate student in civil and environmental engineering, have created a new way to analyze the embodied carbon in more than 1 million buildings in Chicago.

Their research, recently published in Carbon Management, identifies 157 different architectural archetypes in the city and provides the first ever visual analysis tool to evaluate embodied carbon at a granular level and to help inform policymakers seeking to strategically plan for urban carbon mitigation.

"Before, it was often difficult to visualize this concept and to make a case for why we want to preserve and reuse existing buildings," Hu said. "We feel this is a more clear, direct way to help the policymaker or layperson make informed decisions.

"If I were the mayor of Chicago, I could look at this and say, 'OK, before I tear down this building, I have to think twice because there's already a lot of carbon embedded in this structure. Do I want to retrofit and reuse this building, or do I want to knock it down and build new, which will increase the overall embodied carbon?'"

Hu and Ghorbany were able to identify emissions-intensive geographic zones and specific archetypes within the city—delivering actionable data to urban development stakeholders. They also found that increasing the average lifespan of buildings from the current 50 years to 75 years, and reducing their size by just 20%, can decrease their carbon emissions by two-thirds.

Hu emphasized that her research has found no scenario where tearing down an existing building to build something new—even if that new building is more energy efficient—makes sense, from an environmental perspective.

Find out more: Phys.org