The assessment of embodied carbon in the built environment has been challenging due to insufficient data. To tackle this knowledge gap, civil and environmental engineers have developed a new tool that analyzes the embodied carbon in over 1 million buildings in Chicago. Their recently published research highlights 157 distinct architectural housing types in the city and introduces a pioneering visual analysis tool that provides a detailed evaluation of embodied carbon, assisting policymakers in efficient urban carbon reduction strategies.
The constructed environment—which encompasses buildings, highways, bridges, and various infrastructures—contributes nearly 40% of global greenhouse gas emissions, exacerbating climate change.
While many construction standards have aimed at creating “greener,” energy-efficient buildings, efforts shouldn’t just focus on operational emissions, according to Ming Hu, associate dean for research at Notre Dame’s School of Architecture. Policymakers and industry representatives need to embrace a wider perspective that incorporates the impact of embodied carbon in current structures.
Embodied carbon refers to the greenhouse gas emissions linked to a product’s entire life cycle. This includes the extraction, production, transport of materials, the creation of the product or building, and its eventual disposal or demolition. Notably, materials like asphalt, concrete, and steel have significantly adverse effects on the environment in construction.
However, assessing the impact of embodied carbon in the built space has been tricky due to a lack of data. To fill this knowledge void, Hu and Siavash Ghorbany, a graduate student in civil and environmental engineering at Notre Dame, have devised a method to evaluate the embodied carbon in more than 1 million buildings across Chicago.
Their research identifies 157 unique architectural types in the city and offers the first-ever visual tool for detailed analysis of embodied carbon, aiding policymakers in making informed decisions regarding urban carbon mitigation.
“Previously, it was often hard to visualize this concept and understand the importance of preserving and reusing existing buildings,” Hu explained. “We see this as a clearer, more straightforward way to guide policymakers and the public in making informed choices. If I were Chicago’s mayor, I would see this data and think, ‘Before I demolish this structure, I should reconsider because it already contains a significant amount of embedded carbon. Should I renovate and reuse it, or choose to demolish it and construct a new building, which would raise the overall embodied carbon?'”
Hu and Ghorbany successfully pinpointed areas in the city with high emissions and identified specific architectural styles—providing practical information to urban development stakeholders. They discovered that extending the lifespan of buildings from the current average of 50 years to 75 years, while also reducing their size by just 20%, could reduce carbon emissions by two-thirds.
Hu stressed that her research revealed no situation where it would be environmentally logical to demolish an existing building for a new one—even if the new structure is more energy-efficient.
“When considering the building’s total lifespan, renovating existing structures generates significantly lower carbon emissions across their entire life cycle, including both operational and embodied carbon,” explained Hu, who also serves as a faculty member in the College of Engineering. “This is largely because the ‘payback period’ for a new building is typically around 20 years due to the significant greenhouse gas emissions associated with its construction. Therefore, if we can prolong a building’s life cycle to 70 or 80 years, reusing it definitely becomes the more rational choice.”
“We should prioritize reusing buildings. The real question is how extensively we want to renovate or retrofit them.”
Hu and Ghorbany selected Chicago for this study for several reasons: its proximity to Notre Dame, its rich architectural heritage, and the fact that it ranks as the 8th highest city for greenhouse gas emissions globally. They intend to expand this project to evaluate embodied carbon in cities nationwide.
Supported by funding from the National Science Foundation, the researchers used machine learning and artificial intelligence to develop a comprehensive dataset for their analysis, drawing from numerous existing databases, including the National Structure Inventory and Cook County Open Data for Chicago.
By matching different data types using geolocation and categorizing them by features like material composition and roof design, they calculated the total embodied carbon of buildings by multiplying the baseline emissions associated with each housing type by its footprint.
Ghorbany, who is also a Graduate Scholar at the Lucy Family Institute for Data & Society and has an architecture degree, emphasized the importance of creating an accessible, interactive mapping tool for visualizing their results.
“Our aim was to develop a user-friendly platform to engage with this data,” he said. “We designed this tool so users can explore various scenarios by selecting different architectural types and filtering by year or emission types. I hope cities will use this to lower their carbon emissions and combat climate change effectively.”
Hu echoed this sentiment, highlighting that the advantages of this research extend beyond environmental concerns; they also hold cultural significance.
“First, we must have a clear understanding of the embodied carbon in our built surroundings,” she stated. “This is information we’ve never had before, and it’s still lacking on a national scale. Once we achieve this, we can make informed choices to cut carbon emissions, in part by extending the life of these buildings.”
“Moreover, beyond environmental gains, preserving these buildings holds social and cultural value as they contribute to the architectural identity of the city.”
