A new study warns that cities worldwide need to cut greenhouse gas emissions from building construction and infrastructure by more than 90 percent over the next two to four decades to prevent global warming from exceeding 2°C. Researchers from the University of Toronto analyzed emissions for 1033 cities, highlighting the need for radical changes in building design and materials amid growing housing demands. The findings emphasize efficient multi-unit housing and better resource use over simplistic solutions like widespread wood construction.
Global construction accounts for 10 to 20 percent of greenhouse gas emissions, largely from cement production. To align with the Paris Agreement and stay within the 2°C carbon budget, cities must drastically reduce these emissions while addressing housing shortages in places like Canada, the US, and Australia.
Shoshanna Saxe at the University of Toronto notes the challenge: “Canada wants to triple its rate of housing construction. The US has a housing deficit, Australia has a housing deficit, [and so does] basically every country you go to right now. How do we build so much more while also demanding that we pollute so much less?” Her team, surprised by the lack of city-level emission studies during work for Toronto, developed a method to estimate current and future construction emissions.
Team member Keagan Rankin combined the EXIOBASE model, which assesses product lifecycles, with data on city populations, growth, investment, and employment. This approach revealed that continuing to build single-family homes would exceed emission budgets. Instead, cities should prioritize multi-unit housing, efficient designs that minimize wasted space and structure, and materials like wood or recycled concrete—though Saxe cautions against over-relying on wood, as it still produces emissions unless optimistic assumptions about forestry hold.
“We’re already building buildings that meet these targets; we just have to build more of the good and less of the bad,” Saxe says. “We’ve had these skills and this knowledge for decades; we just have to use it.”
Rankin adds that cities are eager for climate action and control construction but often lack resources for budgeting. Prajal Pradhan at the University of Groningen agrees: “Without reducing emissions from the construction sector, we cannot meet the Paris Agreement, even if we reduce other emissions to zero.” Susan Roaf at Heriot Watt University stresses lifetime efficiency, such as natural ventilation, warning against “super-polluting ‘zombie buildings’.”
Saxe also advocates prioritizing projects: in Canada, redirecting resources from oil and gas infrastructure could allow housing for 10 million people without raising emissions. The study appears in Nature Cities (DOI: 10.1038/s44284-025-00379-8).
