University of Toronto – U of T study highlights tension between Canada’s climate and housing goals

University of Toronto – U of T study highlights tension between Canada’s climate and housing goals
University of Toronto – U of T study highlights tension between Canada’s climate and housing goals

Canada cannot meet its emissions reduction targets and new housing simultaneously unless it makes drastic changes to building practices, according to research from the University of Toronto’s Faculty of Applied Science and Engineering.

The new study, published in Environmental research: infrastructure and sustainabilityfound that if Canada is to stay within its emissions targets, homes built in 2030 must emit 83 percent less greenhouse gases during construction than homes built in 2018.

“Our analysis shows that in 2018, the latest year for which we have data, the construction sector in Canada was responsible for the equivalent of 90 megatonnes of CO2,” he said. Shoshanna Saxeassociate professor in the Department of Civil and Mineral Engineering and one of the study’s senior authors. “That was about eight per cent of Canada’s total emissions at the time, but we didn’t produce nearly as much housing as we needed then, let alone what we need now. To restore housing affordability, we need to triple the rate of housing construction by 2030.”

At the same time, Canada’s 2030 greenhouse gas emissions target must be 40 percent lower than in 2005, or 443 megatonnes, Saxe said.

“That means that, if nothing changes, by 2030, nearly half of all allowable emissions in Canada will be from construction alone.”

Saxe is director of the University of Toronto’s Centre for the Sustainable Built Environment (CSBE). The centre studies the construction and urban planning pathways that can help Canada meet housing and infrastructure needs while reducing greenhouse gas emissions, in line with the Paris Agreement, an international treaty on climate change adopted in 2015.

The CSBE team’s first step was to quantify the scale of the challenge. However, they encountered obstacles in collecting data on the carbon footprint of the construction sector.

“What we found was that this data is spread across a lot of different parts of the economy: manufacturing, buildings, transportation, etc.,” Saxe says. “There are also questions about consumption versus production: If a piece of steel is made in China and used for a building in Canada, whose emissions are those?

“Until now, it has been difficult to get a picture of the construction industry as a whole, which is partly why this sector has been overlooked.”

Hatzav Yoffea postdoctoral researcher and lead author of the paper, used what is known as an environmental extended input-output model to conduct a high-resolution, top-down analysis of the Canadian construction industry.

The researchers calculated that residential construction was responsible for the largest share of total construction emissions, namely 42 percent.

Their model also allowed them to ask another question: by how much do emissions per house built need to fall to stay within emissions targets, given the expected increase in house construction?

“You can’t just take the overall reduction target of 40 percent and apply it to the construction sector. That won’t be enough, because you’re also tripling the speed of house building,” Saxe says.

The other members of the research team were: Keagan Rankina PhD candidate in the Department of Civil and Mineral Engineering, Daniel Posenassociate professor at the department of civil and mineral engineering and Christian Bachmannassociate professor at the University of Waterloo.

While the study highlights the tension between Canada’s housing goals and climate targets, Saxe and her colleagues believe it is still possible to reconcile the two, and they are exploring how to address this challenge.

“For example, if you build denser, you use fewer materials to build the same number of units. If you’re strategic about where you place those units, you don’t have to build as many new roads or sewers to service them,” Saxe says.

“We can also think about changing the balance between housing and other types of infrastructure, such as oil and gas infrastructure.

“If we ultimately want to build what we need while avoiding the most disastrous consequences of climate change, we need to think seriously about how we can achieve more with less.”