With conventional construction norms and codes set to produce a 376% overshoot of Canada’s climate commitments if the country meets its housing targets, experts are calling for a systemic shift to best-in-class design of multi-unit buildings, better material use, and “doubling circularity.”
The current “take, make, waste” approach to construction has proved costly for both equity and emissions, write the authors of a recent study by the University of Toronto Centre for the Sustainable Built Environment (CSBE). Based on life cycle consumption, Canada’s construction sector was responsible for around 90 megatonnes of carbon dioxide equivalent in 2018, “equivalent to over 8% of Canada’s total greenhouse gas emissions,” while delivering less than a third of the new housing the country now needs each year.
In the United States, construction creates more than 50 million tons of embodied carbon dioxide emissions annually, equivalent to 138 natural gas-fired power plants, or the annual emissions from whole countries like Norway, Peru, and Sweden, the Rocky Mountain Institute wrote last year.
And in the European Union, emissions from the full life cycle of construction—raw material extraction, manufacturing building products, and final construction or renovation—“accounts for 5% to 12% of total member states’ emissions”, writes Clean Energy Wire.
“Globally, 13% of materials delivered to construction sites are sent directly to landfill without being used at all,” CEW adds, despite rocketing demand for building materials in the urbanizing Global South. Around 75% of the infrastructure needed across the globe by 2050 has yet to be built, CEW says, even though things look very different in Europe: “Up to 95% of the bloc’s buildings expected to be standing in 2050 already exist.”
“We have done our development in Europe,” said Danielle Densley Tingley, a senior lecturer in architectural engineering at the University of Sheffield. “We need to be mindful of what materials we are using and what we should be freeing up for others to use globally when we’ve got limited carbon budgets and limited resources.”
“Applying circular economy principles to construction—keeping materials in use for as long as possible, then reusing them in the next project or recycling them—holds great promise,” writes CEW.
When people think about circular economies, they often envision loops through which materials cycle indefinitely. In reality, “there is a hierarchy to circularity,” CEW says. It demands that buildings be designed and built to last with the lowest possible embodied carbon, and that rebuilds and “adaptive re-use” be considered before the wrecking ball swings. Only then must the recycling (often downcycling) of component parts begin.
But, this hierarchy isn’t always applied, Densley Tingley said. “Designing efficiently often gets left out of the circularity discussion.”
Such neglect is hampering the fight to contain global heating, CEW writes. A 2019 report found that shifting to a circular built environment could reduce global carbon emissions from building materials 38% by 2050, “thanks to reduced demand for new steel, aluminium, cement, and plastic.”
Poor Design Blocks Circularity
Moving in that direction will require closer attention to the minute details of the way buildings are built.
“Poor design and lack of information mean that, globally, only 20 to 30% of construction and demolition waste is recycled or reused,” writes CEW. Hard-to-remove nails, glue, and possible hidden toxins like asbestos continue to make the recycling of construction materials a hard sell.
“While the concept of urban mining has picked up—the notion of finding, extracting, reusing or recycling materials already built into urban areas—there is still no requirement to either assess the re-usability potential of materials inside of buildings being demolished today, or to document what materials go into new buildings or refurbishment projects,” CEW adds.
A business model wedded to premature obsolescence is another “primary barrier”. The typically long lifespan of a building means any profit sharing under a circular model would only occur “decades down the line,” CEW explained.
With the business case for circularity so unappealing, regulation is urgently needed, said Lars Autrup, CEO of the Danish Architects Association. Taxes on carbon emissions, life cycle assessment requirements, and the use of Environmental Production Declarations (EPD) are some of the regulatory tools available.
For Autrup, it’s all about moving to see buildings as “material banks,” rather single-use structures.
Building Circularity In Canada
The emissions benefits of a circular economy in construction are clear, but one size does not fit all. What works for the EU, with a fairly static population, will not be immediately transferable to Canada, where the population is growing, Shoshanna Saxe, an associate professor of civil and mineral engineering at the University of Toronto and Canada Research Chair in Sustainable Infrastructure, told The Energy Mix.
Building resource recycling is rare in Canada simply because “we tear down much, much less than we build,” said Saxe, a co-author of the CSBE paper on construction emissions. Canada’s “massive housing deficit means we have to build at a rate very different than Europe,” Saxe added. “And so how they approach things there, while inspiring and useful, is occurring in a really different context.”
That said, there are a lot of things the Canadian industry can do to become more circular, Saxe said. The first step is to “build more intensely,” maximizing the use of every square metre of space. She praised British Columbia’s effort to change regulations and allow multi-unit buildings to be served by a single staircase, rather than the mandated two. The current model leads to long hallways of wasted space and a dearth of windows, Saxe said.
Saxe is also a big fan of multiplex conversions because they “allow us to more intensively use the thing which we’ve already built.” Saxe echoed Densley Tingley’s comment that “the most sustainable building is the one you don’t build.”
But Canada desperately needs to build more affordable homes, and greening the housing stock while fighting to get that stock built will depend heavily upon one thing, Saxe said: embracing multi-unit buildings of the best possible design.
According to another study published in November, of which Saxe is also a co-author, meeting Canada’s housing targets using conventional construction norms and codes will produce a 376% overshoot of the country’s climate commitments. Avoiding that overshoot will require “a near total reliance on multi-unit buildings and best-in-class design supported by improvements in material manufacturing [and] building within existing urban boundaries.”
Builders will also have to embrace “doubling circularity,” reusing the foundations from previous structures to reduce the need for new concrete, and subdividing existing buildings into multiple units.
