A new model designed by researchers from U of T Engineering’s Centre for the Sustainable Built Environment (CSBE) finds that adopting the right mix of sustainable construction practices could enable Canada to meet it housing goals without blowing past its climate commitments.
“There is an obvious tension between our commitment to reducing our emissions and the need to restore housing affordability,” says Professor Shoshanna Saxe (CivMin), director of CSBE.
“But that tension only exists because of our status quo approaches to housing. As our research shows, we can build 5.8 million homes and cut GHG emissions from construction — it’s just that we must build them differently than we have in the past.”
Previous research from CSBE showed that in order to reconcile these two goals, homes built in 2030 will have to produce 83% fewer greenhouse gases during construction than those built in 2018.
In their latest paper, the CSBE team built what they call the future infrastructure growth (FIG) model. This computer simulation can forecast the emissions associated with new housing and infrastructure construction. It also enabled the team to evaluate the effect of implementing various strategies that aim to lower these emissions.
“We built our model using open data from the roughly 50,000 neighbourhoods we currently have in Canada,” says Keagan Rankin (CivMin PhD student), first author of the new paper published in Environmental Science & Technology.
“We looked at aspects such as how many units there are per neighbourhood, what type of housing stock comprises them, what length of road services them, etc. We then used what we know about current construction methods to model what the embodied emissions would be if you built a given number of new homes in the future, using the same distribution of neighbourhood types.
“Once we had that, we were able to ask the question: how much could we reduce those emissions by adopting sustainable construction strategies, such as denser neighbourhoods or better building design?”
The team looked at five strategies that could be implemented to reduce emissions associated with housing construction. They are:
Urban form
Analysis of existing neighbourhoods showed that emissions per unit are lower for those that contain more multi-unit buildings (either high-rise or low-rise) than they are for those that consist mostly of suburban, single-family homes. This strategy would involve a shift toward more of these multi-unit neighbourhood forms.
Higher infill rate
This refers to placing new housing in existing neighbourhoods — areas that are already built up. Because it reuses existing infrastructure, such as roads and water pipes, this new housing can be built with lower emissions than greenfield developments.
Circularity
This strategy involves re-using existing buildings or infrastructure in the construction of new ones. For example, renovating a single-family home to become a multi-unit dwelling would require fewer materials than razing it and starting from scratch.
Material technology improvements
Innovations in the way that materials such as concrete or steel are manufactured can reduce their carbon footprint. This strategy assumed that by 2030, our main construction materials will be produced with 20 to 25% fewer emissions than today.
Best-in-class design
The team found that some housing designs were associated with lower emissions per unit, such as making the home smaller overall through better layouts.
Another example involves the proportion of residential building that is underground: since basements are typically made of carbon-intensive concrete, the same sized dwelling with a smaller basement would have lower emissions as well. This strategy assumes increased use of these “best-in-class” designs.
Multiple strategies will be required
Using the FIG model, the team showed that building housing at the rate required to restore affordability without any changes to construction practices would cause Canada to overshoot its climate commitments by 437%.
However, if the above strategies are implemented, the FIG model suggests that they would in fact be able to reduce emissions to below the target level.
The model also showed that while all of the strategies were needed to reach the target, some of them had a stronger effect than others. For example, changing urban forms and using best-in-class design together accounted for about two-thirds of the improvements needed. By contrast, the strategies of infill, circularity and improvements in manufacturing each accounted for roughly one-tenth of the change needed.
The researchers found that for the next one to two decades, the most important things we can do to build more sustainably are to design better buildings and build denser neighbourhoods.
“The numbers are very close, and of course there’s a certain amount of uncertainty associated with all of these estimates, but it was good to see that we came in below the line, because it means the situation is not completely hopeless,” says Rankin.
“There’s no question that building 5.8 million homes by 2030 is an aggressive target. We may not get there, and if not, it would of course make it a bit easier to stay within our carbon budget.
“But we’ve done ambitious things as a country before, such as building a railroad from coast to coast in just five years. This analysis shows that the strategies we already know about are sound, and that all of them will be needed if we are going to prevent the worst impacts of climate change while also restoring housing affordability.”
Read a summary of the new paper on the Centre for the Sustainable Built Environment website.
By Tyler Irving
This story originally published by University of Toronto Engineering News