As property values rise in Vancouver, an overwhelming number of single-family homes are being demolished to make way for more energy efficient homes. Yet, according to a new report from the University of British Columbia (UBC) and MountainMath Software, this cycle of demolish and replace may come with a hefty price tag: an increase in overall greenhouse gas emissions.

"The Zero Emissions Building Plan instituted by the City of Vancouver, which aims to eliminate emissions from the operations of new buildings by 2030, has already improved the energy efficiency of new homes," said study author Joseph Dahmen, a professor of architecture and landscape architecture at UBC. "This is a significant accomplishment, but the teardown cycle is preventing many single-family homes from surviving long enough to 'pay back' the initial impacts caused by construction materials, which are not accounted for in the current plan."

Although the newly constructed homes will operate using less energy, their construction is expected to result in one to three million tonnes of additional emissions between 2017-2050.

"In Vancouver, we estimate that new single-family homes will take an average of 168 years for efficiency gains to recover construction impacts," says Dahmen's collaborator and co-author, Jens von Bergmann of MountainMath Software. "The payback time will be shortened as efficiency requirements become more stringent leading up to 2030, but Vancouver's teardown cycle will still cause overall emissions to increase, unless we change residential zoning to permit denser forms of housing."

The research team is now calling for city planners to reconsider how residential areas are zoned in Vancouver, encouraging developers and architects to investigate housing designs that will last longer while also yielding environmental benefits much sooner.

"Single-family homes are among the most carbon-intensive building types. In contrast, low- to mid-rise row housing, such as that found in Montreal, Berlin and Paris, could increase overall housing stock, address affordability and create a more vibrant public realm," said Dahmen. "We could design similar homes for Vancouver using mass timber from sustainably harvested wood from B.C. forests. This would provide additional environmental benefits by removing carbon from the atmosphere and storing it in the building materials themselves."

The research is detailed in the journal Energy and Buildings.

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