Douglas Todd: The hidden climate costs of B.C.’s burgeoning highrises, Part II
Douglas Todd
The Vancouver Sun
Opinion: One study showed a neighbourhood of highrise towers would create 142 per cent more carbon emissions than a Paris-like lower-rise region with the same population.
Highrises create more carbon emissions than lowrises in part because “to build tall you need heavier structures, chunkier concrete foundations,” says Francesco Pomponi, of Edinburgh Napier University, who has produced an original study on the subject. Pictured here, Singapor construction with a backdrop of highrises. Photo by ROSLAN RAHMAN /AFP/Getty Images
Second in a series. Go here for part one.
While politicians claim they’re reducing the harmful daily pollutants caused by glass and steel highrises, that’s not the end of the climate worry.
Research reveals highrises come with elevated “embodied” costs, which refer to the amount of greenhouse gases they emit in their entire lifetime. That begins with the construction process.
It’s often ignored during environmental assessments. But when the massive concrete foundations of highrises are taken into account, their contribution to global warming skyrockets.
“’Embodied’ carbon emissions have been described as ‘the blind spot’ of the building industry,” says Vancouver sustainability specialist Paul Morris. “We need to consider embodied emissions from extraction, transportation, manufacture and construction. Concrete is the worst material for embodied emissions.”
In a groundbreaking study, Francesco Pomponi, of Edinburgh Napier University, has produced original environmental models that support the building of cities in which more people live closer together — but mostly in buildings of 10 storeys and under.
Given the carbon-intense materials needed to construct tall buildings, Pomponi’s team concluded that a neighbourhood of highrise towers would create 142 per cent more carbon emissions than a Paris-like lower-rise region with the same population.
A neighbourhood of highrise towers would create 142 per cent more carbon emissions than a Paris-like lower-rise region — pictured here — with the same population. Photo by JACQUES DEMARTHON /AFP/Getty Images
“Our findings show that high-density, low-rise cities, such as Paris, are more environmentally friendly than high-density, highrise cities, such as New York,” says Pomponi, lead author of the 2021 study in NPJ Urban Sustainability.
To put it another way, Pomponi found that, over a building’s projected lifetime of 60 years, dense, low-rise apartments produce 365 tons of carbon dioxide less per person than their skyscraper alternative.
One reason for that, Pomponi said, is “to build tall you need heavier structures, chunkier foundations.”
While Pomponi recognizes highrises can house more people than low-rises on the same footprint, that doesn’t take into account “you cannot put two highrise buildings as close as you can two low-rising buildings … For a lot of good reasons like privacy, ventilation and daylighting, highrise buildings need to be further apart.”
Even though more low-rise buildings might be needed to match the population capacity of skyscrapers, Pomponi says, despite possible extra land being required, low rises still produce less carbon emissions than building taller. He intends further studies on how the highrise-low-rise debate relates to transportation emissions.
Meanwhile, Pomponi’s work is echoed by a study of 650 buildings led by engineering professors Martin Rock, of Austria, and Marcella Saade, of the University of Sherbrooke in Quebec. They found so-called “energy-efficient” residential buildings emit up to 50 per cent more greenhouse-gas emissions during their lifetime. Much of that is due to the “carbon spike” from construction. The authors, in 2019, wrote, “Profound changes are needed in the production and use of buildings.”
Both Burnaby Mayor Mike Hurley and Sean Pander, the city of Vancouver’s manager of Green Buildings, acknowledged the seriousness of “embodied” greenhouse-gas emissions from the construction of concrete-steel-and-glass towers.
“However there are wide variations from the best to the worst,” said Pander, who, along with Hurley, stressed how their respective councils recently committed to further reducing such emissions, including through the use of “greener concrete mixes.”
On May 17, Pander said, Vancouver council voted to make developers cut embodied emissions. “The recommended requirements will come into effect by 2025 and put Vancouver on a path to achieving” a 40 per cent reduction by 2030, he said.
Gareth Sirotnik laments Vancouver councillors no longer seem to expect developers to make significant contributions to community life, to streetscapes or green spaces. Photo by Francis Georgian /PNG
For her part, Councillor Colleen Hardwick said that while other councillors often talk about “green concrete,” her understanding is it “only reduces emissions by about 15 per cent.”
The studies showing strong emissions from highrises are quite credible, said Hardwick. “It does make me wonder why council has only ever been shown a primarily concrete highrise solution to our housing and affordability needs.”
There is another concern — a third way to weigh the environmental impact of highrises, which focuses on their effects on community and the ecology.
“Green overcrowding.” “Density without amenity.” Those were two of the terms that Wendy Sarkissian, an environmental ethicist, used in her study to describe the arguments of those resisting former Vancouver mayor Sam Sullivan’s campaign to use highrises to create EcoDensity.
Sullivan was often accused of “greenwashing” developers’ crusade for more highrises, which are more profitable.
Sarkissian’s concerns are echoed in a recent book by the University of Chicago’s Kheir Al Kodmany. In a chapter titled Unsustainable Tall Building Developments, the professor of urban design joins planning gurus like Jane Jacobs and Jan Gehl in critiquing towers.
Low-rise neighbourhoods “emphasize the value of human scale and provide abundant opportunity for healthy social interaction,” Kodmany writes. “Therefore, in any urban area, no matter how dense, keep the buildings four storeys high or less.”
Kodmany also found tall buildings packed together create an “urban heat island effect … Dark surfaces that absorb heat from the sun, a lack of greenery, and waste heat and vehicles lead to higher temperatures.”
City of Vancouver handout renderings of the Broadway plan, which was approved by a majority of council Wednesday night. These drawings have been criticized for under-playing the impact of the scores of new highrises. See below for an alternative modeling of the Broadway Plan.
Then there are the wind tunnels. “Tall buildings create an adverse effect on the microclimate due to wind funnelling and turbulence around their bases, causing discomfort to pedestrians.”mfort to pedestrians.”
Birds also suffer. “Bird-glass collisions are an unfortunate side-effect of tall building developments throughout the world,” Kodmany says. Billions of birds perish each year from collisions with glass towers.
To enable people to connect and to combat heat islands, SFU sustainability specialist Alex Boston is among those who would like to see more green space included in the sweeping Broadway Plan, which seeks to house at least 50,000 more residents in highrises in a 500-block area of Mount Pleasant, Fairview and Kitsilano. It was approved Wednesday night in a seven-to-four vote.
Gareth Sirotnik, who lives a block from the first new highrise approved for the Broadway corridor, laments councillors no longer seem to expect developers to make significant contributions to community life, to streetscapes or green spaces.
“I live on the 14th floor of an 18-storey condo at the crest of Burrard-Granville Slopes I bought new 30 years ago. To gain six floors above the 12-floor guideline limit, my building developer signed away nearly 30 per cent of the property as a permanent public park, which we maintain.”
“The days for such amenities are gone. The city just approved a 39-storey building a block away without almost any public amenities beyond a grocery store.”
Even in the face of strong environmental concerns, some who argue for the necessity of highrises object that those who seek density via shorter buildings seem to want to turn every city into a version of central Paris, with blocks of repetitive six-storey apartment blocks.
However, Pomponi says cities don’t need to become monotonously lowrise. “Each building should not be identical to the next, with a very fixed and prescribed height. It’s more about having an upper threshold that, unless you’ve got a really, really good reason, it should not be exceeded.”
Artistic rendering, by Stephen Bohus, of the Broadway Plan. This “massing model” offers an earial view looking east along 7th Avenue, with Vine St. at the bottom. Bohus is a graphic designer with a degree in landscape architecture. He collaborated with architect Brian Palmquist.
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