Even by the standards of London’s glassy skyscraper district, which includes buildings nicknamed for a walkie-talkie and a cornichon, the Tulip would have been a weird one. The design, by the British architect Norman Foster, featured a 50-foot-wide concrete shaft supporting a multilevel observation deck a thousand feet over London Bridge. There was no office space. No housing. Just a big pole with a view, which, in these times, looked less like a flower than a swab testing the London sky for COVID-19.
Last month, the U.K. government rejected the design. Among the reasons were many shortcomings that will sound familiar to American readers: loss of open space, harm to historic structures, limited community benefits. And one that might sound new: “very high embodied energy.”
Never mind that Lord Foster, as the 86-year-old architect of Apple’s ring-shaped headquarters is known over there, was pursuing the highest U.K sustainability rating. When planning inspector David Nicholson referred to the Tulip’s “unsustainable whole life-cycle,” he was making a broader assessment of the project’s environmental costs, from the demolition of the site’s existing structures to the concrete in the tower core.
For decades, sustainability in architecture, engineering, and construction has been evaluated based on a building’s energy bill. Assessing “embodied” energy or carbon instead is a new approach that requires counting the emissions that go into every part of the structure, from the gas-powered chainsaws in the forest to the assembly line in the lumber mill to the flatbed trucks that bring materials to the building site. This calculation might include future building materials, from replacement pipes to office supplies, and even the eventual carbon cost of demolition. The carbon footprint of a new building soars, for example, when you begin to incorporate the environmental cost of cement manufacturing, which accounts for 4 percent of global emissions.
Embodied carbon is an attempt, in other words, to more fully reckon with the impact of buildings on the planet. It requires we think anew about supply chains, development, preservation, and reuse, and it suggests a wholesale reevaluation of which buildings are good for the Earth and why.
That is the premise of RetroFirst, a campaign begun in 2019 by the British magazine Architects’ Journal and spearheaded by its managing editor, Will Hurst. “The architect’s favorite approach is ‘I’m a creative genius and I want to create this stunning building out of thin air that no one has ever seen before,’ ” Hurst told me. “For us, as Britain’s leading magazine for working architects, it felt quite risky to be like, ‘What you’re doing is wrong.’ ”
Whittling the ecological impact of buildings down to their electric bill makes a strong environmental case for new construction, which tends to have tighter fitting windows, central air conditioning, and other state-of-the-art systems. Once you consider the impact of construction itself, however, the argument for preservation gets stronger, in spite of your drafty windows and oil-burning furnace. “The greenest building is one that already exists,” Hurst said. Consumers seem to accept a version of this “embodied carbon” with fashion and electronics—thrifted clothes are more eco-friendly than fast fashion, and advocates fight for the “right to repair” old devices—why not apply the same logic to buildings?
Aside from helping clip the Tulip, this concept has popped up in the discussion of a new headquarters for British retailer Marks & Spencer on London’s Oxford Street, which the head of a national design board accused of “wasting embodied carbon” by planning to demolish rather than retrofit its existing building. It’s reared its head in a controversy over new court buildings in the City of London. When Associated Architects claimed this summer to be building the world’s first skyscrapers to reach net zero, the elusive gold standard for a building’s lifetime energy use, Dezeen founder Marcus Fairs cited the Birmingham, England, project in a column on greenwashing. Not counting embodied carbon in construction, he wrote, meant that the project “is not net-zero at all.”
Hurst has “managed to build enough momentum that the mainstream media is taking notice,” says Rachael Owens, head of sustainability at the British architect BGY, who coordinates the embodied carbon group for the U.K.’s Architects Climate Action Network. Designers tend to think their buildings will last for 200 years, rendering the carbon footprint of construction negligible over the building’s lifespan, she observed. “Lots of people who designed buildings in the ’60s, ’70s, and ’80s thought that too,” she said. “Those are the ones we’re knocking down now.”
Accounting for embodied carbon gives a shot in the arm to preservation and conservation movements, whose political valence in the United Kingdom—as in the United States—is complicated. On the one hand, affordable housing advocates say demolition and rebuilding mostly displaces the poor in favor of luxury housing. On the other, historic preservation is also invoked to keep desperately needed new housing out of rich neighborhoods. The British countryside preservation group CPRE—sometimes criticized as a front for NIMBYism—wants local jurisdictions to have more power to reject new housing on the basis of carbon emissions.
That’s one reason Anthony Breach, an analyst at the Centre for Cities think tank, argues the embodied carbon framework is incomplete. “Buildings in urban areas aren’t just a collection of structures. They create urban forms, and the shape of that urban form changes people’s behavior. Demolishing some buildings to build a much taller building may result in carbon being emitted in that process, but if that means people aren’t buying cars, that’s a reduction in carbon use. If we decide to freeze the urban housing stock, we risk paradoxically increasing carbon emissions if people are forced to live in ways that are less carbon-friendly.” (After Breach expressed his skepticism on Twitter, Hurst dedicated an article to interviewing unsympathetic experts about Breach’s tweets.)
What does all this mean for the big-picture goal of not cooking the Earth in a stew of carbon dioxide? That’s surprisingly hard to say. A handful of analyses places construction’s share of a building’s lifetime carbon emissions between 10 percent and 30 percent, though, as with money, a ton of CO2 now means more to humanity than a ton of C02 a hundred years in the future. That calculation also depends on a building’s lifespan: It’s easier to forgive the carbon expended on the construction of the Pantheon than that of a suburban office park that will stand 20 years before it meets the wrecking ball. Similarly, as architects and engineers fine-tune heating, cooling, and lighting systems toward “net zero,” embodied carbon’s relative role grows larger and larger.
The idea of embodied carbon in architecture, construction, and engineering has familiar parallels in other industries. We ask ourselves about the origins of our food and our clothing. Reporters probe the unsavory roots of supposedly eco-friendly products like electric cars and the grim end of life of green infrastructure like windmills.
Asking the same of concrete, steel, and glass has been the project of Myrrh Caplan, the sustainability director at the construction and development firm Skanska USA. Two years ago, she helped develop the Embodied Carbon in Construction Calculator, or EC3, to assess the carbon impacts of construction, from materials to transportation to on-site energy use. Some of the improvements Caplan counsels can seem picayune, such as insulating on-site work trailers, reducing idling, encouraging construction workers to use transit, and swapping out containers for open-bed shipping.
But the biggest slice of the pie is a big one indeed: manufacturing, for which EC3 evaluates suppliers using something called environmental product declarations—third-party audits performed for window-makers, cement companies, and other suppliers of building materials. Microsoft is using EC3 on its new Redmond, Washington, headquarters, and the company says the tool has helped cut the emissions from construction by 30 percent.
So far, the only incentive to use a tool like EC3 and focus on embodied carbon is good PR—and the PR isn’t even that good, since few people know what “embodied carbon” is. Green building awards such as LEED are mostly focused on operational energy. With some rare exceptions, regulations remain tailored to reducing buildings’ energy bills, with incentives aligned in favor of newer structures, not older ones.
The hope, says Kim Cheslak, the director of codes at the sustainability-focused New Buildings Institute, is that awareness of embodied carbon will change the way people think about design and construction. “The calculus it changes is, one, planning for longevity of buildings and, two, at the manufacturing level, starting to drive lower carbon manufacturing processes. It’s going to shift the whole market.” In essence, it’s a way for climate-conscious urbanites of the developed world to exert their influence on polluting industrial manufacturing processes that have long since been outsourced to the hinterland or overseas. Demand more from architects, and somewhere a timber company will clean up its act.
Step one, Cheslak explains, is just counting up the carbon. Step two is regulatory limits on highly polluting materials. And step three, the hardest part, is debating how that information can be used to decide what gets demolished, preserved, and built.
“Embodied carbon in existing buildings is a red herring, and it’s becoming part of the discourse in a way I think is a little alarming,” she cautions. “Old buildings are not necessarily better buildings. And they come with a lot of problems that aren’t necessarily embodied carbon, like asbestos and lead.” New buildings may not be great for the planet, in other words, but old buildings may have problems embedded in the walls that are worse than carbon dioxide.