Next time you find yourself in a new-ish US office building, scan the walls visible from the entryway. Within seconds, you are almost guaranteed to find a glittering circular plaque embossed with a leaf. It’ll be topped with the words LEED Platinum—or sometimes Gold, Silver, or just Certified.
In the late ’90s and early 2000s, LEED designation, awarded by the US Green Building Council to recognize leadership in energy and environmental design, was generally revered only in the niche world of architects devoted to reducing the carbon impact of the built environment. But the era of corporate greenwashing has transformed LEED into a badge of status. Recent constructions Apple Park, Google Bay View, and Salesforce Tower all boast LEED Platinum medallions. Amazon’s recently downsized HQ2 in Arlington, Virginia, will likely earn a Platinum plaque when it opens.
The proliferation of LEED plaques might suggest that the challenges of making buildings green have been solved. Scan a proposal for a structure from a major corporation and you will find hymns to biophilic properties that encourage plants to grow on a building, water recycling systems, and transparent photovoltaic glass. Sustainable building technology can be downright wild these days. A wood composite called mass timber can replace the high-emissions steel and concrete usually needed to frame new skyscrapers (as previously touted by WIRED). Nearly half of the energy demands of Google’s Bay View campus are met by its glamorous “dragonscale solar skin.”
Yet despite those innovations, the most sustainable building projects do not start from scratch. Reworking the old, unloved, and unsophisticated—even ugly—buildings that populate most of the urban landscape has more power to meaningfully reduce carbon emissions, waste, and pollution from the built environment. While buildings still stand, they embody all of the carbon and energy expended in their construction. “Even if you were to replace an old building with a brand-new, highly efficient building, it could take anywhere from 50-80 years to offset that building impact,” says Ian Zapata, global lead for building transformation and adaptive reuse at architecture firm Gensler.
Major renovations can require 50 to 75 percent of the carbon emissions of new construction, Zapata says. That makes the most sustainable building one that already exists—and there are plenty available right now. The crisis in the office real estate market triggered by the US work-from-home shift has led many cities to incentivize adaptive reuse, the renovation of existing structures into new buildings with different purposes. One of the most popular versions of this is converting offices to housing in places where downtowns have become ghost towns.
Adaptive reuse is not always easy, cheap, or popular, and it may be hard to convert the existing office stock into suitable housing, says Uwe Brandes, director of the urban and regional planning program at Georgetown University. A concrete office block is difficult to break into apartments with windows; conversely, a two-story strip mall poses serious challenges to a company looking for an office tower.
But there might be little else to do with these structures that have been partially or mostly abandoned. Tearing them down completely would be worse financially and for the planet. “People have to accept that they are going to have to lose money in order to retain some value,” Brandes says. “That’s a very uncomfortable conversation.”
If city planners and real estate owners can work through that conversation, adaptive reuse is a massive win for the climate. The emissions associated with the creation and disposal of materials inside existing structures are known in the trade as embodied carbon.
For a sense of scale, the global built environment contributes to about 40 percent of global carbon emissions, with about a quarter of that embodied carbon. The World Green Building Council estimates that the world’s stock of buildings will double in size to accommodate population growth between 2020 and 2040. Without some drastic increase in adaptive reuse, that means a huge spike in carbon released from destroying old buildings and reproducing them with new ones.
For any existing structure, the core materials—mostly concrete in the foundation, steel in support beams, and wood in floorboards—required carbon emissions to create, shape, transport, and assemble. Wood elements also physically store carbon captured by the trees when they were alive.
Ripping down an existing structure means wasting all the energy that went into the creation of its materials. The destruction itself also requires energy, and the waste materials must be moved to landfills. Add that to the energy and emissions required to make, transport, and assemble materials for a brand-new building, and it’s easy to see how making use of what has already been built is the more environmentally sustainable option.
Susan Piedmont-Palladino, director of the Washington-Alexandria Architecture Center at Virginia Tech, spoke to WIRED from inside an office building that embodies this premise. It was built in 1909 as an all-girls elementary school. “It’s a brick building, but the floor structure is all lumber that would have been cut down in the early 20th century,” she says. “Here I sit in this building with that carbon locked up and useful. If we were to demolish it, all of this stuff has to go to a landfill or reclamation.”
It’s now possible to quantify the metric tons of carbon that can be saved by not rebuilding from scratch, which can help persuade clients or planners to take the greener option. Most architecture and engineering firms now have access to software such as OneClick LCA or EC3 that can simulate scenarios for reusing existing materials and structures in a new project. This software can also be used to assess the financial value of old foundations, concrete, aluminum, wood, and other material and plan how to incorporate pieces of existing structure. If a structure cannot be saved, sometimes the materials can be reused—one type of concrete can be broken down and made into a different style of concrete, for example.
“This is approaching common practice,” says Christopher Pyke, a senior vice president at the US Green Building Council and an urban planning professor at Georgetown university. “It’s been a foundational part of the LEED rating system for the last five years, and in Europe it’s being codified in regulation.” LEED plaques on shiny new buildings can now reflect that not everything about a new construction is new or that the structure has been entirely repurposed from an old building.
One concept embraced by some European architects views buildings themselves as material banks—structures that store and save materials for future use. Some buildings are being designed to be easier to demolish in the future so the materials can be easily accessed for new projects.
Piedmont-Palladino, though intrigued by materials banking, is more compelled by the inverse idea—building for long-lasting but adaptable permanence. Making architecture more sustainable requires changing people’s mindset, she says, and resisting the allure of shiny green baubles.
“Architecture has been really quick to tear it down and make it new. The more people associate architecture with trends and with fashion, the more dangerous it gets. Same thing with urban design,” she says. “You are not the last people who are going to be involved with this building.”
Take the final project of Ludwig Mies van der Rohe, who is one of the most important architects of the 20th century but is fading from popularity. He created a modern, minimalist, “skin and bones” style that shaped American urban landscapes in the last 25 years of the 20th century. The Martin Luther King Jr. Library in Washington, DC, one of his final projects, was not completed until three years after he died, in 1972.
“It went through the stock market crash of reputation. Everyone loved it and then everyone hated it,” Piedmont-Palladino says. By the early 2000s, the library was neglected and reviled by borrowers and librarians for its dark, cramped, and unusable spaces. When the library system finally requested proposals for a renovation, many in DC called for it to be demolished and rebuilt from scratch. Piedmont-Palladino, on the selection committee for new architects for the project, was one of many who objected, on the grounds of both sustainability and aesthetics. “Mies, he’s hard to love. But were we really going to demolish this project that represented modernism coming to Washington?”
In the end, they didn’t. The library, which reopened in late 2020, looks shiny and new. The architects added wood, curves, windows, and sound, making the place warm and beautiful rather than austere and intimidating. But the structure retained its Mies’ facade, its history—and its embodied carbon.