Most ‘Green’ Buildings Aren’t Really Carbon-Neutral — Yet

Phoenix House, in the U.K., gets closer than some.
Art: CSK Architects

Behold the building of the future: mossy stones lying strewn around a hill outside the English city of Windsor, carved, shaped, and incised in the fashions of centuries past. These chunks of 18th-century wall and Victorian cornice have lain in the woods for nearly 100 years, remnants of a British country home dismembered, like so many others, so there’d be nothing left to pay taxes on. Now Matthew Barnett Howland, an architect at the Eton-based firm CSK, and the business-communications entrepreneur Andrew Try, the property’s current owner, are hoping to press those relics into service for a new structure. Sure, it would probably be cheaper and certainly quicker to haul them away and import freshly quarried rocks. But to Howland that option would be the essence of wastefulness. Instead, he is designing Phoenix House, reviving old materials with contemporary technology. Every shard is labeled, sorted, cleaned, and recorded as a 3-D scan, so that his team can figure out how to recut and reassemble it in new arrangements, joined like beads on a steel rod. The result is less a reconstruction, more a reincarnation.

“We try to give architectural character to environmental sustainability across the whole of a building’s life,” Howland says. Those modest words portend a revolution, and like any self-respecting architectural guru, he has distilled his approach into a mug-worthy aphorism: Form follows life cycle. It means that a design begins not with a vision of a completed creation, gleaming on day one of its existence, but with a story that simultaneously rewinds to the distant past and projects into a hazy future.

Plundering history’s detritus for new construction has been the way of the world for as long as stones have outlasted the people they sheltered. Cairo is full of medieval buildings that were “quarried” from the skin of the Great Pyramid; salvaged bits of the Colosseum are embedded in walls all over Rome. But that’s not how it works today, when putting up a new structure usually begins with demolishing the one that’s there, carting away the rubble, and scraping the site back to bedrock. Each of those steps produces greenhouse gases. So do most human activities — eating, traveling, staying warm — but construction is in a class by itself. Existing buildings contribute about 40 percent of the world’s carbon emissions, and just churning out concrete and steel to erect more adds another 16 percent. A building pumps out carbon at every phase of its existence, from the moment a rock is jackhammered out of a mountainside until the day, 60 or 100 years later, when workers strip it for parts and pack the waste off to the landfill. To build is to pollute in order to create something that will keep polluting.

Until recently, the effort to mitigate the damage has focused almost exclusively on operational efficiency, which comes into play as soon as the building is complete. We have an array of effective new techniques for keeping the temperature comfortable, the lights on, and the water running, all on a shrinking carbon budget. Now, though, engineers, contractors, developers, and architects like Howland are starting to recognize that they’ve tackled the easiest challenge first. The next job is to cut embodied carbon, the kind produced by quarrying, logging, milling, smelting, firing, manufacturing, assembling, shipping, trucking, digging, carting, craning, pouring, glazing, polishing, installing, glazing, and all the other steps that lead up to opening day.

Urban Sequoia, SOM’s proposal for a truly green skyscraper.
Art: SOM | Miysis

Measuring the total impact of a building is complicated, and it’s made more difficult by the industry’s penchant to trumpet more good news than the data justifies. A collection of activist organizations have published a skeptical primer, called Not Zero that points out that claims of zero emissions are often based on an environmental version of bookkeeping gimmickry. The effort to eliminate emissions — or to appear to eliminate emissions, or to appear to want to eliminate emissions — has churned up some confounding terminology. Unhelpfully, carbon negative and carbon positive mean pretty much the same thing: taking more bad stuff out of the air than you pump in. Net zero often means the opposite: atoning for the carbon you’re spewing now with the carbon you plan to suck up at some point in the future — or that someone will suck up. (The most immediate way to do that is to buy carbon offsets, paying non-polluters to non-pollute while polluters do what they like.) If you could build a skyscraper out of bullshit, architecture would be the world’s greenest profession.

The architecture writer Fred Bernstein, who teaches a Princeton course on embodied carbon, has little patience for such wishful thinking. “If we release enough carbon now to trigger a true climate catastrophe, it won’t matter how efficient our appliances are 50 years from now,” he said in a blistering lecture that accused some prominent figures of high-profile hypocrisy. (He also politely chided me for my insufficient skepticism of Harvard’s House Zero, a supposedly revolutionary laboratory for green building design.) Bernstein pointed out a crucial conundrum: Lowering emissions from operation tends to increase emissions from construction, and vice versa. “Installing lots of stuff to reduce carbon emissions is oxymoronic.”

The green Establishment is dominated by certification programs like BREEAM and LEED, which bestow points for efficient operations but downplay embodied carbon. Foster + Partners’ Bloomberg Building in London, for example, won the 2018 Stirling Prize partly for its environmental ambitions. Dragging down the costs of heating, cooling, and lighting required a lot of sustainability bells and whistles (what Bernstein would call “installing lots of stuff”): a façade full of metal fins for shade, polished-aluminum ceiling panels that reflect light, soften noise, and cool the air (“combining various elements of a typical office ceiling into an energy-saving integrated system”), and extra-large helpings of bronze, steel, sandstone, glass, and wood. The designers themselves have admitted that even the cleanest, greenest of contemporary buildings is still stoking the atmosphere’s fire.

The Sara Kulturhus Center.
Photo: Jonas Westling

Foster’s firm is not alone in its pay-now-save-later philosophy. The crack Norwegian sustainability team Powerhouse claims that each of its buildings operates so efficiently that it wipes out its carbon cost over the course of its presumed 60-year lifespan. Which is to say that the most environmentally virtuous buildings in the industrialized north will keep adding to humanity’s carbon debt until at least 2080. (Not counting the added burden of replacing windows, upgrading systems, and renovating.) In the meantime, just commuting to to an office building can be part of its unacknowledged environmental cost. Aerial photos of Snohetta’s Powerhouse Telemark in Posgrunn, Norway, show a roof covered in solar panels — and, a few feet over, a pair of parking lots for several hundred cars.

The future is a tempting source of energy savings precisely because it’s beyond anyone’s control. But it’s still important to consider. Architects who advocate a life-cycle approach help the next few generations out by making wise decisions now. Top-notch craftsmanship is highly sustainable, says Christine Lemaitre, CEO of the German Sustainable Building Council, and a low-carbon design doesn’t mean much if it starts to fall apart after a couple of decades. “We have to focus on quality. Your building has to last a long time,” Lemaitre says. (And quality doesn’t just mean high-end drawer pulls; beautiful design will prolong a building’s life too. People tend to preserve what they love.)

Thinking about the end of a building’s life even as it’s being conceived yields decisions of immense architectural significance. “You don’t use laminates or hybrid materials. Everything is bolted and screwed so it’s easily dismountable,” Howland says. “You avoid plasters and skins and paints.” A plasterboard wall, he explains, is quick and easy to install, but it’s an agglomeration of different materials (paper, foil, gypsum, scrim, joint compound), each of which may be made in a separate factory and in a different country, so the total number of ship-and-truck miles of that sheet of drywall marking out your living room may be in the hundreds of thousands. Opting out of the global supply chain of industrial building products can be architecturally rewarding — Howland’s best known for Cork House, another southern English residence, where a simple and renewable building material, cork, serves as weatherproofing, insulation, siding, interior finish, and load-bearing wall all in one. “It’s a lot more fun to work with materials than with products,” Howland says. “But if you’re not giving people lovely smooth white walls, there’s a cultural shift required.”

Resurrecting one aristocrat’s demolished home for another wealthy client is hardly a panacea, or even a replicable model. Innovations ooze into the construction world slowly; the stakes are too high to order shiploads of untested materials. One recent exception to that hesitancy is cross-laminated timber, the crunchy alternative to concrete and steel, which in just a few years has gone from boutique obsession to global business. In the northern Swedish city of Skellefteå, White Arkitekter has completed Sara Kulturhus Center, a museum-theater-library complex topped by an ostentatiously dumpy hotel tower made out of structural wood. The stripped-down look is presumably meant to signal a puritanical focus on environmental virtue and a suspicion of architectural self-indulgence. To its enthusiasts, timber is the wonder material, constantly being manufactured by sun, rain, and soil, which are always ready and willing to do it again. Better yet, trees warehouse carbon as they grow; keeping that store intact by transferring wood to buildings extends that process beyond the life of the tree.

Lately, though, even those self-evident truths are starting to look shaky. Cutting logs into panels, gluing them into slabs, treating them with fire-resistant coatings, assembling them into structures, and trucking them into place — every one of these steps produces fumes that need to be accounted for. Wood is clean, but the wood business isn’t; a 2018 study concluded that the timber industry in Oregon was the state’s leading polluter. In addition, feeding the world’s appetite for wood can result in noxious logging practices like clear-cutting, monocultures, and deforestation.

Genuinely low-carbon buildings do exist, they just tend to be in places that have scarce access to industrial building materials and easy access to labor. “You can get close to zero if you’re really radical, like building out of straw bales, but it’s extremely difficult,” says Smith Mordak, director of sustainability and physics at the global engineering film Buro Happold. “What we can do now is create practices that will get us to zero eventually.” Those practices can be codified. Mordak advocates treating embodied carbon as a finite resource that can be capped, regulated, and allocated. “We could deploy our allowable carbon to its most important social need,” they say.

For Lemaitre, simply forcing builders to make public the amount of embodied carbon in each project would be a huge step. “If you generate transparency, that will change the market,” says Lemaitre. “Nobody wants to be the bad guy.” Honestly accounting for embodied carbon would transform a city’s approach to planning, raising the bar on approvals for demolition permits and encouraging adaptive reuse. The Westminster city council, in central London, recently adopted rigorous environmental standards for new construction. And yet the same agency also approved the chain store Marks & Spencer’s plan to knock down its wheezy, cumbersome, landmarked 1929 flagship store on Oxford Street and erect a super-efficient new building designed by Pillbrow and Partners. Simon Sturgis, an architect who serves as carbon conscience to Britain’s construction world, issued a blistering report arguing that replacing the existing building, rather than conducting a thorough renovation, would betray the city’s own environmental goals. “Demolishing useable buildings to replace them with large new build schemes is no way to meet our climate targets,” he wrote. It’s like junking your old subcompact and buying an electric Hummer to save on gas: The atmosphere won’t thank you.

In the construction industry’s search for environmental reputation-laundering, the holy grail is a building that absorbs more greenhouse gases than it pumps out, and quickly enough to make a difference now. That’s the ambition behind Skidmore, Owings & Merrill’s “Urban Sequoia,” a promising but still theoretical proposal for a tall tower that undoes its own damage and then some. The design packs the structure full of technologies that exist but aren’t ready to be deployed at skyscraper scale, such as biobricks made out of algae, which can theoretically inhale carbon like trees, and façade panels packed with micro-algae that reproduce and generate heat, so that the building effectively grows its own fuel. One key component is a set of carbon-capture machines powered by the air that naturally shoots up through a tower’s ventilation and elevator shafts in what’s known as a stack effect. On a global scale, carbon capture is a staggering challenge, but Chris Cooper, a partner at SOM, sees an analogy to solar power, which has become cheap and available enough to be ubiquitous. “The macro concept has gone micro, and it has a big impact,” he says.

Until someone figures out how to erect such self-cleaning architecture — and make it ordinary — the upside of all these carbon-curbing measures is the same as the downside: they make putting up new buildings costlier, slower, and more difficult. In one way, that’s a good thing. So long as construction remains destructive, we should put up only what’s necessary. At the same time, though, housing remains a pressing need, and throwing up barriers to its production, especially in dense and highly regulated cities, means raising prices, exacerbating homelessness, and pushing more people out to car-dependent, energy-gobbling suburbs. One environmental imperative negates another. And while architects try to hack their way through this tangle of priorities, the world keeps simmering.

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