The Metro Toronto Convention Centre, a towering complex of glass, steel, and concrete, is the kind of structure Chris Magwood has spent decades denouncing. Yet the specialist in sustainable construction found himself in the building last March to present at the Green Living Show, a trade fair dedicated to a healthier planet. Since Magwood’s specialty is calculating the environmental costs of various construction materials, the biggest elephant in the room that weekend was the room itself.
Magwood pointed out to me that we were sitting on chairs with plastic upholstery, on a carpet that he says will likely eventually be “ripped up and go in a landfill,” under a steel beam that was created by extracting ore, “heating it up, melting it, melting it again, shipping it,” and surrounded by laminated wooden panels that “can’t be recycled.” Such wasteful building materials, he said, are “very hard to justify.” He gave an apologetic chuckle.
At Trent University, in Peterborough, Ontario, Magwood has been studying embodied carbon—a term for the greenhouse-gas emissions associated with a product’s creation—as it applies to buildings. Usually, architects judge a building based only on its operational emissions—the pollution caused when tenants turn on a light, for example, or run the air conditioning. Magwood is asking architects to look instead at a structure’s entire lifespan. His calculations take into account the environmental costs of manufacturing construction materials, including glass, steel, and concrete, transporting them to the job site, assembling them, then decommissioning them when the building is eventually torn down.
Magwood didn’t invent the term embodied carbon; it has circulated in the architecture world for the last decade or so. Until recently, most architects and engineers insisted that the environmental impact of embodied carbon was near-trivial compared to operational emissions. But Magwood’s calculations show how far off those assumptions could be: in some cases, if architects accounted for embodied emissions in their buildings, they would be admitting responsibility for at least twice the carbon footprint.
A few days before the Green Living Show, Magwood and two colleagues from Vermont, Jacob Racusin and Ace McArleton, delivered the keynote lecture at Boston’s BuildingEnergy conference. It was one of the first times Magwood had presented his work before a broad audience of engineers, remodellers, architects, and policy-makers. Those assembled would already have known that building construction is one of the largest sources of greenhouse-gas pollution in the world. But, that day, Magwood revealed something not everyone was prepared to hear: many of the buildings their firms had created—even the ones bearing the most respected environmental stamps—had caused more pollution than they realized.
Estimates vary, but it’s now safe to say that between 20 and 60 percent of an average building’s carbon emissions are embodied as opposed to operational. The numbers quickly add up: in Canada, a report looking at only nonresidential buildings found that their embodied carbon was responsible for releasing an annual 2.3 million tonnes of carbon-dioxide equivalents (CO2e), a unit that standardizes the way we measure greenhouse gases. (Carbon and carbon dioxide are used interchangeably in many industries.) That value, the report’s authors noted, is equivalent to about 487,000 cars driving nonstop for a year.
“It was like a light turning on,” says Paul Eldrenkamp, a remodeller who attended the keynote lecture in Boston. “We’ve been doing everything wrong.” Like many attendees that day, Eldrenkamp returned to his office, looked at the list of projects on their drawing board, and reevaluated every material they planned to use. By highlighting the environmental impact of preparing and transporting building materials, Magwood, Racusin, and McArleton have “changed the conversation,” Eldrenkamp says.
Since the energy crisis of the 1970s, when industrialized countries became acutely aware of their heavy reliance on oil, the green standard for houses in North America, as set by organizations such as the Canada Green Building Council, has been energy efficiency. For years, architects have worked toward air-tight, well-insulated homes that require little heating or cooling and are able to generate renewable energy. Their efforts culminated in the “passive house” movement, which promotes the construction of “zero-energy buildings.” Touted as the future of green architecture, these self-sustaining homes generate their own power with solar panels, for example. And, though their construction tends to be more expensive than that of the average building, their cumulative energy savings are meant to cut costs for homeowners in the long term.
Over the past three decades, passive houses have surged in popularity across the world, with more than 20,000 units certified by Germany’s Passive House Institute (many more exist without certification). Along with other zero-energy buildings, passive houses have become badges of environmentalism for those who can afford them, and well-intentioned corporations and individuals, including celebrities Bryan Cranston and Julia Louis-Dreyfus, have invested in green homes as a way to reduce their own carbon footprints.
Low-energy buildings, as Magwood sees them, are a dramatic example of how embodied carbon can call into question a building’s environmental impact. Yes, passive houses cut down on energy usage after they’ve been constructed, but some of the materials used to build them come with exceptionally high carbon costs. (And, because net-zero houses, by definition, have no operational emissions, embodied carbon could represent 100 percent of their pollution.)
For environmentally minded architects, the realization that supposedly green construction can be more environmentally damaging is especially painful. Depending which estimate is used, approximately 20 percent of all global greenhouse-gas emissions come from embodied carbon in construction. As architects make buildings more energy efficient, that percentage might only increase. “You think you’re doing the right thing,” says Magwood. “But, if you choose the wrong materials, you could be having the opposite effect.”
The problem is not particular to architecture: it can be seen in nearly every environmental problem (and proposed solution) of the past few years. The practice of “life-cycle analysis,” which helps industries measure products’ overall impacts on the environment, has existed for decades in fields such as agriculture and engineering. But most consumers are unaware of the concept—let alone how to process the resulting data. We’re often told, for example, that it’s better to avoid eating meat because raising animals releases a substantial amount of greenhouse gases. But if the choice is between purchasing locally sourced chicken and quinoa shipped from Bolivia, the plant-based option might actually generate more pollution.
Scholars, including Magwood, are realizing that, unless environmental strategies take life-cycle analyses into account, they often end up being counterproductive. It’s time to refine how we think about environmentalism.
Studies show that it’s usually inaccurate to present actions as either “good” or “bad” for the environment. Environmentally friendly is a relative term; by mistakenly treating the designation as absolute, even the most conscious environmentalists often grasp at climate solutions that exacerbate the problem or deflect it elsewhere.
Kiel Moe, chair of architecture at McGill University, has blamed this tendency for the growth of the “contemporary sustainability apparatus”: techniques that are meant to address one environmental concern but unwittingly aggravate others. We reduce plastic waste by buying cotton tote bags and reusable water bottles, or we install solar panels in our backyards to generate renewable energy. But, while tote bags can certainly reduce plastic waste, cotton derives from an especially polluting industry—organic cotton, even more so. When it comes to greenhouse-gas emissions, an organic-cotton bag needs to be used 20,000 times to be an improvement over single-use plastic bags. The production of one stainless-steel water bottle, according to the New York Times, emits fourteen times more greenhouse gases and causes hundreds of times more toxic risk to the environment than making a single-use plastic bottle. Solar panels can provide renewable energy, but depending where they’re manufactured and where they’re installed—in a solar farm, on a suburban home, in a city with frequent cloud coverage—their construction might expend more energy than they can produce in their lifetime.
It’s easy to think, based on these and other findings, that many of our environmental efforts are so scattered as to be ineffective. But the 2018 report from the Intergovernmental Panel on Climate Change (IPCC) provides some clarity and focus. The world’s top environmental priority, according to the report, should be to limit global warming through the reduction of carbon emissions, with the goal of making all human activity carbon neutral (emitting a net-zero amount of greenhouse gases into the atmosphere) by 2050. Though that’s a stupefying target, it’s also quantifiable. It distills every action or product to its atmospheric impact: How much greenhouse-gas pollution does it represent? To make significant progress, we need to be able to calculate our emissions correctly in the first place. That’s where research like Magwood’s comes in.
Magwood’s calculations of embodied carbon are based on environmental product declarations—a kind of nutritional label for manufactured products that has emerged as part of the life-cycle-analysis movement. Anything, from a block of concrete to a cotton T-shirt, can be evaluated in terms of its “global-warming potential”—the environmental equivalent of a calorie count. One bottle of red wine from the La Rioja region of Spain, for example, has a GWP of just under one kilogram of CO2e, meaning its production has the equivalent effect on our atmosphere as one kilogram of carbon dioxide emissions. A bottle of Swedish single malt whisky, on the other hand, is worth more than two tonnes of CO2e. That knowledge can make the environmentalist’s beverage choice a little easier—depending how slowly they drink their whisky, of course.
Over the past decade, this essentialist attitude has led to a new line of thinking in the environmental movement, in line with the IPCC’s recommendations: if an object or action releases a certain amount of carbon, then its climatic effect can be “neutralized” by pulling the same amount out of the atmosphere—by planting a tree, for example, or by physically capturing carbon dioxide and storing it in the earth. As long as it’s done properly, this approach, known as carbon offsetting, is arguably the most practical way to achieve a net-zero existence.
In British Columbia, a firm called Carbon Engineering is selling direct-capture technology that can “remove CO2 directly from the atmosphere at an affordable price point.” Some airlines will suggest purchasing carbon offsets to make up for the pollution associated with air travel (a single passenger flying one-way from Vancouver to Quebec City represents approximately 620 kilograms of CO2e). Lyft, a ride-sharing company, has announced that it is becoming a “carbon-neutral company” because of the carbon offsets it has purchased to counteract its cars’ emissions.
But, for some architects and engineers, it can be tricky to maximize a building’s efficiency while also reducing carbon output. In their presentation at BuildingEnergy, Magwood and his colleagues showed the potential downsides of spray polyethurane foam (SPF), a substance that is often used in passive houses because of its high efficiency and sealant capabilities. Because SPF is made by combining a cocktail of chemicals, many of which are petroleum-based, under high pressure, its creation releases a large volume of greenhouse gases into the atmosphere—its embodied carbon is especially high. Magwood’s calculations have shown that, when taking into account SPF’s embodied carbon, a low-energy building made with foam could in fact be more harmful to the planet than a standard residential building of the same size.
The long-term benefits of energy-efficient houses also rely on the whims of human behaviour—behaviour that can be counterproductive. The so-called rebound effect has shown that, when people feel warm at home, they would rather wear less clothing than lower the heat, losing the opportunity to save energy. One study in Britain, as reported by the Economist, found that homes meant to reduce energy use by 20 percent ended up saving only 1.7 percent because of their occupants’ habits.
Even if residents do manage to keep operating emissions low, so that their building saves energy compared to a regular building over a period of, say, fifty years, those efforts might be rendered useless by the embodied carbon already released during the building’s construction. “We can’t afford to have emissions today in the name of reducing emissions fifty years from now,” says Melinda Zytaruk, the general manager of Fourth Pig Worker Co-op, a relatively new sustainable-construction company in Ontario. Between 2015 and 2050, the IPCC’s deadline for when the construction industry would have to become carbon neutral, more than 2 trillion square feet of construction and renovation will have taken place—the equivalent of building New York City from scratch every thirty-five days, writes Bruce King, an engineer, in his book The New Carbon Architecture.
It’s not yet mandatory, in any green-building code in North America, to calculate embodied carbon. The Canada Green Building Council “hasn’t figured out how to talk about it yet,” Zytaruk says. If more institutions, governments, and even individuals took embodied carbon into account when planning construction projects, Magwood says, they could easily halve their emissions overnight. And in only a matter of years, by using materials that sequester carbon in construction, many sectors of the industry could meet the IPCC’s carbon-free goals.
The focus of Magwood’s work today is net carbon storage—the next step in the evolution of sustainable architecture. Using materials such as timber and straw, which naturally store more carbon than they release, he can create buildings with materials that pull carbon out of the atmosphere. Straw, for example, is a natural by-product of farming wheat, rice, rye, and oats, so it requires little energy to create and is easily available. It also stores sixty times more carbon than it requires to grow, which makes it one of the most powerful carbon-storing building materials in the world.
Magwood is also proposing new building regulations in Ontario to make GWP computations mandatory. The carbon-storing buildings he has designed cost the same amount of money to build as the province’s code-compliant structures that emit carbon, and they’re just as easy to construct. A typical eight-unit residential building in Ontario today, according to Magwood, emits 240,000 kilograms of embodied CO2e before anyone even steps inside. Magwood says that, by using materials available at a local hardware store, construction workers could be making buildings that emit less than half that amount.
Within two to three years, once they’ve had time to adapt their practices, they could be making buildings that sequester—pull from the atmosphere—11,000 kilograms of CO2e instead. And, within five years, they could be sequestering more than ten times that amount. That shift in practice could make a substantial difference to climate change: by 2025, new homes built in Canada could sequester half a million tonnes of CO2 every year, helping to offset the carbon output of other industries.
Other architects are turning to straw-bale insulation. Anthony Dente, an engineer in California, became one of the first in his field to start measuring embodied carbon in building projects a couple of years ago. His firm, Verdant Structural Engineers, often designs buildings with straw bales and earth. Now that architects and engineers are finally turning their attention to embodied carbon, Dente thinks it will eventually become standard practice. The future of building construction might look like the work of Arkin Tilt, a California-based architecture firm, which often partners with Dente’s firm. They recently completed a mixed-use commercial building with straw and clay that sequestered 10.9 tonnes of CO2e.
Firms like that of Eldrenkamp, the veteran remodeller, have also committed to incorporating Magwood’s findings into their work. They know because of his comparison data, for example, that it is generally better to use material such as hempcrete, a biocomposite made out of hemp and lime mixed with silica, instead of cement: cement represents some of the highest carbon emissions, while hempcrete will instead store—or offset—nearly 4,000 kilograms of CO2e in an average residential building.
But it’s far more complicated to scale up Magwood’s work to the level of calculating the embodied carbon of an entire building. Environmental product declarations, which Magwood uses to mine data, are provided by manufacturers, which means that architects are at the mercy of various industries and just how much they’re willing to disclose about their processes and materials. Whether a product is transported by rail or by diesel trucks, for example, is rarely accounted for in its EPD.
In a 2015 study, Kate Simonen, an architecture professor at the University of Washington, found that about 25 percent of a high-rise residential tower’s embodied carbon came from “additional components”—plumbing, light fixtures, or exterior paving—typically not accounted for in building analyses. As the founding director of the Carbon Leadership Forum, a research group that is developing a digital calculator to help architects determine the net carbon impact of their buildings, Simonen’s goal is to make embodied-carbon data more simple and accessible to construction firms.
Some scientists warn against putting too much faith in carbon-calculating technologies. By treating carbon offsetting the same way they treated energy savings three decades ago—focusing their efforts on one goal—architects risk falling into the trap of helping the planet one way while harming it another. (For instance, studies have found that, while some carbon-capture technologies—the kind used to sell companies carbon offsets—help to reduce greenhouse-gas emissions, they can have other damaging environmental impacts.) So far, however, Magwood has found that building with low-carbon products, such as straw and hempcrete, helps mitigate other harms at the same time.
For architects, one of the biggest challenges in measuring embodied carbon is setting boundaries: it’s hard to know where the calculations end. Should the pollution caused by commuting to and from the job site during construction be part of a building’s emissions? What about the energy used to conduct research and print documents during the initial phase of the project? Or the carbon footprint of the furniture and appliances the house will be equipped with afterward?
Zytaruk points out that many sustainable homes are built in the countryside, which feels like it should be more ecological. But those locations require more driving, so they might cause more pollution than a standard home in the city does. Does that mean it’s better not to build that sustainable home in the first place?
“I think about this all the time. In everything,” Magwood says. He built his first home in rural Ontario twenty-five years ago with his then partner. It was the first house approved in the province to be built with straw bales. He felt satisfied at first, but he was spending “all kinds of time” driving to and from work and other appointments. “I realized that the rural life I had attached to being more environmentally friendly actually wasn’t.”
Magwood built his second home in the centre of Peterborough, where taking public transit, biking, and walking are much more feasible. He keeps track of his home’s environmental impact, and he conducted an analysis of its energy efficiency for the first two years. He knows that the second home, in the city, is a huge improvement over the first. In the end, “there are pretty clear pathways to doing the right thing,” he says. “I calculate the things I can change, but I can’t change everything.”
