Here’s something you probably didn’t know: the construction business accounts for an estimated 23 percent of the world’s carbon-dioxide emissions—5.7 billion tons, according to the most recent estimates. Much of this comes from the use of concrete and steel, the two biggest contributors to emissions in the building sector. As the BBC has reported, if the concrete industry were a country, it would be the third-largest emissions producer, behind China and the United States. And there’s no end in sight: the United Nations Environment Program predicts that humans will put up the equivalent of a new Paris every week for the next 40 years. In the U.S., an architectural publication predicted that some 1.9 billion square feet of new structures will be built in the next three decades.
If only there was a sturdy and renewable building material—one that could actually help curb climate change while giving us more calming and aesthetically pleasing spaces in which to live, work, and play.
Such a miracle substance exists, of course. It’s wood. As you are no doubt aware, trees absorb carbon dioxide and release oxygen back into the atmosphere during photosynthesis. The carbon is sequestered in the tree while it’s standing and remains locked inside wood products after it’s harvested for lumber. (Large amounts of CO2 are released only when wood decays or is burned.) America’s oldest standing wooden home, the Fairbanks House, built in Dedham, Massachusetts, in 1637, is still holding onto 400-year-old carbon today. That’s a major reason why environmentalists fight so hard to preserve existing forests and plant new ones—studies suggest that it’s the most useful thing we can do to mitigate climate change.
Cutting down a tree for lumber, of course, ends its carbon-inhaling days. And even within well-managed woodlands, reforestation takes a significant amount of time, especially when you’re waiting on the large specimens that are traditionally used in construction. Still, over the long term, forests managed for timber sequester carbon nearly as well as wilderness woodlands do. And in the U.S., we’re currently adding more trees to our working forests than we’re cutting down—there’s as much forest today as there was in 1910, according to the Forest Service. We can add a lot more if we develop construction methods that make use of smaller trees, which can be propagated in a few decades, rather than giant ones that can take centuries to grow.
Enter mass timber, a term for a category of innovative products made from smaller pieces of wood—such as two-by-fours and two-by-sixes—that are either glued together or cross-laminated to create beams, structural walls, ceilings, and floors. These pieces can be prefabricated to make building highly efficient. And with the latest milling machinery coming to market, even small-diameter trees like black spruce can be used.
The Nature Conservancy is so bullish on mass timber’s potential to drive reforestation that it commissioned an exhaustive study, involving 16 institutions across Europe and in North and South America, investigating how new practices might move the planet toward the organization’s goal of expanding forests by 500 million acres by 2030. “That would mean 200 billion more trees,” says Mark Wishnie, the Nature Conservancy’s director of global forestry and wood products. “Mass timber isn’t a silver bullet for growing more forest, but we’re hoping that it’s part of the silver buckshot.”
Mass-produced cross-laminated timber (CLT, in industry parlance) was first conceived in central Europe. Austrian foresters, looking to make better use of smaller trees for traditional building techniques that favored large exposed beams—think Bavarian chalets—created the first mass-timber presses more than 30 years ago. Scandinavia followed suit, but the U.S. was slow to embrace the idea. That finally started to change in 2013, after the Forest Service initiated studies of CLT technologies. Around the same time, a few forward-thinking Americans and Canadians began incorporating Austrian-made CLT into one-off buildings. Even so, as recently as 2016, organizers of the Forest Business Network’s annual mass-timber conference could point to only a handful of domestic projects.
Since then, mass timber has taken off. This spring, Woodworks, an advocacy group for wood construction, counted 549 active CLT projects, and analysts expect that to rise into the thousands in short order. Interest in mass timber has been boosted by high-profile buildings like Carbon12 (a mixed-use luxury showpiece in Portland, Oregon, that at eight stories is the tallest CLT building in the country), Minneapolis’s seven-story T3 building, and a hip new hotel in downtown Bozeman, Montana, called the Lark. Sidewalk Labs, owned by Google’s parent company, Alphabet, has proposed creating 3.2 million square feet of new mass-timber buildings in Toronto, some up to 30 stories high, as well as a CLT factory in Ontario. Then there’s Walmart, which in May announced that it will build its new corporate headquarters in Bentonville, Arkansas, using mass-timber materials.
“Mass timber isn’t a silver bullet for growing more forest,” says the Nature Conservancy’s Mark Wishnie, “but we’re hoping that it’s part of the silver buckshot.”
The Department of Defense is also keen on wood. In collaboration with the Forest Service and Woodworks, the Pentagon conducted blast simulations on an assortment of mass-timber buildings; it’s now planning to erect wood-construction hotels on military bases considered to be at high risk for a terrorist attack. Other research suggests that CLT is resistant to earthquakes and—get this—fire. The outer layers tend to char, insulating the wood from the flames, and the lack of oxygen in the highly compressed material offers minimal fuel to burn.
“We’ll never look back,” says Ben Kaiser, the architect and developer behind Carbon12. “We’ll only build using mass-timber products going forward. We’ve seen firsthand that this methodology is approaching a panacea.”
Many experts believe that the real growth opportunity in North America involves buildings between four and twelve stories (which mainly means office parks and apartment buildings). Rosy guesstimates from some analysts have mass timber amounting to as much as 10 percent of U.S. construction within the next 30 years. Part of this will happen because CLT projects can be completed much more quickly, but a major underlying factor is that building habits haven’t changed much since we began shifting away from wood following the 1906 San Francisco earthquake and fire. As venture capitalists like to say, the space is ripe for disruption.
It also helps that architects are excited to return to a beautiful material. “The aesthetics of wood can’t be oversold,” says Craig Curtis, chief architect with Katerra, a Silicon Valley startup that opened a 250,000-square-foot mass-timber manufacturing facility in Spokane Valley, Washington, this summer. Studies have shown that the human sympathetic nervous system, which controls our fight-or-flight response, is less active when we’re around wood, that students are less stressed in classrooms made with lots of wood, and that office workers are happier and more productive in wooden buildings. Like houseplants and windows with park views, wood elicits a calming connection to the natural world.
So what’s holding back the revolution? Predictably, the concrete folks aren’t happy about mass timber. In Washington, D.C., lobbyists are trying to hamstring Forest Service research, claiming that the government is unfairly picking winners and losers in the marketplace. Industry groups have put up billboards disparaging wood construction and making unfounded claims about fire risk.
Simple inertia also makes change difficult: for a century, architects and engineers were trained to build with concrete and steel, and most are still taught that today. Producing mass timber requires expensive machinery, which is slowing the development of domestic CLT mills. The U.S. has just a handful in operation at present and is adding only a few more every year. It will be decades before we have enough manufacturers across the country to keep the material and shipping costs down and the supply up.
Some environmentalists are justifiably wary of the logging and timber industries, having seen supposedly green efforts like salvage logging sometimes used as a smoke screen for what amounted to deregulation. Last year in Oregon, backers of a 12-story mass-timber building faced strong pushback for sourcing wood that wasn’t Forest Stewardship Council certified. So far most of the materials going into mass-timber products in the U.S. come from conventional lumber sources. To get more environmentalists on board, the industry needs to catch up to Europe and incorporate lower-quality wood from smaller trees into CLT layers. This is especially important in the wildfire-prone West, where the wood cleared in thinning operations is often burned on-site. If instead you can find a market for it, small trees can “pay their way out of the woods,” says Michael Goergen, vice president of innovation for the nonprofit Endowment for Forestry and Communities.
Government support is also essential. Oregon has spent hundreds of thousands of dollars to promote CLT in an effort to boost its logging industry, but we need the federal government to incentivize mass-timber construction by favoring it in contracts and offering tax breaks to developers that incorporate small-diameter wood into their projects.
Tree crops don’t always provide the kind of habitat that supports diverse ecosystems. For that we need to continue fighting like hell to protect our remaining old-growth forests. But if you take it as truth that climate change is the greatest threat to the planet, then mass timber offers a rare opportunity—a chance to transform the construction and logging industries so that we reduce emissions while adding millions of carbon-sequestering trees to the landscape. We’ll cut them down and then grow more, gardening the earth as stewards living in a built world made more and more out of wood.
Contributing editor Marc Peruzzi lives in Montana.