Climate Solutions

Forget the log cabin. Wood buildings are climbing skyward — with pluses for the planet.

“Mass timber” construction is gaining ground, although not all environmentalists agree on its potential for slowing climate change.
By

AMHERST, Mass. — Research assistant Conrado Araujo punches a key, mighty electromechanical motors surge, and a giant steel arm begins to bear down on a long wooden beam with thousands of pounds of pressure. In this airy lab on the ground floor of a four-story building made of similar beams, the crucial question is when the wood will break.

Araujo’s computer traces the load with a line that climbs along with the suspense. Sixteen thousand pounds. . . . Eighteen thousand pounds. . . . Twenty-one thousand pounds. . . . Finally, under the weight of nearly six cars, the wood surrenders with a sharp crack.

“Impressive,” Araujo says.

This is no ordinary block being tested at the University of Massachusetts at Amherst. It is “engineered wood,” composed of about 20 boards of eastern hemlock glued together in perpendicular layers to make a thick, extraordinarily strong slab 12 inches wide and 6 1/2 inches high. The potential of such cross-laminated timber — also called “mass timber,” for massive — is exciting builders, city planners, architects and environmentalists around the world.

Builders see it as a way to construct midrise structures faster and cheaper. City planners see a fast track that could help reduce housing shortages. Architects love its light weight and look. And some environmentalists tout its ability to lock up carbon to combat climate change.

“We call it a win, win, win, win,” explains Robert Perschel of the New England Forestry Foundation.

Advocates envision a radical shift in construction, with wood buildings of seven to 18 stories sprouting wholesale in cities, drastically reducing the cement and steel that generate tons of greenhouse gases.

The perceived environmental benefit is key to their enthusiasm, moving discussion of mass timber out of builders’ trade shows and into academic and governmental offices. By utilizing wood, proponents argue, the carbon stored in it during tree growth is retained within floors and walls.

“It’s kind of amazing,” said Nicole St. Clair Knobloch, a climate policy expert who has a U.S. Forest Service grant to promote mass timber in Massachusetts. “That carbon, you put it in a building, it’s going to stay in the building. It’s not going to be released to the atmosphere.”


The John W. Olver Design Building at the University of Massachusetts at Amherst required about 70,000 cubic feet of wood. (Alex Schreyer/UMASS)

Giant slabs of cross-laminated timber and concrete composite were positioned as part of the floor system. (Alex Schreyer/UMASS)

Not all environmentalists are on board, though. The Sierra Club contends that nearly two-thirds of trees’ carbon is lost to the atmosphere when forests are cut and milled, and replanting young trees does not always offset that loss.

“The carbon benefit of such substitution is exaggerated,” the Sierra Club, Natural Resources Defense Council, Greenpeace and 45 other environmental groups and companies wrote last year in an open letter aimed at countering a move by the state of California to encourage mass timber construction.

“It’s a drastic simplification to say that wood stores CO2 and thus it’s a perfect material,” concurred mechanical engineer Jeremy Gregory, a scientist at the Massachusetts Institute of Technology who runs a research group supported by the concrete industry.

Single-family homes and small buildings in the United States have long used “stick” construction — framing with studs and joists made of boards. Very high-rise buildings still require steel skeletons.

But vast numbers of midrise buildings are made of concrete. Producing the cement in concrete typically requires high temperatures, cooking limestone in a process that billows greenhouse gases. Workers who then mix the product must wait for it to dry, which can add months to construction site schedules.

By contrast, mass timber can be prefabricated — designed and produced at a factory, trucked to a location and quickly fitted together with special fasteners as if it were an Ikea bookshelf. There’s no sawing, cutting or pouring. Less time is needed, as well as fewer workers.

The John W. Olver Design Building at UMass Amherst, a soaring classroom and office space that houses three departments and the wood-testing lab, was made in just that way. When faculty member Peggi Clouston saw plans for a project of steel and concrete, she and her colleagues balked. With the help of a $3 million state grant, they persuaded the university to change course.

The result in 2017 was the largest U.S. academic structure made of mass timber. (A five-story wood dormitory at the University of Arkansas in Fayetteville is now larger.) It has an airy atrium, a staircase that seems to float upward, skylights, cabled trusses in the ceiling that hint at a sailing ship’s use of countervailing forces and warm wooden beams that support a cozy rooftop.

“There’s an experiential aspect of wood,” said Andrea Leers, whose Boston architectural firm did the design. “It feels like a connection to nature. Everyone yearns for it.”

Yet beyond the visual and sensory aesthetics, the structure’s 70,000 cubic feet of wood hold the carbon from 2,000 tons of CO2 removed from the atmosphere as trees matured. That’s akin to removing 500 cars from the road for a year, according to the university’s Department of Environmental Conservation.

Clouston, a professor of wood mechanics and timber engineering, is passionate in her promotion of mass timber for more than the climate change advantages. She sees a thriving mass timber market as helping rural forestry communities, as well as spurring intensive replanting and nurturing of forests — one of the most important carbon sinks on Earth.

“We need our forests to clean the air,” she said as strolled about the Design Building, eagerly explaining structural angles and assembly connectors used in the sleek space.

Felling forests to lessen climate change can seem like a counterintuitive argument, she acknowledged.

“Cutting down a tree is something we learned at a very young age is bad,” she said. “But think of the future population and how are we going to house them? If we continue building in concrete and steel, spewing pollution, we won’t have a planet to put people.”

A new report by the nonprofit Urban Land Institute labels cross-laminated timber a “good replacement” for traditional steel. The report predicts that governments will eventually move to regulate carbon, propelling a search for construction materials that emit less pollutants. “Once a carbon tax is passed, developers will have a strong financial incentive to take action,” it says.

Building with wood is hardly new. Some of mankind’s oldest structures are wood — a wooden temple near Nara, Japan, dates to 1,300 years ago — and log cabins are an icon of the American West. But the massive, solid beams used in barns and big factories are mostly gone.

Wood material came along next, thin layers pressed into plywood or boards bundled together called glulam. About 25 years ago, European builders found they could crisscross the boards in layers and use glue and pressure to bind them into a product as strong as steel.

The Design Building's structural frame consists of glulam posts and beams and cross-laminated timber plates.
Durable, lightweight aluminum panels cover its exterior. (Photos by Alex Schreyer/UMASS)
LEFT: The Design Building's structural frame consists of glulam posts and beams and cross-laminated timber plates. RIGHT: Durable, lightweight aluminum panels cover its exterior. (Photos by Alex Schreyer/UMASS)

Regulators here have been wary. The International Code Council, which sets standards closely followed in the United States, Canada and other countries, limited wooden buildings to five or six stories until it decided last year to raise the allowable height to 18 stories after seeing some structures built by exception. An 18-story student residence hall at the University of British Columbia in Vancouver is the tallest in North America; a Norwegian apartment building 105 feet higher claims to be tallest in the world.

Dozens of others are flying off architects’ drawing boards — including a 23-story project in Milwaukee — and most states in this country are expected to eventually follow the international code. Such corporate giants as Walmart and Microsoft are embracing mass timber for new campuses, with the latter saying its project in Silicon Valley will be the “largest mass wood structure built to date in the U.S.” when completed next summer.

Proponents maintain they have answered skeptics’ objections. They say mass timber’s thick, dense beams and panels pass all fire code tests; both char on the outside, which prevents them from bursting into flames. Water can harm wood, so architects design exposed surfaces with a protective veneer of metal or glazing. Insect damage is possible, so maintenance is necessary, just as maintenance of all structures is needed. The timber structures, proponents believe, will be as long-lived and energy-efficient as those made of steel or concrete.

The concrete industry hotly contests these assurances. The website of the Build with Strength coalition, created by the industry, features dire warnings and colorful drawings of wood high-rises aflame.

“I wouldn’t want to live in a building that chars,” scoffed coalition spokesman Kevin Lawler, whose group contrasts photos of concrete withstanding blowtorch heat with a fire that destroyed an unfinished University of Nottingham laboratory in 2014. “It is inherently wood and less safe than concrete by any standard. We are specifically saying these are a fire hazard and have structural integrity issues.”

Mass timber advocates were embarrassed in March 2018 when a 1,000-pound ceiling section of the signature building of Oregon State’s Forestry School came apart and crashed during construction. Inspectors found dozens of faulty cross-laminated timber panels. The manufacturer admitted to fabrication defects of the panels.

“It wasn’t a good thing,” said Stephen Shaler, who heads a building materials research center at the University of Maine in Orono. “But talk to architects. The energy is out there for people to use this material. They are still gung-ho.”

Money is beginning to follow. Both Massachusetts and Maine have offered funds to explore mass timber, and Massachusetts Gov. Charlie Baker (R) has embraced the higher building codes for mass timber. Boston officials are interested in the product to provide much-needed housing more quickly.

Lawyer Jeffrey Hutchins, a former executive director of the Massachusetts Forest Alliance, started a Boston company last year to promote construction. “We see the biggest potential in multifamily housing,” said Hutchins, who named the company Travirke, which means timber in Swedish. He predicts a boom of mass timber apartment projects of up to 12 stories throughout the Boston area. “We’re talking probably about 15 to 20 buildings per year.”

Nationwide, the possibilities depend in part on the availability of the engineered wood. New plants have opened in Washington state’s Spokane Valley to use lumber from the Pacific Northwest and in Alabama to access the vast softwood forests across the Southeast.


When completed in 2017, the Design Building was the country's largest academic structure made of mass timber. (Alex Schreyer/UMASS)

But plans announced by two companies to open mass timber manufacturing in Maine, the most forested state per acre, have yet to move forward nearly two years later.

“The timing of our financing did not work out,” said Casey Malmquist, the founder of SmartLam, which owns cross-laminated timber plants in Montana and Alabama. “We are very intent on building a plant in the Northeast. We are just taking a broader view of where.”

At the end of a gravel road in secluded woods northwest of Boston, New England Forestry Foundation officials say they hope demand will persuade landowners to allow trees to grow taller and thicker. The resulting timber would have more sequestered carbon and represent a more valuable harvest — for strong building material instead of paper towels and toilet paper.

“You can get the wood products and store the carbon at the same time, but you’ve got to manage it,” stressed Perschel, the foundation’s executive director.

Even the staunchest proponents of mass timber don’t claim it will solve climate change, but they believe it can make a difference.

“There’s not a silver bullet out there,” Shaler said from Maine. “But mass timber is one of the silver BBs in the shotgun shell. It’s important.”

More stories

The new plan to remove a trillion tons of carbon dioxide from the atmosphere: Bury it

Why the Amazon is burning, and why it’s likely to get worse

Trump administration proposes expanding logging in Alaska’s Tongass National Forest

The world needs a massive carbon tax in just 10 years to limit climate change, IMF says

national@washpost.com

Credits: Doug Struck

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