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Erecting 40-story highrises out of wood?


Photo Credit: PHOTO BY SHELLY LANGTON, COURTESY OF KPFF CONSULTING ENGINEERS  - A crane operator lifts a massive sheet of cross-laminated timber into place atop the Shoreline Medical Clinic in Washington. It’s rare to see Oregon environmentalists and the timber industry on the same page.

But both camps are high on cross-laminated timber, an engineered wood product that visionaries say can be used to erect highrises up to 40 stories. If this “plywood on steroids” supplants concrete and steel in larger buildings, it could lower carbon emissions and construction costs while creating new jobs in rural Oregon.

“Wood is inherently one of the best building products ever,” says Scot Horst, a senior vice president for LEED, the green building certification system run by the U.S. Green Building Council in Washington D.C. “From an environmental perspective,” Horst says, “how can you have anything better in many ways?”

“We really have an opportunity in Oregon that we can lose if we don’t choose to take it,” says Thomas Maness, dean of the College of Forestry at Oregon State University. “Oregon is the best place in the world to grow this material.”

Oregon’s timber industry is subject to wild swings because it’s dependent on the cyclical homebuilding industry, Maness says, so finding new uses in commercial buildings could help weather future downturns and create more jobs here.

Invented in Austria in the 1990s, cross-laminated timber or CLT is sparking a worldwide competition for bragging rights to the tallest wood building. Melbourne, Australia, now boasts the world’s highest CLT building, the 10-story Forté residential tower. A 14-story project is in the works in Norway.

Oregon, despite being the nation’s top lumber producer, is late to the game. But the Oregon Zoo expects to install the state’s first building using CLT this month. And DR Johnson Co. is reportedly building one of the nation’s first CLT production facilities in Riddle, Ore.

Like a giant Lego piece

Cross-laminated timber is made of 2-by-6s glued together in huge sheets, then cross-hatched in three to nine layers. It can be up to 18 inches thick, 10 feet wide and 80 feet long.

“You’re talking about taking care of a roof with two pieces of this stuff,” says Jim Mitchell, Oregon Zoo construction manager.

Wood already is a popular choice for homes and small commercial buildings. CLT makes wood much stronger, so it can substitute for concrete and steel in bigger, taller structures.

CLT can’t compete with stick framing in homes and small buildings, says Ethan Martin, Northwest regional director of WoodWorks, a nonprofit funded by the lumber industry. It’s niche is in larger buildings, where it becomes cheaper to build with than concrete and steel once a structure gets up to eight or more stories, Martin says.

For now, that’s largely due to construction costs. It takes at least a dozen workers to install reinforced concrete, he says, but only four or five to frame with CLT.

Because crews are working with large components custom-made in the plant, CLT buildings can go up much faster, Martin says — about a floor per week vs. 2.5 weeks for concrete.

Photo Credit: COURTESY ROXANNE WARD - Bridgport House in London is made out of cross-laminated timber. The eight-story Bridgport House went up in London in 10 weeks in 2011, Maness says.

CLT performed well in seismic tests in Japan, though more research is needed, says Joe Mayo, an architectural designer with Mahlum Architects in Seattle.

A greener choice?

“From an environmental standpoint, we ought to be all over this, especially here in Oregon,” says Paul Barnum, executive director of the Oregon Forest Resources Institute.

“It’s a huge difference in greenhouse gas emissions,” Maness says. Wood promoters say it takes less energy to produce than steel and concrete, a prime factor in carbon emissions and air pollutants.

Trees produce oxygen and create habitat for wildlife, and absorb carbon dioxide. Roughly half the weight of wood is carbon, and that remains in a building rather than being emitted into the atmosphere as a greenhouse gas.

“There’s no other material that actually sequesters carbon from the environment,” Mayo says. “None of the other resources are naturally renewable.”

CLT also can be made from lower-grade timber, especially the layers that won’t be visible.

“Basically, you’re avoiding the whole old-growth debate,” Barnum says.

Many environmentalists and timber industry leaders concur that thinning some forests can improve forest health and minimize fire dangers near cities. CLT promoters say it could be a perfect use for smaller trees cut in those efforts. Often that wood is only marketable as firewood, but the price of firewood doesn’t pay for the harvesting work.

“We don’t have a market for that material right now,” Maness says. “This could be a real boon for forest restoration activities that we need to undertake.”

Steve Pedery, conservation director for Portland-based Oregon Wild, says he’s intrigued by the idea of using thinned wood for CLT.

“In general, we feel good about people developing markets for smaller-diameter wood that’s harvested sustainably,” Pedery says.

Comparisons not so simple

Independent analysts caution that comparing the green merits of wood, steel and concrete isn’t as simple as wood promoters make it seem.

Much depends on the type of materials used, where they come from, and how they are produced, says Jordan Palmeri, science and policy analyst for the Oregon Department of Environmental Quality.

The nation’s steel now largely comes from recycled steel. Concrete can last far longer in the environment than wood.

U.S. steel and concrete manufacturers have made impressive gains in energy efficiency in the last decade, lowering their carbon footprint, says Angus Duncan, chairman of the Oregon Global Warming Commission.

And there are raging debates about forestry techniques and how to account for carbon emissions from cutting trees. Some studies show half the carbon stored in trees is released in the first two years after it’s cut, via leaves, branches and bark, Palmeri says.

Environmentalists stress that wood loses its advantages when foresters use massive clear-cutting and herbicides, potentially harming water quality and fish and wildlife habitat. Those are standard practices in most Oregon fir forests.

“It has potentially gigantic impacts if we don’t focus on sustainable forestry practices,” says Horst of the U.S. Green Building Council.

Building codes a game-changer?

British Columbia passed a Wood First policy in 2009 that encouraged developers to build with wood. That helped spawned dozens of CLT construction projects. Structurlam opened one of Canada’s two CLT production plants in 2011, in the B.C. community of Okanagan Falls.

CLT has been slow to gain a foothold in the United States, which many blame on antiquated building codes that limit wood buildings to five or six stories. Those building codes were adopted when fire was an utmost concern, before the advent of modern sprinkler systems that make any building much safer.

But the United States’ new building code should end those height limits, and that likely will get adopted by Oregon next year, Martin says.

Seattle was an early adopter of the new building code, Mayo says, and a handful of CLT projects have been built in Washington. SmartLAM LLC recently opened what it says is the nation’s first CLT plant in Columbia Falls, Mont., and promises to open more. There also are plans to site a plant in Idaho.

Emily Dawson, an architect with SRG Partnership in Portland, proposed Oregon’s first use of CLT at the zoo’s Elephant Plaza Building, a modest facility that includes restrooms and a prep kitchen. Dawson’s design deploys CLT as a cantilevered roof. The material is so strong it didn’t need steel beams to support it, Dawson says.

Other potential projects using CLT are being discussed or designed for Western Oregon University, Portland State University and Oregon State University.

Having a production plant in Southern Oregon also should boost the Northwest’s supply of CLT, Martin says. “It’s a small start, but it’s a good start.”