The World’s Most Sustainable High-Rise Construction Material Is… Wood? A Portland Team Is Pioneering Its Addition to US Skylines

PORTLAND IS GROWING UP—adding high-rises, increasing density, and pricing many people out. But two local firms are exploring a state-of-the-art building material that could help solve the city's affordability problem, create living-wage jobs in rural communities, and help save the planet.

It's wood.

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Right now, Portland-based LEVER Architecture and real estate development firm Project^ are designing a 12-story mixed-use building in the Pearl District that will be made primarily of a material called cross-laminated timber (CLT).

That's an unheard of height for wood structures, which top out at six stories in most of the US. And it's not the project's only unique attribute. Five of those stories will be affordable housing, something Portland desperately needs.

Framework

Lever Architecture

LEVER and Project^ have partnered with Beneficial State Bank (which owns the property at 430 NW 10th), Albina Community Bank, and the housing agency Home Forward on the development, which they're calling Framework.

The team's ideas received national attention: In September, the US Department of Agriculture awarded the project a $1.5 million grant—money that will help alleviate the cost of proving to state and local building authorities that tall wooden buildings can meet safety requirements for earthquakes, fires, and other perils.

The US is late to the party on CLT. Tall buildings made from lumber have been gaining popularity in Europe, Canada, and Australia since they were introduced in the 1990s. Now, the LEVER/Project^ team is looking to increase local support and get building codes changed to accommodate tall timber buildings made from CLT.

If they're successful, they say, the benefits could be huge.

Compared with steel and concrete—materials that make up most high-rises—CLT is cheaper to produce, easier to assemble, and more sustainable, says LEVER founder and principal Thomas Robinson. That combination allows for a product that can be prefabricated at rural mills—creating much-needed jobs—and delivered to construction sites, cutting down on build time in a business where time is money.

"Using CLT in Europe has become common enough where the product is a commodity," says Home Forward Executive Director Michael Buonocore. "This is a huge opportunity for us to harness some of the market and produce affordable housing."

Lever Architecture

CLT IS A COMPOSITE, in which layers of wooden panels or beams are glued together at 90-degree angles, forming a super-strong final product.

"This type of construction is particularly well suited to areas like the Pacific Northwest that are located close to forests," says Robinson. "Our interest in CLT is tied to the potential of being able to use a local product. The 'forest to frame' movement can be compared to the 'farm to table' movement."

DR Johnson Lumber, based out of Riddle in rural Southwest Oregon, is the only US company currently producing structural CLT. The mill can produce panels up to 10 feet by 24 feet. It also makes enormous beams using a similar technique.

The material's got big potential boons for the environment.

Concrete production is responsible for between five and eight percent of the world's carbon emissions, according to a United Nations Environment Program Report. It is the second most consumed substance on Earth after water. Producing one ton of concrete generates more than a ton of carbon dioxide.

Given this, Thomas Maness, dean of the College of Forestry at Oregon State University, says CLT's a natural choice for green Portland.

"[Concrete is] really energy intensive because you've got to pull the rocks out of the ground, haul them, grind them, heat them," he says. "When you're building with CLT, you're basically building with the carbon dioxide the tree has pulled from the atmosphere as it grows."

Wood is also an excellent insulator, five times more so than concrete and 350 times more so than steel, according to Wood for Good, an organization that advocates for sustainable wood construction. That means it takes less energy to heat and cool a CLT building.

Skidmore, Owings, & Merrill, a US architecture firm, determined the carbon footprint of a high-rise built primarily out of timber could be 60 to 75 percent less than a similar building made entirely of concrete and steel.

And CLT can incorporate lumber that might otherwise be scrapped—such as the millions of board feet of US timber decimated by "beetle blight." Since the material is manufactured in layers, blighted lumber can be used on the innermost layers.

"It allows us to think about managing our forests in a way that allows us to do more with what we have," Maness says. "We can use diseased or low-quality smaller trees that are grown for production instead of going out and harvesting from our national forests."

WHEN PEOPLE think of tall timber construction, they often worry about safety. LEVER's Robinson and Project^ partner Anyeley Hallova say their design passes muster.

"The really interesting thing with these structures is that not only will they not fall down in an earthquake, but it's possible there could be such low damage that you could replace damaged components instead of having to tear down the entire structure," Hallova says.

Jason Sturgill

Maness, the Oregon State University dean, talks up the strength-to-weight ratio of timber versus concrete and steel when explaining why they're potentially safer in an earthquake.

"The amount that a building swings side-to-side is a factor of how heavy it is up top," he says. "The more weight there is, the more it's going swing like a pendulum."

He also argues that massive CLT beams and panels are actually stronger during a fire than steel, saying they'll merely char on the outside while steel can melt in extreme heat.

"Traditional wood construction uses small pieces of wood with lots of air between each stick, which makes it more combustible," Maness says. "These are massive blocks and it takes a lot to actually catch them on fire."

But the most hopeful part of building with CLT—at least for Portland—is that it could be a tool to help the city address its affordable housing crisis.

Framework, the new 12-story project in the Pearl, will be a mix of office space, retail, and residential, and its backers plan to include five floors of workforce housing (units that are affordable for tenants making between 60 and 80 percent of the area's median family income).

"Including workforce housing in this project has always been part of the vision," Hallova says. "We intentionally designed this building so it can be as affordable as possible, and with this type of construction we're able to minimize materials and reduce waste."

Vern Rifer, a principal at Portland-based Rifer Development and a Portland State University instructor, says the taller you build with concrete and steel, the more expensive construction becomes per square foot, because the base materials must be stronger and thicker to support the added weight up top. That's not the case with CLT high-rises.

"Wood is a material that's suited to go tall because it's much lighter and only has to support itself," Maness says.

So increasing height in tall-timber buildings doesn't mean increasing construction cost. And the affordability's helped by the fact that CLT is prefabricated. Maness compares the process to building a piece of IKEA furniture.

All that helps immeasurably when it comes to convincing developers that building below market-rate homes is a good idea. Home Forward's Buonocore says he's "never seen this much interest" in producing affordable housing, especially from the private sector.

"We purposefully picked the workforce housing income bracket [for the project] because it's that 'missing middle' that this building is trying to target," Buonocore says. "It's a difficult conversation to have, because it's those earning less than 30 percent of median family income who receive most of the help."

Hallova says Project^ was interested in creating housing options for people who started out in subsidized housing in places like the Pearl District, where market-rate rents are notoriously high. The use of CLT helped make that possible.

"When people start earning too much to qualify for restricted rents... but they want to stay in the area, there's no place for them to go," she says. "We hope Framework will be a catalyst for similar projects in the future."