A rendering of a wooden high-rise building to be constructed in Japan.
Illustration: Sumitomo Forestry Co.

Wooden skyscrapers are fast becoming a trend in sustainable construction, with dozens planned across the country. Two buildings in Portland, Oregon—Carbon12, a new all-timber high-rise building, and Framework, another in progress that will be 12 stories—offer an early look at what it will take for the trend to develop into something more lasting and impactful. But they’re not without controversy.

When it was completed in 2017, Carbon12 became the first high rise in the U.S. to use CLT, a wood panel product made from gluing layers of lumber together with resulting strength that rivals concrete and steel. Despite the all-timber construction being touted as “green,” some environmental groups have pushed back, saying it can only really be sustainable if it’s sourced using responsible logging practices.

Because of Oregon’s green reputation and it being home to the first U.S. certified manufacturer for CLT, D.R. Johnson, located in Riddle, Oregon, it makes sense that the state would debut the new technology. Two dozen new mass timber structures are in progress, more than any other state, according to the developers of Framework, the second all-timber building in Portland.

A rendering of the new Framework 12-story plyscraper in Portland, Oregon.
Illustration: Framework

Building with CLT has two purported climate benefits. First, as trees grow they sequester carbon, which remains stored in timber construction materials while the wood is in use. Second, proponents argue that the process of producing CLT has a lower carbon footprint than alternatives, like concrete and steel.

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“Each of these structures serves as a significant carbon storage unit,” Oonagh Morgan Hurst, of Morgan Communications, which represents Project^, the developer behind Framework, told Earther.

But some environmental groups in Oregon have fired back, questioning how these projects can be seen as green in a state known for using clear-cutting practices.

They worry the new trend of using CLT to construct buildings could create a new market for logging companies that utilize clear-cutting, which they argue turns the forest, a carbon sink, into a carbon source. Oregon’s loggers association has a different view, arguing that clear-cutting mimics natural events like fire and can actually renew the forest.

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Outside of the U.S., all-timber structures like those in Portland have been built in Sweden, Finland, and the U.K. A 24-story so-called “plyscraper” is under construction in Vienna, Austria, and in Tokyo, a 70-story wooden building is planned.

Buildings, including electricity used inside them, account for a large percentage of U.S. emissions. Advocates of CLT say that substituting wood for concrete and steel in buildings would make a real dent in carbon dioxide emissions. A 2013 study found that using CLT can significantly reduce energy consumption in buildings as compared to concrete. It’s also resistant to fire and earthquakes, according to a blog post by the U.S. Forest Service.

Project^ said it would have more information on which sources they will get their timber from as the project progresses.

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“Our team remains committed to working towards the best environmental footprint, given the constraints of the current market,” Morgan Hurst said.

Construction on the Framework building proceeds.
Photo: framework

Environmental groups—including the local chapters of the Sierra Club and Audubon Society, Oregon Wild, and Bark—called on the city, which subsidized part of the cost of Framework, to come up with rigorous standards about how the timber is sourced. Leaders from the groups signed a letter sent to Portland Mayor Ted Wheeler in February.

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“We do not oppose cross-laminated timber as a technology,” they wrote. At the same time, “its environmental effects are determined by where the wood used to fabricate CLT components came from, how it was harvested, and the carbon impacts of the harvest and of the product through its lifecycle.”

Wheeler’s office did not respond to Earther’s request for comment on whether it would consider including FSC Forest Management Program standards in its regulation process for approving plyscrapers. FSC is an international nonprofit aimed at promoting responsible management of the world’s forests. It has come up with a set of standards on forest products and certifies and labels them as eco-friendly.

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“Lots of public money is going into subsidizing CLT buildings in Oregon right now,” Steve Pedery, conservation director for Oregon Wild, one of the environmental groups that signed the letter, told Earther. “To the best of my knowledge none of that money has included any requirement that the wood come from sustainable sources, such as Forest Stewardship Council (FSC) certified timberlands.”

Pedery said that Oregon has some of the weakest state and private land logging rules in the country, and without the requirements they are asking for in the letter it’s “almost certain that these ‘green’ buildings are being built with wood from good, old fashioned clear-cuts.”

Carbon12 said it’s continuing its analysis of the chain of custody for the timber it is using in its buildings.

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“We are extremely aware that for this benefit to be absolute, we need to be very clear in regard to where our wood is sourced,” Ben Kaiser, owner and principal of PATH Architecture, the developers behind Carbon12, told Earther.

To be considered a clearcut under Oregon law, most trees in a forest have to have been logged at once, with standing trees left around water bodies as a buffer, according to Oregon Forest Resources Institute.

“The practice of clear cutting has changed dramatically in recent years in response to public concerns, scientific findings and advanced harvest practices,” according to OregonForests.org.

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The FSC standards differ from Oregon’s current practices in small but important ways.

“In the Northwest, FSC additional requirements over conventional legal practices typically boil down to larger buffers (trees left) along streams, fewer chemicals, smaller clearcuts with more ‘retention’ (meaning trees left behind),” Brad Kahn, communications director for Forest Stewardship Council U.S., said in an emailed statement.

The Center for Sustainable Economy—another group that signed the letter to Wheeler about CLT—did an analysis last year that determined that timber harvesting is the largest source of greenhouse gas emissions in Oregon.

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Given those factors, and with CLT construction becoming more popular, now is the time to consolidate standards on harvesting, the environmental groups said.

Carbon12 developers said it agreed those factors must be taken seriously.

Still, it argued that overall there were myriad environmental benefits to using CLT. Given those benefits, Kaiser sees a bright future for CLT construction.

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“I do think the trend of engineered timber buildings will continue,” Kaiser said. “There are too many irrefutable and positive aspects, in regard to improving the environment, for the trend to slow.”