Tall Buildings Out of Timber? In the Face of Climate Change, Seattle Encourages It

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Tall Buildings Out of Timber? In the Face of Climate Change, Seattle Encourages It

By Katherine Khashimova Long / The Seattle Times

The loggers who worked in Ballard when it was Shingletown, a center of the national logging industry, have long since disappeared. And on Ballard’s low skyline, there are only a few wooden landmarks of the wood heyday, mostly churches.

But as climate change concerns breathe new life into the design of wooden buildings, that could change.

In the years to come, Ballard will house the first tall building in Seattle made almost entirely of wood. Eight floors of Ballard Blossom’s current florist on Market Street will be a hotel built primarily from cross-laminated timber, or CLT – durable panels made from tie layers of wooden boards with glue.

The architects behind the hotel say its wood construction “responds to the historical influence wood played in Ballard”.

More importantly, cross laminated timber is being touted as an environmentally friendly alternative to concrete and steel, which produce large amounts of greenhouse gases when they are manufactured. Lumberjacks and environmentalists say building with cross laminated timber must be part of the response to climate change.

For those who remember the fiery protests of the 1990s over settling on the Olympic Peninsula, building with wood doesn’t seem intuitive.

Mark Wishnie, director of global forestry at The Nature Conservancy, said he understands the whiplash some are feeling about the turnaround in the environmental movement on wood. One of the biggest challenges for the increasing demand for CLT structures are the “scars in people’s memories” – the perception that logging is synonymous with deforestation.

For many, old Shingletown symbolized exactly this type of environmental disaster: the deforestation of the masses, including the deforestation of old growth forests.

It doesn’t have to be, Wishnie said, if logging is well managed. However, he emphasized that cross laminated timber only makes sense if the wood comes from a forest that is managed responsibly.

Since a code change in April made it easier for cross-laminated timber buildings to get city approval, developers have sought permits for three such towers, including the Ballard Hotel – and Seattle architects say many more are on the way.

The code change was “like a dam break,” said architect Jack Chaffin, who is designing one of the new cross-laminated timber buildings. He said he had tried building cross-laminated timber dwellings before but always scrapped the designs because it would have added nearly a year to the approval process.

In anticipation of increased demand from Seattle and other countries, two cross-laminated timber plants – Vaagen Timbers in Colville, Stevens County and Katerra in Spokane – opened this summer, nearly doubling the number of local cross-laminated timber producers.

Cross-laminated timber is a subset of solid wood – ultra-dense blocks of plank that are tied together with glue or nails. Solid wood is anything but new: In 1982 the Tacoma Dome was framed with thousands of glue carriers, a form of solid wood.

Until recently, however, architects could not imagine building towers more than thirty meters high entirely out of wood, as fire safety regulations in cities like Seattle did not allow it to do so.

Enter cross laminated timber: Fireproof wood panels that can replace concrete in floors, walls and ceilings. It is made in 12-foot by 60-foot slabs and cut into pre-made patterns by computer to ensure a minimum of construction waste.

As the Seattle area continues to grow – by nearly 600,000 people over the next 20 years, the state estimates – the city must balance the need to build new homes with the need to eliminate waste and carbon emissions from construction. Environmentalists say.

The enormous environmental benefits of cross-laminated timber are the biggest attraction: According to a study by the University of Washington, building a high-rise made of cross-laminated timber emits around 25% less carbon dioxide than if the high-rise were made of concrete.

Wooden buildings also store atmospheric carbon trapped in the trees from which they were built. And greenhouse gases are bound even further when forest areas are replaced and new trees absorb carbon dioxide.

“When we take the wood out of the forest, we plant new forest and capture new carbon,” said Indroneil Ganguly, associate professor in the UW’s School of Environmental and Forest Sciences and one of the study’s authors. Building with wood, he said, is “almost like multiplying acres of forest”.

But Seattle is months or even years behind other cities in the Pacific Northwest when it comes to developing large-scale cross-laminated timber structures.

As of now, the city has a house and a classroom made from the material. Compare that to Tacoma, where the six-story Brewery Blocks Apartments will open this fall and a 127-room hotel is under construction at Joint Base Lewis-McChord. or Spokane, where the 150,000 square foot Catalyst office building will open next year. The Portland Carbon 12 residential complex opened in 2017 and the University of British Columbia has been using the material for years.

In Seattle, the Ballard Hotel will be joined by two cross-laminated timber apartments on Capitol Hill – an eight-story project at 621 Ninth Ave. and a twelve-story project at 1422 Seneca Street – assuming the plans aren’t correct, they change as the approval process progresses.

All three are concrete-CLT hybrids, and an all-wood tower is unlikely to be coming to Seattle anytime soon. That’s because codes encourage making some of the building’s earthquake-proof elements out of concrete – although cross-laminated timber should theoretically perform well in an earthquake, as long as the rigid panels are put together into a flexible wall system, said Erica Spiritos, pre-construction manager for Swinerton Mass Timber in Portland.

While Seattle technically allows for 18-story CLT towers, most projects will likely stay in a six- to twelve-story “sweet spot” – too high to use traditional wood for fire safety, but too short to get the extra cost of reinforced concrete pencil say architects.

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Cross-laminated timber was chosen for the Seneca Street development because the site is less than 7,000 square feet, making it difficult to assemble the machinery needed to make a concrete tower, architect Lauren Garkel said. (She designed both the Seneca Street project and the Ballard Hotel.)

The cross-laminated timber panels are prefabricated off-site and then lifted into place by a single crane “like an erector set” within a few weeks, Garkel said. “The construction team consists of a handful of people with an exercise.”

Cross-laminated timber buildings are rising rapidly. The developer behind the Joint Base Lewis-McChord Hotel – Australian company LendLease, an early cross-laminated timber user – estimates that it employs half of the people on CLT projects as they do on traditional projects, and only two-thirds of the time.

It can be difficult to get used to the sight of a skeletal crew assembling a 100-foot tower out of screws and bolts, said Chaffin, who designs the Ninth Avenue development. “It’s incredibly quiet sometimes.”

There can be a similar feeling of calm inside the building, where residents are surrounded by wood, which is often left exposed and natural. Cross-laminated timber proponents often point out that buildings with natural design elements cause less stress and improve mood in what is known as the “theory of biophilia”. Scientific evidence to support the theory is limited – but it feels intuitive.

Living in a cross-laminated timber building is like “living in a spa,” said architect Susan Jones, who designed the first cross-laminated timber house in Seattle for her family.

When she first started designing the house, part of the cross-laminated timber drawing was its beauty. In their Madison Park home, as in many cross-laminated timber buildings, the exposed wood – in a myriad of colors and textures – sings from walls, floors and ceilings.

Jones moved to her new home in 2015. By this point she had become a CLT evangelist, helping shape national and state changes to building codes that she hoped would pave the way for more and larger wooden buildings. Now her company atelierjones is designing two CLT towers for customers in Seattle.

“It’s amazing to think that all of this journey began with a desire to build a family home in Seattle,” she said. “And from that, 12-story buildings are created.”

At least some of the excitement about cross laminated timber is exaggerated, however. As if it wasn’t enough that cross-laminated timber is beautiful, quick to build, and sustainable, some proponents also predict that it will fuel local demand for Washington lumber.

A study by the University of Washington and the Forterra conservation group punctured this balloon. It is estimated that by 2040, local demand for cross laminated timber would represent less than 1% of the annual timber harvest in the Pacific Northwest. A CLT boom should therefore not lead to a large number of new forestry jobs.

And some environmental concerns about logging remain. Even if demand for wood increases, it could complicate rather than alleviate environmental problems if foresters fail to manage their land sustainably – meaning forests are thinning and not being cut down. lots of open space around streams; and a longer growth cycle.

“The forest products market is optimized to offer customers the most product at the lowest price,” said Brad Kahn, spokesman for the Forest Stewardship Council, which certifies sustainable deforestation practices. “It’s not optimized for stream protection.”

Environmentalists say no city is currently building cross-laminated timber structures fast enough to stave off the most devastating effects of climate change.

“If cross-laminated timber is to improve the climate, we have to scale it up quickly,” said Wishnie of The Nature Conservancy. “A single building is great. But to really make a difference for the climate, we have to increase the pace quickly.”