By: The Guardian
The concrete jungle has a rival: forests. Two urban building projects, in New York City and Portland, Oregon, will be changing their city’s skylines with an environmentally sustainable, cost-competitive building material. The key ingredient? Wood.
Called mass timber, the material is an umbrella term for large, solid chunks of panelized wood. When used in buildings, the benefits are sky high: flexible, strong, fire resistant and carbon-sequestering. Mass timber could prove to be a viable alternative to concrete and steel for mid-to-high rise buildings.
The two projects in question were nationally recognized last September when each was awarded $1.5m from the US Department of Agriculture’s (USDA) Tall Wood Building prize, a competition that sets out create America’s first modern mass timber building, reaching 80ft or higher.
Moreover, the USDA is looking to these projects to mitigate climate change and support jobs in rural America.
The winning proposals are 475 West 18th Street, a 10-story residential condo in Manhattan’s West Chelsea neighborhood, and Framework, a 12-story mixed-use building slotted for Portland’s Pearl District.
The Manhattan building – a project of 130-134 Holdings LLC, in partnership with Spiritos Properties, Arup, and ShoP Architecture – will be New York City’s first to use mass timber systems.
And apart from building specs, “Spaces that utilize wood in a significant way have been shown to have considerable psychological benefits for the inhabitants, from reduced hearts rates and stress levels to improved productivity,” said Amir Shahrokhi, project director at SHoP.
Portland’s Framework – designed by Lever Architecture and in partnership with developer Project^ – will incorporate offices for landowner Beneficial State Bancorp, ground floor retail space, and affordable housing for area median income tenants. The building will be constructed primarily from cross-laminated timber (CLT), a nation’s first.
Out of the mass timber initiative, CLT might prove to change the construction paradigm.
Essentially, CLT is plywood (actually invented in Portland in 1905) on steroids. It’s manufactured by layering panels of 2-ft-by-6-ft lumber at 90-degree angles, then literally gluing them together on their wide faces.
Similar to panels of precast concrete, CLT is prefabricated, which means most of the work is done off-site, leading to shortened construction cycles and less environmental impact on the site itself.
“The advantage of CLT over concrete is that it’s lighter, so it goes up easier and faster than concrete does … it’s also quieter in construction,” Judith Sheine, department head of the School of Architecture at the University of Oregon. “And if you have to make tiny adjustments, it’s possible to do with wood and it’s not really possible with concrete.”
CLT is nothing new, however. It was invented in the 1970s in Switzerland as a sustainable alternative to concrete, masonry, and steel construction. As such, CLT buildings have cropped up in Scandinavia, Austria, Germany, the UK, Australia and Canada, from commercial high rises to modular construction in housing and classrooms.
But only recently has CLT reached the United States.
According to the USDA, during the recession, the drop in new construction and decline in home remodeling had a serious impact on wood manufacturing. So it’s hoping next-generation wood products can pick up the slack in the non-residential market. Roughly 35 jobs are created for each million board feet of wood processed.
DR Johnson Lumber is the nation’s only manufacturer of structural grade CLT. Conveniently, it’s located in Riddle, Oregon, as the state’s lumber industry has been in decline for close to 50 years.
Anyeley Hallová, at Portland’s Project^, anticipates that CLT manufacturing might boost rural economic development and promote what she calls “a virtuous cycle”.
“Sustainably harvested wood could activate mills in Oregon to engineer wood products, like CLT, which would then be used within Oregon cities,” said Hallová. “So the cities are fueling the cycle, but the products fuel the city.”
The key is keeping manufacturing local, as it supports communities and cuts waste from long-distance transportation. “In the future Portland is going to expand dramatically and wouldn’t it be revolutionary to be able to actually grow those buildings within a couple hours of the city itself,” said Thomas Robinson, principal and founder of Lever Architecture. “I think it’s analogous to the farm-to-table movement.”
The reduced carbon footprint of mass timber and CLT construction, too, is looking hopeful. According to statistics provided by ReThink Wood, the 10-story CLT Forté project in Melbourne, Australia is expected to reduce more than 1,400 metric tons of carbon dioxide (CO2) emissions when compared to concrete and steel – the equivalent of removing 345 cars from Melbourne’s roads.
The Crossroads, a Promega corporation building in Madison, Wisconsin, uses portions of CLT in its ceilings. From that alone, its total potential carbon benefit is estimated at 692 metric tons of CO2, which compares to keeping 132 cars off the road for a year, or providing the total energy to operate a home for 59 years.
Long known as the glue of our civilization, concrete is responsible for about 5% of global CO2 emissions. And for every ton of cement made, one ton of CO2 is produced.
So could mass timber, or CLT, be an industry competitor? CLT’s success “really depends on the market”, said Judith Sheine. “When we have more substantial CLT production in use, I think the prices will be very competitive.”
But the road to approve CLT as a sound building material in the US has been arduous, with engineers and architects working to prove that it complies with codes and is resistant to fire and seismic events.
“Wood has a very high strength-to-weight ratio, that means you’re not attracting as much force,” said Robinson. “The building isn’t as heavy, so it has the ability to be more flexible and potentially withstand a larger seismic event. That in itself is incredibly sustainable.”
So wood structures make sense in seismic-heavy regions, especially in the Pacific Northwest, where a 9.0 magnitude earthquake is expected to hit in the next 50 years. As such, Framework has in fact been designed to exceed the state’s building codes for earthquakes.
But not everyone is excited by new buildings in Portland. Due to its rapid growth and a non-negotiable urban growth boundary, the city is moving to deregulate the height of buildings. Developers will no doubt jump at the chance to build upward, much to the chagrin of some residents.
Michael Mehaffy – an urban development consultant, tall building critic and Portland resident – is skeptical of the “novelty art” approach that often replaces proven and durable industrial design.
Though Mehaffy supports construction that uses sustainably harvested wood, he said “it’s all too tempting to use greenwashing to justify buildings that are otherwise detrimental to the city … I think our first priority ought to be to assure that we re-use older buildings, as the greenest building is the one that’s already built.”
Framework’s construction is scheduled for October 2016. The team sees the project as a trailblazer for more CLT structures in Portland and beyond. “There’s interest at every level of the state in this type of building,” said Robinson.
“The key is developing the supply chain … we need more than one manufacturer,” he continued. “Ideally there comes a day when people can choose between mass timber, steel and concrete. We don’t see mass timber replacing those, it just becomes another option when certain parameters and goals apply to a project.”
By: The Guardian