Michael Green has seen the future of the building industry, and that future is wood. Lots of wood. The Vancouver-based architect is among the most ardent proponents of what is known as mass timber, prefabricated structural wood components that can be used to construct buildings—even large-scale buildings—faster, with less waste and eventually with less money.
Most crucially, Green and others say, building with mass timber can ameliorate climate change because it produces less in greenhouse gas emissions than construction with concrete and steel. And wood has the benefit of storing the carbon dioxide trees absorb during their growth, keeping it out of the atmosphere indefinitely.
“Roughly 11% of the global carbon footprint is related to what buildings are made out of,” said Green, whose mass-timber projects include the T3 office building in Minneapolis (the name stands for timber, technology and transportation) and a pair of buildings for Oregon State University’s College of Forestry, including a research and development facility for the school’s TallWood Design Institute.
It is estimated that nearly 2.5 trillion square feet of new construction will be needed over the next 40 years to support growth in the world’s increasingly dense urban areas, according to the 2017 Global Status Report issued by the U.N. Environment Program. “If we continue to build the way we are,” Green said, “we are absolutely not going to meet any kind of climate objective, and we’re going to change our children’s future forever in a pretty bad way.”
While cutting down trees to make buildings may not sound environmentally sensitive, mass timber supporters argue that wood could be harvested from sustainably managed forests.
Increasing numbers of architects, developers, governments, educational institutions and corporations are embracing wood. In Biel, Switzerland, Swatch Group just completed three buildings said to be among the largest timber construction projects in the world. Designed by Shigeru Ban, an architect admired for his innovative use of wood, the complex includes a serpentine company headquarters wrapped in a spectacular latticed timber facade.
Notably, big players in the tech world are adopting wood. Microsoft is using mass timber throughout its new Silicon Valley campus, while Sidewalk Labs, Google’s sister company, has plans for a new waterfront district in Toronto consisting of wood buildings, some as tall as 30 stories.
“We’re past the tipping point in the acceptance of wood,” said Thomas Robinson, founder of the Portland, Oregon, firm Lever Architecture, which recently completed the Nature Conservancy’s local offices and community center using Forest Stewardship Council-certified wood and is working on an expanded mass-timber headquarters for Adidas. “The people who are the innovators, looking for the next thing, a richer experience for their employees or how they live, they’re turning to mass timber.”
The benefits are aesthetic and environmentally responsible, he added. “People just connect to wood in a way that is visceral.”
Green, who is consulting with Sidewalk Labs on its proposal for Toronto, said mass timber should be embraced for buildings much larger than residential and low-rise structures, which now account for most wood construction. When the seven-story T3 Minneapolis (designed with DLR Group) was completed in late 2016, it was the tallest wood building in the United States. An eight-story residential building in Portland called Carbon 12, has since been built.
A second T3-branded property is planned for Atlanta, and other projects are in the works for Nashville, Tennessee; Denver; Austin, Texas; and Toronto, where two are planned.
At the end of last year, the International Building Code was changed to allow wood buildings of up to 270 feet tall, or the equivalent of about 18 stories, from 85 feet. The U.S. code won’t adopt the revised standards until 2021, but some states will allow projects based on the new criteria to be submitted before then.
In Europe, where mass timber began gaining traction nearly 20 years ago, encouraged by aggressive climate policies, wood buildings are rising to new heights. Last spring the 18-story Mjostarnet office and residential tower by Voll Arkitekter in Brumunddal, Norway, became the world’s tallest mass-timber building at 280 feet (including an openwork wood structure on its top).
Just a few months later, the HoHo Vienna, a mixed-use building designed by Rüdiger Lainer + Partner, was nearly the same height but had six more floors.
To be clear, timber advocates are not pushing for a return to old ways of building, before devastating fires prompted large cities like New York and Chicago to ban most new wood construction in the 19th century. Mass timber refers to a variety of different types of engineered wood components, the most common being cross-laminated timber (known as CLT) and nail-laminated timber (or NLT), in which multiple layers of wood planks, stacked at 90 degrees, are glued or nailed together under pressure to form structural panels. So-called glulams, which are made in a similar fashion and have been around for more than a century, are typically used for long elements like beams and columns.
Mass-timber components have a resistance to burning that is relative to their thickness, as extensive tests conducted by the U.S. Forest Service and the American Wood Council at the Bureau of Alcohol, Tobacco, Firearms and Explosives Fire Research Laboratory and elsewhere have demonstrated. When mass timber is exposed to fire, the outer layer chars, slowing the burn and creating a protective barrier around the core. In multiple fire tests, mass timber’s performance has consistently exceeded building code requirements.
Wind becomes more of an issue as buildings get taller, one reason that most mass-timber buildings higher than several stories are hybrid structures, incorporating some concrete, steel or both to provide rigidity and weight.
For now, a lot of mass-timber projects are about recapturing the spirit of old industrial wood buildings, albeit updated with 21st-century comforts and technology. The New York firm SHoP Architects plans to use mass timber in Toronto’s Distillery District for a sprawling five-story retail and office complex inspired by the area’s historic buildings. It will be SHoP’s first mass-timber project, after plans for a much-anticipated 10-story residential tower in Manhattan fizzled a couple of years ago when approvals stalled.
“People want to live and work in these kinds of buildings—they have a sense of connection to the material,” said Chris Sharples, one of SHoP’s founding partners. “And what we’ve seen from fabricators and builders is that there’s a 35% drop in construction time for mass-timber buildings, which means the carrying costs are less.”
And, he said, the work sites are quieter and cleaner, generating less waste. “When you live near a job site, it’s noisy, with all of the trucks—it’s a horrible quality of life,” Sharples said. “You see these wood buildings go up, and it’s like a barn-raising in the middle of your block.”
© 2019 The New York Times