Artículo

Why timber buildings are catching on

Engineered wood construction is booming, and policy initiatives further encourage its rise

octubre 22, 2019

When Sidewalk Labs, a subsidiary of Alphabet Inc., announced this summer it would build an entire neighbourhood out of mass timber in Toronto, it lent credence to an idea that would have seemed outlandish a decade ago: the sustainable buildings of the future might just be made out of wood.

Timber buildings are sprouting up the world over. There are now nearly 600 built or planned wooden commercial buildings in the contiguous U.S., according to The Wood Products Council. New York City will soon have its first two timber buildings in nearly a century, with a pair of midrise developments in South Williamsburg. Swatch Group’s new headquarters in Switzerland is made of local timber. Developers in Japan and Australia have embraced the building material.

“Mass timber is being considered for a growing range of commercial real estate projects,” says Peter Feigenbaum, a Senior Project Architect at GF55 Architects.

While greater sustainability and lower costs have helped usher in this wooden construction boom, policy initiatives are also playing a big role.

For instance, height restrictions on timber buildings were recently loosened in British Columbia and Oregon. Canada – where a proposed project could become world’s tallest wooden skyscraper – is providing incentives through the Green Construction Through Wood program.

 “It’s aesthetically attractive as well as more sustainable, so it’s getting a lot of attention from both developers and governments,” Feigenbaum says.

Driving the hype: safer, and in some cases cheaper, materials

Inviting aesthetics and occupant wellbeing are a major feature of mass timber construction.

“Developers are starting to realize that wood provides an inviting workplace environment that people want to go to every day,” says Les Medd, Senior Vice President of Project & Development Services at JLL. “And that adds to their well-being, their productivity, and the overall success of the office space itself.”

But it’s not just about doing good while looking good. The materials used to construct these buildings – engineered woods like cross-laminated timber (CLT) and glue-laminated timber (glulam) – provide the strength of structural steel “at a fraction of the weight,” says Medd.

They’re also safer.

“Despite the commonly held concern about combustion of wood, mass timber members actually outperform steel under fire conditions,” he says.

And in some cases, building with wood is cheaper. “With the advances made in mass timber, and its increasing popularity, it is becoming more cost competitive as compared with more traditional concrete and steel structures,” Medd says.  “However, the cost of mass timber can vary significantly depending on the type of system used, and owners are well-advised to explore the various alternative systems that are available in the market to fit within their budgetary and aesthetic requirements.”   

Another advantage of mass timber buildings is the savings on interior finishing costs, as exposed wood is a desirable finish on its own and does not require application of other finish materials, Medd says.

Shortened construction timelines also bring down costs. While concrete takes weeks to set, mass timber walls and floors can go up in hours, with panels produced in the factory at the exact needed dimensions including precision cutouts for doors, windows, and building services.

The superstructure for T3 Minneapolis, a mass timber building that opened last year, was built in only nine-and-a-half weeks.

Sustainable materials

The main draw for policymakers, however, is sustainability. Producing concrete and steel is highly carbon-intensive, together accounting for nearly 10 percent of global emissions. By contrast, trees capture and store carbon dioxide as they grow – around one ton per cubic meter – making mass timber a much more climate-friendly building material.

Because these materials can be made from panels of fast-growing trees like spruce, they can be produced without harvesting old-growth forests.

While there is debate over the exact emissions profile of mass timber when its full production lifecycle is accounted for (like including diesel-fueled logging equipment), it is estimated to be about a third less than a comparably-sized concrete and steel building.

“The environmental benefits are clear, even if they are not yet fully proven,” Medd says.

Design and supply chain challenges

The true obstacles to widespread construction with engineered wood are subtle. While the lightweight, flexible nature of wood improves its performance in earthquakes, this elasticity also poses challenges to open plan offices and other buildings requiring large open spaces.

“Most of the mass timber buildings in the market today have relatively close column spacing, typically not greater than 6m by 6m (20ft x 20ft) spacing,” says Medd. “For developments requiring more open space, mass timber elements have to be sized considerably larger to ensure an acceptable range of vibration for the floor -- and that can drive up the cost substantially.”

Labour and proximity to materials can also pose obstacles.

“Mass timber can be cost-competitive, but there are currently only a few markets close enough to both the supply chain for the materials and contractors trained to work with them,” says GF55’s Feigenbaum.

Because of this, leading lumber-producing regions of Canada and the Pacific Northwest have emerged as early mass timber leaders in North America.

Another roadblock is policymaker support. Despite recent victories, most jurisdictions have been slow to accommodate these materials in building codes.

“There is a long way to go, but the growing popularity of mass timber itself could influence change,” Medd says. 

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