Wooden high-rises could be the future of sustainable cities
Wood is good: Inside our future wooden skyscrapers
Words— Jeremy Freed
With its modest facade and simple rectangular silhouette, UBC’s Brock Commons residence doesn’t particularly stand out amid the high-rise condos and office towers of the Vancouver skyline. Beneath its exterior, however, is a technology that promises to introduce a new era of sustainable architecture to our cities: wood. At 18 stories high, Brock Commons is the tallest “mass timber” building in the world, and according to many experts in the field, it could hold the key to solving some of the planet’s biggest problems.
“[Mass timber] is the option that I want to push for all of the new buildings that I’m doing now,” says architect Carol Phillips, partner at Toronto architecture firm Moriyama and Teshima. In collaboration with Acton Ostry, the firm behind Brock Commons, Phillips won an international competition to design The Arbour, a 12-story mass timber building for George Brown college on Toronto’s waterfront. The building’s designers see The Arbour not just as an important addition to the city’s skyline, but a major step forward in sustainable architecture.
“One of the major issues facing us today is reducing the amount of carbon in our environment,” says Phillips. “Using timber as a building material allows us to sequester the carbon permanently and use it for productive means.” Mass timber construction, she adds, could also be key to providing housing for the world’s booming population, which is predicted to approach 10 billion by 2050. “The reality is that of the three major crises of our time—food security, shelter and climate change—[this] new building system could contribute to solving two of those.”
Brock Common's modular pieces lower the cost as well as the construction time.
Wood has been humankind’s building material of choice for millennia, and for good reason: it’s easy to work with, it’s strong, and it literally grows out of the ground. Here in Canada, many of our heritage buildings are framed with massive Douglas fir beams. This way of building worked well for hundreds of years, but it’s not without its drawbacks. For one thing, wood is highly flammable. For another, those Douglas fir beams aren’t well suited to multi-story structures. When, in the early 20th century, it came time to build the high rises that shaped our modern cities, we switched to concrete and steel and we haven’t look back. Until now, that is.
“[Mass timber] has opened up people’s imaginations to a whole new way of thinking about construction and city building,” says Michael Green, a Vancouver architect and a pioneer in mass timber design. As useful as concrete and steel have been over the last century, he says, these building materials are incredibly carbon intensive. Concrete also takes a long time to pour, set and cure. Wood, on the other hand, is sustainable and renewable, and thanks to recent advances in technology, it can be used to build high-rise towers in a fraction of the time.
The main difference between mass timber and those old Douglas fir-framed buildings is a new kind of wood product called cross-laminated timber or CLT, which is essentially planks of wood glued together under high pressure. Sandwiching wood together with its grain opposed at 90-degree angles maximizes its strength, while allowing it to be produced in a huge variety of shapes and sizes, from supporting beams to massive floor panels. Fire safety remains a frequent area of discussion, but mass timber advocates are quick to point out that fire prevention technologies have come a long way since the 19th century, and any new builds could easily meet or exceed current fire safety codes.
While it may seem counter-intuitive to advocate cutting down trees as part of a carbon-reduction strategy, mass timber’s proponents maintain it can be done sustainably and responsibly. “Generally one thinks about cutting down trees as a bad thing,” says Carol Phillips. “But why it works is that if you start to think of younger trees as a crop, one that you can plant responsibly, and harvest and replant, then you can actually manage it.” According to the builders of Brock Commons, it took Canadian and American managed forests just six minutes to grow the timber needed for the 18-story building, while saving over 2,400 metric tonnes of carbon dioxide from going into the atmosphere.
As interest in mass timber grows, ambitious projects are taking shape around the world. Among these is the Oak Wood Timber Tower, an 80-story housing development that would become the second-tallest building in London if approved and built. Similarly audacious designs have been proposed for Chicago and Tokyo, while Google’s Sidewalk Labs has envisioned an entire neighbourhood of mass timber buildings for Toronto’s waterfront.
London's proposed 80-story Oak Wood Timber Tower.
It’s not just the wood inside these structures that are a radical departure from how things have been done for centuries, it’s also how they’re built. Because wood is so much lighter than concrete and steel, these towers can be built out of modular pieces created in factories and assembled in place like giant model kits. “It means we can control waste, control environmental conditions, control the speed of the process and control the cost,” says Michael Green. “We’re going to be able to drop the cost of construction by 20-30 percent, and once companies are able to do that it’s game over for traditional ways of building.”
The designers of Oak Wood Tower promise to utilize this new technology, thereby significantly cutting the projects’ build times. “When Henry Ford first built a car it was expensive, but once he got it into a factory line the price reduced and reduced,” says Kevin Flanagan, the Oak Wood tower’s architect. “If we can make modular systems that can be used efficiently and effectively, with robots that can assemble the buildings like Lego sets, you have a whole new kind of industry.”
Stockholm's proposed Four 20-storey apartment blocks constructed and finished entirely in Swedish pine.
Humans have relied on trees for shelter since before we walked upright, so it is both ironic and appropriate that now, in an age defined by unimaginable leaps in technology, we are looking back to trees to ensure our survival. As humankind begins to earnestly address the question of how we will continue to thrive on a rapidly changing planet, there has perhaps never been a better time to be reminded that nature is the best architect of them all.