In the wake of the deadly heat wave that recently swept across Europe and destroyed more than 40 buildings, we noted that buildings are partly to blame for climate change. The built environment accounts for nearly 50 percent of all carbon emissions and faces an uphill battle towards decarbonization, especially as mass urbanization will require even more buildings to rise in densely packed cities. A major piece of the puzzle involves building materials—steel and concrete are both construction staples, but account for more than 13 percent of global greenhouse gas emissions thanks to high amounts of embedded carbon.
Over the past few years, architects have been experimenting with a greener substitute: wood. The humble material has been used for centuries, but disasters like the Great Chicago Fire of 1871 have long cast it in a negative light compared to concrete and steel. A novel way of repurposing wood, however, is starting to take hold. Using mass timber, particularly cross-laminated timber, involves sticking pieces of wood together to form large slabs, which are then stacked like Legos. These slabs can exceed the performance of concrete or steel—especially during fires, earthquakes, and blasts.
Mass timber can also reduce the global warming potential of buildings up to 26.5 percent because trees absorb carbon throughout their life cycle. Since the slabs are prefabricated, factories can produce exactly to specifications if they receive detailed plans from architects. This not only drastically reduces material waste, but allows for timber buildings to be constructed 25 percent faster than concrete buildings and with 90 percent less construction traffic. So what’s stopping mass timber from mass adoption? Outdated regulations, mainly. The International Building Code finally approved timber buildings to rise 18 stories for the first time in 2021.
Developers are quickly catching on to mass timber’s appeal, though. In recent months, a spate of buildings around the world have shed light on its potential as a material. In New York, which recently approved the construction of mass-timber structures up to 85 feet tall, Timber House by Mesh Architectures has become the tallest such project in the city. Toronto also revealed the design for a 31-floor residential tower that’s slated to become North America’s largest mass-timber building. Kengo Kuma famously clad the Japan National Stadium, the sylvan centerpiece of the Tokyo 2020 Olympics, in timbers sourced from all 47 prefectures. The material is exploding in Europe, where it covers the 280-foot-tall Mjøstårnet that overlooks Norway’s Mjøsa Lake and features a restaurant, swimming pool, and 72-room hotel.
Not everyone is on the timber train, however. Critics often decry its perceived flammability, but building experts claim that’s a misconception. Large compressed masses of wood are difficult to ignite. Their outer layers often self-extinguish, which protects interior layers and allows the building to maintain structural integrity for several hours in intense fire. Other reservations lie in the supply chain and deforestation—environmentalists fear that North American forests aren’t protected enough to endure sharp upticks in demand, but it’s estimated that United States forests can collectively grow enough wood to create a 20-story building every 13 minutes.
The Vancouver architect Michael Green, a mass timber evangelist, cites one major drawback to the material becoming more widely adopted. “We’re not at the point where (timber is) cheaper,” he told CNN. “And we want it to be cheaper because, at the end of the day, that’s what governs the entire industry—the cheapest solution. We have to solve climate change by making things more affordable, not by asking people to suck it up and pay more, because it doesn’t work.”