- Cross-laminated timber is strong enough to compete with concrete and steel.
- Use of mass timber in construction is likely to take off at scale over the next decade.
- Increased use would help reduce greenhouse-gas emissions in the construction sector.
The biggest new idea in sustainable building is also one of the oldest construction materials around: timber. But this isn’t ordinary wood. Cross-laminated timber, as it’s known, is arguably the first major structural innovation since the invention of reinforced concrete more than 150 years ago.
Cross-laminated timber itself has been in use for decades, particularly in Austria and Germany. Interest in the material is surging along with concern about the greenhouse-gas emissions associated with concrete and steel. The production of construction materials such as steel, cement and glass accounts for 10% of global energy-related CO2 emissions, according to a United Nations report.
By contrast, cross-laminated timber and other engineered wood products can benefit the climate in three ways: trees capture and store carbon as they grow; long-lived wood products lock in carbon; and these products can be used instead of high-impact materials like concrete in many cases.
Crucially, these products - often referred to under the catch-all term “mass timber” - are strong enough to replace concrete and steel in many of the taller buildings going up in cities around the world. And they have inherent fire-resistant properties that allow their use on a commercial scale, according to Lisa Podesto, Senior Business Development Manager at Lendlease, a global real-estate and investment company that has built more than 20 cross-laminated timber structures.
Competing with concrete
“The beauty of this new product type - mass timber - is that it’s competing in a market space with materials that timber couldn’t compete with in prior building generations,” Podesto said during a panel discussion at the World Economic Forum’s Sustainable Development Impact Summit 2021. “It’s opening opportunities to offset carbon in a different landscape.”
The carbon-reducing impact of green building with mass timber goes beyond the sustainable forests that produce these products and the carbon they lock away. While concrete is essential in foundations, timber buildings are lighter so those foundations can be smaller. Mass-timber products are modular and can be produced in a factory, which means faster construction, fewer trucks delivering materials and less disruption to communities around building sites.
Mass timber set for take-off
“Mass timber is likely to take off at scale over the next decade,” said Caitlin Clarke, Senior Conservation Fellow, Supply Chains at The Nature Conservancy, during the panel discussion.
Yet, while the use of mass-timber products can contribute to climate solutions in some places, there’s no one-size-fits-all approach that can be applied around the world, according to Clarke. We need to know more about how increased use of mass timber would affect forests, the carbon they store and the ways we manage them. The Nature Conservancy is part of a broad research effort to model the impact of mass-timber demand on forests.
“We’re doing scientific research that is informing how this is going to happen, and working on safeguards to help inform how it should happen,” Clarke said.
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Making cross-laminated timber panels is straightforward. Layers of lumber cut from a single log are glued together, with each layer sitting perpendicular to those around it. The panel is then hydraulically pressed to achieve strength.
The production of mass timber drives demand for larger pieces of wood - and larger trees. And that means different sustainable forest-management techniques designed to yield products that will be in use, and storing carbon, for a long time.
The challenge for firms that own and manage forests, and manufacture mass timber is that bigger trees take longer to grow, meaning they could be waiting 40, 60, even 80 years after planting to get a return on their investment, according to Ara Erickson, Vice President for Corporate Sustainability at Weyerhaeuser. The sustainable-forest products company has about 11 million acres of timberland in the US and manages millions more under long-term licences in Canada.
Hit the go button
One benefit of mass timber is that we’re driving increased demand for larger pieces of wood, and larger trees, as well as solid products that stay in use for longer, Erickson said on the Forum panel.
And that demand is critical for firms like Weyerhaeuser to carry on replanting and managing their forests, rather than giving land over to agriculture or other uses. So, the industry needs to continue making the case for the benefits of mass timber to drive take up, she said.
“We have science and data to show that,” Erickson said. “It’s deciding that we’re ready to go do it. That’s our challenge - do we hit the go button?”
Mass timber has been around for decades, and a lot of the work to prove its usefulness has been done. Many of the technical barriers have been cleared and fire-safety issues have been worked out, according to Vincent Martinez, President of Architecture 2030, a non-profit think tank created to help reduce the climate impact of the built environment. Building codes are also opening up opportunities for taller mass-timber structures in many places.
“The biggest challenge now is changing social perceptions of mass timber, so the industry has a green light to step up development,” Martinez said on the panel.
That means using global events such as the Sustainable Development Impact Summit to start debunking misperceptions, such as that increased use of mass timber would lead to deforestation.
What is the World Economic Forum doing to promote sustainable urban development?
Cities are responsible for 75% of global greenhouse gas emissions and are home to over half of the world’s population—a number that will grow to two-thirds by 2050. By going greener, cities could contribute more than half of the emissions cuts needed to keep global warming to less than 2°c, which would be in line with the Paris Agreement.
To achieve net-zero urban emissions by 2050, the World Economic Forum is partnering with other stakeholders to drive various initiatives to promote sustainable urban development. Here are just a few:
- The Coalition for Urban Transitions is the first major global initiative aimed at helping countries achieve inclusive, sustainable economic growth through better urban policies. Consisting of 50 partner organizations, the coalition brings national governments into the process of decarbonizing our cities by connecting them with city leaders. Read our impact story to learn how this coalition is making a difference.
- The Zero Carbon Buildings for All Initiative pledges to fully decarbonize all new buildings by 2030 and all existing buildings by 2050.
- The Systemic Efficiency project arose from the Zero Carbon Buildings for All Initiative. Jointly led by the Forum’s Platform for Shaping the Future of Energy and Materials and the Platform for Shaping the Future of Cities, Infrastructure and Urban Services, the Systemic Efficiency project brings global policy-makers, financiers and the private sector together to create systemic change in the urban ecosystem by optimizing energy efficiency in buildings, transport and various industries.
To learn more about our initiatives to promote zero-carbon cities and to see how you can be part of our efforts to facilitate urban transformation, reach out to us here.
“What we’re trying to do is break down these myths in these dialogues to say - we can get started, and we can keep making improvements in this process,” he said. “Turn that light green.”