Is mass timber the eco-friendly future of building materials?
Mass timber is gaining momentum as a future-friendly building solution as the number of public institutions and private developers pledging to attain net-zero carbon emissions increases.
Whether they are leaning on public-private partnership or traditional delivery methods, owners and developers are recognizing the benefits of wood as a versatile, sustainable and structurally efficient feature for their projects. With public and private support for this renewable resource, experts believe mass timber could challenge steel and concrete as favored construction materials.
"Mass timber offers cost and value considerations that developers and clients see as benefits. Mass timber supports regional economies, saves time on the speed of construction, and is a renewable resource—with the added benefits of improved daylighting and interior aesthetics, which benefits the health and well-being of the end-user as well," said Swinerton Builders (Swinerton) Pacific Northwest Regional Director of Preconstruction William Silva.
For example, at Northlake Commons, the utilization of mass timber estimates 1,990 metric tons of avoided CO2e (carbon dioxide equivalent) emissions, with a total carbon benefit of 2,920 metric tons; this is equivalent to removing 558 cars from the road or to the energy required to operate 249 homes for an entire year. It is also estimated that forests in the U.S. and Canada can regrow the equivalent wood volume in four minutes.
Swinerton's commitment to mass timber began in 2016 with the design, permitting, and construction of the then largest mass timber office building in the U.S.—First Tech Federal Credit Union Oregon Corporate Campus—which was delivered four months faster and four percent cheaper than structural steel.
While building designs will continue to push toward net zero energy, reducing operational carbon through better energy efficiency and cleaner energy sources, there is growing policy and regulation emphasizing the importance of reducing the embodied carbon of infrastructure as well. Structure and foundation make up over half of a building's embodied carbon footprint, so they are often targeted first for reductions. Every metric ton of wood used in place of concrete and steel in the structure is estimated to avoid 3.9 metric tons of CO2 emissions, and this is compounded by the fact that mass timber buildings are lighter and reduce the carbon (i.e., concrete) in the substructure.
Life-cycle assessment (LCA) is the industry tool for evaluating the embodied impacts of a building design, but what it cannot account for is the potential carbon "storage vault" mass timber infrastructure offers cities. Mature forests are maximizing their carbon storage while growing forests are maximizing their carbon sequestration. By sustainably harvesting trees off the landscape and storing that carbon in wood structures for the life of the buildings, forests are allowed to sequester carbon more rapidly from the atmosphere and avoid releasing a large portion of the carbon stored in the removed trees.
While the softer benefits of mass timber, sustainability and aesthetics frequently lead project teams to want to use a mass timber solution, the construction benefits are often what enables them to happen.
"We can control costs through early assessment on project alignment with building code and efficient structural layouts that allow for complementary benefits with other building systems and maximize prefabrication," added Silva.
Swinerton offers examples of mass timber projects below:
