Transportation a Key Factor in CLT Sustainability
Want to lower the carbon footprint of a mass-timber structural system? Consider the species of the lumber and where it’s coming from.
That’s one of the central conclusions of a life-cycle assessment (LCA) recently published in the journal Sustainability and summarized in a report by Katerra. Researchers at the University of Washington worked with Katerra—a design–build company that also manufacturers cross-laminated timber (CLT)—to develop the LCA. Other researchers at the university also conducted an LCA of the core and shell of a mass-timber Katerra building.
Overall, the company could achieve a 14% reduction in greenhouse gas emissions from its CLT operation by sourcing wood locally and by choosing lighter species like Sitka spruce instead of Douglas fir, scientists concluded. Although transportation is not typically a major driver of embodied carbon for many materials, “for lower-carbon products, the relative contribution of transportation is more significant,” said Kate Simonen, AIA, S.E., a professor at the University of Washington and one of the researchers who worked on the building LCA.
Other aspects of production that could be reasonably altered to reduce the carbon footprint included the quantity of adhesive, choice of fuel for kiln drying, and amount of wood waste.
An additional LCA of the Catalyst Building, a CLT office building in Spokane, Washington, found that the total upfront carbon footprint was lower per square foot than that of most typical (steel or concrete) office buildings.
Neither LCA took into account the potential carbon impacts of forestry practices, an area of interest for the green building community since preliminary studies have shown that how timber is harvested—and how often—can greatly affect how much carbon is released (see The Urgency of Embodied Carbon and What You Can Do about It). According to Simonen, there is currently “no accepted way of linking forest carbon to forest product LCA beyond the common assumption that forests are at carbon neutral. Carbon neutrality assumptions are commonly done at the national scale and thus do not address site-specific forest-management practices.”
More on mass-timber construction
For more information:
Melton, P. (2020, May 4). Transportation a Key Factor in CLT Sustainability. Retrieved from https://www.buildinggreen.com/newsbrief/transportation-key-factor-clt-sustainability