Peggi Clouston
On timber engineering, education, and species-based design
Peggi Clouston is an engineer, researcher, and professor at the University of Massachusetts Amherst. An author on over 80 publications, she has studied the structural properties of a wide range of biomaterials (i.e. bamboo, straw, grass), with an emphasis on timber engineering.
I first heard about Peggi’s work from her talk at MoMA’s Material Worlds: Mass Timber lecture. It was an absolute pleasure to learn more about her research and passion for innovating with natural materials. We began our conversation talking about a surprising stick in the spokes of timber’s expansion.
Breaking the Cycle
As architects look to design more and more mass timber buildings, they’re running into a bottleneck: not enough engineers are comfortable with wood. We can trace this issue back to universities, where only 52% of surveyed undergrad programs in the US offer wood design courses. Of the schools that do, most are only elective courses or cross-listed as a dual degree. Universities will often combine wood and masonry into a single class even though their properties are wildly different.
When students aren’t taught wood design in school, they are less comfortable working with it, or teaching it, in the future. This explains the current dominant cycle of steel and concrete in engineering programs – it’s what the professors know best. When faculty are less familiar with wood, it’s harder to find the support to squeeze it into already jam-packed degrees. I often joke that I didn’t get to pick a class until grad school…
“As a direct result, approximately half of civil, structural, and architectural engineering students graduating from U.S. schools may have either no exposure or very limited exposure to the proper application of wood as a structural material.“
-Structure Magazine
Elevating timber engineering on par with concrete and steel will produce more wood-experienced engineers, more graduate students in wood design, more research and innovation in wood, more professors teaching wood design…you get the picture. Peggi is working to grow and expand this positive feedback loop of timber innovation. She advocates for wood education at the accreditation level, as well as continuously sharing her knowledge and enthusiasm with students.
Peggi has felt the momentum start to swing towards timber, describing it now as “more of a push than a pull.” Student demand for wood courses is rising — faculty and accreditation bodies are taking notice. One way that Peggi is catalyzing wood adoption is by demonstrating its potential in her own backyard. The John W. Olver Design Building at UMass Amherst puts wood design and local timber on display for the world.
Regional Timber
The Olver Design Building brings together the departments of architecture, building construction technology, and landscape architecture under a single, magnificent, wood-truss roof. The design features glulam post-and-beam construction with CLT floors and a 3D space truss in the atrium. The state-of-the-art building also showcases a wood-concrete composite system - part of Peggi’s timber research.1
The project was as much about displaying mass timber design as demonstrating its feasibility in the Northeast. Mills have been closing by the hundreds across New England as the lumber industry faces decreasing demand. Part of the project’s funding was based on the argument that buildings like this could revamp regional timber markets. All of the wood from the Olver Design Building was sourced from Northern Quebec and processed in the region. The market is shifting, in part because Peggi is researching how to expand its supply.
If you’re asking why the wood didn’t come from the Northeast, you’re in good company. One of Peggi’s latest projects has been studying the feasibility of incorporating more species of wood into CLT design; Lindsey Wikstom stressed the importance of this pursuit in our conversation.
The Northeast is a wealth of forest resources, but most of it isn’t permitted in mass timber. Only acceptable-grade spruce-pine-fir (SPF), Douglass-fir-larch, and Southern Pine are allowed in CLT by current standards. New England has a couple alternatives worthy of consideration.
The most abundant saw timber on Massachusetts’ timberland is eastern white pine.2 It’s fast growing, easy to work with, and currently has a growth to removal ratio of 5:1.3 Eastern hemlock, the fourth most abundant saw timber, is strong, straight and critically under attack. Almost half of all eastern hemlock trees are infested with a terminally invasive pest called the hemlock wooly adelgid.4 Kickstarting CLT manufacturing with these species not only adds jobs to the area, it removes woody debris and increases the value of our forested land.
Peggi and her team found that eastern hemlock CLT was a good fit for widespread CLT adoption.5 Visually graded eastern white pine was less of a home-run, but could find a use in CLT with lower structural demands. The unlocking of new species for mass timber could change the landscape of regional wood design – assigning new value to currently disregarded timberland. Peggi is currently working on building with eastern hemlock CLT; I’m very excited to see her results in a few months.
The Sweet Spot
I asked Peggi how she feels about mass timber’s ‘race to the top.’ She thinks the competition of building taller with wood is fun, and it has served its purpose of popularizing the potentials of mass timber. Taking a step back, she acknowledged that larger timber buildings are not necessarily the most sensible. There is a “sweet spot” for mass timber building height that we could be leaning into.
John Klein has found that mass timber has become “very competitive with concrete and steel for buildings between eight and 12 stories.” Klein sees this as a perfect pairing for mid-rise mixed-use developments - the focus of many of his projects at Generate. At a time when the US is in a housing supply crisis, and younger people (who need housing) care about sustainability more than any other generation, mass timber could help fill the gap.
Peggi is looking for opportunities to increase mass timber’s feasibility through the design of buildings and their components. She is researching ways of developing healthier, more productive relationships with our forests while increasing biomaterial use. Most importantly, she is sharing her knowledge with the next generation of engineers – helping forge a positive feedback loop of mass timber knowledge, research, and curiosity for the future.
Quote I’m Pondering
“We don't seem to appreciate that we're never really taking stuff, we're just breaking it down and moving it about, often making it useless to the ecosystem in the process. We never really consumed that carbon, we just shifted it into the atmosphere and a few people amassed great privilege in doing so.”
- Smith Mordak in Dezeen
What I’m Reading
“We can’t detox our built environment by swapping out fossil-fuelled building materials for timber” by Smith Mordak in Dezeen
The description: We can’t simply plug timber into our current practices. This article asks us to reassess our assumed framework for carbon and forests. I found this article enlightening, and I encourage you to check it out!
"‘No Dumb Questions’: Is there a deadline to fix climate change?" by Dave Levitan, Angelo Leotta, and Tom Nagorski in GRID
The description: Climate change “deadlines” don’t exist. Different governing bodies and organizations’ imaginary lines in the sand have been petrified into apocalyptic points of no return - but climate change doesn’t work that way. As the authors put it, “the ‘deadline” to slow climate change is today, and then tomorrow, and then the day after that.”
See you next week,
Tom
Alaa T. Al-Sammari, Peggi L. Clouston, and Sergio F. Brena, “Finite-Element Analysis and Parametric Study of Perforated Steel Plate Shear Connectors for Wood-Concrete Composites,” Journal of Structural Engineering 144, no. 10 (Oct 2018).
Hamid Kaboli, Peggi L. Clouston, and Seth Lawrence, “Feasibility of Two Northeastern Species in Three-Layer ANSI-Approved Cross-Laminated Timber,” Journal of Materials in Civil Engineering 32, no. 3 (March 2020).
Ibid.
Ibid.
Ibid.