Why Wood? AND OTHER BIOPHILIC CONSTRUCTION QUESTIONS
BY ALLISON MILLS
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ike farm-to-fork for the local foods movement, forest-to-frame is a new way to think about using wood for construction and building stronger regional bioeconomies. Rather than going back to hand-hewn cabins, the future of sustainable construction for skyscrapers, cars, classrooms, and homes relies on mass timber and innovative wood products. One such material is hardwood cross-laminated timber (CLT). It’s an oldie, but a goody: Crossed grains in boat hulls—pinned in place with dowels—sailed the world for hundreds of years. Modern CLT panels are pressed boards of low-grade pulpwood that fit together like toy building blocks and can be custommade, cutting down on waste, and the material has become a prime choice for earthquake safety. Currently, only softwoods like pine and other conifers are included in building codes for CLT, but hardwoods like maple and poplar may have equal or even better chemical and mechanical properties. In Michigan, with more than 19 million acres of timberland and more maple than you can shake a stick at, that makes hardwood CLT a major untapped market. “It’s easy to sell high-value veneer and timber logs, but the challenge is what to do with lower-value pulp logs,” says Mark Rudnicki, professor of practice in forest biomaterials and
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the coordinator of industrial research, innovation, and commercialization at Michigan Technological University. Rudnicki points out that Michigan already grew a forest economy with logging, lumber, paper, pallets, furniture making, maple syrup, and tourism. But as the pandemic’s timber prices illustrate, supply and demand is subject to change—and grocery coupons, pancakes, and Adirondack chairs alone cannot seed future forests’ potential. “Softwoods—which we really mean are conifers instead of angiosperms—are graded for construction, while hardwoods—which have a lot more variety in material behavior—are graded for appearance,” Rudnicki says. “It’s not rocket science, but someone has to do all the detailed tests to make hardwood CLT accepted for construction.” Michigan Tech, West Virginia University, and Virginia Tech are leading U.S. testing for hardwood CLT. Rudnicki works alongside Xinfeng Xie, associate professor of forest biomaterials at Michigan Tech, and Munkaila Musah,a Michigan Tech doctoral graduate now at Auburn University. When they talk about hardwood CLT, they get a handful of common questions.
DO WE HAVE ENOUGH TREES?
When forests are managed properly, trees can be renewable and grow as
WOOD BENEFITS
WoodWorks, part of the Wood Products Council, and Think Wood, funded by the Softwood Lumber Council, gather data on CLT, mass timber, and other wood construction. In Europe, wood and natural construction are called biophilic designs. Here are their main selling points: % wood buildings can cost less and earn more % carbon dioxide emissions can be reduced 15% to 20% % rapid on-site assembly is easy with modular units % re d u c e d we i g h t m e a n s smaller foundations % wood’s vibration properties improve earthquake and wind safety % heavy beams may improve structural integrity and fuel contribution during fires and softwood CLT panels hold up to International Building Code (IBC) standards
fast as they’re harvested, which means 1% to 2% of our forests each year. But most people hear “logging” and picture the clear-cut landscapes of yore. Rudnicki replies, “That’s not forestry; forestry came after. That wasn’t forest management, that was denuding the landscape.” Landscapes today in Michigan have thicker forest stands with more dead and downed trees, which pose wildfire hazards. Selectively harvesting prime logs and clearing some of the spindly competition is a more sustainable way to fell trees and this mix of wood is what interests Rudnicki, Xie, and Musah. The pulp wood slated for pallets and paper could also be used for the modular CLT construction blocks first developed in Austria in the early 2000s.
