A consortium of timber and CLT companies have teamed up with the U.S. Army and Lendlease to test the blast capacity of timber structures in the real world, setting the stage for more mass timber buildings.
By T.H. DeLuca, dean of the W.A. Franke College of Forestry and Conservation at the University of Montana
In this age of changing climate and declining forest health, I believe there’s an enormous opportunity to find common ground through sustainable forest management and mass timber products—specifically, through cross-laminated timber.
During the latter part of 20th century, US forestry leaned toward maximum production and away from the conservation ethic that spawned the establishment of the National Forest System. From the 1950s to 1980s, the practice of conservation forestry as envisioned by inaugural Forest Service Chief, Gifford Pinchot, was overtaken administrators’ economically driven focus on achieve maximum allowable yield, with only localized emphasis on the health of the environment. Predictably, the capacity of the federal forest system to deliver ecological services (clean water, habitat, and aesthetics) quickly declined.
As the impacts of these practices became clearer, the public began to equate forestry with other extractive industries, such as mining and oil exploration. This shift in public perception fueled demand for greater conservation of public lands, and also helped drive major policy changes to federal forest management. The result was an abrupt reduction in forest harvest on federal lands from the mid-1990s to today (timber harvest in Montana is about 20 percent of what it had been in the 80s), leaving what were once heavily managed forests in a state of unmanaged regeneration. The impetus for these changes—preserving our forests—was fully necessary, yet wholly unmanaged regeneration, without the purifying and random influences of fire or wind-throw, has created widely spread over-stocked forest stands that are neither appropriate as wildlife habitat nor productive as forests.
So the question is, “How can forestry and an engineered wood product simultaneously bridge our ecological and social divides?”
A quiet revolution in wood building products began is just now reaching the US. That revolution is the generation of mass timber products—extremely strong panels and beams created from the glue lamination of boards and slabs—that can be used as structural components in large buildings. These panels help create buildings that are structurally sound and that are actually more resilient in the face of earthquakes or fires.
Because CLT is built from small dimensional lumber, one can use smaller-diameter trees in their manufacture. This creates greater value for trees from restoration or fuel-reduction harvests in western and central Montana and creates an economic incentive to conduct habitat-improving activities that might not happen otherwise.
In the last few years, this wood product has brought together foresters, environmentalists, lumber mills, green architects, urban planners, and agency personnel around a shared vision for a sustainable future. This group might be formerly have had very different or even antagonistic interests, but are now sharing a unifying goal of balancing sustainable forest management with green building, rural community well-being, and reduced suburban sprawl.
There’s still a lot more to learn about CLT, and how best to build an industry that will uphold the many values that need to be served, but perhaps the agreement around CLT exemplifies what is needed to overcome polarization and accomplish shared goals through a lasting bond.
Organizers of last week’s International Mass Timber Conference in Portland, Ore., devoted a whole track of the three-day event to environmental and sustainability aspects of the mass timber sector — an indication of the importance of sustainability to the tall timber building brand.
Manufacturing of cross laminated timber, or CLT — the product used to construct tall timber buildings — has the potential to revitalize the timber sector and the rural communities in Oregon that have fallen on hard times because of the widespread closure of timber mills across the state, reports Oregon Business.
But experts concede the environmental benefits of CLT are complex and difficult to measure.
Structural engineers look at the lifecycle emissions of CLT when assessing the environmental impact of tall timber buildings. The lifecycle analysis takes account of the greenhouse gas emissions from the harvesting of the wood, through the manufacturing and construction of tall timber buildings, to their eventual demolition.
When taking this cradle-to-grave assessment, the environmental benefits of CLT are not clear.
By Gillian Flaccus and Phuong Lee / The Associated Press
RIDDLE — John Redfield watches with pride as his son moves a laser-guided precision saw the size of a semi-truck wheel into place over a massive panel of wood.
Redfield’s fingers are scarred from a lifetime of cutting wood and now, after decades of decline in the logging business, he has new hope that his son, too, can make a career shaping the timber felled in Southern Oregon’s forests.
That’s because Redfield and his son work at D.R. Johnson Lumber Co., one of two U.S. timber mills making a new wood product that’s the buzz of the construction industry. It’s called cross-laminated timber, or CLT, and it’s made like it sounds: rafts of 2-by-4 beams aligned in perpendicular layers, then glued — or laminated — together like a giant sandwich.
The resulting panels are lighter and less energy-intensive than concrete and steel and much faster to assemble on-site than regular timber, proponents say. Because the grain in each layer is at a right angle to the one below and above it, there’s a counter-tension built into the panels that supporters say makes them strong enough to build even the tallest skyscrapers.
“We believe that two to five years out, down the road, we could be seeing this grow from just 20 percent of our business to potentially 60 percent of our business,” said Redfield, D.R. Johnson’s chief operating officer. “We’re seeing some major growth factors.”
From Maine to Arkansas to the Pacific Northwest, the material is sparking interest among architects, engineers and researchers. Many say it could infuse struggling forest communities like Riddle with new economic growth while reducing the carbon footprint of urban construction with a renewable building material.