Cross Laminated Timber is poised to turn infrastructure projects greener for the greater good
By Casey Malmquist
Most emphases on sustainability practices in construction have applied more to structural work and less to infrastructure. A dearth of durable options with proven performance is the likely reason many architects and engineers offer in their defense. As alternative materials like Cross Laminated Timbers grow both in popularity and adoption, those reasons are beginning to fade and awareness grows of an opportunity to embrace a greener future without sacrificing construction schedules or budgets.
When it comes to infrastructure and the higher standard of durability associated with such projects, the need for the strength found in typical structural building components like masonry, concrete, and steel has deflected scrutiny over their large carbon footprints. Concrete production alone represents roughly 5 percent of world carbon dioxide emissions, the dominant greenhouse gas. A new alternative from an old construction material source.
The wait for an appropriate, sustainable alternative may be over. A product called Cross Laminated Timber (CLT) has been used in Europe for a couple decades now, and has proven to be a startlingly green alternative to traditional “industrial age” building materials. This engineered wood building system is made from several layers of solid lumber boards, stacked crosswise and bonded together, providing dimensional stability, strength and rigidity. The resulting product boasts more features than are commonly found in materials some might call time-tested:
Durability: With proper design and maintenance, wood infrastructures can provide long and useful service lives equivalent to other building materials. The key is careful planning and understanding of environmental loads and other external factors likely to impact a building over its lifetime.
Strength and Stability: Cross lamination provides for superior dimensional stability and offers significant shear strength performance at a very unique weight to strength ratio compared to other common structural materials. CLT panels outperform anything currently available in the USA.
Seismic Resilience: CLT panels can create an effective lateral load resisting system. Researchers have conducted extensive seismic testing on CLT and found they perform exceptionally well with no residual deformation, particularly in multi-story applications.
With proper design and maintenance, wood infrastructures can provide long and useful service lives equivalent to other building materials.
Fire Resistance: A thick cross-section provides valuable and superior fire resistance for a CLT panel. Their mass means they char slowly, slowing and eventually stopping combustion. With fewer concealed spaces, fire cannot spread undetected. Compared to concrete and steel structures in a catastrophic fire event, CLT structures suffer less degradation.
Environmental: Wood is the only major building material that grows naturally and is renewable. Studies consistently show that wood outperforms steel and concrete in terms of embodied energy, air pollution and water pollution. CLT also has a lighter carbon footprint as wood products continue to store carbon absorbed by the trees while growing, and engineered wood manufacturing requires significantly less energy to produce than concrete and steel.
Life Cycle Analysis: The longevity of CLT components ensures that the future value of any structure remains high. CLT buildings are easily altered and remodeled and are also fully recyclable once they reach the end of their useful life.
Cost Effectiveness: Comparing the cost of CLT versus certain concrete, masonry and steel building types and including the advantages of faster construction time and lower foundation costs, the estimated total costs of CLT structures can be very competitive.
Design Flexibility: CLT has unique structural properties that provide increased design flexibility, allowing for distinctive and innovative projects. Due to wood’s inherent ductility and unique strength to weight ratio, wood offers many advantages over the other common structural materials such as masonry, concrete, and steel.
Speed of Build: From one-person builders to large construction companies, CLT structural systems arrive on-site ready to assemble, saving time and money with a swift and accurate building process.
Reduced Waste: CLT panels are manufactured for specific end-use applications, which results in little to no job site waste. Plus, manufacturers can reuse fabrication scraps for stairs and other architectural elements.
Bridging the gap from concept to proof
The solution looks good on paper, but even better in practice. My company, SmartLam, partnered with the Montana DNRC to design and build bridging solutions to create environmentally friendly temporary bridges to access Montana State Lands for timber harvesting. Our CLT bridging solution replaced the conventional stream crossings that required excavation of the stream bed, placement of a culvert, and covering.
Using CLT in place of the old standards like steel or concrete is one way to reduce the environmental impact of infrastructure projects without compromising on the advances we’ve made in modern construction practices. It is also more cost effective and can benefit a construction schedule – offering the promise of an all-around brighter future.
Casey Malmquist, President and General Manager of SmartLam, has served in this position since SmartLam’s inception in January of 2012, and has led the SmartLam team from the ground level to becoming a globally-recognized producer of Cross-Laminated Timber products. He may be reached at smartlam.com.