Benefits of Building with Cross Laminated Timber
As more customers include sustainability as a building specification, many construction professionals have come to terms with the fact that measuring environmental impact of a building project is more pro forma and less of a special request. In order to more efficiently deliver a project without creating additional work of procuring proof of sustainability, many professionals are turning to sustainable building systems, such as cross laminated timber and glue laminated beams and columns, or mass timber projects.
Cross Laminated Timber (CLT) has been used in Europe for a couple decades now, and has proven to be a solidly 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 end product is one that marries the strength and stability builders expect from less-sustainable resources, but a smaller overall impact on the environment.
Typical structural building components like masonry, concrete, and steel have large carbon footprints and require great amounts energy to produce. Concrete production alone represents roughly 5 percent of world carbon dioxide emissions, the dominant greenhouse gas. Supported with data from the U.S. Green Building Council revealing that 40 percent of national CO2 emissions come from buildings, it is more than clear that alternative building materials made from engineered wood products can make a meaningful impact on reducing green house gas emissions and thereby positively affecting global climate change.
As many professionals ask when getting to know a new building technology: does CLT really do the job it's supposed to do? There are many features of CLT that answer that question:
Durability: With proper design and maintenance, wood structures 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.
Thermal Performance: CLT panels are better insulators, requiring little or no insulation. Since CLT panels can be manufactured using CNC equipment to precise tolerances, the tighter-fitting panel joints results in better energy efficiency for the structure. The solid panels also mean nearly zero air infiltration into the building envelope. Interior temperatures of a finished CLT structure can be maintained with just one-third the normally required heating or cooling energy.
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.
Moisture Management and Vapor Diffusion: Wood is naturally hygroscopic, serving as a moisture management system within a building envelope. Ideally manufactured at 12 percent moisture content, wood's ability to absorb and emit moisture can naturally stabilize an indoor environment. CLT buildings "˜breathe', minimizing the risk for mold growth and maximizing the comfort of its occupants.
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.
Healthy Indoor Environment: The only constituents of a CLT building system are wood and a non-toxic/non-VOC adhesive. CLT building materials do not introduce any toxins into the indoor environment providing clean indoor air quality. CLT wall systems are naturally breathable. Integrated with appropriate mechanical systems, this creates a healthy indoor environment that maximizes occupant comfort and health.
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 is proving to 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.
If you're looking for a stateside proof of concept, look no further than Whitefish, Montana. A multilevel building currently under construction selected a CLT elevator shaft. If the construction team was using concrete masonry units (CMU), the common and traditional method, they would have to budget for a process involving eight to 12 people, several inspections, added equipment to stack and cure the shafts, and allow three weeks for the entire process. Compare that to a CLT shaft, prefabricated in the SmartLam facility with zero impact from weather conditions, that can be assembled on site with just three people and a crane operator in just a matter of hours. The cost of a CLT modular structure is in the neighbourhood of 70 to 75 percent of conventional methods and saves nearly three week's time in the overall project schedule
As mass timber building systems become more common and mainstream, energy conservation expectations increase at a commensurate rate. Using CLT in place of the old standards like steel or concrete is one way to reduce the environmental impact of a building without compromising on advanced modern structural integrity. It is also more cost effective and can benefit a construction schedule. It's a solution for the future.