The Benefits of Cross-Laminated Timber
By Sharon Thatcher
The construction of a 78-foot bell tower at a church in North Carolina is seen as a "huge step forward in terms of sustainable construction," according to a spokesman for the North American organization, WoodWorks.
"The pending availability of CLT in North America means that building designers will soon have greater flexibility—for taller wood buildings, in particular," said Patrick Schleisman, P.E., regional director of WoodWorks in the Southeast.
WoodWorks, an initiative of the Wood Products Council, maintains that wood is the only major building material that's renewable and sustainable, and that CLT offers a use for wood in building sustainable structures not previously identified with wood.
"Life-cycle assessment studies show that wood products are responsible for less air and water pollution and fewer greenhouse gas emissions than other materials," the organization notes, adding: "The process to manufacture CLT is also energy-efficient and environmentally friendly. Prefabricated panels eliminate jobsite waste, and CLT buildings are proven to maintain their ambient temperatures with less energy."
WoodWorks introduced CLT to North American design professionals in 2009, when it hosted a series of seminars by Andrew Waugh, the architect who designed the world's tallest mixed-use wood structure—a nine-story apartment building in the U.K. that includes eight stories of CLT over one story of concrete.
Between the greenhouse gas emissions avoided by not using steel or concrete and the fact that wood products continue to store carbon absorbed during a tree's growing cycle, Waugh estimated that the U.K. building saved about 300 metric tons of carbon. For comparison, he presented the developer with concepts for two almost identical structures, one in CLT and the other in concrete. The wood structure was estimated to cost approximately $2,208 USD per square foot, compared to $2,722 per square foot for concrete, a savings at the time of 15 percent.
The CLT building was also projected to weigh four times less than its concrete counterpart, which lowered transportation costs, allowed the design team to reduce the foundation by 70 percent, and eliminated the need for a tower crane during construction. It took four carpenters just nine weeks to erect nine stories—and the entire building process was reduced from 72 weeks to 49.
Reprinted with permission from Rural Builder Green/F+W Media, Inc.