March 27, 2013 Leave a comment
Wood derived from responsibly managed forests is gaining traction among eco-friendly designers as the preferred building material primarily because the source is renewable and greatly offsets a project’s initial carbon footprint.
Unlike steel and concrete, both of which generate varying amounts of carbon during production, trees absorb carbon from the atmosphere as they grow and permanently sequester it in their fibers unless they rot or burn. Concurrently, advances in software and manufacturing technologies, coupled with innovative assembly techniques, are making it technically possible to quickly and economically design and build iconic shapes and large-scale buildings with wood-based products. Europe and, more recently, Canada are leading the way, but proponents believe that the approach will become more widespread as manufacturers ramp up production capability and building officials reassess outdated codes.
The caveat is that the wood must be sourced from responsibly managed forests. “We are not talking about clear-cutting,” stresses Peter Busby, managing director of the San Francisco office of Perkins+Will. He notes that the relatively recent increase in availability of sustainably harvested woods at reasonable prices makes environmentally minded practitioners feel more comfortable about specifying wood today.
Because natural lumber is limited in size, and the long-term preservation of our forests is yet another environmental priority, architects working on larger projects are increasingly turning to engineered-wood products to obtain the structural dimensions they need while lowering a building’s carbon footprint.
According to Karsh, it can take hundreds of years for a tree to grow large enough to supply solid-wood timber for traditional post-and-beam construction, whereas it takes about 40 years for a tree to supply the 2x6s that are typically used to manufacture glue-laminated timber, or glu-lam, an engineered-wood product that has been on the market for decades. And it takes only about 10 to 15 years to grow the trees used to produce wood chips for laminated-strand lumber (LSL), another common engineered product. When the life cycle of timber production is shortened, our forests become more productive. “If we manage our forests responsibility, which includes generating products that have a shorter renewal period, we don’t risk depleting our forests,” states Karsh.
Engineered woods have many other benefits as well, notes Nabih Tahan, chief sustainable officer of CREE Buildings in San Francisco. For example, they can be manufactured to desired performance standards; are very stable, so they will not twist or shrink; and can be cut to very fine tolerances so components will fit together exactly in the field.
Proponents of large-scale wood construction cite outdated building codes as one of the biggest barriers to this new approach. Most codes limit the height of wood-constructed buildings out of concerns about fire. But these codes were written primarily with stick-frame construction in mind; that functions very differently than mass-timber construction in a fire. While thin wood members will burn quickly, the exterior of massive timber will burn for a bit but then create a layer of char that insulates the remaining interior wood from damage. Furthermore, many of today’s fire codes were written decades ago, before fire sprinklers and computer-controlled fire-monitoring systems were developed. “Those advances change how we look at fire,” notes Karsh. Practitioners working on large-scale wood projects in Canada indicate that they must currently provide equivalency reports to satisfy the code, but Karsh believes that will likely change with the next iteration of Canada’s National Building Code, scheduled for 2015.
Another barrier, at least in North America, is a shortage of manufacturers. According to Podesto of Woodworks, only three companies make structural-grade CLT in Canada, and none in the United States.
But Karsh is not deterred, noting that it took decades for steel and concrete to evolve into the modern systems we use today. “Modern wood construction is 100 to 120 years behind. Only in the last 20 years have we developed it into a truly modern construction material.” He believes the product will become more sustainable in the years ahead. “The idea of building high-rise timber may seem crazy now, but it won’t in five to 10 years.”
(Excerpt of article by Nancy B. Solomon, AIA from Architectural Record. NOT AFFILIATED WITH LAMBOO)
As the world leader in the industrialization of bamboo, Lamboo is striving to implement Laminated Veneer Bamboo (LVB), a rapidly renewable construction material. Through species selection, patented adhesives, and manufacturing processes Lamboo is able to create bamboo panels and components that far exceed traditional timber’s performance in nearly every aspect.
Bamboo as a resource is unmatched in its potential as a environmentally friendly and structurally stable building material. Bamboo produces 30% more oxygen and sequesters 35% more carbon than a like sized timber forest area. With a growth rate of 6-8 years to maturity and root structure that eliminates the need for replanting bamboo can be produced on a large scale with much more ease than timber forests cutting costs and limiting energy consumption. Testing and forecasting by experts has led to Bamboo being referred to as “the next super material” due to it’s amazing attributes and resiliency.
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Blog by: Dustin Dennison