A new technique for building wooden mid- and high-rise buildings may unlock a critical strategy for reducing the construction industry’s massive carbon footprint. Although forestry, construction and climate experts disagree on the extent of its benefits, mass timber is a promising substitute for concrete and steel, materials that contribute 5 percent of global carbon emissions each. Buildings in general are responsible for 40 percent of all emissions and architects are calling this new green building technique “the next great disruption to the construction industry.”
What is mass timber?
In order to be considered ‘mass timber,’ buildings must use wood products (typically engineered panels) as the primary load-bearing structure. More than just wood-framed houses, mass timber is a more extensive building style that can be used for mid- and high-rise buildings. Builders can use a variety of woods, often from small trees, to create a strong structure where the wood grain is stacked perpendicularly to further fortify the building.
Because of its versatility in terms of wood types, mass timber projects can be sourced sustainably by capitalizing on small and diseased trees that are cleared to manage forests and prevent wildfires. It also means that sourcing can be localized to further reduce carbon emissions during transportation.
Although deforestation is a major concern around the world, forests in the United States are sustainably managed. A collaboration between the mass timber and sustainable forestry industries has the potential to support this budding construction industry niche with profound implications for fighting climate change.
The benefits of mass timber
The primary benefit of using wood instead of concrete and steel is the reduction in carbon emissions. Since concrete and steel emit greenhouse gases during production and transportation, it is believed that using locally sourced wood will reduce the overall carbon footprint of the building’s construction.
In addition to a lower emission profile, wooden panels, posts and beams also sequester carbon. The wooden panels are lighter and stronger than steel and potentially could be made to be fireproof. Wooden interiors are naturally warming, so they also encourage energy efficiency and reduce heating bills. With rising popularity, especially in Europe and the northwestern U.S., the wooden interiors are also increasingly sought after as an aesthetically pleasing and trendy look.
“Say the typical steel and concrete building has an emissions profile of 2,000 metric tons of CO2; with mass timber, you can easily invert so you are sequestering 2,000 tons of CO2,” architect Andrew Ruff said. “Instead of adding to climate change, you are mitigating climate change. That’s the goal
Furthermore, the construction process has multiple benefits when compared to traditional concrete and steel. For example, the construction process itself is quicker and quieter (making for happy neighbors during construction!), and the materials are less sensitive to weather fluctuations during building.
“Mass timber is the future,” said Russ Vaagen, a fourth generation lumberman in Washington. “It has a lighter carbon footprint; is at least 25 percent faster to build with and requires 75 percent fewer workers on the active deck; comes from forests that are renewable and that, in many cases, need thinning to reduce the danger of wildfire and disease; holds great promise as affordable housing; and even increases homeowners’ health and well-being, according to several studies of wood’s biophilic attributes.”
Is mass timber just a passing trend?
Not everyone is sold on mass timber’s benefits, or at least the extent to which this technique can impact climate change. Its trendiness has re-opened sawmills in Oregon and sent loggers back to work, but is it really all that it is cracked up to be?
“We want to debunk the myth that mass timber is in any way, shape or form related to some kind of environmental benefit,” said John Talberth, president of the Center for Sustainable Economy in Portland.
Most researchers agree that there is simply not enough data to make such large claims about the benefits of mass timber — nor enough data to prove it false. For example, the carbon sequestration calculations need to take into account the transportation, manufacturing and logging of all wood materials when making comparisons to concrete and steel emissions.
According to a recent paper on forestry and climate mitigation, the forest product industry is Oregon’s No. 1 contributor of carbon emissions, so it is not exactly a clean industry. Furthermore, the wooden beams would need to be reused beyond the predicted life of the building itself in order for the carbon sequestration benefits to be realized, because the decomposition of wood also emits carbon dioxide.
Mark Wishnie of The Nature Conservancy explained, “To really understand the potential impact of the increased use of mass timber on climate, we need to conduct a much more detailed set of analyses.”