ShareThisWhen Forests are Well-Managed, Wood is the Most Sustainable Building Material
Sustainability-minded builders have long chosen wood over cement and steel, when possible, to deliver structures with lower embodied carbon emissions. When you compare wood and wood-alternatives side by side, wood always wins in terms of lower embodied direct emissions. But what about the potential unintended consequences of using wood whenever and wherever possible?
For example, could high demand for wood and thus higher prices lead to unsustainable harvests of forests and even the conversion of land once used for food production into commercial forests? How much could this change how well wood stacks up to other materials in terms of sustainability and emissions?
Researchers at the University of Washington set out to answer these questions by undertaking a detailed analysis of the cradle-to-grave emissions associated with wood and other products under a number of different scenarios involving the substitution of wood products for more fossil-fuel intense alternatives.
Not surprisingly, they found that an important pathway for reducing carbon emissions is to grow trees as fast as possible, harvest the wood before the trees become mature and growth begins to taper, and to use the wood in place of other building materials that are more energy-intensive to produce. This contradicts earlier studies that had a more narrow application of lifecycle analyses and often led to incentives to not harvest trees.
Even if this is old news to you, you may want to check out the study (or even the press release) for the wealth of lifecycle assessment numbers provided comparing wood to other building materials. For example, the study compares:
“…replacing steel floor joists with engineered wood joists, thereby reducing the carbon footprint by almost 10 tons of carbon dioxide for every ton of wood used. In another example, wood flooring instead of concrete slab flooring was found to reduce the carbon footprint by approximately 3.5 tons of carbon dioxide for every ton of wood used." 1
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Carbon emission reductions by displacing non-wood products |
Of course, none of this will be news to our neighbors in Sweden, Austria, and Germany, where highly managed forests are the norm and innovative products like cross-laminated timber (CLT) have been in use for decades.
Are you using CLT here in the U.S.? We’d love to hear about it!
[1] http://www.washington.edu/news/articles/wood-products-part-of-winning-carbon-emissions-equation-researchers-say
The University of Washington is also known as the University of Weyerhaeuser. Any study they do is highly skewed to their heavy donor. First, the soil is soon depleted under the heavy management scenario described. Second, the study fails to look at the entire carbon picture such as energy use of the structure. The mass in concrete is a highly desirable feature for solar design and construction. My passive solar home’s walls are concrete with rigid insulation on the exterior. There is no break in the insulation, or air penetration around studs as in wood structures. My colored concrete floors sit on a gravel pad, and don’t have wood or steel joists. The mass is a benefit, and the colored concrete is the finished floor not requiring another cover. The walls are plastered and are the finished surface such that drywall is unnecessary. This exposes the mass to the interior space for comfort and energy efficiency. The energy use of my home is so low that a 3kW PV system produces twice the amount of electricity that is used on an annual basis. I sell power to the grid.