As sustainability becomes an increasing component of real estate decision making, some stakeholders have tried to push for a return to the era of structural wood construction in midrise commercial buildings. While centuries of experience with the challenges of building and maintaining midrise wood structures mean we need little education on why we long ago turned to steel construction, the wood industry’s environmental claims require some skeptical investigation. Here are six questions to ask when looking at a “sustainable” wood-framed building:
What do we know about the “new wood?”
This isn’t traditional wood construction -- the latest trend is building from manufactured cross-laminated timber (CLT) and other manufactured wood structural products, which their producers tout as the “future” of construction. Unfortunately, the use of CLT in midrise construction is new enough that real-world long-term durability and safety data are also still in the future.
What about upkeep?
Wood structures require more upkeep, inspection and maintenance than those built from steel. If left unchecked, problems such as termites and dry rot can create significant issues that aren’t readily apparent until too late. Potential owners of existing wood-framed structures will need to ensure that inspections are especially thorough and performed by inspectors with expertise in the many challenges of wood building upkeep.
What does wood construction do to our forests?
While the wood industry touts that “total forest cover” in the United States has been steady or increasing over time, that’s only true when they count artificial tree plantations the same as actual forests. Academic and government researchers agree that logging plantations have lower biodiversity, lower productivity, capture less carbon and are generally no substitute for the forests cut down to be turned into “green” building products.
How much of your “green” building material was wasted?
A significant amount of wood is wasted long before it makes it to the construction site. Once a tree is harvested, only about half of its mass will become sawn wood products. Much of what remains is often burned as furnace fuel at the sawmill to support the claim that these facilities are “powered by renewable energy.” Eventually planting a tiny tree to replace the mature tree that was cut down doesn’t make it “renewable” and “sustainable,” especially when you’d burned much of the mature tree to generate the energy to convert the other half into a building product.
Does materials choice impact insurance costs?
The cost of builder’s insurance for a midrise wood structure is generally higher than for a comparable steel building due to increased risks before fire suppression and management systems are installed. Given the newness of CLT and other manufactured wood structural materials and the lack of long-term data on safety and durability in these applications, it’s impossible to say how underwriters will view today’s wood buildings in the future.
What happens at the end of my building’s service life?
It may seem like a distant future, but end-of-life should be taken into account when considering sustainable structural materials. Wood used once as a structural material can only be “downcycled,” often becoming landscaping mulch, pallets that end up in landfills or wood pellets to be burned as fuel. Simply put, recycled wood can never be used to produce a new wood stud, while all steel products can be recycled into other steel products; a steel beam can become a new beam, or even a car or soup can or refrigerator. In the United States, more than 90 percent of structural steel is recycled at the end of a building’s life.
Simply because structural wood products were once part of a tree doesn’t mean that they’re a truly sustainable building material that makes sense for building owners or tenants. A century ago, structural steel revolutionized construction and the very nature of our cities and society – calling a return to the very material that steel replaced “sustainable” should make the real estate industry skeptical.
Mark A. Thimons, P.E. is vice president of sustainability with the Steel Market Development Institute, a business unit of the American Iron and Steel Institute. He is responsible for overseeing the Steel Recycling Institute as well as research projects that demonstrate the life cycle advantages of steel in all markets.