Rethinking the things we thought about wood

A staircase in a modern office buildingA recent article from David Roberts on Vox resurfaces the benefits of using mass timber (aka, “cross- laminated timber” (CLT)). Over the last century, the design and construction industry has leaned away from wood, especially for non-residential construction, and moved toward more manufactured materials, such as steel, concrete, and iron, in the name of safety. But over the last decade, the assumption of safety has been slowly eroding through new studies and testing of CLT for fire and earthquake resistance. Advocates for using CLT also think that it can play a mitigating role in climate change, infrastructure demand, affordable housing, and economic development.

Starting with climate change, Roberts notes that 11% of global greenhouse gas emissions come from building materials and 28% come from building operations. That staggering number of 39% is something design and construction professionals can (and should) address despite perceived industry challenges. The article argues that CLT has the potential to reduce the 11% of emissions from building materials through a number of ways, but most specifically through emissions avoidance. By not using concrete and cement, which account for 8% of global greenhouse gas emissions, and not using iron and steel, which account for 5% of global greenhouse gas emissions, emissions can be greatly reduced. Roberts also suggests that clean energy sourcing is one way to eviscerate the 28% emissions from building operations. If building power supply is electrified with no fossil fuel sourcing, renewables can supply all energy needs, especially when the buildings themselves are designed or retrofitted to demand less energy through net zero or net positive design paired with battery storage.

Supply of CLT is a challenge nationally, but that challenge could easily be turned into an economic opportunity through manufacturing and supply chain infrastructure development that offers communities an economic boost and a new value proposition. Roberts points out that our forests, especially softwood forests in the northwest and southeast, are located in struggling communities where mills have been closed and jobs are in short supply. There are plenty of concerns raised by environmental groups that depending on the forestry practices used, sourcing of wood for CLT could stir up more emissions, essentially voiding out any savings. But if proper sustainable logging processes could be instituted in these regions with manufacturing and supply chain businesses in demand, a real boost in economies could be realized while reducing building emissions.

There’s also the benefit that CLT offers operational and environmental efficiencies in the construction process. Because CLT is factory-produced, it can be cut with precision to the specifications for doorways, windows, and other modular construction methods with cut-outs for plumbing and electrical, among other elements. This means that not only is there less site waste to discard, but the construction process as a whole requires less on-site labor, leading to quicker turnaround and reduced costs.

Lastly, there’s an appealing “kill two birds with one stone” angle that deserves exploration. We’ve all seen the images of out-of-control fires in California and Australia and we know that the causes for these fires aren’t just related to climate change and severe weather, but also poor forestry management and the culpable over-growth. What if the timber supply needed to make the CLT could be sourced from overgrown forests? According to Roberts, CLT does not need to be sourced from large trees; instead “logs with tops as small as 4.5 inches will work.” This is an interesting way to boost the supply and solve another problem at the same time. With infrastructure and affordable housing demands as they are, prompting the use of CLT in larger projects, which can be built quicker with reduced emissions, less labor, and more efficiently all while creating new economic opportunity, it’s worth another look.

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