The World’s Most Advanced Building Material Is… Wood

cross-laminated timber

cross-laminated timber

Thought folks might be interested in this piece from Popular Science here.

Why the sudden interest in wood? Compared with steel or concrete, CLT, also known as mass timber, is cheaper, easier to assemble, and more fire resistant, thanks to the way wood chars. It’s also more sustainable. Wood is renewable like any crop, and it’s a carbon sink, sequestering the carbon dioxide it absorbed during growth even after it’s been turned into lumber. Waugh Thistleton estimates that the wood in Stadthaus stores 186 tons of carbon while the steel and concrete for a similar, conventionally built tower would have generated 137 tons of carbon dioxide during production. Wood nets a savings of 323 tons.

Demographers predict that the planet’s urban citizenry will double in 36 years, increasing the demand for ever-taller structures in ever-denser cities. Whether architects and construction firms build those towers from unsustainable materials like steel and concrete or employ new materials like CLT could make a huge difference in the Earth’s health. Put differently, the world’s urban future may just lie in its oldest building material.

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But the biggest driving force behind the turn toward wood is a growing awareness among architects and developers about their field’s contribution to climate change. “Our industry leads all others in terms of its impact on the planet and human health,” Waugh says. Concrete and steel require enormous amounts of energy to produce and transport, generating more than a ton of carbon dioxide per ton of steel or concrete.

Wood, on the other hand—even engineered wood like CLT, which requires additional energy to cut and press into sections—is far more environmentally friendly. According to Wood for Good, an organization that advocates for sustainable wood construction, a ton of bricks requires four times the amount of energy to produce as a ton of sawn softwood; concrete requires five times, steel 24 times, and aluminum 126 times. Wood also performs better: It is, for example, five times more insulative than concrete and 350 times more so than steel. That means less energy is needed to heat and cool a wood building.

When CLT is used to build high-rise towers, the carbon savings can be enormous. The 186 tons of carbon locked into Stadthaus are enough to offset 20 years of its daily operations, meaning that for the first two decades of its life, the building isn’t carbon neutral—it is actually carbon negative. Rather than producing greenhouse gases, Stadthaus is fighting them.

10 Comments

  1. Pack home the trim ends from laminated beams and try to burn them in the wood stove. I did that when I was putting in my three week rotations as a Weyco management trainee in the 1960s. They don’t burn. They char and take up space. You get dirty cleaning out the stove and throwing the ends away.

    Weyco had two laminated beam factories in those days. One in Cottage Grove at the old Baldy Woodard mill, and one in Ashland, Wisconsin. So the race riots in Chicago in the 60s resulted in an A&P or Safeway, a grocery store, being burned. The contractor went in with a front end loader and cleared the inside of the building. Then a crane company came and disassembled the laminated beam shell. The arches, beams, bents and summers were sent to Ashland and the char planed off, and then sent back to Chicago. They put in all new electrical conduits and piping, poured a heated concrete floor over the top, installed new freezers, coolers and shelving, and the store was rebuilt. You can’t do that with metal or concrete buildings. The industry knew that more than 50 years ago.

  2. This article tells half the story and draws some questionable conclusions. For instance, it says “Wood is … a carbon sink, sequestering the carbon dioxide it absorbed during growth even after it’s been turned into lumber.” In truth, forests are a carbon sink, while wood products are inseparable from logging which is a source of carbon emissions. In virtually all situations, logging accelerates the transfer of carbon from the forest to the atmosphere. Only a small fraction of the carbon in a a forest ends up in woods products, most of the rest goes to the atmosphere more rapidly than it would if left in the forest. Across the full spectrum of products, wood products rot and decay at about the same rate as dead wood in the forest. The argument that fire is a source of carbon is also unsupported because forests across time and space grow more than enough to replace carbon lost to fires. The argument that wood products substitute for more carbon intensive building materials has some modest merit, but the magnitude of this benefit is vastly overstated by timber industry promoters like CORRIM. In short, the discussion is not advanced very well by shallow, one-sided articles like this.

    • Yep, no mention of how forests are being converted from healthy forests into brushfields. Just how much goes up in smoke and doesn’t grow back?!? The Rim Fire is a perfect example of long term lost carbon storage. For the last 50 years, carbon storage remains very low, due to re-burns. If we don’t salvage and replant the Rim Fire, using herbicides, the land is again doomed to perpetual brushfields, especially with humans continuing to cause fires in an area that also has plenty of lightning fires. Yes, we can pretend that forests will return in 100 years but, we don’t know that “whatever happens” will support that. AND, just HOW MUCH carbon can be stored in brush that burns every 40 years?

    • 2ndLaw, your points are mostly well taken. I think though, that if you can say “forests across time and space grow more than enough to replace carbon lost to fires,” you should also consider that forests across time and space grow more [or less] enough to replace carbon lost to logging. And even if that is less true of logging than of fire, it is way more true of logging than of concrete or steel production. I.e., you’re wanting to compare logging only to not-logging. I think it’s fair for the wood-products boosters to ask us to compare building the same things without wood, and not logging, to building them out of wood.
      Similarly, the large fraction of removed wood matter that, as you correctly say, goes into the atmosphere more rapidly, can partly be used to substitute for fossil fuels. Yes, boosters tend to vastly overstate the potential benefit in that area too; but still, if it’s done right there is some benefit, which deserves to go into the equation.
      If the object is to leave forests alone to sequester more carbon globally—not just in our own neck of the woods—I think local and regional preservation efforts are not very effective. We would have to get serious about reducing demand globally, especially for the most wasteful uses of wood fiber in packaging and paper. There should be real benefits if a much smaller proportion of timber harvest goes in those directions, and more into materials that can last a century or more. (The architects who are excited about using CLT are also seriously trying to plan for their wood materials to be reusable in other buildings after the present one is obsolete.)

      • The difference between fire emissions and logging emissions, is that fire is a natural and unavoidable part of the forest carbon cycle, while logging is not part of the natural carbon cycle, and it is avoidable. Forest growth across space and time can compensate for fires, but it cannot compensate for the cumulative effects of fire + logging. This is made quite clear by the fact that forest carbon stores in the western U.S. today (influenced by logging and attempted fire suppression) are vastly reduced from their historical levels (influenced by fire) even though the total acreage of forest has not changed very much. Also, Bev Law at OSU showed that on average logging in western Oregon removes about 55x more carbon from the forest on an annual basis compared to fire. In this context, the effects of logging are clearly on a unprecedented scale and quite unlike fire.

        Substitution is a complex issue. I agree that it must be accounted for, ACCURATELY, and the comparison should be between wood, all other materials, not just virgin steel and portland cement. Alternative building materials include annual fibers, recycled steel, modern formulations of concrete with a lower carbon footprint. The greater longevity of some of those products must also be accounted for.

        • And, AGAIN, you always avoid some big issues, supplying your own flawed assumptions. Also, using outdated private logging practices in Federal scenarios will always result in flawed conclusions. AGAIN, using carbon storage as the only parameter to gauge management ignores so very many issues. Should we sacrifice forest health in favor of preserving flammable biomass? Should we sacrifice old growth habitats, in favor of “whatever happens”? Regarding building materials, we sure seem to have a huge excess of trees to thin from. AND, I tend to think that most people like things made out of wood.

          • Let’s look at another way to apply such reasonings. If you take all of the vehicle emissions from each and every Sierra Club member, that huge number would indicate that we should ban the Sierra Club, altogether. Such is the way of narrowly analyzing human activities without a comprehensive and honest analysis. Regarding log trucks, does anyone think that if we shutdown all logging, that those trucks would be retired and not used to ship trinkets made by Asian workers to retail outlets? Yes, there ARE bigger pictures!

        • 2nd Law

          In addition to what others have mentioned here, the extremely significant thing that you are missing is that all carbon stored in trees is eventually released whether it is because the trees die and rot or for any other reason. As long as the forest is managed on a sustainable basis with suitable regeneration then your point is a meaningless short term view that will disappear in the long term and could even have a significant negative long term impact if the age distribution is short on young growth and over heavy to old growth as it is now. If the old stuff dies in a relatively short period and leaves a gap in the age distribution at the old end then we have simply put off until tomorrow what we could have spread over the interval between now and then and dealt with in a more manageable way with less of a single time period deficit to possibly drive the global impact over some threshold.

          Contrary to your statement above, loss of carbon and sterilization and erosion of soil from catastrophic fires is not inevitable. The risk of loss to insects, disease and fire can be reduced by sustainable sound forest management which would also provide for more uniform carbon cycling.

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