The use of wood in taller buildings is big news, and now Melanie Sevcenko​ of the Guardian covers the story of the two towers being built in Portland and New York City. There are some arguable points (plywood was not invented in Portland) and a few howlers (It is not manufactured by layering panels of 2-ft-by-6-ft lumber, that would be awfully big), but it is a good introduction for the American reader.

But the real fun is in the comments, which repeat, over and over, every misconception that there ever was about building with wood. Some get really angry AND USE UPPER CASE!!!! All of these eye-rollers have been heard before, but I thought it might be a good idea to address them all in one place. Consider it a public service; I read the comments so that you don’t have to.

1) Deforestation

Government of Alberta/Public DomainThe harvesting of trees in the Pacific Northwest and in Canada is not the deforestation that is contributing to climate change; that is the tropical deforestation where forests are cleared for farmland and palm oil plantations. In fact, thanks to the mountain pine beetle infestation that is killing so many trees, cutting them while still alive and turning them into CLT would be a very good thing for the climate; we should be harvesting more, not less. The wood is sustainably harvested and trees are replanted which have a net positive effect on sequestering carbon, and leads to more trees, not fewer. In fact, according to the US Department of Agriculture, “Sustainable forestry practices can increase the ability of forests to sequester atmospheric carbon while enhancing other ecosystem services, such as improved soil and water quality.” Sounds like a good thing to me.

Carbon Dioxide

CO2 graph/CC BY 2.0

Here you are. Note how that in every single building component, wood has a far lower carbon footprint than any of the alternatives. As for the long term, wood buildings last for hundreds of years; there are dozens of warehouses all over North America built this way. In Bologna I have seen wood that has been holding up buildings since the 13th century.

Glue

Lloyd Alter/ CLT Press/CC BY 2.0

Most CLT is made with one-component polyurethane adhesives which are formaldehyde free. This system was developed in Europe where they have much higher standards for health than there are in America, and where they take the precautionary principle seriously. See more on REACH and European standards in TreeHugger

© Structurecraft/ Perkins + Will

However not all tall wood buildings are made with CLT; there are other technologies, like NLT or Nail-laminated timber or Brettstapel, where it is connected with wood dowels, that have no glue at all.

Fire!

© Fire test/ FP InnovationsHeavy timber doesn’t need chemical flame retardants. It has been known for decades how wood burns, how it develops a layer of char that actually insulates and protects the wood under it. Knowing the rate at which it burns, designers add an extra sacrificial layer of wood to ensure that even after it burns and chars there is enough wood left to do the job structurally. Those hipsters may not know history but the architects do.

And as Timothy Snelson of ARUP notes, massive CLT and glulam elements are hard to get burning; “you don’t start a fire with a log, you start it with bits of kindling.“Health

Listen to Amir Shahrokhi of sHop Architects, designer of 475 West 18th St, one of the two buildings discussed in the article. He goes on to talk about fire safety too. Wood makes for a quieter, more comfortable building and thanks to biophilia, makes us feel better. A British Columbia study found:

We used to build in wood and stopped!

Lloyd Alter/ Bullitt Center/CC BY 2.0There are a number of reasons that people stopped building tall buildings in wood, but one of the main ones is that it was getting harder and harder to find the big first growth timber needed after it got logged out. Now, big beams are built up out of small pieces of wood, like these glue-laminated beams in Seattle’s Bullitt Center, described as the greenest building in America. (Those floors are nail laminated timber, or mill decking as it used to be called).There were also limits in height that you could go with traditional solid wood; the engineered stuff we are using today is a lot stronger and more consistent. And we have sprinklers.

Maintenance

© Ema Peter Photography via Hemsworth Architecture

Cross Laminated Timber is not approved for exterior use, so it’s exposure is not an issue. Wood is used a lot for exterior cladding now, there are better treatments that keep it looking good for as long as other materials.

Jobs!

© D. R. Johnson

Unfortunately, there is a near monopoly in CLT suppliers too these days, with only one plant in the States and three in Canada. However this will change as demand increases, and will be a big opportunity to put people back to work. Oregon BEST, which is investing in CLT, discusses the impact of Oregon’s new DR Johnson plant:

And finally, a Three-in-one!

© Wood vs Concrete/ FP Innovations

On every effect of producing a structural material, from carbon to resource use to smog, wood comes off better than steel or concrete.It is absurd to say that concrete is “quarried from limestone.” Cement is cooked from limestone using fossil fuels, which releases a molecule of CO2 for every molecule of CaCO3. Five percent of the world’s CO2 is generated in this process. Cement is then mixed with aggregate that is quarried and driven in heavy trucks to where it is mixed. Because it is so heavy, foundations have to be far bigger than with any other material.Traditional steel production is a huge polluter and CO2 emitter.

The overall impact of steel will be less than this because much is made from recycled steel melted in electric arc furnaces, but it is still a very different thing from wood.And as noted earlier, engineered wood is made with formaldehyde free and solvent free adhesives and is not chemically treated. And as for the “plethora of chemicals and treatments”, they do not exist except in the glue, discussed previously, and they are pretty benign compared to the plethora of fireproofing materials needed to protect steel.