What's the Best Way to Build in Wood?

In some cases, cross-laminated timber and robotic wood frame can both do the same job. Which should you choose?

My wife tells me that I got "mansplained." I was attending a panel discussion at the Toronto Wood Solutions Fair, where Sandra Frank, Marketing Director of Folkhem, a Swedish home builder, showed a low rise apartment building built of Cross Laminated Timber (CLT), and Tad Putyra, President & COO of Great Gulf Homes, Low-Rise Division, described how his company built houses and low rise apartments out of wood frame using sophisticated Swedish tools.

Panel at Wood Solutions Fair/ Lloyd Alter/CC BY 2.0I asked a question about about their choices and they both answered, and then this guy got up after and said in a totally condescending voice, "I'm an engineer (so I guess I really got engineersplained). Sometimes we use CLT and sometimes we use wood frame, depending on the circumstances and the needs of the client."

And I thought no, Jerkface, you are not answering my question. You did not understand my question, which perhaps wasn't explained well enough, so I will start over at the beginning.

Waugh Thistleton's first timber tower/ Lloyd Alter/CC BY 2.0

Since CLT was invented in Austria 25 years ago and first received serious exposure with Waugh Thistleton's first timber tower a decade ago, interest in and use of the material has exploded. CLT manufacturing plants are being built wherever there are trees. Timber towers are getting taller. It is marvellous stuff that is displacing a lot of concrete. I like it and I write about it a lot.

Detail of Murray Grove Tower from V&A; show/ Lloyd Alter/CC BY 2.0

You can see in this detail of the Murray Grove building, made for the plywood show at the V&A.; It goes together really easily; it's just big slabs of wood held together with metal brackets; it's no wonder that it could be built in nine weeks by four workers.

© Randek

Meanwhile, robotic tools like those from Sweden's RANDEK are revolutionizing wood frame construction so that panels are as precise and accurate as a CLT wall. There is a reason that America was stick-built; it is fast and cheap and material-efficient. But being site-built, it was sloppy and leaky. The new machines change all that. They bring wood framing into the 21st century, and they use about a fifth as much wood as CLT does.

We say that wood is a renewable resource and it's true; Sandra Frank noted that the wood in her company's Strandparken project was replaced by new growth in 44 seconds. But as I learned recently from Grace Jeffers, trees might be renewable, but forests are not.

Lloyd Alter/ Grace Jeffers presenting/CC BY 2.0

It is fallacy to consider wood only as an agricultural product: While wood may be planted, grown and harvested as any other agricultural crop, this activity should not be mistaken for a forest, because it is monoculture. Just as a field of corn is not a prairie, a valley planted in a single species of tree is not a forest.

Since hearing Grace Jeffers speak, I have been wondering (and this was the gist of my question, Jerkface Engineersplainer):

Given the pressures on our resources, do we not have an obligation to choose the system that uses the least amount of material, even if it is renewable? Sandra Frank answered the question by saying, "If we use more wood, we are then growing more trees and absorbing more CO2," but we are also eating up more forest, and it may not even be true that we are absorbing more CO2; a study published in Nature found that old trees actually absorb more CO2 than young ones. CO2 absorption is a function of leaf area, and big trees have a lot more leaves.

"Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree."

Bucky Fuller famously asked architect Norman Foster: "How much does your building weigh?" I can't help but think that this is a question that we still have to ask with everything we design. How can we use the least amount of stuff?

© Strandparken/ Folkhem

There are many places where one would choose CLT over wood frame. Some use it where it is exposed, for the aesthetics and to eliminate horrid drywall; that's why it is so wonderful in the Kiss House and Susan Jones' house. Sandra Frank said they used it in her Strandparken project because it was really high end; when you look at its marketing, it is clear that it's part of their pitch:

© Strandparken/ Folkhem

Wood dominates everywhere. You notice it as soon as you enter the stairwell. Floors and steps have a real feel that no concrete surface can imitate. Even the acoustics are different – a softer, solid, muted effect that only wood with innumerable, tightly packed annual rings can produce.

© Lindbäcks Group AB, Sweden

But Lindbäcks in Sweden has demonstrated that one can build really terrific housing using sophisticated, prefabricated computerized wood frame construction, using a lot less material, and probably at a lower cost.

My wife tells me that every single day, smart and professional women have to deal with men who talk down to them. I am more sympathetic after having to listen to Jerkface Engineersplainer. He wasn't entirely wrong, but sometimes there are other factors that have to be considered. There is a bigger picture.

I believe that everything that can be built out of wood should be, but am beginning to think that you can have too much of a wood thing. I am really coming to wonder if CLT has not become too fashionable, when there are other, simpler wood solutions that use less material, save more forest, and build more homes.