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For more than a century, the designers of tall buildings have used mostly concrete and steel. But advances in structural engineering have sparked new interest among architects in one of the world's oldest building materials: wood.
Here & Now's Jeremy Hobson talks with Michael Green, a Vancouver-based architect who says wood is just as strong as concrete or steel -- and more sustainable.
His firm, Michael Green Architecture, just finished construction on the first tall timber building in the U.S. — a seven-story office building in Minneapolis called T3. It's also planning construction of a 35-story tower in Paris, which, if completed, would be the world's tallest residential building made out of wood.
Interview Highlights: Michael Green
On the safety of a skyscraper made out of wood
"It is always the first question and with any building you have to worry about fire, and of course with a wood building there are some special conditions that we work with. And so the analogy I often use is, little pieces of wood catch fire, big pieces of wood are very difficult to catch fire. So we all know that in our fireplace. Little sticks will start a fire, but if you tried to light a big log, it will never catch, or it will be very hard to catch. And so the premise is we use huge-scale wood that resists fire naturally and burns very predictably in a very similar way to control a fire as it would be in a steel or a concrete building."
"What we do with all the buildings is we cover them in a envelope. So it's a lot like, if you think about our bodies, we are a skeleton. Building structure is what we're talking about, it's the skeleton, and we cover up in layers that protect our skeleton and we do the same in buildings to prevent them from weathering conditions and insects and so forth. So, we always protect the structure from that."
On the limits of skyscraper construction with wood
"So, what's interesting about this is the sky is almost the limit. About a year ago we were asked to do an exercise to see, could we have built the Empire State Building in wood? And the Empire State, being 102 stories, we thought well that should be a challenge. But we did some schematic engineering, and sure enough we could've. So, it really is, the capacity of wood to carry its weight over these huge heights is absolutely there. And I sort of again point out that if you take three of the trees that grow in our forest out here in western North America and stack them end to end on top of each other, three trees equal the height of the Empire State. So, of course wood can carry that weight and go that high."
On the outlook and demand for taller wooden buildings
"The issue is one of increments. So these ideas are really picking up on what we were able to do 100 years ago in tall buildings in wood. We have a building in Vancouver that's nine stories tall, for instance. And now, we've re-picked up the conversation with new engineered wood products and starting to push our heights increasingly higher, but it's a matter of step by step. And so we're gonna get to 30 stories, we're gonna get to 35. Whether we get much higher, it depends. If the market wants it, we certainly can get there. But it's step by step."
On the advantages of building with wood
"There's so many reasons to that, and I think the first reason for me is that we should build out of natural materials. We should build out of materials, wood, that has the capacity to sequester carbon dioxide and help us address issues of climate change. We should build out of renewable materials rather than these high-carbon materials of steel and concrete that together represent 8 or 9 percent of our manmade greenhouse gas emissions just for the making of those materials. We need to move to these organic materials, and so wood, if harvested from very responsible forest practices, gives us incredible capacity to build more environmentally and more climate-sensitive buildings."
"We are using a lot of what's called mountain pine beetle wood, which is trees that have been killed off by a pine beetle that's unfortunately ravaging the forests of Canada and now into the United States. And those trees stand and can be harvested and quite effectively turned into the products that build these big buildings."
On the cost of building with wood compared to other materials
"The challenge is steel and concrete have about a 100-year head start on these new wood concepts. So it's really become a challenge mostly because of lack of competition of producers of these wood products, the lack of knowledge in communities and within design community around it, but we're trying to fix that. And we're catching up very quickly. So I think there's a way that these buildings can be dollar-for-dollar equal to steel and concrete, and I think in time we're going to see them be much more cost-effective, because they're not attached to energy costs like steel and concrete are."
"At most, [it's] a couple percent more expensive [to use wood]. And I think with smart design we can actually make it equal-equal."
This segment aired on September 27, 2016.
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