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Why Doesn't the World Have More Wooden Skyscrapers?

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This week, an ambitious proposal for the world's tallest wooden skyscraper was unveiled in Vienna, Austria. The 275-foot, €60M timber building will be built next year, and follows in the low-carbon footsteps of recent timber structures in Canada, Australia, and England. The idea of fashioning tall towers from the earth's natural materials, and not concrete or steel, first began gaining traction in 2013, when the Canadian architect Michael Green introduced the concept to the wider world via a TED talk that has now been viewed more than a million times. "I believe that wood is the most technologically advanced material I can build with," Green said in his talk. "It just happens to be that Mother Nature holds the patent."

In recent years, architects have been thinking up elaborate ways to make new and existing buildings more environmentally friendly, from the wind turbines that were just mounted on the Eiffel Tower to the solar heating panels on thousands of new condos. But it turns out the solution may have been right in front of them the entire time, frequently deployed for single-family houses, floors, and paneling, but never trusted enough for use in tall buildings.

Unlike concrete and steel, synthetic materials that together represent eight percent of man's greenhouse gas emissions, wood has the opposite effect: it takes in massive amounts of carbon dioxide, an obvious upside when cities are growing ever denser. "One cubic meter of wood will store one tonne of carbon dioxide," Green explained in his TED talk.

"If we built a 20-story building out of cement and concrete, the process would result in the manufacturing of that cement and 1,200 tonnes of carbon dioxide. If we did it in wood, in this solution, we'd sequester about 3,100 tonnes, for a net difference of 4,300 tonnes. That's the equivalent of about 900 cars removed from the road in one year."

At the time when Green gave his talk, the world was home to at least two existing timber structures that could have been considered towers: the Stadthaus residential building by Waugh Thistleton Architects in London, which has nine stories, and the Forté apartment complex in Melbourne, Australia, designed by Lend Lease developers with ten floors. Both buildings were made from panels of cross-laminated timber, which is a form of engineered wood that was originally developed as an alternative to stone and masonry. Unlike typical 2-by-4s, these panels made from many pieces of wood glued together are enormous, around eight feet wide and 64 feet long.

It's also fairly difficult to get cross-laminated timber to catch fire, which appears to be the main concern of supervisory bodies in cities where architects are attempting to use the material in their buildings. Vienna, which will soon have the tallest structure of this sort, has instructed its fire service to conduct special tests on the new building, which will already be required to install more sensitive sprinkler system than those required for other towers.

"It's hard to start them on fire, and when they do, they actually burn extraordinarily predictably, and we can use fire science in order to predict and make these buildings as safe as concrete and as safe as steel," noted Green, who built a six-story building out of cross-laminated timber, the Wood Innovation and Design Centre in Prince George, Canada, the year after his talk.

To Green, who has been at the forefront of wooden skyscraper design for as many years as the field has existed, the challenge is not in the construction or the engineering. It's in getting society to change its opinion about the necessity of continuing to build with energy-zapping synthetic materials from the last century. Clearly, there are better options these days, but most of them only exist in renderings released by risk-taking European firms like Bjarke Ingels Groups.

But change is already afoot; last year the U.S. Department of Agriculture introduced a $1M competition for high-rise wooden buildings, so it seems the U.S. will see a few of the innovative, green structures soon. It's long past due. As Green noted in his TED talk, "this is the first new way to build a skyscraper in probably 100 years."

· Vienna Plans World's Tallest Wooden Skyscraper [Guardian]
· All Metropolis 2.0 posts [Curbed National]