Original Source: The Economist, April 2, 2014
MORE than 15 years have elapsed since America, the birthplace of the skyscraper, was last home to the world’s tallest building. But though it lacks the highest high-rise made from traditional concrete and steel, America may yet boast the world’s tallest skyscraper made from dead trees. Last month the US Department of Agriculture (USDA) announced a $2m competition to demonstrate the viability of a new generation of wooden “plyscrapers”.
The idea took root several years ago when Michael Green, a Canadian architect,proposed 20-storey (60-metre) structures made from cross-laminated timber (CLT) panels. These sheets are made from cheap, sustainable softwood, glued or pinned together in precise layers. While the raw material itself might be weak and of variable quality, the panels can be engineered to be virtually identical and even stronger than concrete. They also resist fire well, charring at their surface instead of catching alight like the lumber used in most American homes.
The biggest benefit to reaching for the sky with wood, though, is environmental. “Mass timber” products like CLT are naturally renewable, take less energy to make than concrete and steel, and capture carbon dioxide (rather than belching out greenhouse gases during their production). The USDA believes that a modest four-storey building made from mass timber would cut emissions to a degree similar to taking 500 cars off the road for a year.
Conveniently, it would also use around six times as much wood as one made with conventional framing techniques, making it the perfect poster technology for the USDA’s new “Made in Rural America” initiative, which aims to get such wooden high-rises off the ground. “We’re going to help offset costs for at least one project,” says Tom Vilsack, America’s secretary of agriculture. “Design challenges, engineering studies and compliance with building codes all have additional costs that could discourage someone from using these materials.”
Until now, America’s conservative building regulations and a lack of interest from developers (and their customers) have meant few interesting wooden buildings have been built there. In contrast, Europe and especially Canada are embracing the emerging technologies.
March 22nd saw the topping-out ceremony of the tallest contemporary wood building in the world, and the first that might be considered a true skyscraper, the 30m Wood Innovation and Design Centre (pictured) in Prince George, British Columbia. Its designer, Michael Green, says, “Frankly, we aren’t breaking a sweat. It’s only public perception and emotion trumping science that stalls us moving higher.” He hopes to start work on a 20-storey vertical food-farm in Vancouver later this year.
“The challenge for us is to catch up and we’re going to do that,” says Mr Vilsack. As well as the high-rise prize, the USDA will fund an industry body providing technical support to architects, and push other federal departments to adopt the new technologies. “Cross-laminated timber can be used for emergency shelters, to quickly rebuild communities after hurricanes or floods, and by the Department of Defence to rebuild barracks. There’s even infrastructure that could be built with this,” says Mr Vilsack.
If wooden skyscrapers are to grow in America, the “Made in Rural America” claim will need to become more than just a slogan. There are currently no commercial manufacturers of CLT in the country, and most of the innovation in wood construction is happening north of the border and across the Atlantic. Builders are unfamiliar with mass timber and so even eco-minded customers are not offered it, giving little incentive for local and state authorities to update building codes.
But there are signs of change. Skidmore, Owings & Merrill is the architecture firm responsible for both America’s tallest building (the new One World Trade Centre in New York) and the world’s tallest building (the Burj Khalifa in Dubai). In a study last year, they conceded that a 125m-high skyscraper made (mostly) from mass timber products is technically feasible, economically competitive and could reduce its carbon footprint by up to 75%.
– By M.H.| BOSTON