Reaching to the Sky — With Wooden Skyscrapers
WHY YOU SHOULD CARE
Because greener large-scale construction may not need futuristic materials so much as a return to basics.
By Tracy Moran
Look, up in the sky. It’s a bird. It’s a plane. No, it’s a skyscraper that’s made of … wood.
In a head-spinning step, a handful of researchers from Cambridge, England, are experimenting with one of man’s oldest building materials — the kind from trees — instead of steel as the primary structure for buildings. Already, there is one timber apartment building with nine stories in London, a 10-story structure in Melbourne and a 14-story building in Norway. But all that is dwarfed by talk of a wooden building that someday could reach 70 stories into the sky.
Architectural engineers behind the idea, which has recently been gaining momentum, say they are looking for cheaper and more environmentally friendly materials to use than steel and concrete. Those materials have dominated tall buildings since the early part of the 20th century. But relying on timber takes some doing; for it to succeed, it will require not just great architectural skills but the expertise of biochemists.
Cambridge University, for one, has set its sights on creating that 70-story skyscraper made out of timber.
It doesn’t take a degree in architecture, of course, to know that wood has long been criticized for being too weak for high rises — not to mention a towering inferno just waiting to ignite. Indeed, builders have been far more likely to opt for steel for both medium- and large-scale structures.
Yet environmentalists have long argued that the construction world needs to urgently become greener. For years, the creation of homes, offices and skyscrapers has been one of the biggest contributors to climate change. All told, these activities lead to nearly half of the U.S. global CO2 emissions. By 2050, the U.N. estimates that nearly 80 percent of the world will live in urban areas, adding up to a lot of planet-damning construction unless something changes — and soon.
Scientists are making inroads by studying the molecular level of certain building materials, including wood and concrete. Cambridge University, for one, has set its sights on creating that 70-story skyscraper made out of timber. For now, it’s in the design stage, but by better understanding the molecular and cellular structure of wood, professor Michael Ramage and his team from the university’s department of architecture say they are certain they can strengthen the material by bolstering its weakest links — where the giant timber slabs connect at walls and floors.
“I think there’s quite a lot to be gained from looking at the smallest level of building blocks and working upwards,” says Ramage.
To accomplish this, they will need to deconstruct how plants get their strength from the rigid cellulose wall surrounding each cell. Another part of the team stems from Cambridge University’s department of biochemistry, where professor Paul Dupree is taking what he’s learned with biofuels to apply to this project. Translation: They’re genetically engineering stronger plants and unlocking the potential for (sun-fed, sustainable) wood.
Ramage and his researchers are also working to strengthen existing plant materials by impregnating them with polymers. Already, the team has had enough success in modifying spruce and willow to net a five-year, $2.8 million grant for further research and attract commercial interest in their work.
Concrete’s primary ingredient, cement, accounts for 5 percent of global carbon dioxide emissions.
Surprisingly, wooden skyscrapers aren’t as prone to fire as one might think. While small homes go up like kindling, “massive timber buildings are not flammable,” Ramage says, because the timber burns and chars on the outside just enough to provide a good insulator that protects the rest. “Looked after properly, wood can be just as sturdy as brick and is more resilient,” he adds.
Steel, meanwhile, is more vulnerable to heat than people often realize. The material itself doesn’t burn, but everything around it does, heating up the alloys and rendering them less stable.
Then there’s concrete. While hugely useful — concrete absorbs heat by the day and releases it by night — it’s not considered a green material. On its own, concrete’s primary ingredient, cement, accounts for 5 percent of global carbon dioxide emissions, and its production is growing 2.5 percent annually. As the most-used construction material on the planet, concrete is an easy target, yet nobody has fully understood how it worked at the molecular level — until recently.
By getting to the heart of what’s in the substance, MIT professor Roland Pellenq and his team may just save concrete’s reputation. “There’s no other solution to sheltering mankind in a durable way,” Pellenq has said.
While cement combines different materials in various ratios, no one had ever studied the material’s differing molecular structures in such detail until Pellenq came along. His work has proven that reducing the ratio of certain materials can make concrete nearly twice as resistant to fractures while cutting concrete emissions by as much as half. In short, he and his team are paving the path for stronger, greener concrete.
The next steps will require ratcheting up production to suit the building sector, and Pellenq expects a great deal of interest from construction, gas and oil industries.
This OZY encore was originally published Nov. 16, 2014.