Wood is making a comeback as a construction material and is increasingly being used in high-rises. Thanks to new technologies, wooden construction elements can now be as stable and fire-resistant as steel. Using wood instead of steel could even cut global carbon emissions. John Dyer reports from Boston.
Engineers in the United States and Europe are taking a hard look at tall wooden buildings.
“Advanced wood products, when engineered to the highest standards, are a safe alternative to other traditional building materials,” said Valerie Johnson, co-owner of D.R. Johnson Wood Innovations in Oregon.
Johnson said business has been growing. Her phone has been ringing with calls from builders. “We see a horizon that’s very promising out there,” she said.
Plyscraper in Manhattan
A new wooden 10-story ‘plyscraper’ apartment building recently opened in Lower Manhattan in New York City near the famed High Line, a former elevated subway track that’s been converted into a pedestrian mall.
Plyscrapers are cropping up elsewhere, too. The University of Massachusetts’ new design department’s hall now under construction includes a new kind of wooden superstructure and steel interior. The University of British Columbia is supposed to complete an 18-storey wooden dormitory this year, too. A 19-storey wooden tower in Sweden and a 12-story wooden tower in Portland, Oregon are also due for completion soon.
Lower carbon emissions
“Explore how U.S. based timber production can help revitalise rural manufacturing communities and benefit urban centre in a wide range of ways,” said a recent press release for Timber City, an exhibition at the National Building Museum in Washington, DC.
Exhibition organisers cited a 2014 Journal of Sustainable Forestry study, which found that replacing wood for steel in most construction would cut global carbon emissions as much as 20 per cent.
“As the only building material that can both reduce carbon emissions and remove carbon from the atmosphere, timber is uniquely positioned to move us towards more sustainable, healthy and beautiful buildings and cities,” they said.
Traditional construction material
Wooden skyscrapers are a major advancement, but they’re also just the latest in a long tradition. From log cabins to two-by-four-plank houses to modern tract homes and mountain chalets, wood has long been a construction material.
“We believe people have a greater affinity for taller buildings in natural materials rather than steel and concrete towers,” said Michael Ramage, director of the University of Cambridge’s Center for Natural Material Innovation.
“The fundamental premise is that timber and other natural materials are vastly underused and we don’t give them nearly enough credit.
New CLT technology
Advancing to towers as high as 60 stories entails gluing 30-centimetres-thick layers of timber together in meters-long long slabs called cross-laminated timber, or CLT. Steely crossbeams called glulam are similarly pressed and cut into massive bones for the tower’s skeleton.
“Gluing a stack of cards together produces something stronger than building a house of cards,” said Do Janne Vermeulen, an architect and principal of the Netherlands-based Team V Architecture.
Her firm designed the current tallest wooden building: the 21-story Haut in Amsterdam.
She and others played down fears of fires, saying that they were not more susceptible to fire and their safety more than equals that of steel skyscrapers.
“Cross-lamination establishes a new level of quality control and fire protection,” said Kevin Flanagan, a partner with PLP Architecture in London. Light wood floors could even be added to existing structures.
Superglue on molecular level
The potential of wooden skyscrapers has been growing lately due to technological advances, too.
Late last year, University of Cambridge Biologist Paul Dupree announced a new kind of glue that works on the molecular level to bind tough plants like trees together in fibres 10,000 times narrower than the width of a human hair. The discovery was hailed a major advance in the quest to build towers of trees.
“We knew the answer must be elegant and simple,” said Dupree, who is studying how to build skyscrapers out of wood with Ramage. “And, in fact, it was.”
He added that the same advances in understanding the cell walls of green plants could apply to other wood-related industries.
“Take paper production – enormous amounts of energy are required for this process.” Dupree said. “A better understanding of the relationship between cellulose and xylan could help us vastly reduce the amount of energy required for such processes.”