Wood: Structural systems for towers

A smaller carbon footprint for wooden residential high-rises.

CONTINUED FROM PAGE 9 stories or fewer — and construction methods. Architects, engineers, contractors and, crucially, developers will have to be convinced that wooden buildings can be safe, attractive and profitable. (They are generally more expensive than conventional towers, although in some areas of construction there can be savings because the slabs can be erected fairly quickly.) Fire protection is a particular concern, but advocates for wooden buildings say mass timber does not ignite easily and forms a layer of char that slows burning. They say wooden towers can meet fire safety standards for steel or concrete buildings.

Production of steel and concrete produces significant amounts of the greenhouse gas carbon dioxide, while wood holds the carbon from CO2 removed from the atmosphere through photosynthesis. So using wood in the structural elements can help offset the carbon emissions from the other parts of the construction process and from the operation of the finished building. This is not conventional frame construction, in which thin elements are nailed together, but more akin to building with concrete slabs. The use of so much wood raises the issue of the potential impact on forests if wooden buildings were to become prevalent. Mr. Baker said as long as forests were managed, sustainable wooden buildings should not have much of an impact. There are also millions of fir trees in North America that were killed by a beetle infestation and that could be used to produce the timber panels.

The Skidmore, Owings & Merrill system uses a type of engineered wood called glued laminated timber, or glulam, for the building columns, and cross-laminated timber slabs for the central core, floors and shear walls, which provide stiffness against wind loads. But the concept calls for concrete beams along the perimeter of each floor and elsewhere to allow for longer spans and more flexibility in layouts.

Mr. Green, in his report, presents a system that could be used to build towers in seismically active areas like Vancouver. Rather than concrete, he uses some steel beams to allow the building to better respond to earthquake forces.

Andrew Waugh, a British architect whose nine-story apartment building in London, completed in 2009, has become a showpiece of the wooden-tower movement, said both reports would help build momentum for buildings taller than 10 stories.

“It’s such an exciting time,” Mr. Waugh said. “It feels like the birth of flight — it’s one of those kinds of moments in engineering.”