Wood is on the rise in cities around the world as the global construction industry embraces mass timber construction.
In Tokyo, a 70-story, wood-hybrid tower is in the works. In Sydney, Australia, a six-story complex was wrapped up last year. There’s also the seven-story office building in Minneapolis, the 18-story dormitory in Vancouver or the 11-story proposal in Newark.
Although fire-shy policies have kept tall timber at bay in the Big Apple, an ongoing review of the city’s building code could allow more high-density wood projects as soon as 2020.
However, even if timber gets the green light from city hall, it might hit roadblocks trying to get on work sites.
Donal O’Sullivan, president of Navillus, one of the largest commercial concrete layers in the city, said an increase in cross-laminated timber — wooden beams that are glued together for greater strength and fire resistance — doesn’t mean the end of other building materials.
“Often, concrete and cross-laminated timber are combined, a prime example being one of the most advanced CLT buildings in the U.S., the University of Massachusetts building in Amherst,” he said, referring to the school’s three-story academic building. “So even if it does become more mainstream down the line, we don’t see it eating up the concrete share of the market.”
Creating concrete — particularly Portland cement, the most common type used in construction — generates tremendous amounts of carbon dioxide and other harmful emissions. Also, the dry-time associated with cement drives up already-high labor costs.
Despite concerns about global warming and building expenses, O’ Sullivan said traditional materials still have an edge on timber for fire safety, at least in terms of perception. New cross-laminated timber beams can last three hours or more when exposed to open flames, whereas steel, under extreme heat, will melt and leave buildings vulnerable to collapse. Still, that’s no easy sell to billion-dollar underwriters.
“Fire resistance and strength are key attributes of concrete and leading reasons for its success,” O’Sullivan said.
“While mass timber has surprisingly good fire properties … the longstanding resistance to wood remains a significant obstacle to its more widespread use in the city, especially for larger buildings.”
Steve Conboy, a former carpenter who now works in fire prevention, said building large buildings from mass timber is not only key to improving sustainability but also a potential tool for the creation of affordable housing.
While other countries, such as Canada, have jumped to the forefront of mass timber construction, Conboy said the U.S. has been consumed by its fear of flames.
“This movement is happening all over the world, the engineering is there, the technology is there,” he said. “It’s going to come around sooner or later but, for now, it’s all about lowering the perception of risk.”
Conboy’s company, M-Fire Suppression Inc., has created a spray-on treatment that wards off fire by inhibiting combustion at a chemical level. His product is being used by several ongoing projects throughout the country, including a multifamily development in Yonkers. The FDNY hired M-Fire as a consultant two years ago when it was reviewing its first and only mass timber building application, a 10-story condo in Chelsea designed by SHoP Architects. Ultimately, the city rejected the project, in part, because it didn’t trust the fire assurances, Conboy said.
“I agreed with FDNY in that instance,” he said. “Perception is nine-tenths of the law.”
Environmental watchdogs have shifted their attention from operation emissions more toward embodied carbon, CO2 emitted during the production and transportation of building materials as well as during the actual construction process. Developers are being encouraged to seek out less harmful materials than steel and concrete.
The U.S. Green Buildings Council, which administers LEED certifications, encourages builders to calculate whole-life emissions for their projects and it rewards the use of low emissive materials with credits. “There’s definitely the recognition that the buildings industry is one of the main sources of global emissions and there’s work being done to improve that,” Green Buildings Council Senior Vice President Melissa Baker said. “We know that just moving to more energy-efficient buildings isn’t going to be enough.”
O’Sullivan said his company dabbles in alternative materials, such as concrete made from fly ash, a byproduct of burnt, pulverized coal that is actually less environmentally harmful than Portland cement. Navillus used this material most recently on One Vanderbilt, which is targeting LEED Platinum certification.
Everard Martin, president of the Broadway Construction Group, said his firm is on constant lookout for alternative materials that can be used to cut costs. Assuming regulators sign off on it, Martin said he wouldn’t be surprised to mass timber spread like wildfire in the near future.
“I can’t see why, if the right criteria are put in place, why this wouldn’t be a viable option,” he said.