Conference says buildings as high as 12 stories can be built with wood, helping loggers and the climate 

  • This 18-story building near Oslo, Norway, is generally considered the tallest timber building in the world. American building codes do not generally allow buildings of that height to have wooden structural elements and floor spanning systems. ARchitect.com—Courtesy

Monitor staff
Published: 10/11/2019 3:54:46 PM
Modified: 10/11/2019 3:54:31 PM

Tackling the biggest problems of the world today and in the future could benefit from technologies of the past.

“This is back to the future,” is how Joe Short, vice president of Northern Forest Center, put it at the start of a conference Friday discussing mass timber, which uses wood to replace steel and concrete in buildings as tall as a dozen stories. “We’re re-learning how to use our own resources.”

Mass timber, also called engineered wood, is a general term for methods of combining relatively small pieces of wood into large beams or sheets which can be used in commercial or industrial construction. The pieces are planed and dried, then glued or nailed together into various configurations that are strong enough to replace steel beams, masonry walls or concrete pillars. Timber can then be used as a weight-bearing material in mid-rise office buildings or in large, open structures like libraries or conference halls, rather than just as framing for houses and small commercial buildings. 

Mass timber is of great interest to the logging industry because it uses a large variety of trees, not just those big enough to be cut into long, wide boards. Softwoods as small as 4 inches in diameter are often used in mass timber, the conference was told, creating a market that would benefit loggers and forest owners in New Hampshire.

The bigger social benefit comes from the fact that growing trees removes carbon from the atmosphere, while making steel and concrete releases carbon – enormous amounts of it, in the case of concrete. Putting lumber inside buildings locks away the carbon for decades or more, so using mass timber can turn the construction of a building into a carbon-neutral event.

Friday’s two-hour conference at the UNH law school in Concord was held by the Northern Forest Center, UNH Cooperative Extension and the New Hampshire Division of Forests & Lands. It drew an audience that included architects, planners, environmentalists and people involved in the timber industry.

The technology has been used in Europe for more than a decade and is spreading in the U.S., where more than 400 buildings have used it to some extent, according to Marc Rivard, an engineer and regional director for WoodWorks, which advises and assists with wood construction. He was one of two speakers at the conference.

That includes projects in neighboring states. Massachusetts is home to a design building at UMass-Amherst that has become a four-story showpiece for mass timber construction, while Millinocket, Maine, looks likely to become home to New England’s first factory producing CLT or cross-laminated timber, a type of mass timber.

So far, however, New Hampshire has seen no activity.

“I don’t know why,” said Rivard. “Other states have reached out to us.”

Friday’s conference was designed to change that by spurring interest from people who design, pay for and create buildings.

“There’s interest on the supply side, but we need more on the demand side,” said Short. “When you’re looking for capital to build a CLT factory, that’s what investors want to know: What is the demand?”

Mass timber is usually more expensive than steel or concrete, organizers said, but construction goes more quickly and mass timber usually requires fewer people on the job site, savings that can more than compensate for higher material costs.

“You don’t have to weld things together, there’s no bolting. You just screw it down and move on,” said Rivard.

He was one of two speakers at the two-hour conference.

Mass timber has other advantages but aesthetics is currently a main driver for buyers, said Rivard. “People like the way it looks,” he said, showing pictures of many types of exposed wood in mass timber buildings throughout the U.S.

Surprisingly, it is also fire resistant, since it slowly chars rather than burst into flames like smaller lumber.

A mass timber beam can even withstand high temperatures better than an equivalent steel beam, which warps and loses strength, said Rivard. He gave an example where steel connectors holding together wood beams were covered with engineered wood to improve fire safety.

“Covering steel with wood to protect it in a fire, that feels backwards to most people,” he admitted.

Parts of the two-hour session delved into details of the construction business, such as the difference between Type IV-C and IV-HT buildings, which building codes hold sway in New Hampshire, and volatilizing vs. non-volatilizing glues. But much of the talk by Alan Organschi, a Connecticut architect, took the high-level view of battling climate change.

Organschi said that constructing and operating buildings is responsible for about half of the greenhouse gases produced in the U.S. Using more timber can reduce that sharply, he said.

“Can we store this material, carbon, in buildings that we’re going to build anyway?” he asked, following a presentation about the potential carbon benefits of managed timber harvest creating new buildings in empty parts of New Haven, Conn. “Can we start to pull that level back down using the same tools that produced the problem in the first place?”

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)


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