A rendering of the 35,683-sq.-ft. hangar planned for the Concord Municipal Airport. (SMP Architecture rendering)
Business boosters in Concord, N.H., are excited about the expansion of biotech firm United Therapeutics in their city, but the corporate hangar it will build at Concord Municipal Airport is exciting for another reason: Glulam. Lots and lots of glulam.
"The entire skeleton and truss system is glulam," Evan Herron, project manager of Silver Maple Construction of New Haven, Vt., told the Monitor. "We've never done anything like it, and I don't think many have."
Glulam is a term for wood beams and panels made by gluing together smaller layers of wood, or laminations, into pieces that are big enough and strong enough to replace steel and even concrete in commercial buildings.
It is part of the industry trend toward using engineered lumber — which has several names including mass timber — that combines smaller pieces of wood in novel ways to build large construction projects.
Engineered lumber is still uncommon, but its use in growing, and around the world it has replaced structural steel and concrete in buildings as tall as 25 stories. At least one commercial building has been built in New Hampshire with engineered lumber, an office block in Portsmouth made with cross-laminated timber, or CLT.
The 210-ft.-long by 170-ft.-wide airplane hangar planned at Concord's airport by United Therapeutics, a Maryland medical research company, will be the first structure of its kind in the area, according to the Monitor. In addition, the hangar will be about 56 ft. from the floor to the peak of the structure's curved barrel truss.
Engineered Lumber's Biggest Benefit is Environmental
The advantages of engineered lumber are partly aesthetic in that it can be shaped in interesting ways and made to be eye-pleasing since it is wood.
But the big benefit it provides is environmental.
Using wood in commercial buildings can lock away tons of carbon contained in the trees and, more importantly, avoids the carbon pollution that would have been generated by making steel or concrete, both of which produce large amounts of greenhouse gases.
Increasing the use of engineered lumber in commercial and industrial construction is one of the many changes needed to limit future damage from the Earth's climate emergency, Evans said, adding that is a big reason United Therapeutics is using glulam in Concord.
"They don't care just about building nice buildings, but environmentally sustainable buildings," he noted.
The Concord Monitor reported March 27 that Art Massif, the Quebec firm making the glulam beams, estimates it will trap 522 tons of CO2, which it claims is equivalent to removing 104 cars from the road for a year.
Engineered lumber has another advantage for heavily forested New Hampshire. It provides a new market for loggers for those trees that cannot be turned directly into boards.
Costs Are High in Near Term
The big drawback of engineered lumber for the near future is cost, the newspaper noted. Evans estimated that the glulam structures were about 50 percent more expensive than traditional steel supports. This cost should come down as more manufacturing facilities are built, and as architects and developers become more familiar with using it.
Using engineered lumber may also require changes in how nearby fire departments respond. The product tends to char rather than openly burn like traditional lumber used in home construction but does carry more fire risk than steel supports.
Another novel aspect of the construction, Herron said, is the use of prefabricated wall panels made at Silver Maple's Middlebury, Vt., factory.
"It's also a case study in pre-fabrication," he said. "It will greatly speed up construction in the field."
United Therapeutics, through Silver Maple Construction, hopes to break ground on the airport hangar by the end of April.
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