Two great conflicting challenges in modern home building are affordability and super-energy efficiency. Conventional wisdom holds that you can’t have them both, unless construction is heavily subsidized by the federal government.

Along comes an Augusta builder with a brand new way to build a house that he says is both affordable and super easy to heat. CJ Thouret of Crux Homes calls his system the triangle arch, which allows him to frame the walls and roof as a series of continuous ribs. The ribs are built offsite using I-joists and assembled on site to form a rigid structural shell with no interior supports.

CJ Thouret after completing the framing of the first Crux Home in North Carolina Photo courtesy of CJ Thouret

The completed framing looks more like an airplane hangar than a house.

Thouret has built only a single home in North Carolina using the triangle arch system with two others under construction. He said the North Carolina home cost $200/ square foot to build, which is considered affordable in today’s residential construction market. The 16 inches of insulation in the walls and roof are rated at R-60 or more, which is more than twice the minimum required by Maine’s energy code.

“This has high performance, aesthetics and affordability,” said Thouret, owner of Crux Homes. “I feel like the triangle arch is the answer.”

Thouret’s innovation is joining I-joists into load-bearing trusses. Manufactured I-joists are common structural elements in construction, but they are only certified for use as floor framing. Thouret fabricates his own I-joists, using plywood and laminations of pine sourced from Mose Yoder sawmill in Whitefield. He relies on structural engineer Helen Watts of Criterium Engineers to certify the structural strength of his construction technique. Watts has a lot of experience in timber frame construction. She admits she’s “going out on a limb” in certifying the unconventional truss system, but she went beyond desktop calculations by witnessing the construction of two trusses and even helped build one truss. She said she examined it thoroughly and found it to be “so robust, so durable.”

I-joists ready for assembly on site Photo courtesy of CJ Thouret

“Mentally, I took it apart, I put it back together, I took it apart again,” she said. “I can see no reason this method is going to fail.”

The triangle arch was born out of Thouret’s tinkering mind and his fascination with construction technologies. Thouret has a background in construction, construction management, and building performance testing. He’s both drawn to and put off by earthen homes that rely on thermal mass for heating and cooling, and typically built off-grid.

“They’re super-efficient buildings, but they’re weird looking,” he said.

Thouret appreciates the look of conventionally built homes but he’s also troubled by the construction cost of high-performance design, which typically feature double-stud wall, insulated concrete forms or structural insulation panels.

“If you want a normal looking house that is high performance, they are very expensive to build,” he said.

A few years ago, Thouret discovered a designed pioneered by a British builder, featuring curving Gothic arches, and got permission to use the design in a house he was going to build for himself.

“It was a real challenge dealing with curving walls. Ultimately, the project fell through, which I think was a good thing” Thouret said. He modified the Gothic-arch truss design, evolving it into the triangle truss, using only straight members. He said the design is an improvement in many ways. “It’s less expensive, easier to build, easier to build with.”

Using I-joists to save labor and increase energy efficiency is not entirely new. The Klingenberg wall system, using I-joists as wall studs, has been around for two decades. Klingenberg and the I-Joist manufacturers have walked away from the use of the joist material in walls due to the undefined strength of the joint between the web and the bottom chord, according to Watts. Another use of I-joists are non-structural Larsen trusses, which are tacked on to exterior sheathing after the house is framed to create more space for insulation. Thouret’s design lacks a continuous layer of insulation, which is a common design feature in today’s high-performance construction, which reduces the heat loss of thermal bridging. Compensating for that is the depth of the trusses and narrow web, according to Thouret.

I asked Watts why no one has thought to use I-joists in quite the way Thouret is and she said the glued joints give some engineers pause. “Everyone’s scared of glue,” she said. While Watts is convinced of the strength of the North Carolina house, she would like to explore the limits of triangle trusses. “The next step would be to make ten of these, long ones, and then break them,” she said. “We haven’t figured out how far they can go. How wide a barn could we build? How much wind could it take? We really need to do testing.”

Thouret with partial triangle arch assembly behind him

An architect with no direct experience with Thouret’s design but deep experience with high-performance design systems says triangle trusses hold promise, but may remain a niche product because of builders’ resistance to change. “I can definitely see the potential,” said Michael Maines, co-author of Pretty Good House, a manual aimed at demystifying and popularizing super-energy efficient home construction. Maines said moisture buildup might be an issue with such thick walls, so a vapor-open building wrap would be an important element.

As for widespread adoption, Maines said “it can be surprisingly difficult” to persuade builders, even high-performance builders, to adopt new construction methods. He recommends pitching the method directly to homeowners, rather than builders. “It needs to be a client-driven thing,” he said.

Thouret says he’s gratified at the response to a demo model he put on display at the Common Ground Fair in September.

“Quite a few people were interested,” he said. “Two are talking to architects, three or four others are reaching out. A couple of builders said they were interesting in building with arches. I’m fine with that. Let others do the building, I’ll stick with the building science.”

Thouret is now working to streamline truss production. The first trusses took a lot of time, partly due to cutting out knots from lower-grade pine. He’s also planning to use oriented strand board (OSB) in place of plywood. He thinks he could double output with a simpler assembly process, hired help and an expanded shop. He’s also interested in producing arches and instructional videos for do-it-yourselfers.

“My process is the secret sauce,” he said.

Builder takes framing in new direction

© 2022 Local Wood WORKS