Lara Swimmer

Rising from undulating topography in Idaho, a new basketball arena showcases the innovation of long-span mass timber construction and spotlights the local timber heritage through the grand scale of its mass timber beams and timber curtain walls.

“I love this stuff and I can't get enough of it,” says Chris Roberts, AIA, associate principal at Opsis Architecture in Portland, Ore., and the architect for the Idaho Central Credit Union basketball arena in Moscow, Idaho.

When many would naturally turn to aluminum for a complicated curtain wall design, Roberts utilized timber curtain walls as part of the University of Idaho’s new, more than 4,000-seat Idaho Central Credit Union basketball arena.

Constructed with two million board-feet of timber from the university’s forest on Moscow Mountain, the $51 million building includes 854 mass timber Douglas fir beams and several timber curtain walls that span up to 40 feet tall and up to 150 feet wide.

How does the arena represent Idaho?

Unlike many modern, nondescript sports arenas, Idaho Central Credit Union arena uses form and material to pay unique homage to Idaho’s rich forests and the local rolling Palouse hills.

“They wanted the building to mimic the natural landscape as much as possible,” says Andrea White, director of architectural sales from Sierra Pacific Windows, the company responsible for the timber curtain wall system. “And part of that is the distinctive wave roof line and following the building’s freeform structure. It required a little bit more conversation to make sure that we could design what they wanted to do with the wood.”

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What’s the benefit of wood?

Beyond the sustainability appeal of locally-harvested wood and the spectacle of seeing mass timber span such lengths, a timber curtain wall system has other benefits. As part of an active arena, the material’s acoustics are important and wood absorbs sound better than smooth aluminum.

Wood curtain walls also offer some flexibility in accommodating electrical, hardware, and ventilation systems, as it’s possible to design and route those elements into the wood beams. Plus, mass timber’s structural integrity withstands fire because of the char factor—after it chars, it can no longer burn so it’s no longer flammable.

What were the challenges?

As timber curtain walls are still a newer option and unusual for a large building, there is some extra work involved in taking the design feature from drawings into the built form.

“Each project is pretty unique and has its own unique features,” White says. “With the curvature of the arena’s roof, almost every beam is a different height.”

The team at Sierra Pacific Windows carefully created the custom timber curtain walls collaboratively with Opsis Architecture and the project team, and the installer came to the factory where they were working on the timber curtain walls to go over all of the details. “There were a lot of very tedious conversations about how it would come together when they're installing it,” says White.

They also had to accommodate for 2 1/2 inches of possible building movement. That engineering challenge was solved by anchoring the top and the bottoms of each wall with pin anchors.

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Why is it partially handcrafted?

The massive timber curtain wall construction is partly made by machine and partly handcrafted. There is a small crew at Sierra Pacific Windows who just work on this timber curtain wall product line that has been offered for about 6 years. “It's almost like building hand crafted furniture,” White says.

For the arena, White says the beams “were so big that they couldn't go through the equipment, so we have to do the sizing by hand.” Still, the company is automating as much as possible, as there is growing interest in timber curtain wall construction.

Why is there growing interest in timber curtain walls?

Following the 2021 International Building Code change that increased the maximum height of mass timber buildings from six stories to 18 stories, there has been a swelling interest in mass timber construction. With that IBC change, the option to use timber for long spans in sports complexes and other large buildings became a more viable and reasonable possibility.

While it took almost 50 years of fundraising and planning to replace the 93-year-old gym at the University of Idaho, the new basketball arena may not have become the same undulating timber showpiece if it had been built earlier. And, as more mass timber buildings are planned, the Idaho Central Credit Union basketball arena demonstrates some of the possibilities of how mass timber curtain walls can be used as a more distinctive choice to encapsulate a building’s natural surroundings.

Learn more about timber curtain walls at Sierra Pacific Windows.