When that apocryphal cow kicked over a lantern and burned Chicago down in 1871, it made manifest the dangers of a wooden city and allowed steel-frame construction to emerge as the predominant high-rise material. The thought of building tall with wood has been seen as outside the scope of architects since skyscrapers became a common typology, and IBC code compliance has ensured load-bearing structures made of wood are height-regulated.
But with environmental awareness rising, and environmental stressors being placed upon the industrial production process, many in the AEC industry see mass timber as a promising material to decrease embodied carbon in new construction buildings.
In recent years, wood has been elevated to a new status as a sustainable, economical, and, yes, noncombustible material in which to build up. Progressive designers—and market pressures—are pushing for code reforms (IBC is slated to change its height standards for mass timber construction in 2021) and are now employing mass timber to build up to new heights.
Carbon12, in Portland
Carbon12 is an eight-story, 14-unit condo building in Portland, Ore., designed and developed by Path Architecture and Kaiser Group. Its 85-foot presence hovers over the street corner in a sleek yet understatedly modern manner, signaling its luxury status like many projects designed for similar demographics in urban cores across America.
Yet dig deeper under the façade and Carbon12 is one of the more signifi cant contemporary residential buildings to be constructed in the United States. It is essentially a high-rise treehouse, with a building frame made from cross-laminated timber (CLT). CLT is a tightly wound wood product made from gluing small beams of wood together at high pressures, producing boards that provide the same structural sturdiness as steel but at a fraction—nearly 20%—of the weight.
“It is the only renewable structural material that we have to work with at this scale, and it sequesters carbon along the way,” says Kristin Slavin, AIA, architect with Path Architecture.
Slavin sees the project and the adoption of mass timber as an infl ection point for consumers, the fi rm (which is engaged on additional mass timber projects already), and the building industry at large.
“We are at a point in the world where most people recognize the need for immediate climate action in all aspects of life, and this is one way that architects and developers can make a positive impact on our carbon emissions,” she says.
Mjösa Tower, in Brumunddal
The Mjösa Tower (or Mjøstårnet) rises out of the lush valley of Brumunddal, a small, densely populated municipality that hugs Norway’s largest lake. Mjösa Tower—a hotel, housing, and office development—opened in March 2019, and assumed the mantle of the “world’s tallest wooden building.”
Its 18 stories extend 278 feet into the sky, a looming beacon to sustainability that ups the ante on the heights that wooden buildings can attain. One reason for that increased stature is how architects Voll Arkitekter made use of glue-laminated timber, or glulam, to add volume to the building mass.
As opposed to CLT fabrication, in which the wooden boards are glued together with grains alternating at 90-degree angles, the glulam process layers laminates along the grain, producing longer lengths.
Mjösa Tower is situated in an area with a heavy forestry industry, and the building materials were all sourced from local Norwegian and Finnish vendors.
River Beech Tower, in Chicago
Perkins and Will’s Todd Snapp, AIA, likes to view perceived diffi culties as “challenges” to be fi gured out. That mindset led to the designs for River Beech Tower, a proposed 80-story building in Chicago that would far surpass the height of any existing mass timber building.
“We believe that reducing environmental impact is critical, thus it was important that we research and test feasible ways to use renewable materials,” Snapp says. “Ultimately we sought to prove that a structurally sound tower could be both made of wood and safe enough for residential use.”
River Beech Tower is, for now, still an academic exercise. Perkins and Will intends to “build a full-size modular residential unit using the nodes we’ve constructed and tested,” Snapp says.
Conceived in collaboration with engineering firm Thornton Thomasetti and researchers at the University of Cambridge, the idea behind River Beech Tower is to create a building so impressive in its mass, its sustainability, and, ultimately, its performance, that it solidifies the case for mass timber construction to become the standard.
Visit thinkwood.com for more information.
