Sitting atop the Yankee Hill neighborhood in Milwaukee, Wisconsin, is Ascent, a 284-foot luxury apartment building made mostly of wood. The first of its kind, Ascent is also the tallest timber-concrete hybrid building in the world.
Tim Gokhman, one of the developers of Ascent, says building costs are comparable to more traditional structures, but he found that building with wood has advantages over steel and concrete.
“Concrete is imprecise, it’s labor intensive, and it has a heavy carbon footprint,” Gokhman said. “Steel has advantages. It can span much better than concrete and mass timber, but it’s even heavier, and it has the heaviest carbon footprint.”
Manufacturing both steel and concrete comes at a cost to the environment, with steel generating 7% of all global greenhouse gas emissions, according to the U.S. Department of Energy.
Ascent was built using pre-fabricated pieces of wood glued together, forming mass timber. It’s strong, light and cheaper to produce than steel and concrete. It took a crew of only 12 workers just six months to construct Ascent’s core.
When asked if we have enough trees to make our cities more mass timber friendly, Gokhman said, “I think we do. The largest cause of deforestation is a lack of demand for forest products, which causes our forest to be converted to industrial, agricultural, residential uses.”
It’s also easy to deconstruct and recycle. But for all its advantages, wood has one real disadvantage: it burns. That’s why Ascent beams were sent to the U.S. Forest Services’ forest products laboratory at the University of Wisconsin.
Before Ascent was even built, its timber was tested in a furnace at the lab, where temperatures can reach over 2,000 degrees Fahrenheit. Once it’s cooled, engineers will be able to see just how much and how deep the char got, giving them an idea of its fire resistance rating.
Laura Hasburgh, materials research engineer at the lab, found that while Ascent’s mass timber burned, it burned slowly enough to meet building codes.
“We provided all of our data so that they could feel safe that people would be able to evacuate the structure with an appropriate amount of time, as well as first responders entering the building would be protected from structural collapse,” Hasburgh said. “It’s really awesome to see that these structures are being built and they can be built safely.”
When asked what the future holds, Gokhman said they’ve been coming up with plans to make Ascent a prototype they can “repeat multiple times across the country.”
Other projects with mass timber are also underway in multiple U.S. cities, including Boston, Cleveland and Portland.
