Milwaukee’s Ascent building is a model for sustainable architecture
Milwaukee: Prepare to enter the record books.
Ascent, the second of two mass timber structures in the city, will open its doors to residents on July 15, 2022.
But unlike Milwaukee’s first mass timber structure, Timber Lofts in Walker’s Point, this $80 million building will stand 25 stories high — 284 feet — making it the tallest mass timber building in the world, knocking Norway’s Mjösa Tower out of first place.
Located at 700 Kilbourn Ave. in downtown Milwaukee, the 259-unit building will offer one-bedroom (starting at $1,715 per month), two-bedroom (up to $4,450 per month), and threebedroom apartments (up to $7,860 per month).
Compared to typical buildings — which are constructed using concrete and steel — timber structures like Ascent use treated wood sourced directly from nature: trees.
And like the forests they came from, mass timber buildings actively remove carbon (CO2) from the atmosphere, locking it inside the structure for as long as the building stands.
Milwaukee enters the global dialogue
Alex Timmer, assistant professor at the University of Wisconsin-Milwaukee’s School of Architecture and Urban Planning, said a mass timber building like Ascent places Milwaukee in the spotlight.
“The conversations happening around timber right now are happening globally,” Timmer explained. Currently, the most notable mass timber structures are in Europe, so it’s unique that a building of this type is being built in Milwaukee.
Ascent will serve as a test for future technology advances in architecture. Rather than asking, “How does a building like this happen in Europe?” Timmer says we can start to ask: “How does a building like this happen here in Milwaukee, in the state of Wisconsin ... and globally?”
Assessing how Ascent performs in our city will potentially open the door for more conversations concerning mass timber as an entire industry — rather than as a one-off example in one city, one state.
Construction is consumption
Timmer and a team of collaborators from Rivion, WoodWorks and the Forest Products Laboratory are currently working on collecting life cycle data for Ascent, an effort that measures the building’s total environmental impact.
Timmer explained that they are analyzing Ascent’s “embodied carbon” and “embodied energy” — measures of how much energy is required for production and how carbon is produced during construction.
“Architecture is almost purely consumption — it consumes energy,” which, in turn, releases carbon, he said.
This is important to consider any time a new building is constructed.
Experts estimate that the demand for new housing will double by 2060, requiring 2.4 trillion square feet of new housing — the equivalent of adding the entirety of New York City to the world every month for the next 40 years, according to the 2021 Global ABC Global Status Report.
That same report states that the construction industry accounts for 47% of global CO2 emissions each year. And approximately 22% of global CO2 emissions come from construction’s two biggest offenders: concrete and steel.
“Embodied carbon is the most important for us as architects to tackle because it has the most immediate impact,” he said. We can change how we build new buildings, turning the industry into one of reuse, reduction and sequestration.
This starts with mass timber.
Mass timber is a “no-brainer”
Mass timber structures directly address embodied carbon because they involve considerably less construction on-site. For Ascent, the building process was estimated to require 90% fewer vehicles and 75% fewer workers to complete the work in a quarter of the time, according to the building’s website.
Mass timber buildings not only reduce embodied carbon, but they also directly pull CO2 from the atmosphere and store it within the structure for decades.
According to CD Smith Construction Co., the company contracted for Ascent’s construction: “An 18story mass timber building has a negative carbon footprint equal to taking 2,350 cars off the road per year.”
“Mass timber is definitely one of the really, really important tools that architects have right now,” Timmer said. “It’s a no-brainer.”
Sourcing timber mindfully, sustainably
With mass timber structures, significantly less steel and concrete is used, making it more sustainable than the typical high-rise.
That’s not to say these materials are completely absent. Steel and concrete are still needed for the Ascent’s foundation, parking garage, pool, stairwells and elevator shafts.
This is part of the trade-offs that exist when designing any structure. As Timmer explains, a building is rarely made using one material; functionality has to be a factor.
“You’re not going to build a pool out of mass timber, right?” he said. “What’s interesting about (addressing) embodied carbon is that it allows you to make an informed choice about what material you’re using.”
This informed choice means making a meaningful choice: Harvesting wood sustainably.
Timmer explained that it’s important to look for Forest Stewardship Council standards before purchasing any wood product. This group has standardized metrics that identify whether a material was harvested sustainably.
“As great as mass timber is at sequestering carbon, if you’re destroying a tree farm in order to produce it, you’re preventing it from being a sustainable product,” he said.
“As long as those trees are sustainably forested, sustainably harvested, we potentially have a renewable resource, and we can sequester more and more embodied carbon.”
Ascent redefines building codes
While mass timber represents a future for sustainable architecture, building codes have not caught up to technology improvements.
Timmer explained that the current U.S. building codes prescribe safety standards that a building must meet. These mandates originally prevented Ascent’s height-to-timber ratio due to fire safety concerns.
Ascent was exempted from this code by doing something differently: Providing performative measures, rather than prescriptive ones.
Developers showed that when mass timber burns, it burns only on the outside, creating a ‘char zone.’ This char zone protects everything inside it, keeping the structure intact. “It is completely safe,” he said.
By Ascent’s example, Timmer predicts that we’ll see building codes evolve and become more sophisticated.
“We’re going to get better at building buildings, and we’re going to understand them better,” he said. “This means that we will be able to ask more of this particular construction typology, and we can ask more of it from an environmental standpoint.”
Building a structure like Ascent is part of an experiment that comes with constructing any building, Timmer said. “You learn a ton through the process of building. As much as we do an immense amount of testing in laboratories on these materials, it’s that the actual construction, the actual building that teaches you.”