City living isn’t necessarily more sustainable than suburbs, says study

It’s a given, especially by green design advocates, that downtown density and urbanism leads to more efficiency and energy savings. But a new research paper from the Council on Tall Buildings and Urban Habitat (CTBUH), which examined energy usage in downtown and suburban Chicago on a household-to-household level, suggests our assumptions about the “dense vertical city” versus the “dispersed horizontal city,” may not always be correct.

Downtown High-Rise vs. Suburban Low-Rise Living: A Pilot Study on Urban Sustainability isn’t a perfect study. Comparing life in a downtown high-rise near the Loop and Lakefront areas of Chicago with a suburban existence in nearby Oak Park—as opposed to a wider, more representative sample of these living styles—is bound to create interesting comparisons and exceptions.

For instance, many of the city-dwellers in the Loop had much better park access, due in large part to having one the city’s premier public landscapes, Millennium Park, nearly at their back door.

But by looking at sustainability at the household level, combing through individual energy bills and family transport patters, the study’s building-by-building approach also offered some unique insights and conclusions, especially about how energy use isn’t always inversely related to urban density.

Researchers Dr. Peng Du, who teaches at the College of Architecture at Chicago’s Illinois Institute of Technology and Dr. Antony Wood, the organization’s executive director as well as a research professor at IIT, looked roughly 250 buildings of each type, examining five criteria to determine their true environmental footprint: home energy use, embodied energy (what it took to construct each building), home water usage, mobility and transport, open space access, and quality of life.

Council on Tall Buildings and Urban Habitat (CTBUH)

Many of the results, and their conclusions, reinforce established beliefs. Downtown dwellers required much less infrastructure per person (1.1 versus 9.4 meters) as well as 73 percent less water, the result of less spacious and spread out housing and little-to-no lawn care. Sprawl does have resources costs. Not surprising, more embodied energy was required to erect a steel-and-glass high rise than a standard, family-size suburban dwelling.

The study of annual energy usage, however, surprised the researchers. They discovered that residents of downtown residential towers consumed 27 percent more energy per-person than suburban residents. While that result was skewed by the prevalence of empty nesters and singles in the city versus families and children in the suburbs, even just a straight comparison by floor area found that residential towers still burned through 4.6 percent more power than low-rise suburban housing. That the Oak Park building stock, mostly wood-framed homes, was 98 years old on average just added insult to injury.

The authors argued that residential high-rises, which require power for common areas and shared facilities, including elevators, end up leading to increased per-person power consumption. But perhaps family living, versus singles living solo in large downtown condos, also explained part of the difference.

But perhaps even more surprising was the transportation analysis. While urban residents walked twice as much as their suburban counterparts, took more than four times the bike rides, and had much shorter commutes to work (153 kilometers versus 450), they also favored the car, which made up a higher percentage of their trips (63 versus 57 percent).

“Downtown residents actually traveled 9 percent greater distance by automobile than suburban residents,” the study noted. “The automobile was found to be the most used mode of transport.”

Demographics again skewed the results: suburban households shared car trips with kids, while single downtown took more solo car trips (think of all those Uber rides). By dispensing with generic takes on urban versus suburban living, this study found that lifestyle, not just location, plays a big role in sustainability.