A Garden in the Sky: Chicago’s Green Rooftop Revolution

It’s not uncommon to see Chicago’s rooftops covered in grass. With over 500 green roofs and 13 rooftop farms, the city is one of the greenest in America, reaping the benefits of biodiversity, mitigating rainwater runoff and the urban heat island effect and saving thousands of dollars in utility bills. Restaurants are also taking advantage of the city’s sustainability, harvesting produce to serve a “rooftop-to-fork” dining scene. Cover graphic by Ramona Wolff for Midstory.

People living in fast-paced cities tend to keep their heads down and mind their own business. Look up, however, and amidst the concrete jungle, you might just catch a glimpse of, well, a real jungle. 

Chicago has long been a leader in green roofs — in fact, it once had the most out of any city in the U.S. According to the Department of Planning and Development, Chicago boasts over 500 [vegetated] roofs, at least 13 rooftop farms and over 5,500,000 square feet of green roof coverage.

“They got very popular in the ‘90s,” Richard Hawke, director of ornamental plant research at the Chicago Botanic Garden, said. He attributed the rise of interest in green roofs to former Chicago Mayor Richard Daley, whose administration included a robust environmental department dedicated to green infrastructure and green roofs in particular.

Green roofs were born in Chicago out of the CitySpace program in the 1990s, which partnered with NGOs (Non-Governmental Organizations) and neighborhood organizations to cultivate vacant lots and plant trees. This was reinforced by the 2004 Sustainable Development Policy, which required private developers receiving assistance from the city to include sustainable elements in their designs. Today, if 50-100% of a building’s roof area is covered with vegetation, it can earn points toward LEED certification.

The Rice Plant Conservation Science Center’s 16,000-square-foot green roof features 200 different species and 50,000 individual plants. Image courtesy of Richard Hawke.

This is all a part of the city’s larger sustainability scene — Chicago has been ranked as America’s greenest city more than once, with nearly 70% of its space green-certified. 

“What the government does can often affect what the general public does, and I think that the positive aspects of green roofs — certainly the ornamental or aesthetic aspects — encouraged people to add green roofs to their buildings, especially new construction,” Hawke said. 

A green roof in the Canal Trustees Neighborhood. Image courtesy of Jeramey Jannene.

This momentum, however, has begun to falter. In 2008, the Chicago Climate Action Plan set the goal of 6,000 green roofs by 2020, a number the city is far from reaching today.

“Chicago was one of the leaders, [but] I think we’ve stepped back from that, unfortunately,” Hawke said. “[Rahm Emanuel's administration] gutted the environmental department — pretty much eliminating it — which of course eliminated a lot of Daley's programs. … The city not putting as much of an effort into [green roofs] did affect how they’re done — but they are still being done.”

Nonetheless, green roofs in general have stood the test of time. Some date the origin of green roofs to the 1960s in Germany; others hail the idea to be as old as ancient Mesopotamia, from the trees and shrubs covering the Ziggurat of Nanna to the hanging gardens of Babylon.

Hawke believes the “sod roofs that were on buildings in Europe” are the origin of green roofs; Europe is, in fact, where Daley was first inspired to install a green roof on City Hall in 2001. Today, the City Hall rooftop features more than 150 species of plants and 20,000 individual plants, most native to the Chicago region. Its bees produce 200 pounds of honey every year. 

The Hanging Gardens of Babylon. Image courtesy of Ferdinand Knab.
A sod-roofed cottage at Dingle Bay, Ireland. Image courtesy of the Library of Congress.
From inspiration comes innovation: City Hall’s rooftop garden is one of Chicago’s most famous green roofs. Image courtesy of TonyTheTiger via Wikimedia Commons.

Integrating a piece of nature into a metropolis, however, is no easy feat. 

“It’s a challenge, but it’s also an opportunity because of the microclimates,” Kelly Larsen, the director of operations at Windy City Harvest, said. 

In the city, plants get approximately two extra months a year to grow because of the warmth. 

Chicago Botanic Garden's Windy City Harvest rooftop farm. Image courtesy of Brian Plunkett.

And, once implemented, green roofs bring a host of advantages.

“By adding a green roof to a building … you provide a habitat for insects, birds — perhaps small mammals, depending on how high up it is,” Hawke said. “[That’s very positive], especially in a harsh urban environment that doesn't have a lot of green space within a densely populated area.”

If the green roof includes pollinator species, migratory birds and insects are benefited as well, Larsen added.

The 2.5-acre green roof on top of Millenium Park's garage is widely considered the largest green roof project in the world. Image courtesy of JR P via Flickr.

Green roofs also filter rainwater and improve water quality, as well as mitigate runoff by holding the water, “therefore not rushing it into the sewer system,” Hawke said. “Plants take it up and utilize it.”

Particularly relevant to Chicago is the ability of green roofs to mitigate the heat island effect, where urbanized areas experience higher temperatures than outlying areas due to heat-absorbing infrastructure and limited greenery, according to the U.S. Environmental Protection Agency. Green roofs absorb less heat than traditional roofs, which are often built with materials that radiate heat back into the environment. 

Vegetated rooftops save money, as well. According to Hawke, not only are their lifespans up to seven times longer than a traditional roof, but their ability to insulate and cool buildings also reduces energy costs. Temperature measurements taken in 2007 found that City Hall’s green roof was only 70F, while a neighboring roof was 104F. The green roof saves City Hall $5,000 a year on utility bills.

City Hall’s green roof in 2008. Image courtesy of the Conservation Design Forum.

In Chicago’s popular farm-to-fork dining scene, green roofs also provide chefs with the unique opportunity to cultivate and harvest organic produce for their restaurants. 

“[It] has a big value to a shop and to a food service provider who’s doing niche events,” Larsen said.

One such example is the green roof on McCormick Place, a joint project with the Chicago Botanic Garden and SAVOR…Chicago at McCormick Place’s exclusive food and beverages provider. 

The McCormick Place Rooftop Farm. Image courtesy of the Chicago Botanic Garden. 

“Around 10 years ago, McCormick Place and SAVOR […Chicago] wanted to really look at the opportunity to transform [the green roof] into food production,” Larsen said. “We [decided to] focus on Ark of Taste [food] varieties, … or rarer varieties that are more heirloom. … The chefs wanted to make sure that they were focused on preserving taste, flavor and heritage-kind of varieties.” 

Generating more than 8,000 pounds of organic produce each year, crops grown on the green roof — nearly 100 varieties, including tomatoes, basil, peppers, radishes, turnips and fruits — are used in the kitchen of 23rd Street Café and Market, the convention center’s restaurant.

“[They can] utilize rooftop flowers, herbs and crops to do special hors d’oeuvres or dishes that are unique to the roof,” Larsen said.

The McCormick Place Rooftop Farm. Image courtesy of the Chicago Botanic Garden.

Today, McCormick Place boasts the largest farm-to-fork rooftop garden in the Midwest.

“It’s a surprisingly peaceful space,” Larsen said. “When you’re in Chicago, it’s very hectic. … On the east side [of the rooftop farm], you can see all brand new buildings, … but if you watch our west terrace … you’ll see [a lot of the older buildings]. But then you look at your immediate surroundings, and there’s food and beautiful plants. … You kind of have this juxtaposition of a farm and the city.” 

While political support for the green industry may not be as robust as in previous years, green roofs still continue to breathe life into hundreds of buildings in Chicago, bringing a touch of nature to steel and asphalt. 

“Don’t just think of a tray of sedum or … a monoculture — think of a landscape,” Hawke said. “It’s about the story … about how this is a living, [breathing] landscape in a place you wouldn’t expect to see it.


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