A green roofs check-in

A listener asked us to examine one of the city’s highest-profile green initiatives. Does ‘The City on The Prairie’ still want prairies on our roofs? How much good have they done, anyway?

August 13, 2012

Anthony Martinez

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Jenn Lawrence of Schaumburg, Ill., was inside of a Chicago high-rise recently when, out the window on a nearby roof, she spotted a patch of green. Jenn had heard of buildings putting greenery on roofs before, but wanted to know more, so she asked Curious City:

“Are the tops of skyscrapers still being planted with green space and what have the benefits been?”

Like Jenn, most of us have probably heard of or maybe even seen what’s known as a “green roof,” but unless you’ve got one on top of your own house or building, you might not know a whole lot about exactly why they’re up there.


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“We need larger scale implementation of green roofs to actually show that there are benefits."
- Dr. Milind Khire

So with Jenn in tow we headed out to check the status of Chicago’s green roof trend and whether it’s done much good.

City on the prairie? There’s actually a prairie on City Hall

When we first searched for sources to talk about green roofs, nearly everyone pointed us in the direction of Michael Berkshire, the Green Projects Administrator for Chicago’s Department of Housing and Economic Development. He’s tasked with making Chicago a more environmentally responsible city, especially when it comes its buildings. Among his areas of expertise: green roofs, which, he quickly told us, is “vegetation on the roof ... typically a system that includes the plants, growing media, drainage system, and root barrier.”

Berkshire showed us an example at an unexpected place: 11 stories above LaSalle St., in the heart of the Loop. The top of City Hall hosts one of the city’s premier green roofs, which takes up nearly half a city block.
 
Berkshire described this particular roof as “a prairie in the Loop.” He added, “When you talk about the spectrum of green roofs that are out there, this is definitely on the Rolls Royce end of the spectrum.” Home to a multitude of indigenous plants and flowers, the roof even has beehives that produce approximately 200 pounds of honey each year.
 
Jenn and I marveled at the beautiful contradiction of it all, but as we walked Berkshire admitted that not every green roof in Chicago is as remarkable as the one atop City Hall.

“We see a lot of very simple green roofs that are a nice palate of sedum which are a ground cover. They’re succulent, they’re very drought tolerant,” said Berkshire. “So when you’re talking about the spectrum, that’s kind of on the Volkswagen side of the spectrum.”
 
There are plants on the roof because … ?

While Jenn and I were in awe of the roof’s beauty, we both wondered just why anyone would bother putting plants on a rooftop in the first place. Aren’t plants supposed to grow in the ground?

Berkshire guided us off the roof and down into his office to explain how there’s more to green roofs than just their looks. He said green roofs can do some pretty amazing things: lower air temperatures, extend a roof’s life expectancy, and save on utility costs by insulating buildings against extreme heat and cold. But what city officials like best is that green roofs absorb and retain rainwater, something they believe can help relieve one of their biggest environmental headaches.
 
“We have a combined sewer system, meaning all of the rainfall rushing off the rooftops, sidewalks, streets, goes into the same pipes as the sanitary sewage,” Berkshire told us. “During heavy rainfalls those pipes are overwhelmed and that’s what causes basement flooding throughout the city, and also at some points we have overflows from that system and raw sewage goes directly into our rivers.”

The city knows it can’t manage stormwater all on its own, which is why in 2004 officials asked private developers to play a part. The city implemented the Sustainable Development Policy, which required any private developer getting assistance from the city to include sustainable features in project designs. Among the menu items of sustainable features developers can choose from: green roofs.

The policy kicked off a green roof boom in Chicago, with the amount of green roofs increasing from a few early adopters (such as City Hall) to many, many more. Berkshire said that a satellite imaging study completed in 2010 identified 359 green roofs in the city, adding up to almost 5.5 million square feet. That count makes Chicago the nationwide leader in the number of green roofs installed, with 82 percent of those roofs built thanks to the Sustainable Development Policy.
 
Jenn’s original question was whether or not green roofs were still being built in the city. The city’s study only accounted for those built through 2010, so I set out on my own to talk to a company that’s still in the green roof business. 

Green roof growing pains

I found that LiveRoof, a green roof company, was in the process of installing a green roof on top of a seven-story renovated building (now being used as for storage and office space) at Orleans and Ohio, in Chicago’s River North neighborhood. There, I found Rich Dix, the company’s sales specialist. He’s been a part of Chicago’s green roof scene for more than six years and told me he watched the recession take a toll on new green roof construction. Today, though, he’s feeling more optimistic. 

“If you look at the skyline you see a number of cranes now and it’s kind of encouraging given our past economic climate that there’s some building going on again,” said Dix.

However, Dix added that demand  for green roofs has been slow to catch up to the supply, even with the city’s encouragement.

“There’s lots of suppliers out there and there’s surely many more suppliers than projects. In past year, it’s a very competitive environment,” he said.

So, yes, new green roofs are still being installed in Chicago, but the economy is weak and there’s less new building going on, all of which puts a damper on the green roof business. That answers the first part of Jenn’s question, but she also wanted to know what the benefits of our currently-installed green roofs have been.

The big picture

Doctor Milind Khire is an associate professor at Michigan State University and a member of the school’s Green Roofs Research Program, which is putting green roofs to the test by studying their carbon sequestration and stormwater retention rates, among other things. Khire said the studies are driven in part by curious city officials who’ve noticed Chicago’s significant number of green roofs.

“The cities and municipalities are asking questions: How much energy savings can they really achieve? How will it impact the stormwater infrastructure if more and more people use green roofs, because that will save the cities money on infrastructure and maintenance costs,” said Khire.

Khire agreed that individual green roofs can provide the positive effects Michael Berkshire and other city officials mentioned: cooling buildings, extending the lifetime of a rooftop, and controlling stormwater runoff. But he says no one understands — for sure — what the effects, if any, could be for an entire city. That goes for Chicago, too.

Khire’s using his background in civil engineering to develop a computer model to predict what would happen if cities built lots of green roofs, not just one here or there.

“Right now green roof implementation is at the best, ad hoc,” he said. “We need larger scale implementation of green roofs to actually show that there are benefits. It’s the catch-22; until we can demonstrate that, it’s expensive to build them and realize the benefits.”

Khire hopes that once he completes his model, and can show cities what they stand to gain, green roofs will catch on in more areas — making the sky the limit to just how high their numbers can go.

“We will need to educate more people and cities for the benefits,” he said. “I think we’ll be looking back 20 years from now and saying we have a lot more green roofs and we did the right thing.”