How Chicago Ignited The Explosion of Green Roofs in America

– Posted in: Garden Design, Sustainable Gardening

“Look deep into nature, and then you will understand everything better.” Albert Einstein

It should come as no surprise that Chicago, commonly known as ‘Garden In The City’, has been a trailblazer in the green roof movement in America. **

It has 359 green roofs, totaling  5.5 million square feet, more than any other city in North America. Last year, it added 600,000 square feet more. The momentum to make Chicago a city of green roofs continues at a rapid pace. Within the next one to two years, green roofs in the city will top 7 million square feet.

Chicago City Hall Green Roof

Photo Credit – City of Chicago

The birth of green roofs in Chicago didn’t happen in a bubble. It was after the terrible heat wave in July 1995, when there were more than 700 heat related deaths, that it was decided to find ways of making the city cooler in spite of rising temperatures.

Chicago’s rich gardening history combined with Mayor Daley’s mission to make it the ‘greenest city in America’ and a settlement from ComEd, created the ideal setting to build a huge, show stopping green roof on the top of City Hall .

“As part of an EPA study and initiative to combat the urban heat island effect and to improve urban air quality, Mayor Richard M. Daley and the City of Chicago began construction of a 20,300 square foot semi-extensive green roof in April 2000. It was completed at the end of 2001 at a cost $2.5 million, funded by a settlement with ComEd. Encompassing one square block and twelve stories high, this retrofit application serves as a demonstration project and test green roof. The project was completed in the summer of 2001.” (Green Roofs for Healthy Cities)

It was one of the first studies in the U.S. – if not the first – on the effectiveness of green roofs in mitigating the urban heat island effect – it happens when concrete and pavement, which absorb and trap heat, make cities like Chicago hotter than surrounding rural areas. Buildings soak up the sun’s rays during the day and release that heat into the night.

The City Hall rooftop garden was planted with over 20,000 herbaceous plant plugs of 150 varieties – including 100 woody shrubs, 40 vines, and 2 trees. It was designed with a supplemental irrigation system – rainwater is harvested – to aid plants while establishing themselves and to be used during extreme periods of drought.

Chicago City Hall – Photo credit: Michael J. Curry. Not to be re-printed.

“The project was intended to demonstrate the benefit of green roofs in moderating summer temperatures within ultra-urban environments. The roof is monitored to demonstrate these benefits. The City Hall green roof is currently, on average year-round, 7 degrees cooler than the surrounding roofs and as much as 30 degrees cooler in the summer.

The rooftop habitat is home to more than the usual pollinators that visit perennial gardens. The city has a beekeeper that tends to two beehives. In 2010 Roofmeadow celebrated the 10 year anniversary of the installation of the Chicago City Hall green roof.” (Source: Roofmeadow )

Another example of an outstanding green roof in The Windy City is at  Chicago Botanic Garden – one of the most visited public gardens in North America , with 958,000 visitors annually.

Chicago Botanic Garden Green Roof

Photo Credit – Chicago Botanic Garden

“The 8,000 square foot north roof contains alpine and rock garden plants, cultivars and bulbs from around the world. The equally sized south roof contains native species. Combined, the roofs hold over 300 different taxa at planting depths of four, six, and eight inches. A permanent irrigation system is installed, but since establishment the entire roof has only required it twice.”  (Source: Green Roofs For Healthy Cities)

Chicago Botanic Garden Green Roof

Photo Credit – Chicago Botanic Garden

There is a wealth of information about on green roof at: Green Roofs For Healthy Cities (of which I am a member) and

I have been using a book written by Noel Kingsbury and Nigel Dunnett, Planting Green Roofs and Living Walls, as a resource on green roofs since it was published in 2008. I highly recommend it!

** When Chicago officially incorporated as a city in 1837, it adopted the motto Urbs in Horto, a Latin phrase meaning ‘City in a Garden‘.

NOW IT’S YOUR TURN. Do you believe in the importance of green roofs in urban areas? What’s your favorite one?

Fran Sorin

Fran is the author of the highly-acclaimed book, Digging Deep: Unearthing Your Creative Roots Through Gardening, which Andrew Weil, M.D., recommends as "a profound and inspiring book."  

A graduate of the University of Chicago with Honors in Psychology, she is also a gardening and creativity expert, coach, inspirational speaker, CBS radio news gardening correspondent, and Huffington Post Contributor.

Learn more about Fran and get free resources that will help you improve your life at

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Fran Sorin
12 comments… add one

Leave a Comment

Jason January 16, 2013, 2:19 pm

Chicago has plenty of problems, but I am glad we’ve been leaders on green roofs.

Fran Sorin January 16, 2013, 11:45 pm

Jason- Every large American city has problems – I’m from Philly – But having lived in Chicago, hands down, your city is one of my favorites. Lake Shore Drive is a one and only. 🙂 Fran

Debbie January 17, 2013, 7:00 am

Our garden club visited the roof garden at CBG…the garden staff & volunteers are doing a phenomenal job in testing and observing the habits of a rooftop garden.

Fran Sorin January 17, 2013, 8:16 am

Debbie – That’s great news. I hope they continue testing new varieties to help expand the repertoire of plants that are hardy on chicago’s greemroofs. Fran

Lynn January 18, 2013, 10:34 am

Yes! As a new and somewhat reluctant Chicago dweller, I was happy to discover this. The beekeeping at O’Hare, where the old orchards were, is also encouraging. Flying in recently, we saw the green roof atop the Home Depot on Western Ave. I was astounded! That is not exactly a tourist destination, but very very hopeful. It and lower-growing roofs like CBG’s are more realistic than the pricey but gorgeous one on city hall. U of Chicago’s new Logan Art Center employs green roofs, and Cornell in NY is setting a great example with at least 5 on the Ithaca campus.

Cherie Smith January 18, 2013, 10:43 am

So good to see Chicago is a leader in roof gardens and being green.
With the help of Dave Fross of Native Sons Nursery here, I put a green roof on my little studio in our backyard several years back and it helps to keep the studio cool in summer, in San Luis Obispo, and warmer in winter.

Reed Pugh January 18, 2013, 11:56 am

Awesome, I was involved with one in Boston about 5 years ago.

Fran Sorin January 19, 2013, 12:05 am

Cherie – Lucky you. Can you send photos of it to me [email protected]? 🙂

Fran Sorin January 19, 2013, 11:05 pm

Lynn- If you moved to Chicago this winter, I understand why you were reluctant. But it is the great American city – as far as I’m concerned. Thanks for the reminder about Home Depot- I know that the big box stores haven’t gotten into green roofs – which is good news.
Funny- I just read the story about the green roof at The UofC where I went for college. It made me smile. Thanks for stopping by. Fran

Fran Sorin January 19, 2013, 11:06 pm

Reed-That’s terrific….commercial or residential? Fran

Sheila Schultz January 20, 2013, 5:49 pm

What a wonderful post Fran. I can’t believe I just saw it and I’m laughing since I mentioned Chicago in my note to you earlier in the week. We moved to Denver in late 2005, the Green Roof movement has exploded since then. I am so proud of the city I called home for 34 years!

Fran Sorin January 21, 2013, 9:38 am

Sheila – You and I are both laughing – we do seem to cross each others paths.
I LOVE CHICAGO! I think it’s the great American city!

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