A few weeks ago I was able to walk through the most unusual prairie
in Illinois. I found myself photographing a mound of coneflowers still
covered with morning dew. I snapped a few shots of native grasses
swaying in the breeze. Then I focused on a dragonfly, which was hardly
Yet, why is this prairie so unusual? Coneflowers, native grasses,
and dragonflies, though spectacular in mid-summer, are hardly new
to most of us. What distinguishes this prairie is its height: 14 stories
above street level on the roof of Chicago’s City Hall.
This rooftop garden, which has become a potent symbol of Mayor Daley’s
crusade to make Chicago the greenest city in the nation., regularly
receives visits from environmentalists from all over the country.
Many foreigners used to associate Chicago with gangsters or Michael
Jordan. Now they identify Chicago as the place with the rooftop prairie
– as the showcase in the American Mid-West for green building
This rooftop garden, whose construction began in the fall of 2000,
now includes over 20,000 specimens from over 100 species. Except for
a few paving stones, a few annuals here and there, and the noise from
LaSalle Street below, you might think you were at a prairie anywhere
in Jo Daviess County.
This green roof has produced some interesting statistics. On the
hottest days of the year the temperature of the air just above the
green roof at City Hall has been measured between 95 and 110 degrees
Next door, at the adjacent Cook Building, the air just above a black
tar roof is 165 degrees. Since the installation of the green roof,
City Hall’s electric bills for heating and cooling have dropped
by three to four thousand dollars each year.
Chicago’s Department of Environment has produced a slick little
guide for rooftop gardening. It shows that going green with roofs
is not as complicated as it might seem.
It just takes some thought about the structural capacity of roofs
and how they’re built – usually with filter mats, drainage
layers, insulation layers, root barriers, and waterproof membranes
above the standard roof deck. Thought also is needed for how rooftop
gardens will be accessed, and, when planted, how they will be maintained.
Chicago has clearly demonstrated that green roofs offer profound
benefits. They can be an option for many buildings, private or public,
residential or commercial, small or large. Yet, green building strategies
hardly limit themselves to green roofs.
The City of Chicago is working with permeable (unpaved) alleys, green
fueling stations, large-scale brownfield remediation sites, green
housing demonstrations, and enterprise development zones for businesses
supplying and servicing green buildings.
The Chicago Center for Green Technology is a municipally owned resource
where developers, architects, home owners, and community gardeners
can learn about the latest in technologies, from rooftop gardening
and recycled building materials, to solar panels and sustainable landscaping.
If you can’t include a stop there on an upcoming visit to the
city, you may learn more about their programs with a visit to their
Nor are Green technologies limited to urban settings. They make
just as much sense in predominantly rural areas like Jo Daviess County.
If our buildings are green, they’re helping to achieve the goals
of the County’s general plan. Guardians have had some recent
success in promoting lighting that’s friendly to dark skies.
We can play an important role in promoting the benefits of green
buildings, too. It seems that every few days there’s a report
of some emerging technology or product to help make buildings green.
Some of this could be quite helpful to our members — for development
of their own residences or for guiding projects in our communities.