Inspiration Case 14: Green Rooftops

INSPIRATION CASE 14: GREEN ROOFTOPS General Information Green rooftops, like our inspiration case of the City Hall in Chicago, USA, are not just beautiful oases that contribute to more diverse living in a city. As positive side effects, they help to improve air quality and save utility expenses by reducing building’s maximum temperatures in the summer and providing natural insulation in the winter. Therewith, green rooftops can mitigate the urban heat island effect and actually save on expenses; for this example Chicago City Hall’s green rooftop saves substantial $5,000 a year on utility bills, according to Michael Berkshire, Green Projects Administrator at The City of Chicago.

Inspiration & Parametres for change a) mixed use of built environment, playing with private and public space

As buildings are inevitable for human dwellings, their often unused roof space can be utilised with roof gardens. This opens up a private building for the public and provides common goods as beauty and nature.

b) natural beauty, leisure and impact on life quality

Whilst designing a green rooftop, mostly unused space in a city becomes an oasis of greens, flowers and beauty where people can spend time on for leisure. But furthermore, these roofs improve air quality in the city, contribute to its biodiversity, and saves utility expenses within the building by cooling down in summer and providing an additional insulation layer in winter. This in turn mitigates the urban heat island effect that many cities with hard surfaces have. As an example: In 2007 scientists flying over Chicago in a helicopter equipped with thermal cameras pointing at a regular black tar rooftop connected to the City Hall measured more than 40°C, whilst the green part of the City Hall itself came to 21° C only.

INSPIRATION CASE 14: GREEN ROOFTOPS Our inspiring example: Chicago City Hall, Chicago IL USA, 2001

ÂŠ Clear Village 2011

The Chicago City Hall roof top has partly been designed green to start an extensive measurement project on the effects of green roofs on live quality in the building and its environment. In a retrofit concept more than 20,000 herbaceous plants with more than 150 varieties were installed as plugs on a surface of 20,300 sq ft which are irrigated mainly by collected rainwater.

How does the City Hall project in Chicago work in detail? In an extensive research and study project on air quality improvement and combating the urban heat island effect carried out by the American Environment Protection Agency EPA, Mayor Richard M. Daley and the City of Chicago reconstructed the 38,800 square feet roof area as a semi-extensive greenroof in April 2000 and completed it at the end of 2001. In line with the study, and since the City Hall occupies half of the building, only one half of the roof is designed green and the other one left with tar. Weather stations have then been assembled on both sides of the roof to measure the success of green roofs. The roof is now home for over 20,000 herbaceous plants in more than 150 varieties including 100 woody shrubs, 40 vines and 2 trees. For irrigation, rainwater is being collected. In periods of drought, a supplemental irrigation system is in place to make sure that plants survive.

What does this mean for the local community? The City Hall project was firstly initiated as a measurement project, which offered the local community a green oasis within the city center of Chicago. But much more interesting, as it proved to be highly effective in terms of combating the urban heat island effect, it kicked off an extensive series of re-designing cityâ&#x20AC;&#x2122;s roofs: In 2008, more than 450 green roofs were either in place or under construction. In this series, more communities get the benefits of green roofs and its effects on air quality and the urban heat island phenomenon.

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