Green roofs are commonly associated to the idea of energy efficiency, environmental friendly architecture, and proficient economic decisions. Nevertheless a 2001 green roof competition had some shocking results. This was established by then-Chicago’s Mayor Richard Daley with the purpose of finding out which building in Chicago could reduce their electricity bill the most.
The great battle was set between the Cook County buildings against the Chicago City Hall. Both buildings located in the Loop, the Cook Country building featured a white roof top while the Chicago City Hall designed and built a green roof, this featured 20,000 plants of more than 150 native to the Chicago region species from shrubs, vines to even two trees .
The Chicago City Hall takes pride of its green rooftop for the distinctive improvement of the city’s air quality, energy conservation, storm water runoff reduction, and urban heat island effect. The garden was able to achieve 75% rainfall retention, a temperature reduction on averaged 50 to 70 degrees during summer, and an annual $22,000 electricity bill reduction .
To win the competition, the Cook County building decided to cover the building’s roof and side facade with white-coated roofing membranes. This application not only resulted in a longer roof life cycle, but it reflects solar radiation and ultraviolet waves resulting in a lower energy cost; so low, that it allowed the Cook Country Building to beat the Chicago City Hall by reducing the summer building temperature and extra 2 degrees over the Chicago City Hall’s, moreover it was also able to save up to an annual $65,000 on their electricity bill, $43,000 more savings than the City Hall’s savings count .
But not only can a white roof help save a lot more energy and money than a green roof, it is also much more affordable to install and a lot less time consuming to maintain. While green roofs are great for reflecting heat, tackling air pollution, collecting rainfall water, and processing greenhouse gas emissions, they don’t come anywhere near the amazing results that white-coated roofs have accomplish. Green roof cost up to $30 per square foot to maintain .
Even though economics are a very important part of any building architectural decision, green roofs brings some hard-to-ignore facts to the table. For the most part, green roofs are open to employees and or the public, provide pocket habitats for urban birds, quiet areas of parkland in the middle of the city density, and work as extremely efficient rainfall collectors.
So which is better — white or green? From an economic stand point of view white is the undoable choice, but if you do happen to not care so much about money and more about statics, functionality, and human and natural advantages, green is definitely the way to go.
 Daigneau, Elizabeth. (2012) Chicago’s Battle of the Roofs: Green vs. White. Online: http://www.governing.com/topics/energy-env/gov-battle-of-roofs-chicago.html
 City of Chicago. (2013) City Hall’s Rooftop Garden. Online: http://www.cityofchicago.org/city/en/depts/dgs/supp_info/city_hall_green_roof.html
 Cook County Government. (2011) Facilities Management. Online: http://www.cookcountygov.com/portal/server.pt/community/facilities_management/294/facilities_management