Chicago is using a grant for the US Environmental Protection Agency to study green roofs. A green roof has been planted on the City Hall building. According to the EPA:
Projected total direct electricity savings were 9,272 kilowatt-hours per year, and the corresponding savings in natural gas for heating were 7.372 therms per year. (This calculation compares the base case R-value, or thermal resistance value To definition provided on the glossary page , of 5.9 with the treated roof – garden and insulation – R-value 21.2.)
Additionally, the article provides specific details as to the plant life as well as the construction methods and materials.
In major cities, such as Chicago and New York City, the city government imposes a tax on the amount of storm water runoff each building contributes.
Green roofs in these cities help reduce that tax by having the green roof system store and use the storm water.
Additionally, green roofs add to property values, as they reduce the heating and cooling costs, as well as providing additional aesthetic appeal.