The urban heat island is the overheating of urban and suburban areas, relative to the surrounding countryside, due to increased paved, built-over, and hard surface areas. Aver-age summer temperatures in major cities across North America have been on the rise over the past decade. These artificially high summer temperatures have a range of direct and indirect negative impacts on our quality of life. The urban heat island effect increases the use of more electricity for air conditioners and it increases the rate at which chemical processes generate pollutants such as ground level ozone. It also exacerbates heat-related illnesses. Green Roofs intercept the solar radiation that would strike dark roof surfaces and be converted into heat thereby improving energy conservation. Like urban forests and reflective roofing surfaces they absorb and/or deflect solar radiation so that it does not produce heat. An ASHRAE simulation conducted by the City of Chicago of their City Hall Green Roof showed that every one degree Fahrenheit decrease in ambient air temperature results in a 1.2% drop in cooling energy use. The study suggests that if, over a period of ten years or more, all of the buildings in Chicago were retrofitted with Green Roofs, (30% of the total land area), this would yield savings of $ 100,000,000 annually from reduced cooling load requirements in all of the buildings in Chicago. The cooling would also slow the chemical processes that produce ground level ozone, nitrous oxides and smog, and help offset the production of sulphur dioxides from coal fired utilities.