EPA website green roofs green roofs EPA website green roofs 0.7 percent Green roofs can further reduce the energy consumption US EPA - Using Green Roofs to Reduce Heat Islands heat island effect US EPA help roofs with gardens cost of installing a green roof 90°F (50°C) warmer. University of Michigan study enhanced water quality. green roof into an existing structure heat island EPA website EPA website Create a green roof on our roofs as well green roof green roof roof gardening The Process EPA Using Green Roofs to Reduce Heat Islands. heat island effect EPA study incorporating a green shell and roof expensive enterprise 30–40°F cooler EPA website