Looking Up: How Green Roofs and Cool Roofs Can Reduce Energy Use in Southern California

Southern California faces multiple threats stemming from the expansion of our urban and suburban environment. First, urbanization and development transform landscapes into impervious surfaces, increasing the volume of runoff that results from precipitation. More runoff means more pollution carried by stormwater to our rivers, lakes, and beaches. Second, climate change, brought about in part by increased energy use, threatens our water supply, particularly the availability of freshwater resources like the Sierra snowpack, jeopardizes progress in air quality, and endangers human health. Third, dark impervious surfaces in our cities absorb and radiate heat back into the surrounding atmosphere at a far greater rate than the natural landscape does, causing a heat island effect that raises ambient air temperatures in developed areas, resulting in human health problems and additional energy use for building cooling. Green roofs and cool roofs offer the potential to address many of these issues and improve the sustainability of urban areas in Southern California.