Reduce the effects of ‘urban heat Island effect’
Due to all the hard paved surfaces and traditional roofs, cities are retaining heat and maintaining temperatures 10 degrees higher than the surrounding area. In the summer heat, the temperature on green roofs can be 20-60 degrees cooler than conventional roofing. (pomegranate green roof manual 2005)
Control building temperature
For hundreds of years, living roofs were used in various countries to prevent heat from escaping or penetrating during different seasons. Controlling a building’s interior is possible by replacing the asphalt surface of the roof with plants and soil, which act as insulators to keep buildings cooler in summer and warmer in winter. (pomegranate green roof manual 2005)
Reduce the volume of storm water runoff
Green roofs are known to retain 50-60 percent of the total annual runoff volume of a roof. Most importantly, the soil retains 90-100% of the critical first hour of heavy rainfall that can overwhelm storm water management systems. In urban and suburban centers, this could aid in alleviating the cost of storm water management and help in flood control. (pomegranate green roof manual 2005)
Impervious layer - An artificial surface that doesn’t allow water to flow through it.
Greenhouse gases– Gases in the Earth’s atmosphere that prevent heat energy the Earth has absorbed from the sun from escaping back into space.