Living roofs cut urban temperatures up to 40°F, study shows
Research finds that vegetated roofs can be as much as 40°F cooler than conventional roofs, offering a natural way to mitigate city heat.
Urban surfaces absorb solar energy and release it after dark, raising city temperatures above those of surrounding rural areas. A recent investigation compared conventional roofs with vegetated ones and found the latter to be about 30-40°F cooler on sunny days. The temperature drop results from plant shade and the evapotranspiration process, which consumes heat as water moves from soil to the atmosphere.
Data from a southern Italy extensive green roof showed surface temperatures up to 63% lower than a standard roof, reducing heat swings in both summer and winter. Beyond cooling, green roofs slow runoff, supporting storm-water management and providing habitats for insects and birds. Different roof types—extensive and intensive—offer trade-offs between cost, structural demands, and potential for human use, allowing cities to tailor solutions to local conditions.
Why it matters
Cooler roofs lower building energy use and help cities combat heat islands and storm-water overload.
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