Fighting Urban Heat Islands.
Fighting Urban Heat Islands.

The urban heat island effect plagues big cities coast to coast. Metal roofing is an effective tool to fight this urban warming.

The Cool Metal Roofing Coalition has this to say about the subject:

About half of the North American population lives in urban areas. The prevalent use of energy-absorbing, dark building materials and dark pavements, coupled with a lack of vegetation, creates a microclimate where ambient temperatures are higher than in the surrounding areas. For some cities, this urban heat island effect can increase the local temperature as much as 12F (7C). 

Cool metal roofing is one way to mitigate the urban heat island effect. Roofs with higher reflectance have lower surface temperatures, which help reduce ambient air temperatures. This improves air quality since less smog is formed. Also, air pollution associated with burning fossil fuels at utility plants is reduced because of less peak load demand. 

Oak Ridge National Laboratory research has shown that metal roofing retains solar reflectance over time better than other roofing products because it resists the growth of organic matter and sheds dirt more readily than other materials. 

Metal roofs are included on the U.S. EPA’s Energy Star Roof Products Program. Metal roofs are also represented on the California Energy Commission’s Cool Roof Savings program listing.

Source: Cool Metal Roofing Coalition