In terms of reflectivity, white metal roofing actually doesn't perform as well as white flat and white barrel tiles. It reflects about 66 percent of the sun's energy away from a roof. But white metal roofing does have one edge: Compared to other roofing types, it cools faster at night, and holds less heat for shorter periods [source: Better Homes and Gardens].
Most metal roofing will cost 20 to 30 percent more than traditional roofing, but in energy savings, durability and lowered maintenance, it is a cost saver overall [source: Metal Roofing Alliance]. In order to maximize the benefits of metal roofing in warm climates, however, treatments and installation are major factors. Most metal roofs are steel and aluminum, with copper options more on the high end, and most types should be treated for corrosion resistance. They also need to meet minimum code standards for wind resistance and placement. If installed at an angle without slope planning and glare considerations, no matter how cool the white metal roof is, it won't be cool to nearby residents and drivers who get blinded by the reflected light.