In a Climate Quest, the Roof as White Knight - Green Blog - NYTimes.com

Another study published this year by researchers with the Berkeley Lab used sophisticated global climate models to determine the cooling benefit of increasing the albedo, or reflectivity, of both roofs and roadways [on a white roadway, how well does snow and dangerous ice melt?] in large cities. The study found that increasing the reflectivity of those surfaces in urban areas with a population of over one million would offset the heating effect of 1.2 gigatons of carbon dioxide emission annually, the equivalent of taking 300 million cars off the road for 20 years.

Cool roof - Wikipedia, the free encyclopedia

Cool roofs in cool climates

No matter where cool roofs are installed, they cut down on the urban heat island effect, however they do not always lower a building’s carbon footprint. In climates where there are more heating days than cooling days, white reflective roofs are not typically a worthwhile investment in terms of energy efficiency or savings. The cooling benefits of a highly reflective roof surface do not outweigh the winter month heating benefits of a less reflective, or black, roof surface in cooler climates. Heating accounts for 29% of commercial buildings' yearly energy consumption, while air conditioning only accounts for 6% of that same yearly energy consumption. Therefore, in cooler climates, it is more beneficial to utilize a dark-colored roof surface to help lower heating costs, which far outweigh annual air conditioning expenses. Energy calculators generally show a yearly net savings for dark-colored roof systems in cool climates.