It makes so much difference and is so easy to do that NYC is in the midst of a massive effort to paint all its roofs white.
Since 2010, NYC °CoolRoofs has coated 2.6 million square feet of New York City rooftop, and a million more square feet will be painted this year … all by volunteers.
And the NYC nonprofit, White Roofs Project, is also on a painting spree, going national. Founder Juan Carlos says painting 5% of the world’s rooftops every year would, by 2030, save the emissions produced worldwide in 2010.
Cool roofs reduce internal building temperatures by as much as 30%, making the building cooler and more comfortable during hot summer months.
If cool or green roofs graced half the buildings in Southern California, enough energy would be saved to power 127,000 homes and cut $211 million in utility bills, while reducing the emissions equivalent to 91,000 cars each year, says the Natural Resource Defense Council in a new report. Green roofs also reduce stormwater runoff that pollutes beaches and waterways.
Columbia University’s Center for Climate System Research set up a NYC °CoolRoofs monitoring station and found that on July 22, 2011 – a record-setting day for electricity use – white roofs were 42°F cooler than dark roofs, which reached temperatures of 170°F.
Some argue that cool roofs aren’t appropriate for cold climates and could result in higher heating bills in winter. Although higher heating costs could outweigh savings in air-conditioning in areas with severe winters, scientists say cool roofs are beneficial as far north as New York or Chicago because of the heat island effect.
Cool roofs are available in a wide range of colors today, not just white.
If 5% of the roofs that are replaced each year had cool colors, it would take 20 years to transform the US to “cool,” says Hashem Akbari at the Lawrence Berkeley Lab, which developed the range of colors.