Question:
We have a flat roof on our house, which like most is black, and it
absorbs so much heat from the sun in summer as to make that part of the
house unbareably hot. (If solar panels weren't so expensive, we'd be
putting some up there like a shot, but back to the point...) I've
wondered therefore about painting it white so it reflects more light
instead of absorbing it
So this makes me wonder... all those roofs not being put to good use
for solar energy or planted up as wildlife habitats, they're almost all
black or dark grey, what if we all painted our roofs white - would the
commulative effect reflect back a significant enough amount of sunlight
to offset the reduction in ice-covered area at the poles?
Answer:
Ask energy efficiency expert Art Rosenfeld what Los Angeles needs in
order to save $500 million a year in energy costs, and he will probably
say a can of white paint. This is the simple tool used in warm climates
worldwide to combat the "heat island effect that plagues many congested
urban areas and drives air conditioning costs through the roof.
Heat islands form when asphalt and dark rooftops absorb enough solar
radiation to make the average temperature of warm-climate cities 5-8
degrees Fahrenheit higher than surrounding areas. In the US, five to ten
percent of urban electricity demand during peak hours feeds air
conditioners used to offset heat-island warming. In his report,
"Mitigation of Urban Heat Islands," Rosenfeld, director of the Center
for Building Science at Lawrence Berkeley Laboratory, claims that by
whitewashing roads and roofs, residents can cool their cities and save
vast amounts of energy.
