In
the effort to slow the pace of global warming, researchers and policy
makers are encouraging the use of lighter colors for rooftops and
streets worldwide. Dark, non-reflective surfaces which are common for
asphalt and asphalt shingles, absorb heat from the sun and create a
"heat-island" effect, plus a greater need for air conditioning. Lighter
surfaces would reflect the sun’s rays back to outer space, reducing
ground-surface temperatures and overall energy requirements.
This is an effort that
has been promoted aggressively by the US Department of Energy (DOE)
Secretary, Steven Chu. Talking with Jon Stewart on the "Daily Show",
Chu said "when you're thinking of putting on a new roof, make it white.
It costs no more to make it white than to make it black." In fact, Chu
has instructed all DOE offices to install "cool roofs" on new
department buildings or when replacing old ones.
"Cool roofs
are one of the quickest and lowest-cost ways we can reduce our global
carbon emissions," he said in a DOE statement. It is one of the easiest
ways to fight global warming. All it involves is choosing a lighter
color when installing a new roof.
The same concept can go with
all urban surfaces. Researchers at the Lawrence Berkeley National
Laboratory (LBNL) determined that for cities with populations over one
million, increasing surface reflectivity would be equivalent of
offsetting the heating effect of 1.2 gigatons of carbon dioxide
emissions per year. It is also equivalent to removing 300 million cars
off the road for twenty years.
Roofs and paved surfaces cover 50
to 65 percent of the planet's urban areas, where more than half the
world’s population lives. There are experts that predict that with
population increase and migration to the cities, almost three quarters
of the world will live in urban areas. This means more buildings, more
roofs, and more roads.
It is also important to transition to
lighter color roofs and surfaces because it makes economic sense. Air
conditioning is one of the largest energy consumers during the hot
summer months, and the main reason why electricity bills sky rocket.
Darker roofs absorb solar heat into the house, while lighter roofs
reflect it away. The LBNL researchers found that outfitting eighty
percent of air-conditioned buildings in the US with white roofs could
save $735 million per year by reducing utility bills.
There is no
reason why light colored roofs shouldn't be adopted on a large scale.
Sure a white roof may look funny on your house compared to your gray or
black roof, but it doesn't cost any more. The question isn't, why do
it. The question is, why have we not done it already.
For more information: http://newscenter.lbl.gov/news-releases/2010/07/19/cool-roofs-offset-carbon-dioxide-emissions/
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