Green Building? Try a white roof!

15th of September 2008 - 1:41 PM

White roofs can cut a buildings energy use by 20 percent and save consumers money, says California Energy Commissioner Art Rosenfeld.

 A study conducted by California scientists have worked out a way to
calculate how much carbon dioxide (CO2) can be offset by increasing the
reflectivity of urban surfaces like rooftops. The news was announced at
the California Energy Commission's Fifth Annual Climate Change Research
Conference.
"The potential energy savings in the U.S. is in excess
of $1 billion annually. Additionally, by conserving electricity we are
emitting less CO2 from power plants," Rosenfeld added.

Scientists have known for centuries that putting white roofs on
homes and buildings is a simple and effective way to reflect the sun's
powerful rays. Similarly, cool-colored pavements aid in the reduction
of "urban heat islands." When rooftops and pavements are more
reflective, global warming can be reduced.

Since 2005, commercial buildings with flat roofs in California
have been required to have white roofs. Residential sloped roofs are
also becoming more efficient. Beginning in 2009, new residential roofs
and retrofit constructions in California will be required to have
"cool-colored" roofs which reflect a higher fraction of the sun's rays
than current roofing materials of the same color.

Because white roofs act as a geo-engineering technique to cool
the earth on a global scale, Akbari, Menon, and Rosenfeld propose an
international campaign to organize 100 of the world's largest cities in
tropical and temperate zones to develop programs to require white roofs
and "cool pavements" when roofs are initially constructed and pavements
installed. The projected estimate for worldwide CO2 emissions in 2025
is 37 billion metric tons; a proposed global CO2 offset would be 44
billion metric tons, valued at $1,100 billion, and enough to offset
more than one year of the total global CO2 emissions.

"This idea of a 'cool cities' campaign could lead to significant
energy savings, improved air quality, reduce the heat island effect in
summer, and more importantly, cool the globe," says Hashem Akbari.
"This simple and effective idea can organize the world into taking
measured steps to mitigate global warming. Our findings will help city
leaders and urban planners quantify the amount of CO2 they can offset
using white roofs and cool pavements."