L.A. Seeks Sanctuary under Cool Roofs from the Onslaught of Global Warming

Wednesday, December 25, 2013

“Oh, when the sun beats down and burns the tar up on the roof,

And your shoes get so hot, you wish your tired feet were fireproof,

Under the boardwalk, down by the sea,

On a blanket with my baby is where I'll be.”

–Lyrics from “Under the Boardwalk”

And you should be there too, if you know what’s good for you or have failed to install a “cool roof” on your home.

That’s pretty much the song from the city of Los Angeles, which last week became the first major city in the nation to require that new and refurbished roofs use light- and heat-reflecting building materials to save money on energy bills.

They’re called “cool roofs,” and the L.A. City Council voted unanimously to approve an ordinance that will literally change the way the city looks. Cool roofs, which are often white, can be other colors, including red. In addition to lowering electrical bills, the ordinance could lead to fewer power outages, fewer hospitalizations, an increase in roof longevity, a decline in greenhouse gas emissions and better air quality.    

They can reduce surface temperatures 50°F, lowering temperatures inside by several degrees—just in time for global warming. Recent research at UCLA projected that Los Angeles would grow 3.7° to 5.4° warmer by 2050. Downtown can expect three times as many days when temperatures top 95°.

The state established guidelines for cool roofs in 2005 as part of Title 24 Building Energy Efficiency Standards. California’s Green Building Standards Code (CalGreen), which took effect in 2011, gives a shout-out to cool roofs. There are separate standards for different buildings, but the technology can be applied to flat tar roofs, steep shingle roofs and everything in between.    

The advantage of cool technology is particularly acute in dense urban areas where roofs and pavements cover 50% to 65% of surfaces. Those cities are subject to a phenomenon called the “heat island effect,” where clustered heat-generating sources combine to produce an effect that is greater than the sum of their parts. More than half the world’s population lives in cities, but that is expected to climb to 70% by 2040.

Reuters cites estimates that cool roofs in 11 metropolitan cities could save the country 7 gigawatts in energy usage, the equivalent power of 14 power plants. Researchers at Lawrence Berkeley National Laboratory calculated in 2010 that raising the reflectivity in Northern American cities with more than 1 million people could reduce CO2 emissions by 57 gigatons. That’s twice the amount of CO2 emitted in the world in 2006.

But as study co-author Hashem Akbari noted, “Two years worth of emissions is huge, but compared to what we need to do, it’s just a dent in the problem.”

–Ken Broder


To Learn More:

Los Angeles Becomes First Major City to Require “Cool Roofs” (by Ari Phillips, ThinkProgress)

Painting Bill Clinton’s “White Roofs” into Reality (by Juan Carlos Pineiro Escoriaza, Reuters)

Global Model Confirms: Cool Roofs Can Offset Carbon Dioxide Emissions and Mitigate Global Warming (by Julie Chao, Lawrence Berkeley National Laboratory)

Radiative Forcing and Temperature Response to Changes in Urban Albedos and Associated CO2 Offsets (by Surabi Menon, Hashem Akbari, Sarith Mahanama, Igor Sednev and Ronnen Levinson, Environmental Research Letters)

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