Global Cooling: Policies to Cool the World and Offset Global Warming from CO2 Using Reflective Roofs and Pavements Page: 4 of 15
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" The 2005 California Title 24 Standards prescribe cool materials for low-sloped roofs
on nonresidential buildings in all California climate zones (but one coastal region) and
offers credits for steep-sloped roofs on residential and nonresidential buildings in all
California climate zones.
" The 2003 International Energy Conservation Code allows commercial buildings to
comply by satisfying the requirements of ASHRAE Standard 90.1, which at the time that
IECC 2003 was written offered cool-roof credits.
" The Chicago, IL Energy Conservation Code prescribes a minimum solar reflectance and
thermal emittance for low-sloped roofs.
" The 2004 Florida Building Code prescribes cool materials for all roofs on non
residential buildings that are essentially the same as those in ASHRAE Standard 90.1-
" Hawaii. In 2001, 2002, and 2005, respectively, the counties of Honolulu, Kauai, and
Maui adopted cool-roof credits for commercial and high-rise residential buildings based
on ASHRAE Standard 90.1-1999.
" U.S. EPA ENERGY STARTM Label. The U.S. EPA currently requires that low-sloped
roofing products have initial and three-year-aged solar reflectances not less than 0.65 and
0.50, respectively. Steep-sloped roofing products must have initial and three-year-aged
solar reflectances not less than 0.25 and 0.15, respectively.
" LEED Green Building Rating System. The Leadership in Energy and Environmental
Design (LEED) Green Building Rating System assigns one rating point for the use of a
cool roof in its Sustainable Sites Credit.
" Cool Roof Rating Council. The Cool Roof Rating Council was established in 1998 to
"develop accurate and credible methods for evaluating and labeling the solar reflectance
and thermal emittance (radiative properties) of roofing products and to disseminate the
information to all interested parties."
California: Cool Roofs and Climate Targets
In California and many other states, cool roofs are an accepted measure to reduce air
conditioning load (Akbari and Levinson 2008), thus decreasing electric bills and CO2 emissions.
However, to date, none of these codes have taken account of the effect that cool roofs and
pavements have in reducing radiative forcing. Noting that, on average, existing urban surfaces
can be changed to cool surfaces over a 15-year period, this effect is several times larger than the
CO2 emissions avoided through reduced electric load over this 15 year period.
Most roofs are replaced every 10 to 25 years (residential roofs every 20 to 30 years, non-
residential roofs every 10 to 20 years), while most paved surfaces are resurfaced approximately
every 10 years. By our calculations, an aggressive 15-year state-wide campaign to implement
cool roofs and pavements in California would effectively be the equivalent of reducing
California emissions by 31 Mt CO2/year for 15 years. This is 18% of the annual target
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Akbari, Hashem; Levinson, Ronnen; Rosenfeld, Arthur & Elliot, Matthew. Global Cooling: Policies to Cool the World and Offset Global Warming from CO2 Using Reflective Roofs and Pavements, article, August 28, 2009; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc1015141/m1/4/: accessed January 16, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.