Cooler Tile-Roofed Buildings with Near-Infrared-ReflectiveNon-white Coatings

Journal Article · Fri Jun 25 00:00:00 EDT 2004 · Building&Environment

OSTI ID:928227

Levinson, Ronnen; Akbari, Hashem; Reilly, Joeseph C

Owners of homes with pitched roofs visible from ground leveloften prefer non-white roofing products for aesthetic considerations.Non-white, near-infrared-reflective architectural coatings can be appliedin-situ to pitched concrete or clay tile roofs to reduce tiletemperature, building heat gain, and cooling power demand, whilesimultaneously improving the roof s appearance. Scale model measurementsof building temperatures and heat-flux were combined with solar andcooling energy use data to estimate the effects of such cool roofcoatings in various California data. Under typical conditions e.g., 1 kWm-2 summer afternoon insolation, R-11 attic insulation, no radiantbarrier, and a 0.3 reduction in solar absorptance absolute reductions inroof surface temperature, attic air temperature, and ceiling heat fluxare about 12 K, 6.2 K, and 3.7 W m-2, respectively. For a typical 1,500ft2 (139 m2) house with R-11 attic insulation and no radiant barrier,reducing roof absorptance by 0.3 yields whole-house peak power savings of230, 210, and 210 W in Fresno, San Bernardino, and San Diego,respectively. The corresponding absolute and fractional cooling energysavings are 92 kWh yr-1 (5 percent), 67 kWh yr-1 (6 percent), and 8 kWhyr-1 (1 percent), respectively. These savings are about half thosepreviously reported for houses with non-tile roofs. With theseassumptions, the statewide peak cooling power and annual cooling energyreductions would be 240 MW and 63 GWh yr-1, respectively. These energysavings would reduce annual emissions from California power plants by 35kilotonnes CO2, 11 tonnes NOx,and 0.86 tonnes SOx. The economic value ofcooling energy savings is well below the cost of coating a tile roof, butthe simple payback times for using cool pigments in a rooftile coatingare modest (5-7 years) in the hot climates of Fresno and SanBernardino.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE; California Energy Commission / Energy InnovationSmall Grant Program
• DOE Contract Number: DE-AC02-05CH11231
• OSTI ID: 928227
• Report Number(s): LBNL-54902; R&D Project: 80XY10; TRN: US200815%%790
• Journal Information: Building&Environment, Vol. 42; Related Information: Journal Publication Date: 2007
• Country of Publication: United States
• Language: English

Related Subjects

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AESTHETICS
ATTICS
CLAYS
CLIMATES
COATINGS
CONCRETES
ECONOMICS
GROUND LEVEL
HEAT EXCHANGERS
HEAT FLUX
HEAT GAIN
INSOLATION
PEAK LOAD
PIGMENTS
POWER DEMAND
POWER PLANTS
ROOFS
SCALE MODELS
tile roof cool coating near-infrared reflective buildingsimulation cooling energy cooling power California cool roof COOLTILE IRCOATINGS