Solar-reflective roofs stay cooler in the sun than solar-absorptive roofs. Such "cool" roofs achieve lower surface temperatures that reduce heat conduction into the building and the building's cooling load.The California Energy Commission has funded research in which Lawrence Berkeley National Laboratory (LBNL) has measured the electricity use and peak demand in commercial buildings to document savings from implementing the Commission's Cool Roofs program. The study seeks to determine the savings achieved by cool roofs by monitoring the energy use of a carefully selected assortment of buildings participating in the Cool Roofs program. Measurements were needed because the peak savings resulting from the application of cool roofs on different types of buildings in the diverse California climate zones have not been well characterized to date. Only a few occupancy categories (e.g., office and retail buildings) have been monitored before this, and those were done under a limited number of climatic conditions. To help rectify this situation, LBNL was tasked to select the buildings to be monitored, measure roof performance before and after replacing a hot roof by a cool roof, and document both energy and peak demand savings resulting from installation of cool roofs.We monitored the effects of cool roofs on energy use and environmental parameters in six California buildings at three different sites: a retail store in Sacramento; an elementary school in San Marcos (near San Diego); and a 4-building cold storage facility in Reedley (near Fresno). The latter included a cold storage building, a conditioning and fruit-palletizing area, a conditioned packing area, and two unconditioned packing areas (counted as one building).Results showed that installing a cool roof reduced the maximum roof surface temperature of each building by 60-75ºF.In the retail store building in Sacramento, applying a cool coating reduced the maximum roof surface temperature elevation by 60-65ºF, and reduced the underroof temperature in the conditioned area by as much as 40-50ºF. For the period of 08/08/2002 to 09/30/2002, the estimated savings in average air conditioning energy use was about 83 kWh/day (52%; 6.7 Wh/ft 2 /day). On hot days when the afternoon temperature exceeded 100°F, the measured savings in average peak demand for peak hours (hours 12-17) was about 12-13 kW (about 1 W per square foot of conditioned area). • • •In the school building in San Marcos, the reductions in the maximum roof surface temperature and under-roof temperature were about the same as for the retail store. For the period of 07/08/2002 to 08/20/2002, the estimated savings in average air conditioning energy use was about 22-26 kWh/day (17-18%; 3.9-4.5 Wh/ft 2 /day). On hot days when the afternoon temperature exceeded 90°F, the measured savings in average peak demand for hours 10-16 were about 3.1 kW (about 0.5 W per square foot of conditioned area).In the cold storage facility in Reedley, coating reduced the maximum roof surface temperature elevation by 65-75ºF...

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