Dark roofs raise the summertime air-conditioning demand of buildings. For highly-absorptive roofs, the difference between the surface and ambient air temperatures can be as high as 90°F, while for highly-reflective roofs with similar insulative properties, the difference is only about 20°F. For this reason, "cool" roofs are effective in reducing cooling energy use. Several experiments on individual residential buildings in California and Florid a show that coating roofs white reduces summertime average daily air-conditioning electricity use from 2 - 63%.

This demonstration project was carried out to address some of the practical issues regarding the implementation of reflective roofs in a few commercial buildings. We monitored air-conditioning electricity use, roof surface temperature, plenum, indoor, and outdoor air temperatures, and other environmental variables in three buildings in California: two medical office buildings in Gilroy and Davis and a retail store in San Jose.

Coating the roofs of these buildings with a reflective coating increased the roof albedo from an average of 0.20 - 0.60. The roof surface temperature on hot sunny summer afternoons fell from 175°F - 120°F after the coating was applied. Summertime average daily air-conditioning electricity use was reduced by 18% (6.3 kWh/1000ft²) in the Davis building, 13% (3.6 kWh/1000²) in the Gilroy building, and 2% (0.4 kWh/1000²) in the San Jose store.

In each building, a kiosk was installed to display information from the project in order to educate and inform the general public about the environmental and energy-saving benefits of cool roofs. They were designed to explain cool-roof coating theory and to display real-time measurements of weather conditions, roof surface temperature, and air-conditioning electricity use.

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A description of the Demonstration of Energy Savings of Cool Roofs project

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