Demonstration of Energy Savings
of Cool Roofs

The Heat Island Group was funded by the Environmental Protection Agency to demonstrate the cooling energy savings of light-colored roofs on commercial buildings. We monitored, reroofed, and analyzed three commercial buildings during the summers of 1996 and 1997. The buildings were:

	Kaiser Permanente Medical Office Building, Davis, California ~31,000 ft2 on one story light gray capsheet roof
	Kaiser Permanente Medical Office Building, Gilroy, California ~61,000 ft2 one-story converted warehouse light gray capsheet roof
	Longs Drug Store #264, San Jose, California ~26,000 ft2 plus 7000 ft2 mezzanine tan capsheet roof
Link to: Demonstration Project Photo Gallery

Before instrumenting these buildings, we collected data on building characteristics and performed DOE-2 simulations of energy use and savings. Characteristics we noted included:

Floor area Number of stories Roofing material, age, and reflectance Roof system Attic ventilation Heating, cooling, and air-handling systems Duct systems Building schedules Lighting and systems schedules Thermostat settings

Link to: Davis Schematics with Monitoring Locations Gilroy Schematics with Monitoring Locations San Jose Schematics with Monitoring Locations

The Davis Energy Group of Davis, California, was hired as a subcontractor to install and calibrate non-intrusive monitoring equipment in each building. The equipment measured:

• Weather: wind speed and direction, outdoor ambient air temperature and relative humidity, and solar flux (measured by a weather tower at fifteen-minute intervals).
• Energy: whole-building electricity use, cooling-electricity use, and heat flux through the roof. The cooling energy use was measured using current transducers. All data flow into a data logger (one in each building) that was remotely connected to our computers at Berkeley Lab. We observed and collected data at least once a day. This permitted immediate trouble shooting and debugging of our instrumentation during the early phase of the project. We collected data for each of these buildings for 6-12 weeks, before installing reflective roofs.
• Buliding Temperatures: temperatures of the roof's surface and underside, the ceiling plenum air temperature, and the indoor and return air temperatures.

We also provided information to the community by placing a temporary display kiosk in the lobby or waiting room of the building. This kiosk provided information about the energy-saving potential of white roofs, as well as real-time data about the roof temperature, the building cooling energy use, and the cooling energy saved by using a white roof.

After monitoring the buildings throughout the heating season of 1996, the roofs of the buildings were painted with reflective coatings that increased the roof reflectivities from 0.20 to 0.60. The infrared image of the roof showed an immediate reduction in roof temperature of about 40°C (70°F) after the application of the coating. Link to: Demonstration Project Results

A white coating reduced the roof temperature by about 40°C (70°F).

For further information about the Demonstration of Energy Savings of Cool Roofs, please contact Steven Konopacki

Read the report