Heat gain through a home’s roof and attic makes up about 20% of the air conditioning load. Conventional wisdom and early research both point to light colors and smooth finishes to reflect the sun’s heat at the exterior roof finish. But not all light colored roofs perform the same. From 1997-2005, UCF researchers put off-the-shelf roof finishes and a few innovations to the test in controlled, side-by-side laboratory studies as well as full scale field studies to see which ones kept the most heat out.
Years of Research: 1990 – 2005
Sponsored by: Florida Energy Office, U.S. Department of Energy Building America program
This home in Cocoa, Florida was damaged in the summer of 2004 by Hurricanes Frances and Jeanne. A white metal roof was installed over the damaged shingles to reflect summer heat. Initial measured data show a 19% reduction in air conditioner energy use.
- Comparative Evaluation of the Impact of Roofing Systems on Residential Cooling Energy Demand in Florida
Six side-by-side highly instrumented Habitat for Humanity homes located in Ft. Myers, Florida with identical floor plans and orientation, R-19 ceiling insulation, but with different roofing systems designed to reduce attic heat gain. A seventh house had an unvented attic with insulation on the underside of the roof deck rather than the ceiling.The types of roofing systems studied include:
- Standard dark shingles with standard ventilation (control home)
- Light colored shingles
- Terra cotta “barrel” S-style tile
- White “barrel” S-style tile
- White flat tile roof
- White galvanized steel 5-vee roof
- Standard dark shingles with R-19 insulation applied to the underside of the roof decking and a sealed, unvented attic.
- Flexible Roofing Facility — Summer Test Results
This report focuses on:
- Average attic air temperatures
- Rank order on reducing cooling season impact to duct system heat gains and air leakage
- Maximum attic air temperatures
- Rank order on reducing peak impact to duct system heat gains and air leakage
- Ceiling heat flux
- Rank order on reducing cooling season ceiling heat flux
- Estimation of overall impact of roof
Demonstration of Cooling Savings of Light Colored Roof Surfacing in Florida Commercial Buildings: