Florida Power & Light Company announced today the results of a study that confirms what many homeowners living in the Sunbelt have thought for years -- the whiter, and therefore, more reflective the roof, the lower the electric bill. In the first study of its kind, FPL sponsored a tightly controlled test project that compared commonly used residential roofing materials to evaluate their relationship to home cooling costs.
The four-month study is the first to quantify cooling performance on identical residences during realistic weather conditions. The six roofing materials evaluated were: Dark gray shingles, white shingles, white flat tile, white S-shaped tile, terra cotta S-shaped "Spanish" tile, and white metal.
Study findings indicate energy savings are most strongly influenced by the solar reflectance of roof materials. The study proves dark gray roofs reflect a mere eight percent of the heat associated with sunlight, while white shingle and terra cotta tile roofs reflect 25 and 34 percent, respectively. White metal and cement tile roofs provide the most dramatic results, reflecting 66 to 77 percent of the sun's energy.
"The results of the study clearly demonstrate that white, galvanized metal roofing material saves the most energy as a result of its high reflectance and superior ability to cool quickly at night. This information, when applied, will not only result in lower energy consumption and cooling costs for the single-family resident in Florida, but for residents throughout the southern United States," said Craig Muccio, Conservation Program Evaluation Coordinator, for FPL.
A white, galvanized metal roof should save a customer who lives in an average-size 1,770 square foot home approximately $128 or 23 percent annually in cooling costs, compared with a dark gray shingle roof on the same home. For the same size home, white, S-shaped cement tile produces the second-best savings of $110 or 20 percent of annual cooling costs followed by white, flat cement calculated at $96 per year for a 17 percent savings compared to the dark gray shingles. White shingled roofs trim $24 or about four percent off the annual cooling bill, while terra cotta S-shaped cement tiles net a modest $15, or three percent compared to dark gray shingles.
"Choosing a roof for a home, whether it's a new home or a replacement roof, is a major decision for most homeowners. The purpose of this study is to provide homeowners with additional information to help them make the best, most informed decision. Every little bit we do to help our customers stay informed should ultimately conserve energy as well as save them money," Muccio said.
The study, titled "Comparative Evaluation of the Impact of Roofing Systems on Residential Cooling Energy Demand in Florida," was conducted in Fort Myers, Florida, by Florida Solar Energy Center for FPL with the cooperation of Habitat for Humanity of Lee County, Florida.
The six identical, side-by-side, newly constructed Habitat for Humanity homes were built using various roofing materials. The homes were operated identically to ensure study accuracy. For example, temperature controls on the air conditioning thermostats of all the houses were set at a constant 77o F.
And, all six homes were studied unoccupied and occupied. FPL plans to use the results as a basis for a recommendation to update the energy performance calculations of the state building code and to examine how to best promote the selection of white and light-colored roofs to help homeowners conserve energy and save money on cooling costs.
FPL Group, with annual revenues of more than $7 billion, is one of the nation's largest providers of electricity-related services. Its principal subsidiary, Florida Power & Light Company, serves 3.9 million customer accounts in Florida. FPL Energy, LLC, FPL Group's independent power production subsidiary, is a leader in generating electricity from clean and renewable fuels. More information is available at http://www.fpl.com/.
SOURCE: Florida Power & Light Company