Executive Summary: Comparative Evaluation Of The Impact Of Roofing Systems On Residential Cooling Energy Demand In Florida

Roof and attic thermal performance exert a powerful influence on cooling energy use in Florida homes. Unshaded residential roofs are heated by solar radiation causing high afternoon attic air temperatures. The large influence on cooling is due to increased ceiling heat transfer as well as heat gains to the duct systems which are typically located in the attic space (Figure E-1). The Florida Power and Light Company and the Florida Solar Energy Center instrumented six side-by-side Habitat homes 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: (RGS) Standard dark shingles (control home) (RWB) White Barrel S-tile roof (RWS) Light colored shingles (RWF) White flat tile roof (RSL) Standard dark shingles with sealed (RTB) Terra cotta S-tile roof attic and R-19 roof deck insulation (RWM) White metal roof All seven houses were completed by June 26th, 2000 with extensive testing to assure the buildings were similar. Each home was monitored simultaneously from July 8th - 31st in an unoccupied state. Building thermal conditions and air conditioning power were obtained on a 15-minute basis. Each of the examined alternative constructions exhibited superior performance to dark shingles. Figure E-2 plots the maximum daily air temperature to the maximum recorded at mid-attic in each construction. Figure E-3 shows the average daily attic air temperature profile