Comparative Summer Thermal Performance of Finished and Unfinished Metal Roofing Products with Composition Shingles

摘要

This paper presents an overview of results fromexperimental research conducted at FSEC's FlexibleRoofing Facility in the summer of 2002. The FlexibleRoof Facility (FRF) is a test facility in Cocoa, Floridadesigned to evaluate a combination of five roofingsystems against a control roof using dark shingles.The intent of the testing is to evaluate how roofingsystems impact residential cooling energy use.Recent testing emphasizes evaluation of howincreasingly popular metal roofing systems, bothfinished and unfinished, might compare with othermore traditional roofing types.All of the test cells had R-19 insulation installedon the attic floor except in the double roofconfiguration which had R-19 of open cell foamblown onto the underside of the roof decking. Thetest results were used to determine relative thermalperformance of various roofing systems under typicalFlorida summer conditions. Measured impactsincluded changes to ceiling heat flux and attic airtemperature which influences loads from unintendedattic air leakage and duct heat gain. We also developan analysis method to estimate total cooling energybenefits of different roofing systems considering thevarious impacts.The results show that all the options performbetter than dark composition shingles. White metalperforms best with an estimated cooling energyreduction of about 15%, but the spectrally selectivemetal shingles (12%) and unfinished Galvalumeroofs (11%) do surprisingly well. Galvanized roofingdid less well than Galvalume (7% reduction) andworse performance in the second year of exposurewas observed due to corrosion of the zinc surface.The sealed attic with a double roof produced anestimated cooling energy reduction of only 2% --largely due to increases in ceiling flux.