Visit the Energy Systems Laboratory Homepage.
Comparative Summer Thermal Performance of Finished and Unfinished Metal Roofing Products with Composition Shingles
Loading...
Date
2004
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Energy Systems Laboratory (http://esl.tamu.edu)
Texas A&M University (http://www.tamu.edu)
Texas A&M University (http://www.tamu.edu)
Abstract
This paper presents an overview of results from
experimental research conducted at FSEC's Flexible
Roofing Facility in the summer of 2002. The Flexible
Roof Facility (FRF) is a test facility in Cocoa, Florida
designed to evaluate a combination of five roofing
systems against a control roof using dark shingles.
The intent of the testing is to evaluate how roofing
systems impact residential cooling energy use.
Recent testing emphasizes evaluation of how
increasingly popular metal roofing systems, both
finished and unfinished, might compare with other
more traditional roofing types.
All of the test cells had R-19 insulation installed
on the attic floor except in the double roof
configuration which had R-19 of open cell foam
blown onto the underside of the roof decking. The
test results were used to determine relative thermal
performance of various roofing systems under typical
Florida summer conditions. Measured impacts
included changes to ceiling heat flux and attic air
temperature which influences loads from unintended
attic air leakage and duct heat gain. We also develop
an analysis method to estimate total cooling energy
benefits of different roofing systems considering the
various impacts.
The results show that all the options perform
better than dark composition shingles. White metal
performs best with an estimated cooling energy
reduction of about 15%, but the spectrally selective
metal shingles (12%) and unfinished Galvalume
roofs (11%) do surprisingly well. Galvanized roofing
did less well than Galvalume (7% reduction) and
worse performance in the second year of exposure
was observed due to corrosion of the zinc surface.
The sealed attic with a double roof produced an
estimated cooling energy reduction of only 2% --
largely due to increases in ceiling flux.