October 2006

Cool Roofs

Lead – Danny Parker (FSEC)

Lessons Learned:

  • Reflectivity is fundamental.
  • Spectrally selective products show excellent promise
  • Long-term reflectance of metal products is generally superior.
Sealed attic constructions should emphasize reflectance for best performance.

Improving attic thermal performance is fundamental to controlling residential cooling loads in hot climates.  Research shows that the influence of attics on space cooling is not only due to the change in ceiling heat flux, but often due to the conditions within the attic, and their influence on duct system heat gain and building air infiltration.

To comparatively evaluate performance, BAIHP uses its Flexible Roof Facility (FRF) to evaluate five roofing systems at a time against a control roof with black shingles and vented attic (see picture). The testing evaluates how roofing systems impact summer residential cooling energy use and peak demand.

Photo of the flexible roof testing facility at FSEC>
FSEC's Flexible Roof Facility (FRF) allows side-by-side testing of multiple roofing systems.
Photo: Nick Waters

Research over the last five years has achieved industry-changing results:

  • Established the large influence of roof reflectivity on attic thermal performance regardless of roofing type (shingles, tile, metal).
  • Long-term performance of painted and unfinished metal roofing systems.
  • Demonstrated the potential of infrared reflective spectrally selective pigments leading to innovation of “cool colors” by U.S. roofing industry (BASF, Shepard Paints).
  • Provided research underscoring the need for more reflective shingles leading to industry innovation (Elk Corporation, Cool Shingles)
  • Comparative performance of different attic ventilation levels on thermal performance and attic humidity
  • Performance of sealed attic construction with roof deck insulation, demonstrating the powerful combination of this method when combined with more reflective roofing.


Pertinent research articles can be viewed at:
http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1514-05.pdf and at http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1220-00-es/index.htm


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