Cool Roofs for Hot Climates

Florida Solar Energy Center researchers compared the air-conditioning power use of seven identically built houses with different roof coverings. Reflective roofing dramatically reduced total power use (bottom chart) and had an even greater effect on peak A/C power demand (middle chart). Insulating the roof deck and sealing the attic, without using a reflective roof, cut total energy use somewhat but did not reduce peak cooling loads noticeably.

Kynar roof coatings using spectrally selective pigments from Ferro Corporation allow Classic Roofs to produce aluminum and steel shingles in several dark colors that meet Energy Star minimums with solar reflectances better than white asphalt shingles.

Tests indicate that the colors will sharply reduce solar heat gain through the roof.

Unfinished galvanized steel roofs may look shiny when new, but they age quickly to become very nonreflective. The infrared thermal scan shows the drop ceiling at a radiant temperature of almost 90°F under the metal roof of a strip mall building, despite insulation below the roofing.

When FSEC researchers applied a reflective coating, the building's air-conditioning power use dropped 16%, and tenants reported improved comfort. One tenant even called to thank the landlord for fixing the air conditioner. (He hadn’t.)

Radiant barrier foil under the rafters stops heat from radiating into the attic, because the foil will not emit heat radiation even when it's hot.

Rafters after applicaiton of radiant barrier foil.

Lo/Mit lowemissivity silicone coating spray-applied to the roof underside is a cost-effective alternative method.

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