We describe methods for creating solar-reflective nonwhite surfaces and their application to a wide variety of residential roofing materials, including metal, clay tile, concrete tile, wood, and asphalt shingle. Reflectance in the near-infrared (NIR) spectrum (0.7–2.5 μm) is maximized by coloring a topcoat with pigments that weakly absorb and (optionally) strongly backscatter NIR radiation, and by adding an NIR-reflective basecoat (e.g., one colored with titanium dioxide rutile white) if both the topcoat and the substrate weakly reflect NIR radiation. Coated steel and glazed clay-tile roofing products achieved NIR reflectances of up to 0.50 and 0.75, respectively, using only cool topcoats. Gray-cement concrete tiles achieved NIR reflectances as high as 0.60 with coatings colored by NIR-scattering pigments. Such tiles could attain NIR reflectances of up to 0.85 by overlaying a white basecoat with a topcoat colored by NIR-transparent organic pigments. Granule-surfaced asphalt shingles achieved NIR reflectances as high as 0.45 when the granules were covered with a white basecoat and a cool color topcoat.

Miller, William
Joedicke, Ingo
Reilly, Joseph
Suzuki, Yoshi
Vondran, Michelle

Ronnen Levinson, Paul Berdahl, Hashem Akbari, William Miller, Ingo Joedicke, Joseph Reilly, Yoshi Suzuki, Michelle Vondran, Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials, Solar Energy Materials and Solar Cells, Volume 91, Issue 4, 2007, Pages 304-314, ISSN 0927-0248, https://doi.org/10.1016/j.solmat.2006.06.062.