|Title||Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials|
|Publication Type||Journal Article|
|Year of Publication||2007|
|Authors||Levinson, Ronnen M., Paul Berdahl, Hashem Akbari, William A. Miller, Ingo Joedicke, Joseph C. Reilly, Yoshi Suzuki, and Michelle Vondran|
|Journal||Solar Energy Materials and Solar Cells|
|Keywords||absorption, asphalt shingle, clay tile, coating, concrete tile, conversion coating, Heat Island, metal, Methods & Protocols, near infrared, pigment, reflective, residential, roofing, scattering, Solar, treatment, wood|
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.