Increasing IR Reflectivity in TiO2 Pigments for Cool Coatings

 
Passive cooling of structures through enhanced reflection of solar radiation allows for reduced electricity consumption. While the most effective colour for this purpose is white, consumer preferences for the exterior of buildings often trend to darker colors. Using a combination of conventional or specialty color and white pigments can maximize infrared (IR) reflectance. High IR reflective white pigments are typically rutile TiO2 with a large particle size. We produced larger particle size TiO2 and tested these materials in paints for total solar reflectance (TSR). These pigments show increased IR reflectivity with some variability in reflectivity curve shapes. We compared our larger particle size TiO2, conventional TiO2, and commercial larger particle size TiO2. The TSR results showed that the overwhelming determinant of solar reflectivity is the brightness of the paint, (L*). None of the larger particle size pigments appreciably alter TSR beyond the brightness effect. These results indicate that pairing conventional TiO2 pigments at the highest L* allowable with specialty IR reflective color pigments may be the best way to maximize IR reflectivity for darker color paints.