CertainTeed's proprietary CoolStar granules utilize naturally occurring rock that has been stable for millions of years. The base mineral granules are 100% opaque to UV radiation and, therefore, will protect the asphalt coating on the roofing membrane, thus maintaining granule coverage. This type of roofing granule has been used for over a century with proven success on traditional residential shingles and low-slope membranes.
CertainTeed's CoolStar granules are surfaced with a highly reflective ceramic coating to achieve high solar reflectance. This ceramic coating has the same chemistry as that used for traditional roofing granules that have been used successfully for over a century, demonstrating excellent durability.