Colored roofing granules with increased solar heat reflectance, solar heat-reflective shingles, and process for producing same

What is this patent about?

’500 is related to the field of asphalt roofing shingles and the protective granules used to coat them. Specifically, it addresses the thermal challenges of dark-colored roofs, which typically absorb significant solar heat in the near-infrared spectrum. This absorption leads to elevated surface temperatures, increased cooling costs for buildings, and the contribution to urban heat-island effects. The invention seeks to provide roofing granules that maintain aesthetically pleasing, deep-tone colors while achieving high solar reflectance.

The underlying idea behind ’500 is the strategic decoupling of visible color from infrared absorption through specialized multi-layer coatings and advanced pigments. Rather than relying on traditional metal oxides that absorb heat, the invention utilizes infrared-reflective functional pigments—such as light-interference platelets or mirrorized silica—that reflect heat even when they appear dark to the eye. By layering these pigments over a highly reflective white base coat or incorporating them into a transparent outer shell, the granules can mimic the appearance of conventional shingles while rejecting a much higher percentage of solar radiation.

The claims of ’500 focus on several structural configurations for roofing granules that utilize a binder and at least one infrared-reflective component. These include granules where a single coating contains a colored, infrared-reflective pigment, as well as multi-layer systems where an inner coating provides a reflective white foundation (using titanium dioxide or zinc oxide) and an outer coating provides the visible color. The claims also encompass designs where a color-providing inner layer is shielded by an infrared-reflective functional pigment in the outer layer, specifically targeting shingles with low lightness values but high solar reflectance.

In practice, the invention works by applying these specialized coating compositions to mineral particles ranging from #8 to #70 mesh size. The binders can be inorganic silicates cured at high temperatures or organic polymers that allow for lower-temperature processing and improved moisture resistance. By using light-interference platelet pigments based on mica or alumina, the granules achieve a pearlescent effect that effectively scatters near-infrared light. This allows for the production of shingles with a lightness value (L*) of less than 60—appearing as deep browns, reds, or grays—that still exceed a solar reflectance threshold of 25%.

This approach differs from prior solutions that relied on simple metal oxide coatings or aluminum flakes, which often struggled to balance aesthetic variety with thermal performance. Traditional dark shingles typically reflect only 5-15% of solar heat; however, the multi-layer architecture described here allows the granule to reflect heat that has already penetrated the outer color layer by bouncing it off the white internal primer. This dual-action mechanism significantly reduces the thermal stress on the underlying asphalt substrate, extending the service life of the roofing material while maintaining the deep-tone colors preferred in residential architecture.