Abstract: An algae resistant roofing material includes a portion that is normally exposed when the roofing material is installed on a roof. The exposed portion of the roofing material includes a substrate coated with a coating. The coating includes an upper surface that is positioned above the substrate when the roofing material is installed on the roof. The roofing material also includes an application of metallic particles applied to the upper surface of the coating. The metallic particles include at least one ingredient that inhibits the growth of algae. The metallic particles have a large surface area characterized by at least one of the following: (a) a mean Particle Irregularity Factor of at least 1.5; (b) a mean apparent density of not greater than 3.5 g/cm3; and (c) a mean specific surface area of at least 0.02 m2/g.

Abstract: An algae resistant asphalt-based roofing material including a portion that is normally exposed when the roofing material is installed on a roof. The roofing material comprises a substrate coated with an asphalt coating. The asphalt coating includes an upper surface that is positioned above the substrate when the roofing material is installed on the roof. A surface layer of granules adheres to the asphalt coating. An application of metallic particles is applied to the upper surface of the asphalt coating. The metallic particles contain a component that inhibits the growth of algae. The metallic particles are applied such that greater than fifty percent of the metallic particles are covered by the asphalt coating, or by the granules, or by both the asphalt coating and the granules. The covering of the metallic particles provides sustained algae resistance at a low cost and prevents premature loss of the metallic particles.