What are algae resistant shingles?

• A. Shingles that require algae to form
• B. Shingles coated with copper granules on the weather side to prevent algae discoloration
• C. Shingles designed to encourage algae growth
• D. Shingles resistant to algae growth by paint color

Answer: (B)

Algae-resistant shingles achieve their effect through copper-containing granules embedded in the surface that faces the weather. When rain or moisture runs over these granules, copper ions are released and inhibit algae from growing on the shingle surface, which prevents the common discoloration seen in humid or shaded roofs. The weather side is targeted because that's where algae is most likely to take hold. This method stops the staining without relying on the color of the shingle, and it’s not about promoting or encouraging algae. Simply painting or choosing a color doesn’t reliably stop algae growth, and the goal is to prevent the discoloration caused by algae, not to foster it.