Certified Algae-Resistant Roofs: Granules, Coatings, and Care

Roofs age on two clocks. One is obvious, the cycle of sun, wind, and rain that every homeowner expects. The other runs quietly in the background, fed by humidity, shade, and airborne spores. That second clock is algae. In humid regions and along coasts, I have watched perfectly good shingles turn blotchy in three to five years, with dark streaks sliding from ridge to eave. Aesthetics aside, alg