Algae, mold, moss, mildew, and lichen growth are common on roofs and often leaves signature black streaks and spots on your shingles. These organisms thrive in humidity and hot temperatures as well as shaded areas and spreads throughout your roof, having a destructive effect on your roof. Once your roof is affected, it begins to lose its ability to reflect UV rays and eventually rots the shingles. Untreated growth on your roof shortens its lifespan. Soft washing is the only way to effectively remove these organisms without damaging the shingles and voiding any warranty. The Asphalt Roofing Manufacturers Association recommends low-pressure bleach or detergent assisted washing as the preferred method for cleaning asphalt roofs in order to prevent damage to the shingles.