Roof cleaning is the process to remove algae mold, mildew, lichen and moss from roofs.Roof cleaning can extend the duration of a roof's ability to function. Algae and other types of build-up often form on the north and west parts of roofs that are shaded or receive less sun, and can reduce a roof's life expectancy. The presence of soot, dirt, or biomass can affect how much sunlight is absorbed by a roof and thus the amount of heat a building absorbs. Cleaning may be accomplished with a bleach or vinegar solution, various cleaning products or commercial cleaning services. The addition of zinc strips near the roof's peak may reduce the regrowth of algae and moss. However, do not mix bleach and vinegar.