Change the Environment

• Do not let trees shade roofs.blooming garden trees over a roof top image by Alexei Novikov from Fotolia.com
  
  One of the best ways to control mildew and moss is remove its favorable environment. Often moisture on roofs result from excessive shade from nearby trees. Prune tree limbs away from the roof and thin tree canopies to allow sunlight to reach the infested areas. Keep tree leaves and branches off of roofs as well.
  
  

Clean the Roof

• Use a stiff push broom to remove mildew and moss from roofs.garden tools. image by mdb from Fotolia.com
  
  Once the environment has been made unsuitable for growth of mildew and moss, the existing infestation needs to be removed. Use a pressure washer to remove mildew and moss as long as the pressure is maintained at a level that does not damage the shingles. Or, use a stiff push broom, wire brush or flat-edged shovel to remove the mildew and moss.
  
  

Zinc Strips

• Zinc strips installed along roof peaks controls mildew and moss.building roof peak image by Jim Mills from Fotolia.com
  
  Zinc or galvanized metal strips provide a long-term solution to mildew and moss control. Install these strips on each side of the ridge caps along roof peaks. Control will be effective up to 15 feet below the installations. The disadvantage of this control method is that if zinc washes off the roof, it could injury plants.
  
  

Bleaches for Mildew

• Chlorine bleaches offer good chemical control of mildew.cleaning mailbox 2. image by mdb from Fotolia.com
  
  Chlorine bleach is one of the best control agents for mildew and stains. For roofs, a mixture of bleach and trisodium phosphate (TSP) is needed. These compounds will injure susceptible plants and is not recommended for asphalt shingles because of deterioration. Spray plants with water prior to and after treating the roof with bleaach and TSP to avoid plant injury.
  
  

Fatty Acids for Mildew Control

• Potassium salts of fatty acids provide low-risk, long-lasting mildew and moss control.antique paper - colour series image by pdtnc from Fotolia.com
  
  Potassium salts from fatty acids also provides good control of mildew and moss. There are several products on the market that are formed from naturally occurring, biodegradable fatty acids. These products are non-staining on most surfaces and will not harm plants. They are normally sold as ready-to-use products and are applied by simply attaching a water hose to the container.