Oxygen Bleach
Oxygen bleach works by releasing oxygen when added to water to clean and bleach out stains. It is non-toxic and color-safe. Some popular brands of oxygen bleach are OxiClean and Oxi-Boost. You can buy these products at many home improvement stores, supermarkets or on the Internet.
To clean your roof, mix a solution of oxygen bleach and water into a pump-style garden sprayer. The ratio of bleach to water will vary depending on the concentration of oxygen bleach you are using. You will generally need four to six ounces of oxygen bleach per gallon of water.
Use a ladder to reach the roof and spray the cleaning solution on dark-stained areas of the roof first. Then, apply a coat of the oxygen bleach mixture to the entire roof surface. Go back to the stained area and apply a second coating of the oxygen bleach. Allow the cleaning solution to sit on the roof for about 20 minutes.
Use a garden hose with a spray nozzle to rinse the cleaner from the roof. Set the water pressure on the nozzle to the strongest setting and hold the hose about three feet from the roof to effectively remove the stains. Work from the top of the roof, spraying downstream when rinsing to avoid re-staining the cleaned parts of the roof.
Spray & Forget
Spray & Forget is a commercial cleaner that has no hazardous chemicals. It boasts an eco-friendly cleaning solution that will effectively clean a roof. You can buy Spray & Forget at Ace Hardware, True Value and a variety of other home improvement stores. It is also readily sold on the Internet. Spray & Forget is easy to use and requires no rinsing.
Begin by mixing one part of Spray & Forget concentrated cleaner with five parts warm water into a pump-style garden sprayer. Add the water to the sprayer first and then mix in the Spray & Forget. Spray the mixture over the entire surface of the roof. This product should be applied no less than 24 hours before an expected rain or snowfall. Leave the product on the roof without rinsing. Over the next several months, the dirt and stains will continuously lift from the roof.
Other Commercial Products
A variety of other eco-friendly commercial roof cleaners are also available, including Wash-Safe Roof Wash and Roof-A-Cide. Check the label of the product to be sure the ingredients contain no toxic or hazardous chemicals. Most eco-friendly roof cleaners will display information on their packaging regarding product safety for the environment.