A lot of people do not know what the black streaks on asphalt shingle roofs are. Well, they are a hardy type of airborne algae that has landed on the roof for particular reason and have begun to feed on the shingles. This algae will find nutrients in the limestone that is used in roofing shingles. Once it lands on your roof it will only get worse. It will never get better or go away unless treated. The roof algae will lessen the longevity of your shingles because it will not allow the shingles to reflect heat like they need to. It can also raise your home heating and cooling costs. The algae will usually first be noticeable on the north facing side of the roof. This is the side with the prevailing amount of shade and moisture. It is the same reason moss will grow on the north side of a tree. The good news is this roof algae can be killed, cleaned, and removed from your roof. Roof cleaning is a service that is available in most areas. The key to successful roof cleaning is to use what the major shingle manufacturers suggest using, which is a mix of bleach and trisodium phosphate (TSP). They recommend it be applied using low pressure so no harm is done to the shingle room. They warn against the use of a pressure washer. Never allow anyone to pressure wash your roof using excessive pressure. This will wash away the shingle granules which are there to protect the shingles. Low pressure and the right chemicals is the key. Like any surface that is exposed to the elements, roofs need cleaned and maintained occasionally so they last as expected. Shingle companies will not warranty shingles that are suffering from roof algae. They will tell you to have them cleaned using low pressure. Find a reputable roof cleaning company in your area.
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