Abstract Algae-resistant roofing granules are formed by extruding a mixture of mineral particles and a binder to form porous granule bodies, and algaecide is distributed in the pores. Release of the algaecide is controlled by the structure of the granules.
Application number: 10/600,809 Publication number: US 2004/0258835 A1 Filing date: Jun 20, 2003 Inventors: Keith C. Hong, Husnu M. Kalkanoglu, Ming L. Shiao, Anne B. Hardy, James A. Salvatore, Andrew G. Johnson
Even with the 3M product they only guarantee it for up to 20 years max and that may be a 30-35 year shingle. Normal range is 5 to 15 years on the no algae warranty.
I think these are the AR shingles. If so, I cleaned about 10 roofs with these shingles last season. They're a joke really. The AR stands for algae RESISTANT,...not proof. In my area it takes a typical new roof 3-5 years to start seeing the discoloration from the disease.
In that same 3-5 years with the AR shingles, the copper that is in the roof is washing away every time it rains, thus after 3-5 years the copper must be all gone,...and was in a sense working when it didn't matter anyhow. Hope I explained that properly so everyone understands.