Even algae resistant shingles need to be cleaned
The first line of defense is to purchase algae resistant (AR) shingles.
The manufacturers produce a copper roofing granule that is purchased by many asphalt manufacturers.
Based on twenty-five years of research on growth-inhibiting effects, findings are that roofing granules that evenly distributed, at a minimum ten percent application, give uniform protection to all roofing granules.
It should be noted that not all companies purchasing the cooper granule adopt the ten percent application in their production. Only companies who subscribe to the ten percent system are permitted to advertise the Algae Block trade mark. Those using the product in lesser quantities use other phrases like, algae resistant, or use their own trade names.
Check the manufacturer's warranty for limitations on the algae resistance effectiveness. You will find a range out to fifteen years duration.
The trouble with Algae Resistant shingles, is that the manufacturer remedy to an AR shingle that has algae, is to CLEAN the shingle with Bleach!
Wasn't the idea to prevent the algae? or replace the shingles if algae appeared?
Yes, but read the warranty..
Even the manufacturers understand that this is a hardy algae..
ARMA (Asphalt Roofing Manufactures Association) technical bulletin Catalogue No.217-RR-89, on algae
discoloration of roofs, states, algae is difficult to remove from roofing surfaces, but may be lightened by
applying a solution of chlorine bleach (also known as Sodium Hypochlorite or SH) , trisodium phosphate, and water.
However, these ingredients may
vary between manufacturers and the amount of discoloration.
Adding, "the effectiveness of such cleaning
techniques is only temporary, and discoloration will likely recur."
Further, cautions from ARMA state, "be sure to apply it carefully to avoid damage to other parts of the building and its surrounding landscape."
A concern for home owners using bleach (an organic complex containing chlorine) is that it can cause
premature chemical degradation of asphalt roofing shingles. In short, causing a shingle to become brittle.
Chlorine-based cleaning solutions are also harmful to plants!
Don't lighten the Algae! REMOVE IT!!
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