“Mildew resistant shingles are a sure thing to prevent roof algae.” This is a myth. Many homeowners that paid a premium for “mildew resistant” shingles discover five to seven years latter that they are not so resistant to roof algae.
A case in point, we cleaned an algae infected roof that had “mildew resistant” shingles. The homeowner notified the shingle manufacturer of the problem. The manufacturer stated they would reimburse the homeowner up to a certain amount. The homeowner paid us for the job, sent the invoice to the manufacturer and they sent a check back to the homeowner. Unfortunately most similar situations don’t have such happy endings because there is a catch. The homeowner must have a copy of the shingle warranty or proof of purchase. Most homeowners either don’t get a copy or the contractor that built the house or last replaced the roof doesn’t give that to the homeowner. Then years later when the black streaks begin to appear, a warranty or proof of purchase is no where to be found and the homeowner has to flip the bill.