So I have seen a few houses in my area that have light colored shingles, and in front of the plumbing vent its faded? just wondering what will cause that.
Steven, what I see around here is a light color below the vent boot and/or stack, its caused by the zinc in the galvanized metal washing down the roof which prevents and/or kills the alge and mold. Not sure if thats what you are referring too but its especially noticable on dark colored roofs and the north facing slope.
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They should make an all galvanized ridge cap or ridge strip
Most buy AR shingles now, which takes care of the problem. They do make zinc strips that you can install on the ridge for non-AR shingles.