On Mar 7, 3:37 pm, "S. Barker" wrote:
what you need is a strip of galvanized metal all along the ridge or just
under the ridge shingles. The galv prevents the algae from growing. It
won't remove what's already there, however.

s

The strips (zinc) do little or nothing here in Oregon. I have the
Algae resistant shingles, and haven't seen a sign of algae in two
winters now. Pretty good for the Pacific NW and also having a couple
trees near the roof. Not sure how they'll do in the long run, but so
far so good.
As for the original poster, the contractor is full of BS, do nothing
until you see the first signs of moss, then get it treated. BTW it's
not a coating, the shingles are embedded with copper.