Do zinc strips prevent black algae AFTER algae removed?
Grumpy, the roofing god, apple roof cleaning, Barry M, johnk, and All,
Noticed your suggestion of zinc strips AFTER black algae removed, Grumpy--have you/anyone in northern climate had positive experience with strips preventing algae re-growth AFTER algae removed?
...other posts say that zinc strips don't work/only work for 2-4 feet of roof, but these posts don't make clear whether or not the black algae was removed first.
My situation: northern climate--in E.Massachusetts, just south of NH border--black algae on N-facing 43-degree pitch on a Cape-style house...black algae streaks formed on roof cross-section directly above the "slanted" interior 2nd-floor walls, just started past 2 years after very thorough insulation done (by contractor)...i'm guessing because space between slanted interior walls and joists above the slanted walls was dense-packed with cellulose (above fiberglass batting, kraft-facing next to ceiling), without propavent, so North-side ventilation from knee-wall area (Hicks vents) blocked from flowing over the slanted walls up to the ridge vent (propavent was installed on the S side).
The insulation job increased comfort and decreased heating costs
significantly, so some algae (and a couple of pencil-erase-size green mosses just getting started) not a huge price to pay I guess, but doesn't look too hot and am concerned about possible long-term damage to roof (2 layers asphalt, 40-yr architectural 10 yrs ago over 20-yr flat, in very good condition)...so plan to wash off the algae and moss, just wondering whether or not to install zinc strips after (and if you've had good luck with zinc AFTER cleaning, would like to know which brand--Shingle Shield 3-ft pieces, Z-Stop continuous, or other?)
Many thanks, any experience-based comments appreciated!
Just install it if you can. It helps. I install it when I put the roof on. Mine is 6 years old and no algae. Have retro installed it by removing the cap and putting it under the cap. Roof stayed clean.