One of the things I notice from the number of houses I visit, plus the house I own is the accumulation of moss on the roofs in our area. This happens most often on the north side of a house, or if there is a tree that is shading a portion of the roof. The moss is a slow growing organism that will over time cause enough damage to considerable shorten the life of the roof.
I recommend the following:
- Inspecting the roof annually
- Remove the accumulated moss
- Copper and Zinc can inhibit future moss growth
Now since I am not a contractor (roofing, or otherwise) here are a couple of links to some articles about moss removal.
This Old House (video about installing Zinc Strips. I like the idea, but would prefer to use copper if accessible and affordable. Later in the video, they recommend using a bleach solution to kill existing moss, most sites I saw recommended against using bleach)
Or Ace Hardware shows online that they sell a moss removal spray for $20 and that they have zinc strips for about $20 for 30 feet (although they show they are sold out at this time).
ZincShield online shows that they sell a 50 foot roll for $36.50.
I could not find affordable copper strips.