We live among the redwoods here in California and don't get a heck of lot of sunshine on the roof. Certain areas have developed a green plant growth, a sort of moss or algea on the shingles. I don't believe that this hurts anything, but visually it looks messy. Is there any way to combat this on the existing roof? Also, we need to replace our roof in the next 2-3 years - are there any shingles that would work better in a moist enviornment? How about the new rubber shingles? Any hints or tips would be appreciated.