Hi All, Master toxic substance avoider John Fischer here with KLCC's Living Less Unsustainably.
Every year, Oregonians spread tons of toxic heavy metals into the environment to solve a problem that may not even exist. Zinc based moss killers are poisonous to fish and other aquatic creatures. The over application of powdered moss killer often means most of the zinc is washed off the roof and into rivers and streams before it even works on the moss. If you use the product, follow the directions or use less to avoid excess run-off.
Zinc strips have a much slower release rate, can last for many years, and put much less zinc into the environment. You've probably noticed that moss doesn't grow below galvanized metal flashings. Sodium bicarbonate and sodium percarbonate are much less toxic alternatives used by eco-friendly moss removal companies. You can use them too. A soft bristle push broom, using top down motions, will take off most of the moss without any chemicals. You can find a couple of moss removal links - including the city of Eugene's - below.
But my experience has me wondering if moss is as bad as the companies that make products to remove it want you to believe.
The roof of my shop was replaced in 1962 following the Columbus Day storm. I moved here 20 years later, and have never seen the composition shingles on that 60-year-old roof because they are under a thick lovely layer of moss. And the 60-year-old roof doesn't leak. I know it's a small sample size, but it reminded me that we never worried about moss 50 years ago. Now moss removal is a big industry.
The easiest solution to moss worries is a metal roof. It will save you money over time, and is easily recyclable.
Whatever path you choose though, always be careful when working on your roof.
I'm John Fischer with living less toxically.
Links:
Northwest center for alternatives to pesticides.
