Chemicals that kill roof moss and lichen often contain copper, zinc and iron sulfate that may wash into waterways. Use alternatives to chemical treatment to help protect our water resources. For example, keep your roof free of leaves and debris that hold moisture and promote damage and fungal growth. Consider non-organic roofing materials that resist moss growth.
Roof treatment: Have you thought about where the moss, chemicals and debris go? In urban Washington County, rain drains carry water to the nearest wetland or creek. If treatment is needed, use less toxic products in minimal concentrations as recommended on the product label. Treat roofs only in dry weather to allow the treatment to soak into the roof. When applying liquid treatments, direct the downspout to soil. After treatment, monitor the runoff. Reconnect downspouts after at least three rainfalls, or when there is no visible chemical residue or sheen. If you hire a roof treatment professional, ask what they use and how they manage runoff.
