Your roof is most likely to develop the appropriate environment for moss growth in the winter. Moss will grow on your roof shingles in shaded and damp areas. Mosses reproduce via airborne spores. If a roof is covered with moist organic matter or soil, and if minerals and fixed nitrogen are present in the dirt on the roof, moss can grow from the spores carried there. If the roof shingles are clean and free from dirt and debris, moss cannot take root.

For existing moss, cleaning with special formulations can help however, prevention is the best method. Keep your roof clear of debris, such as branches, leaves and pine needles and keep tree limbs cut back from over the roof to minimize shade. Trees produce sap and will naturally drop some of the sap onto a roof when in very close proximity to a home. Tree sap contains nutrients and sugars that are considered fine dining for moss. Sap from trees on a shaded roof area can accelerate micro-organism growth verses a roof not influenced by trees. Trees will also shade a roof from the sun, allowing moisture to be retained on a roof surface and, depending on the size and type of trees, may inhibit air flow across the roof. All of this combined with dropped tree leaves, branches and pine needles make a perfect environment for moss growth.

When i lived in Sitka AK (rain forest) we ran a bare copper wire along each side of the peak of the roof. It prevented any moss growth on the roof/shingles.

Both copper and zinc help. Some shingles come with it in the aggregate.

Posted By jonr on 12 Jul 2011 08:14 AM
Both copper and zinc help. Some shingles come with it in the aggregate.

Thanks for sharing the information as how to aggregate shingles.....

It is more economical to prevent moss than to let it grow and then remove it.

This is very good informative thread thanks for sharing this.

Greetings,

Yes, good info as I just put a new roof on. I'm also planning on spraying a clear acrylic paint with ceramic beads added to act as a first line RB and substantially reduce the shingle temp.

Prior to the 80s it was unusual to see moss on the roof. Now you see moss anywhere you go. If you do some investigating you'll find that the manufacturers down graded the quality of the base material, went from paper to FG, and added "stuff" to the asphalt to reduce costs.

Shingles used to last at least 30 years, now your lucky to get 15.

God bless capitalism.