I took note this past week of seeing moss on a lot of roofs in Kelowna. We have gotten an uncharacteristic amount of rain this year and this fall season. The moisture, cool temperatures and trees that have an acidic factor are the winning combination.
Working with home inspectors in this industry I have been told that a zinc wash will eliminate the moss. There are a number of products that can be used. Its just important to get rid of it. Leaving it to build will act like a jack under the car and slowly lift the shingle. This will allow other debris to trap underneath or if a good wind should blow could potentially rip of some shingles. One of the dont's is to NOT use a high pressure hose to wash it off. Check out your roof while you are putting up those Christmas lights, visit the hardware store or call a roof repair business. Just don't let it go unfixed.