How to address mold/moss on newer roof?
Actually, there's a great suggestion in one of my favorite general-knowledge renovation books about how to prevent moss growth. This is a much more permanent way to solve the problem, IMHO.

Tack up a line of copper wire (not zinc) just after the first line of shingles (close to the top). Copper is bad for plant life, and so the slight copper solution from rain washing over it will kill off moss. Obviously the wire needs to be bare, so if you're using scrap, be sure to give it a good wipe with 80 grit sandpaper before putting it up. Sorry I don't have the book in front of me, so I can't name the page number or quote it precisely.

Of course, take care tacking up the wire to observe common-sense principles about putting holes in your roof. Depending where &amp; how you attach the wire, you might want to cover the nails, staples, etc with roofing cement.

Also, while this solution makes sense to me, I haven't used it. I'm basing my suggestion on the stellar reputation of this book.