Some while ago, I read on (I think) this forum that bare copper wire was a good solution to the prevention of moss growing on roofs.
Well it works quite well. Not a trace of moss on my garage roof. Its a slightly sloping corrugated roof and what used to happen was the moss would clog up the channels, then the rain would back up and overflow the joints.
I just ran some stripped from 2.5mm T&E (2x2.5 + 1x1.5), bared copper wire loosely laid across the roof from one side to the other, close to the high end - last year I think.
Since when, nil moss growth.