Q: I have a northern exposure to the front of my house. It does not get direct sun. … I have black streaks and a slight green color (moss?). I recall you talking about running a strip of copper under ...

A green, moss-covered roof may make you think you’ve wandered into a fairy tale, complete with a quaint little woodcutter’s cottage. But, in the real world, moss is much less a fantasy than it is a ...