Chlorine works very well cleaning roofs. I apply with a shur flow pump on roofs I can walk. I mix it up around 30% with a higher percentage for really bad staining or lighter roofs. I mix it with some dawn for added cling. I just got my x jet and plan on cleaning a roof with it as soon as the weather gets up to 50 degrees or better.
my roof mix is 1:1 6% bleach. most roofs come clean first application. this past week i had a roof that was black, but the shigles were tan. i sat down on the top of the roof and wondered why it didnt come completly clean after two applications of 1:1 bleach. i was frustrated with it but i thought about the problem. after years of the fungus living and dying it had made a carbon build up that was so thick it covered the granules. i had to hit it 3 times to get it clean. you can loose like this because i figured the chem cost in on the bid. turns out i used 3 times more but it was the final lesson on the question of roof mixes.