Eric here in Santa Cruz. Im a general contractor and have a roof maintenance company. I have now been reading for months Preparing a business dedicated to roof cleaning. Theres alot to doing it right. This site has been invaluable.
The key for having dirty roofs in our area is the haze we get on the central coast its pretty much there all through the summer, burns off around 12:00. Inland its much less of a problem. Best price I can find on SH is $2.60 a gallon. I'm very excited about roof cleaning here. By the way, great posts Jeff.