I have cleaned roofs longer than anyone I know of? With a pressure washer from 1989 to about 1994.
I honestly thought I was inventing “No-Pressure” roof cleaning. However, in my attempts to build a system back in around 1994, I ran into a company cleaning some shingled apartment building roofs, with a fairly proper system [ except they were using a 1.something gpm Sure-Flo pump and 1/4" id hose. They had come from 40 miles away, so they just flat out taught me everything they knew and within a couple of weeks, I was the only one I know of, cleaning roofs without pressure in my area? { Charlotte and Southern Sarasota County Florida ]
Anyway, what they told me, still stands true:
Buying 10.5 to 12% SH - use 25-35% on shingles and 40-50% on tile. They used a lot of some kind of soap as a surfactant and I went through that stage myself. Now, I just use SH + H20 unless a roof is really badly blackened with algae [thick] then I add surfactant, but no more than necessary and occasionally, TSP for tile.
Remember - what the surfactant does for the roof cleaning, it does to the plants around the house too!
While giving credit, where credit is due, I learned many tips of this trade at Chris Tucker’s RCIA. Chris knows his stuff and is a good teacher as well.
https://www.youtube.com/watch?v=0h_OaQg2LiU
I meant to say— "I have cleaned roofs without using pressure longer than anyone I know of?"
When did Chris start and when did AC start? Both them have claimed to me that they invented it.
I don’t know? I never heard Chris say he invented it?
AC would lay claim to everything in this business though LOL
It’s his nature! 
