I used simple green on an aluminum sided home last year. The customer was concerned about her plants and flowers. We wet them down and covered them prior to washing to apease her. The simple green we used because it is very earth friendly. there is no msds per say, because there is no toxisity. the results, well, we had to hand scrub the entire home as we cleaned to remove all dirt and mold. Bottom line, simple green is a great general purpose cleaner, but doesn't quite cut it as a siding cleaner. Perhaps if I mixed some sodiumhydroxide in with it. This year, I decided to clean my way. The job took about half the time, and no hand scrubbing. I used a cleaner called Film Fighter. (oops, only one problem. one side of home was badly deteriorated and streaked as aluminum siding can. I will have to paint that side.)Bottom line, I don't think simple green is a good solution to the residential home power washer industry, there are many other cleaners that cost less, and are created specifically for washing homes.
My two cents worth of knowledge - That's all the cents I have.