Hot water doesn’t matter on that. This is my bread and butter. Already done over 200K sq ft of this this year.
Use your washer to clean the crap off the surface. Then direct application of chem (either pump up or 12v). Go with a mix of 5-6% SH, 2 cups degreaser (that has sodium hydroxide in it) and some surfactant (go heavy - yeah you will rinse a bit more, but it will help to stick to the wall and do its job). Example - 1/2 gal 10% SH, 2 cups degreaser, 3 oz surfactant and 1/2 gal water.
I find most of the time it takes multiple applications - chem, dwell, rinse. Chem, dwell, rinse. Longer dwell times with misting to keep chem from drying out.
You aint washing vinyl siding here - Just the front in that picture will take you 3-4 hours.
Good Luck!
