I was reading a local website today and found someone using sodium metasilicate to clean roofs.
All of the RCIA certified masters including the ARMA and shingle manufacturers do not recommend using this chemical.
It is too alkaline with a ph of 12.5-13, which is too corrosive and damaging to asphalt shingles. It will soften and melt the tar/asphalt, decreasing the longevity of the roof.
For those of you using TSP substitute cleaners, check the ingredients to see if sodium metasilicate is in it. If so, STOP using it!
It's not as bad as sodium hydroxide (ph 14), but it's still not good.
The best roof chemical concoction using sodium hypochlorite should have a ph of around 11-11.5, using tri-sodium phosphate. Without TSP, the ph will be lower, and will still work well using isopropol alcohol (Apple Cider).