We used a product from Zep called "Morano". Suposed to have a chemical make up simalar to "gutter zap" (which is not available in Canada). We diluted it to what the instuctions said.Tested it on my own house,not amazing but OK. Tried it at a customers house,now I have to replace their eaves as it removed the paint off the underside. No damage to the fronts,or facia. Other than sorry about your luck,any "constuctive " comments are welcomed.