Ian
I am with you on this one, if there is no room for expansion due to the glass being too tightly fitted, when it expands, through heat (hot water) then it will put extra pressure on the glass and with nowhere to go it will crack.
Unfortunately when you clean windows you cannot know the history of every single window and the quality of the fitting. One window cracking on one property would be too many for me. I am building a second residential window cleaning business and it is coming through on recommendation alone.
I wouldn't even contemplate saying it wasn't my system, if I broke or cracked a piece of glass, I would just replace it!
Apart from a short period last year, after I sold the big round I have been cleaning windows or large commercial glass canopies/windows for over 9 years, I have never needed a hot system, I may need to scrub a little harder on baked on bits but I get few complaints, if any and have a lot of new cleans, window cleaning and conservatory roofs/full upvc cleans.
Is it necessary to improve my business, will it make it anymore money, do I need it, I don't think so.
Are there questions arising from user capability and knowledge on its potential problems, can thermal shock happen whilst using it, probably
I think that you have put a valid argument forward and my opinion is that it is an over rated gadget, over priced and not necessary for 99.9% of window cleaning businesses.
Rob