If its a wooden window frame, I just turn the flow right down, really just to brush out the cobwebs etc, then turn up the flow a little for the glass.
I did a 1st clean this afternoon, the windows had masking tape residue on the glass from the decorators, the hot water just melted away the glue it was great, whacked it right up to 70 deg, massive double glazed,.sash windows high flow..great stuff.
This morning I did a property with single glazed lead windows, (real lead, not the stick on lead) and used it cold, on a very low flowrate.
So you need to adapt your methods to suit the job.