I did quite a large house last Friday, its the type with modern uPVC georgian windows' it also has vents above the top horizontal bar.
I went back today to do a gutter clean there.
There were a few, and only a few panes with either some random spotting or the top inch of glass had small dried patches on it. On closer inspection it was apparent that the smudged patches were where the water had ran down from off the vents and dripped onto the glass; the top bar also had this on it, it was quite apparent how it had occured.
Lesson? Avoid them vents and do the top bar next time and from then onwards.
Also yesterday I did a place with old sash windows on it on one side of the property, once Id finished I went back and got the ladder off to have a good look. I was disappointed with them and traded them. They had runs, which could happen on any window but also it looked like where the water had run off the top sash and across the underside of the bottom bar, picking up dirt as it went and depositing this on the bottom pane in large blotches. Solution? Do them trad or maybe on a real low pump setting when I first turn up, then go back and rinse again JUST the glass before I leave after doing the rest of the house.
How does that sound guys?
Matt