Northam Saint
Forum GOD!
Not sure about windows but we saw them flying in our shed once, sure enough there was the start of a nest. Quick google said that a paper bag attached to the roof was the idea. Working on the basis that the wasp see it and think “crap someone else’s nest !”, and they fly away. Not having a paper bag I made one, cone shaped, from grease proof paper. That was a few years ago now and no wasps !Are fly nets an option?