Fly-free apartment - windows open in the shade
Flies are attracted to the warm sunlit windows. So - windows too! If the sun has "moved on", you can open the now lying in the shadow window again.
If I was not at home in the summer during the day, the only open window for me was my north-facing bedroom window, because that is always in the shade.
I found the tip in an old household book, tried this summer - and had a completely fly-free apartment.
