I also have glass panes at the top of my door and it does not seem to matter. But you can test this just by holding the unit above the open door panes (don’t obscure the sensors with your hands) and watching the status on say your phone with the unit’s web page and look at the distance measurement and see if it makes sense and is stable. It does not need to be connected to the door opener yet for this to work. You do need to power it of course. I used a portable usb power pack.