I applied some reflective film to the inside of some of my windows today and it seems to have had some effect, though the window is pretty hot to the touch now

I applied some reflective film to the inside of some of my windows today and it seems to have had some effect, though the window is pretty hot to the touch now and apparently this kind of film can cause windows to crack through thermal stress. It makes sense for any coating to be on the outside of your window but I wonder how much better hanging a reflective space blanket outside would be than this yoghurt layer or similar.