There should be a “questions” section, which is basically what I’m posting here.
I’d like to know if glass meshes should be single faced or have thickness. Other realtime renderers require windows’ glass mesh to be single-faced and then you can apply the glass material in the inversed normal side of the glass as well.
In the real world, glass has both single and double layers. Double glass can simulate a more realistic reflection effect. But the key is that the glass must have a certain thickness.