"LinkTech"
Glass only starts acting as a lossy medium when over 8 Ghz.

Depends how far over 8 GHz...

Most common glass is reasonably low loss in the 400 to 700 THz
(terahertz, 10^12) 'band'.

;-)

More seriously, 'Low-E' (low emissivity) glass has a thin metal
coating that might make the glass less transparent at RF. I'm not
sure about the magnitude of the effect at RF. It certainly works at
IR.