Mine are not double pane.
Can't say as I've ever seen frameless windows as double pane. It would be easy to do on the windows which do not open.
However, many frameless windows have a scissors type deal to extend out the lower section of the window when you want it open for ventalation. Not sure how double pane would work there.
I have to go out to the rig today, I'll take some pictures of details and post them in a few hours.
I will say they have a more 'modern' look, but I wonder about the longevity of the seals, and the 'air tightness' of them.
I also think that they will not provide as much free air flow as traditional slide type windows. Could be wrong about that - ask me in six months.