double pane windows for Winter condensation and insulation

[brycesteiner]

I noticed the other night in the RV there was condensation on the windows of the RV. I didn't think that would happen unless we were living in it with the heat on but I guess it does (am remodeling though) with being real cold/snowy and rainy. The issue seems to be the windows are thin and only single pane.
Anyhow, I was thinking of cutting out some clear poly/acrylic/plexiglass and putting it over the aluminum window frames to act as a double pane and an air gap. When it's not winter, I would just remove them since we like open windows.
I remember back many years ago my dad would put plastic cloth over the windows at home to help with keeping the house warmer and in the spring would remove it.
I've asked a couple people about adding the hard plastic and they thought it would work too. I would use a double sided tape and maybe sheet metal screws to attach to the frames. Then I would number them to make sure that each year they would go in the same place.
Anybody done this? Any caveats that might be an all out reason not to consider installing these?