Originally Posted by Nelmes
I do not want to separate the door.
Well, that leaves adding something to the interior and doing something with the window.
Is the interior of the door fiberglass WITHOUT any upholstery, rat fur, ensolite, etc? If there is, I'd remove it and add extra reflectix under it. If there isn't, maybe you could make something out of reflectix and put it in a nice cover and either snap it to the door or velcro?
You can create an inside panel out of plexiglass and install that to the inside of the door window to create a faux dual-pane window.
Other have any ideas?