Removing door panels to work on windows...

[deQuincey]

The vapor barrier is a cheap alternative to using a door card material that doesn't crumble with moisture. It's easy enough to cut a bit of thin plywood, seal both sides with poly, and you'll never have to scrw around with the staining, gummy stickum that's used to hold the vapor barrier again.

charlie, if it were my car i will use both, the sealed door card is good, but the vapor barrier is essential too, as the door card does not close all the gaps being only retained by clips situated 10cm or more one from the other
regards