Curious: I know you can use rockwool on the outside of your house for exterior insulation and reducing thermal bridging, but wasn't sure how it would work installed in a vehicle door. Rockwool is moisture resistant, but haven't researched how much so. I can see some huge benefits of a proper installation: greatly reduced road noise, improved acoustics within the door panel, obviously be thermal insulation, etc. One would have to insure it doesn't interfere with the window of course.
There are several types of this insulation, ranging from loose and lofty to dense and stiff. Safe N' Sound is a common one I see a lot. Would be rather worthless to try and attach to the skin of a door, but some of the Roxul 60 or 80 boards might work. Unsure of how to adhere it best to the skin of a door, but if you could, it would work really well I'd bet.
Anybody tried this before?