Originally Posted by railroaderone
There is no insulation on mine just the house wrap.
This must be a new camper. The manufacturers ran out of batt insulation and started using the vapor barrier insulation.
If it were me, I would put up fiberglass batt insulation, cover that with the "housewrap" material and then cover this with cloroplast plastic sheeting using lots of sheet metal screws and fender washers. Seal as appropriate to finish the project.
The Flex Seal might not be a bad idea on the underbelly before you begin insulation. Just don't cover wires, pipes, etc. as previously mentioned in reference to spray foam.