Ok,
The stuff I am talking about is a very dense fabric like product with reinforced foil on one side. Most Vendors sell it for $30 a roll. You put it foil side up on the roof and foil side down on the floor. Then put another layer foil side up on th floor.
Foil tape the whole thing good and then put carpet over the top.
I would hope that everyone is building a truck that is not like the DWI commercials with the water level half way up on the glass. In wet areas get the kind that hardware stores sell that won't soke water. Hope this helps
