See my youtube... Airgapped reflectix closest to van metal, then spray foamed foamular, cavities filled in with polyester fiber, floor has radiant barrier with air gap too, I made a video on it
1" pink XPS lined with carpet, plywood and spray-foam insulation.
The walls were filled with 1" hard foam and held in place with expansion foam. If I were to do this again I would elect to use spray foam instead, the time savings alone would be worth it. The paneling is 1/4" plywood with a good face.
Ceiling is foam board.
4 Layers of Insulation and Sound Deadening (Spray Foam, Wool/Denim, ESP Low-E EZ Cool Professional Car Insulation, Polysio Rigid Foam)
Stained plywood over foam board with reflective layer. Plus spray foam insulation.
Rattle trap, timber strips, foam board, plywood, click vinyl flooring.
Foam underlay. Vinyl planks from Lowes over insulating foam underlay
Sealed with resin/fiberglass. Then 20mm extruded polystyrene foam boards.
Multiple adjustable panels to create more bed space. 28" from mattress top to ceiling. Panels stack when full bed size not required.
2" high density foam + 2" memory foam + hand-sewed case
5" memory foam from Lucid Mattress
Twin foam mattress 4-5" thick, cut to fit around wheel wells. Plus sleeping bag.