Walls, Ceiling and Insulation: The plan, w/ price & source

The walls will be assembled as a sandwich panel: 5mm ply>1/2" foamular>reflectix>foam tape air gap>2mm underlayment>metal wall.
I will use spray glue to attach 2mm foam roll to the metal first, completely covering every inch. Then I will  use spray glue to attach reflectix, with foam tape (Or some other product?) adhered to the reflectix, used as spacers to create an air gap in between the 2mm underlayment and the reflectix.
Next, the XPS/foamular boards (Which have low thermal conductivity) will be friction fitted & taped in between the pillars. Spray foam will be avoided as sailboaters report moisture problems esp. if the skin gets punctured. Furring strips will be avoided in order to decrease the depth of the walls.
Finally, a sheet of 5mm ply will be fastened to the walls with 1/4-20 pre-bulbed plus nuts, which are superior in this case to rivnuts. The bolt heads will be covered with something  to avoid condensation and heat transfer via thermal conductivity.
I am considering leaving holes up high and down low on the sandwich panels to allow the air gap to breathe.


$30 Polyethylene underlayment

This will be spray glued to the metal, so that there is no exposed metal for moisture to condense upon. This may not be the best price available, and I may use polystyrene roll instead.


$57 Radiant barrier, 200 sq ft

The all controversial Reflectix (I have listed a cheaper knock off), which must have an air gap. If it is laid against the bare metal (As most people do, with spray glue) it will conduct heat into your van. The outside of a vehicle gets very hot in the sun. I want to reflect heat radiating from the metal body of the van. If I were to have reflectix closest to bare metal, with an air gap, condensation would build up on the metal body of the van major time. All of the metal must be covered. You will have to come to your own conclusions. My method is experimental.

1/2" Foamular XPS closed cell insulation board



Fiberglass absorbs moisture and causes mold. I chose XPS over polyiso because it performs better in the cold (R-max loses R value when you need it) and because XPS is moisture proof. This will be spray glued to the reflectix.

$10 1/8" x 4' x 8' Plywood

Wood is about my only option, because I don't want the intense heat from the wood stove to cause any kind of offgassing from fiberglass, plastic, or other materials. I don't like automotive carpeting because it absorbs moisture.




$34 Noico 80 mil butyl sound deadening

Fatmat, rattletrap, etc, use asphalt products, resulting in offgassing smells. Higher end sound deadening tiles, like Dynomat, use butyl, which has no smell and supposedly better performance. You only need about 20% coverage of the whole van for it to work . This has to be put down before the walls & insulation, directly on the van metal.


Soundproofing info:

https://www.sounddeadenershowdown.com/camper-van-conversions