Another insulation question , about installing foam board

[Tallbald]

I considered posting this at the end of my other insulation thread but was afraid it might become lost in the questions I asked earlier. So here goes. I'll follow the advise and insulate with foam board sides and ceiling. I have done this to several garage doors down through the years, and cut snugly to fit which required little other attachment. I'll use duct tape to seal seams too. But please tell me this. I know when one insulates a building ceiling, you put foam trays in place between the roof sheathing and fiberglass bats, so that there's air flow between the two and a way for moisture condensation to flow away from the wood sheathing. Otherwise, I am told, the condensation will eventually saturate the batting and wood, setting up rot and mold. Must I leave an air gap between the foam board and the aluminum sides/roof of my conversion? Or should I have the foam directly up against the skin of the sides/roof? I suppose I could attach 1/4 inch furring strips with construction adhesive as a standoff from the sides if need be. The ceiling shall be covered with 1/8 inch plywood over the foam board, and the sides will have the factory plywood.Thank you all for advise. Don.

[Wolfscout]

I didn't and haven't noticed a problem.
What I do as precaution -- keep a container of DampRid in my Trailer no matter what the useage though. I detest the thoughts of mold and mildew.

[Treeview]

In houses its easier to set up aid channels between the hot and cold surfaces where condensation will form. Besides the air space there needs to be sufficient volume for air to flow. the moving, dry, air will flow across the dampened surface and evaporate the condensate. Once the water is vaporized the air can move it out.

It seems to me that trying to setup air channels and airflow in a camper/trailer is more bother than its worth. Hard to solve too.

here's a quote from this page:

www.energybooks.com/pdf/D1142.pdf

Where Should the Vapor Barrier be Installed?
Vapor barriers must be installed on the warm side
of the insulation. This is because condensation occurs
as water vapor moves from the warm side of the wall to
the cold side. If a vapor barrier is installed on the cold
side, it traps moisture inside the envelope, making
moisture problems worse.
This poses a dilemma in climates where the weather
can be hot and humid in summer, but cold in winter.
The deciding factor is how cold it gets. Where the
winters are seriously cold, as in Minnesota, the best
compromise is to install the vapor barrier on the inside.
In humid climates where winter temperatures are mild,
as in Houston, the best compromise probably is not to
use a vapor barrier. If this decision is made, the envelope
should be made of materials, such as masonry, glass,
and aluminum, that withstand periodic dampening.

Rot shouldn't be an issue in a CT conversion unless wood is used for firring strips. My plan is to use Z-channel for the walls of my ToyBox, a former Uhaul Toyota one ton cube.

A solution is to make sure that there is a lot of air exchange in the trailer. This isn't hard to accomplish while camping/traveling. When it's parked keep some vents open to allow air to circulate.

Tom