New Shedio set-up

[anditsinthefish]

Mine was painted on the outside first to ensure no water can penetrate the wood before it was lined.
The polystrene sheets had a foiled paper-like covering on each side, we just cut the sheets to fit between the batons - not had any problems with damp at all.

I did exactly the same thing under my flooring. it has some air gaps to breath and no problems at all. No insulation on the walls and it does get rather chilly in the winter but nothing a heater and some gloves doesn't solve.

[oliver90owner]

25mm of kingspan (or similar trade names) would far exeed the insulation of bubblewrap.  Kingspan is about a third better than expanded polystyrene, so likely worth the extra expense. Fitted carefully, it can be recovered for use elsewhere when/if you change to a better/more permanent studio construction.  Good insulation soon pays for itself, either in energy use,  extra usable space, or other advantages.

RAB