Batten size to dry-line outbuilding

[BAGGIES1]

please excuse my limited knowledge but i'm in need of guidance..

i want to dry-line the inside of my outbuilding wall...

my original plan was for 2x4 and plasterboard with an insulating material...

i understand now i will need smaller wood battens...any clues?

the plasterboard will have to be thermal (foil backing).
can it be screwed to the wood battens or must it done using adhesive??
also my readers digest books says thickness sizes start from 18mm. do i need it be this large?

the wood battens needs to be treated with wood preservative . sounds reasonable.

the insulation can be Celotex ot Kingspan. ok. how thick does that come?
i've heard 1". in which case should i use smaller wood battens.

baggies1 signing off praying for the divine intervention of a kindly thread poster..

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No sign of one yet.
I've changed to Thread Title so it means something.

Mod Rupert
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[noseall]

do you intend using the out building as habitable space?

will this space be heated using your house heating system?

if it's connected to the main building will you have an external door separating out building from habitable?