Vapour barrier / Breathable membrane

[Thesearcher]

Hello,
I have a SIPS structure built and I'm putting 25 mm lats inside with plasterboard over the lats. Do I need a Vapour barrier / Breathable membrane in between the plasterboard and SIPs structure on the inside of the building? SIPS Structure is 175mm.
Thanks

 

[Branz]

whats the makeup of the sips from outside to inside

 

[Thesearcher]

whats the makeup of the sips from outside to inside

There will be cement board on the outside of the building over lats and a breathable membrane on the exterior of the external sip panel. The SIPs itself is 175mm OSB on both sides of the insulation.
Thanks

 

[Branz]

ideally you need a wind barrier on the external face as I assume you are just using the CB as a rain shield, with vents top and bottom?
Yes re the vapour barrier on the inside face.
Are you using the space behind as a service cavity, if so maybe make it a bit bigger