Vapour barrier when Insulating internal wall with sheep's wool?

[Martynfaul]

I want to add t&g cladding to an internal wall as a feature but would like to include a layer of insulation as this is an exterior wall and not insulated at all. It is on the first floor which is wood framed above a ground floor of brick construction. I am thinking of using sheep’s wool insulation and my question is do I need a vapour barrier and what is the most worthwhile thickness to use? (up to about 15mm room available) thanks.

[stoneyboy]

Hi martynfaul
Yes you must use a vapour barrier but may have to accept condensation forming around the perimeter.
Regards S