Vapour Membrane or not???

Hi All

I have a large sectional concrete garage/workshop which im about clad in timer loglap to make it more pleasing to the eye.

The plan is to create a 75mm cavity between the concrete and the cladding which will be insulated.

Now my question is, should I be using some kind of membrane between the cladding & insulation to stop it getting damp? Or would it be unnecessary??

Any pointers would be appreciated