Wall Board Insulation Stone Wall Wet

[Cauvin]

Hello, new on this forum, I allow myself to ask for advice after several reading on this forum.

My friend has a barn watch with a barn, so a wall is half buried. Previously, this stone wall was hidden by a red brick wall covered with plaster with an air gap between the 2 walls.

Wanting to completely renovate this ground floor, we broke everything to put the stone wall appearing. The wall in its most buried part was wet, without oozing and since now 2 months, it has dried well but some part, especially its base, are still wet.

So now room for renovation: I wish in a first so much, to protect a little stone wall put a gobetit lime covered with lime plaster Saint Astier, then leave a blade of air and then put a Fermacel partition with insulation that does not fear moisture.

I also thought to leave this apparent wall with just a nice lime plaster, the remaining moisture would then be absorbed by the VMC of the house.

Someone advise me to fill the air gap with pozzolana with a high and low ventilation grid ??? so in this case, put a brick wall and no longer in Fermacelle. What do you think ?

My 2 questions are:

- Should I make a blade of air.

- and if so, should I vent this air space? outside or inside? From what I have read, this is not obvious. Indeed, by creating aeration, all the humid air of the interior or exterior of the house would be deposited on the cold wall of the stone wall, would condense and thus aggravate the phenomenon. Has anyone been confronted with that, that solution exists?

Thank you for your advice, to come I hope :-)

Sébastien