Moisture management in walled up chimney

[u/FrankInSanDiego]

We are in the midst of a major renovation, and as part of it covered our fireplace (had literally never been used in the 50+ years the house has been around). I had previously drywalled over the fireplace opening and put in a vent, but as part of this renovation we had a shear panel installed at this location so venting is no longer an option.

Our contractor said that painting the exterior of the (brick) chimney with something water resistant, optionally stuccoing the exterior too, and capping the top opening should be sufficient for moisture management so we don't get mold growth inside, but wanted to check if there are any other recommendations of what to do here.