We are planning to finish our basement and the work has begun. The walls were already up when we moved in. While removing drywall in one spot for the fireplace I found that although the walls are insulated, there is no vapour barrier. We have not had a problem with moisture as of yet but behind the insulation there is frost on the concrete wall. I am wondering if I should rip out all the drywall and put up a barrier or will it be okay as is. I would rather not rip it all out as this creates more work and more expense.