Hello group. New guy here. I'll try to detail as much as I can about the issue. Yesterday the wife noticed some green mold growing in our spare bedroom that we use primarily for storage. The ceiling had 2 wet spots on the tile, close to the corner of where the exterior walls meet. The wall paneling has buckled but I'll deal with that later. The ceiling tile is the 12x12 tongue in groove stuff you staple to the boards that will hold it. Anyway here is the layout. Seems to be sheet rock ceiling, then the tile. Then new boards fastened to that with new tile over that. Styrofoam panels were put in between the boards as insulation. I tore out about a 1/4 of the tiles in the room, around that corner and area of wet spots and found some condensation. I cannot remember definitely whether the area with the condensation had any Styrofoam under it nor not. This room is just storage for us. We've been In the home 3 years now and have had no issues until now. We keep the door shut. It does not get much heat and is usually cold when we do enter. We have a pellet stove in the living room that will heat the whole house if we leave doors open. Roof was new in October 2018 and I've verified no leaks and no sign of water. What gives? I need to replace the ceiling now and probably wall panels. But I want to fix this to avoid doing it agsin.

I have a 1/4 bath (vanity only) that has a ceiling made of 12" square tile which are basically thick paper/cardboard that has been painted. I shaved a sample off the edge and submitted it for asbestos testing, which came back negative and described them as 87% cellulose. I think these are glued onto the ceiling. There are hairline cracks between them. Would priming/sealing the surface with Gardz, then skimming it with a couple of coats of lightweight hot mud be any better at resisting cracks than just a couple of coats of a good latex paint?