I am having a mold issue in my attic. Not all that bad. But I don't want any mold period. The problem is that I did not use a poly vapor barrier before installing the 2nd floor ceiling drywall. Then laid the fiberglass batt insulation from the attic side. So the vapor barrier that is the paper on the bats do not have a proper seal. The paper tabs do not lap over the face of the studs. However the worst areas are where there are interior partitions. Seems that the moist air is migrating inside the wall cavity and condensing once it hits the underside of the plywood floor of the attic. I would have never known, had I not removed a few pieces of the plywood. What would be the best way to remedy this problem?

By the way I used a poly vapor barrier on all of the exterior walls. Besides that the insulation was applied with the tabs lapping over the studs. Therefore there is in effect a double vapor barrier on the exterior walls.

So far I have thought of painting the second floor ceiling with a Sherwin Williams ceiling paint that is supposed to act as a vapor barrier. The other option would be tear out all of the plywood in the attic. Then remove all of the insulation. Then use one of the closed cell spray foam kits to spray a thin layer on the back side of the drywall as a vapor barrier. I wold have to do this a half of the attic at a time. Otherwise I would have to remove all of the content of the attic. That would include the plywood and insulation. No way am I doing that.

Is there a better way to do this? I was a carpenter for many years and never came across this situation. I guess leaky construction has its benefits after all.

Another point to consider is that I heat my house with a wood stove centrally located on the first floor. The boiler is always switched off. That is with the exception of the odd night here and there in the shoulder season. We will generally keep a pot of water on the stove in order to keep the RH in the low 30's. So the temp on the first floor is typically in the mid 70's with an RH of around 33. Then the second floor will be around 65 with an RH of about 45 or so. I am not totally sure as I do not pay much attention to the RH up there. We live and sleep on the first floor. But the temperature differential is enough to drive the RH higher on the second floor. I would think that this would not make any difference. Because the amount of moisture that reaches the attic will be the same regardless of the shift in temp and RH on the second floor. But I could be wrong. That is why I am providing as much information as possible.

I can't believe I made such a stupid over site regarding the tabs on the insulation. But I would never have imagined this would be the result. Again I have never seen this happen and people never put vapor barriers in there homes in the past.

James