Condensation on basement insulation

[Starchy]

My 8 year old house with a poured concrete foundation has a condensation problem. I have an 8' x 8' x 42' L concrete room under the front veranda. The ceiling of that room, (the veranda floor) is a poured 4" slab. The entire room has been finished into a storage area, with one end finished into a wine room. This room measures 8' x 8' x 8' with a through the wall 2" diameter hole to the exterior for a cold air source to keep the room cool for wine storage. There is an electric baseboard heater that is thermostatically controlled to 50 oF during the winter months and typically the hole to the exterior is sealed during the winter. I live in a very cold winter climate area.
The room was finished as follows: 2" rigid ship lap styrofoam was glued to the concrete ceiling, and 1" foam was glued to the exterior walls. The room was then framed with 2x4's and the cavities were filled with 3 1/2" fibreglass batts. A 6 mil poly vapour barrier was then applied with 16" overlap as required. Prefinished masonite was used to cover the walls and ceiling.

Now the problem; the wine room has had a moldy, musty smell for some time. Once, there was condensation on the end (outside) wall above grade on the masonite. This was dried and washed up. Sometime later, mold appeared on the room side of the masonite. This was cleaned with a bleach solution, but the smell has lingered. Today, I have completely emptied the room and removed the masonite. The underside of the masonite was clean, with no evidence of mold. I removed some of the 6 mil poly on the exterior walls and there was no moisture condensation on either side of the poly, and when I removed the fibreglass batts, both sides of them were dry, as well as the exposed rigid foam. However, when I removed the 6 mil poly and the fibregalss batts from the ceiling,(the 4" poured slab veranda floor) there was a lot of condensation between the fibreglass batts and the 2" rigid styrofoam. The entire 8' of the ceiling was exposed however the condensation was only found on the first 4' away from the end (outside) wall that has the 2" direct vent to the outside. I removed a 6"x4" piece of the ceiling rigid styofoam from an area with condensation, and the exposed slab appeared dry. So what has caused the condensation between the rigid Styrofoam and the fibreglass batts, and what do I do now to prevent a re-occurrence?
1. Should I remove and not re-install the fibreglass batts? Is just the 2" foam the way to leave the ceiling?
2. Did I have this problem because I had rigid foam then fibreglass batts then a 6 mil poly vapour barrier? Did I trap moisture between the batts and the foam?
3. Is the hole to the outside the problem? Should I seal that hole?

Obviously my objective is to prevent further condensation before I redo the walls and ceiling. I also want this room to stay cooler instead of warmer to keep the wine at optimum temperature. Thanks for any help anyone can provide.

[Drywall DIY Guy]

Condensation is the result of air that has a dew point (moisture level) that is higher than the temperature of the surface. In this case, somehow high moisture content air is getting at that cold surface. Hard to know exactly what you have but it seems removing the fiberglass and replacing with 4" of dense foam (in addition to what you already have) might be the solution. And make sure the dense foam is sealed/caulked in air tight at the edges. You will gain R-value as well as seal off the colder surface from any moisture.

[Starchy]

Thanks Drywall DIY Guy. Given that the framing is in place, adding more foam is difficult, however, I will try to seal the edges of the existing foam and will try to seal the ends of each piece of foam as well. Thanks for your thoughts.

[canajan]

Hello Starchy,

How did your repair go?

I have a similar problem. IIRC, does the foam on the ceiling not act as insulation AND vapor barrier? When you add the fiberglass and the vapor barrier did you not create a SECOND vapor barrier?

John

[Starchy]

Thanks to all who responded. I finished the refit just before Christmas, and then got busy with grand kids etc. I removed and scrapped, all of the paneling, fibreglass on ceiling and walls, and the poly vapour barrier. I was able to remove the ceiling studs. I then used red house wrap tape to seal all of the joints of the existing blue foam board on the walls and ceiling. Next I spray foamed the edges where wall foam boards met ceiling foam boards. Then I glued 2" blue shiplap foam board at 90 o to existing board joints to the existing 1.5" foam board already glued to the concrete ceiling. Taped the joints and foamed the edges of this. I sealed the vent hole through the wall to the exterior. Then I re-paneled with new Masonite prefinished white panels. Room is still kept at 10 oC (50 oF) for my wine. The walls were moist, especially the ceiling when I tore out the poly vapour barier. I ran a dehumidifier in the room for 2 days, and raised the temp to 18 oC (68 oF) to do the work, This helped dry out the visible moisture, before adding the second layer of foam on the ceiling. Now I have only one vapour barrier, the foam, and more of it on the ceiling where I get most value, and ultimately less insulation on the walls by removing fibreglass. Probably a wash for energy loss, and maybe slightly better off. Hopefully no more odours in there, at least none yet. Will tackle the other end in a few days as I now seem to know what was causing the odour.
Cheers, and I hope, canajan, that you can solve your situation as relatively easily as I was able to do. And if I didn't asnwer your question, yes I did have a doulble VB and that was the root of my problem