In order to be effective you’ll have to put a complete vapor barrier up in your cellar, which is easy to do since a vapor barrier is essentially a thin plastic sheet nailed to the studs over the insulation. In the case of your foam board insulated foundation walls you won’t have to worry about reduced r-values, since the foam boards are impervious to wicking, but the mold issue is still worth taking care of. So, wrap that vapor barrier all around your walls.
Another layer of protection one should consider on those exterior walls is applying a paint like vapor barrier before you apply the foam panels. It’s an easy step, definitely DIY, and will help keep moisture from wicking through the walls and into your basement, even if your cellar is nicely sealed.
And speaking of sealed, there’s one more step to completing your properly sealed walls: Taping the seams! Getting just a bit a head of myself here, though, since we should talk about sheetrock for your walls. Since the cellar is maintained at fairly low temperatures the dew point is also fairly low, causing potential humidity conditions that could prove problematic for wood siding (although I have had cedar siding in my cellar for years without issue) and even for regular sheetrock. I strongly recommend using the green or blue waterproof sheetrock that is typically used in high moisture areas such as bathrooms. It might be more expensive today but you’ll save yourself headaches for years! Once you get your rock up, make sure to tape all the seams with waterproof plastic tape to ensure that you have a near perfect vapor barrier.
Chapter 3: Ceilings and Lighting in the Cellar
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