We are in PA and our house is on a slab - no basement. We recently found mold in one of our bedroom walls from faulty flashing. I removed all of drywall and insulation to find that the sheathing was completely rotted through. So now we are looking at the metal siding on one wall about 6.5 feet high by 4 feet wide. Parts of the studs and sill were also rotted so I was going to replace them as well.

Our bedroom gets quite humid during the spring/summer so we run a dehumidifier. Also, in the winter, it gets somewhat chilly (about 60 degrees) in there.

So my question is, while rebuilding this portion of wall, should I install a vapor barrier? Inside the insulation (I was going to use foam board) or outside? There is so much conflicting info on the web and I'm finding arguments for both ways. I don't want to trap moisture inside the wall.

Also, while checking out the sill, I noticed that there is a small area where I can actually see the ground/light from outside. How do I plug that up???

I realize that a professional could better handle this situation but unfortunately, that's not an option.

Thanks,

Tina