Hi, I am from Wisconsin and I have a 30×30 section of my wood stud metal exterior pole shed that I am looking for some more information on.  In between the horizontal 2×6 girts there is 1.5″ R-Tech EPS foil faced(facing interior) foam board cut to size, foamed around the small gap left next to girt, and foil taped at every seam.  Over the top of this is R-11 Kraft faced fiberglass.  The shop is heated only when I am working by a vented propane unit heater.  The shop walls will be covered with white steel interior sheeting.  In one corner of the shop (that receives little sunlight) when I reach my hand behind the fiberglass there is some moisture on the foam board, where was the rest of the entire shop feels dry when reaching behind and feeling the foam.  The spot I am feeling the moisture has not yet been sheeted over with the steel as a wall covering.  My question is would placing a 4-mil plastic vapor barrier over the Kraft facing fiberglass in the walls solve this ?  Or should the walls be left as is so they can “breathe” to an extent.  It has also been in the 40s during the day and teens at night with large snowmelt during the day driving the humidity in the shop in the 70% ranges.  Any help/advice on this insulation and condensation topic would be greatly appreciated.