To summarize: I am putting together a 6' x 8' "root cellar" in the NW corner of a barn, below grade on 2 sides, framed and insulated on 2 sides and the ceiling. Most texts on this recommend 4" diam vents. I am located in the Rocky Mtn foothills, cold, dry and windy, and was thinking that perhaps I could/should reduce the size of those vents since excess moisture is unlikely to be an issue for me, but too much air flow in our winds might be. Any thoughts on this?
Also, a general question on wall material for the framed walls and ceiling.