I am remodeling my house. I have 2 by 4 walls and some areas I had to add a 2nd 2 by 4 wall to help strengthen the building. I have now decided to add a 2nd 2by 4 throughout on the ext. walls. I was thinking of doing staggered studs and using unfaced fiberglass on 2by 4 by the osb and faced fiber glass on the inner 2 by 4 wall. My question is there any known vapor issues in this style of wall with this insulation I am planning. I am doing fiberglass because of cost and I live Maine so very cold winters.