Ok going to start a new project of reinsulating home! I live in California in very mild climate but our home has no wall insulation and very minimal on the roof!! I was planning on ripping out the dry wall in a few rooms so I could fix some problems ans add resest lighting. My question is would I bennifit from adding a vapor barrier over the insulation on the walls as a air barrier. Vapor barriers are not needed in my climate. But its a old home and it does not even have plywood exterior just stucco over tar paper on the studs. I thought maybe if I added a 6mil sheet between the studs and sheet rock It would give me a better envelope! Opinions?