We are gettin ready to put an addition on our home. The old laundry room was in need of replacement due to mold, rot, etc. Anyhow, the last time we had an energy audit done, the people running it said no to vapor barriers. I was always taught it was required in our zone (5 I believe) in Ohio, due to some cold winters. I decided on re-using the old siding shingles, not only to match the current home, but save money. The 1/2 osb will be covered in 30# felt and the shingles will go over this. The walls will be 2x6" and I'll concentrate on airsealing before insulating with batts. I almost went with housewrap, but decided against it for there's too many unknowns, and the original Dutchlap siding under the felt was in perfect condition. Do I need a vapor barrier behind the drywall? Thanks.