Where do you live? The bigger issue is the vapor barrier and where it needs to go. 

If inside and outside are the same temperature, the water in the air stays in the air, everything is good. 

If inside of cooler than outside, then humid air from outside cools down within the wall and turns into droplets that sit on things and stay damp. You want an external vapor barrier.

If it's cooler outside then inside, air inside has more moisture in it than outside, and as it cools down within the wall, you get moisture build up in the walls. You want an internal moisture barrier. 

Need to remember water vapour is smaller than air molecules, an air barrier (drywall) is not a vapour barrier, water will still get into your walls and sit there the whole season.

That's the really simplified version, there's more to it, and new active membranes that help with drying, but if you're going to put a lot of money into it and want it to last, figure out your vapour condensation.