Air sealing behind T&G wainscot – GreenBuildingAdvisor

Hi,

I am in my fourth year building a large home in the mountains of Colorado, Zone 5A or 6A depending on which map you look at.  The house is a hydronically heated 4″ insulated concrete slab.  The exterior walls envelope from the outside in is:

Hardi Plank, 1.5 in rainscreen, house wrap, two layers of 1.75″ Poly iso properly lapped and taped, another layer of house wrap, 7/16″ OSB, 2×6″ studs, R21 faced fiberglass batt (properly detailed and installed), drywall or drywall with white pine T&G wainscot.

The wainscot only covers 48″ from the floor, then drywall to the ceiling.  Only sections of the exterior wall have wainscoting, not the whole exterior wall.

My question is about the best way to do the interior vapor barrier on the exterior wall when there is wainscoting.

I already purchased faced R21 fiberglass insulation for the exterior walls.  I intend to install it correctly.  My calculations indicate that with only 3″ of Poly iso, there are times when the OSB will hit condensing temps.  To prevent condensation on the OSB, I need a plan that isn’t too expensive.

If I install the fiberglass and then tape every seam, tear, cut, etc. with Siga Majrex, ProClima Intello, or 3M Air and Vapor Barrier 3015NP for the entire wall (not just the bottom wainscot portion).  Will that be sufficient, or do I have to start looking at peeling all the facing off the fiberglass in those walls and installing a smart vapor barrier?