I am having a new home built. One builder wants to install (Poly) vapor barrier (outside walls) between insulation and drywall. Other builder states no as house needs to breath and states tyvek is good enough. Tyvek is for wind or dust, not moisture, correct. Yes or no with poly and reasoning. R-19 faced insulation in walls and R 38 in ceiling. Thanks

The idea that a house needs to breath, at least in the context of the one builder is a myth. The structure breaths from the point of the vapor / air movement barrier our.

The simple truth is that the tighter, the better. It does, however, require that you take a pro-active view of indoor air quality. This can be done by either an air exchanger, or by central ventilation system that accounts for make-up air.