House wrap can protect straw-bale walls only if it allows for permeability. The 2024 IRC now allows a water-resistive barrier with a vapor rating of five perms or higher, yet a tight plastic sheet still risks trapping moisture and ruining the bales. In this updated guide, we explain when a vapor-open WRB makes sense, where a rain screen provides added protection, and why lime or clay plaster remains the most effective first defense.