How critical is my interior air barrier?

So, my father in the Bangor, ME area is building a new home. I know what I would suggest, but he’s only willing to do an interior vapor barrier (Siga… So, my father in the Bangor, ME area is building a new home. I know what I would suggest, but he’s only willing to do an interior vapor barrier (Siga…Read MoreGreenBuildingAdvisor