That s how the barrier is made effective.
Faced or unfaced insulation in walls.
Any time you use a faced insulation the paper needs to be facing toward the living space.
Faced insulation is a type of fiberglass batt insulation wherein the facing is either stapled to the sides or to the face of the studs.
Paper faced insulation means that one side of the insulation material comes lined with paper.
Unlike unfaced insulation faced insulation has a vapor retarder that keeps moisture out.
To this end you insulate your home.
The primary function of the vapor retarder is to keep moisture from spreading within the walls and throughout the house.
Unfaced insulation the type without paper is what you would use if you are adding insulation to your attic or to place between floors when living space is above and below.
Among the many insulation options available for the homeowner there is one that stands above the rest.
This is usually kraft paper but sometimes other types of paper can be used.
Insulation comes either faced or unfaced which is when the paper is attached to one side.
Unfaced batts on the other hand fit in wall cavities by friction.
Faced insulation has flanges on the outside of the batt that need to be stapled to the wall studs and joists.
Kraft faced insulation includes a paper vapor retarder which helps prevent mold and mildew.
Kraft faced insulation should be installed in exterior walls exterior basement walls and attic ceilings by pressing the product into the wall cavity with the paper side facing outward towards the installer.
Without stapling moisture still has a path into the room.
So in an attic the paper faces downward and in a crawl space it faces upward.
More often than not faced insulation is made out fiberglass.