If your attic has no insulation, you will need R-30 kraft-faced insulation, or maximize your energy efficiency with R-38. If you’re adding to existing insulation, you should always use unfaced products.
Kraft- or Foil-Faced Insulation with Vapor Retarder
This type of insulation has either a foil-backed facing or kraft paper layer attached. The attached facing layer helps control the amount of moisture vapor that passes through the insulation that could collect inside ceilings, exterior walls and floors. Kraft and foil facings are combustible and have to be covered with an approved interior finish (i.e., drywall).
Unfaced insulation has no foil- or kraft paper-faced vapor retarder.
Rolls are long strips of insulation rolled into bales. You measure the length you need and cut it off with a utility knife. Rolls are best for covering large open areas, like attics and floors.
Batts are pre-cut lengths of fiberglass insulation. Batts are available unfaced, or with aluminum foil or kraft paper facing.