What are the pros and cons of installing a poly vapor retarder over fiberglass insulation?
Mel writes from Monsey, New York: “I am renovating a very old home that has 2″ x 4″ framing at the exterior walls. I would like to know the most effective method of insulating these walls versus cost? Also, what are the pro’s and con’s of installing a poly vapor barrier over fiberglass insulation?” Answer: The best way to insulate a 2×4 exterior wall is to use Kraft-faced R-13 Fiberglas™ insulation. The vapor retarder should be placed toward the warm-in-winter side of the wall. Owens Corning believes its Kraft facing is a sufficient vapor-retarder. The use of poly over Kraft or instead of the Kraft paper is, however, acceptable. Check with your local building code to be sure there are no special vapor retarder requirements in your area.
