Why can the additional insulation be installed with the plastic towards the roof?
Joe writes from Moreno Valley, California: “Our attic has insulation with a plastic barrier facing towards the roof (original construction). The plastic is deteriorating & of course the insulation is showing plus it has compacted over the years. I would like to add more insulation but your brochure states that when adding more insulation the plastic barrier should be down towards the ceiling of the house. I expect to go into the attic periodically, although it is not a living space, & am concerned about inhaling the fiberglass fibers. Why can’t the additional insulation be installed with the plastic barrier facing towards the roof to prevent ingesting the fiberglass fibers?” Answer: The plastic or paper retarder has a purpose and that is to keep moisture or condensation out of fiberglass insulation. Essentially, the vapor retarder slows the movement of humid air to a cold surface where it could cause condensation. In an attic floor, the bottom of the insulation will be the warm side an
