Eva writes from Ossining, New York: "Is there a need to change the insulation in a home attic over time? Like 20 years or so? Also, how much insulation should we have for the under the floor area of our home?"

Answer: There should be no need to remove existing fiberglass insulation if it is dry and still enclosing the tiny pockets of air that give it insulating value. For an under-floor application we recommend using R-25 Kraft-faced insulation with the paper vapor retarder up toward the living space. If the existing insulation is in good condition it should not need to be removed. We recommend adding unfaced insulation to any existing attic insulation.