Jud writes from Bedford, New Hampshire: "I am replacing the attic insulation in my 26'x54' foundation, 1969 built, split-level home which has 2x6 ceiling joists. The attic has 3 large gable vents which are 26"x32". The roof does not have ridge or soffit vents, but the large gable vents seem to provide the ventilation needed. I will be installing a gable vent fan to help with air movement as well.

THE QUESTION: The floor of the attic contains the insulation, which is 2x6 joists. They had a significant mouse problem, so I've removed all of the old insulation and mouse 'evidence', bodies, etc. There is a plastic vapor barrier under the joists (and on top of the drywall) which I wonder about. Should I remove the plastic before putting in the Kraft faced insulation I've purchased? Or is it ok to simply install the insulation (Kraft paper facing down) over the plastic? I've read some things that say it is preferable to have that vapor barrier, and some that say the Kraft paper also acts as a barrier, but not 100%, which is actually desirable to allow the attic to 'breathe'. It would be great to NOT have to remove all that plastic."

Answer: Kraft paper is rated as a vapor retarder. It tests at 1.0 perm. A vapor "barrier" would have perm of 0.0. That being said, only one vapor retarder is needed in this type of application. It is recommended that the Kraft facing be slashed when being used over 4-6 mil poly.