Vapor Retarder & Basement Insulation

Q. In the March/April 2004 Today's Home magazine you gave some advice to someone inquiring about finishing their basement. In the last paragraph, you said, "...on centers AND NO vapor retarder. CERTAINLY NO POLYETHYLENE PLASTIC TYPE VAPOR BARRIERS. Then use typical unfaced batt insulation with no facing or vapor retarder."

I have been putting up Owens Corning Fiberglass Insulation with vapor barrier/Kraft faced in my walk out basements framed wall. It would be expensive to remove it and buy unfaced batt insulation and place it in.

My question to you is, why is the vapor barrier insulation wrong to use? You do not say why and when I read something that has been put all in caps it concerns me.

A. NO WORRIES! Kraft faced "vapor retarder" is fine for basements and Kraft faced is the preferred vapor retarder. The only real problem/mess/time-bomb is the polyethylene plastic which then makes a vapor "barrier". This plastic can trap moisture inside the wall cavity which can be very bad.

Relax, no need to remove your Kraft paper vapor retarder at this point. Kraft faced allows moisture to pass both directions in & out of the wall cavity ... which is good. However due to the inevitable moisture in basements with little ventilation or moving air, I advise no vapor barrier in basements to allow as much moisture exchange as possible and the air to be dried by the heating and a/c system in the basement area.

Sorry for any confusion with my previous explanation. I support the use of Kraft faced vapor retarders and advise strongly against any and all polyethylene vapor "barriers" in this latitude in the USA. St. Louis is neither north/cold nor south/warm and therefore the building practice needs to progress to Kraft faced vapor retarders.

Safety also warrants some covering over unfaced fiberglass insulation in open walls like your basement. In my home I would actually do what you have done with the Kraft faced "skin" between the interior of the basement and the raw fiberglass insulation until I could cover it with drywall. I would likely leave the Kraft faced insulation and cover the walls with drywall to complete the process.

Great question! Thank you for allowing me to clarify this for you.

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