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Basement wall, am I insulating it right?

PLIERS | Posted in General Questions on

Trying to insulate basement walls, don’t want to end up with black mold in walls. Any advice is greatly appreciated.  I live outside New York City in climate zone 5.  I have 2 exterior walls, one has a 4in sewage drain pipe running across it. On wall with pipe I’m going to put 2 layers of pink foam board so it is flush to pipe.  (4in foam) On wall without pipe I will use 1 inch pink board.  I will then build 2×4 walls in front of foam on both walls and fill bays with unfaced insulation. Not sure which one to use here.

I also have interior foundation walls separating areas of basement.  On those walls I want to put 1/2 inch foam board just to separate 2×4 wood wall from concrete.  I will not be filling bays since it is an interior wall.

I have seen an example where someone built this exact setup but then put a plastic vapor barrier over entire wall before putting drywall. Am I suppose to use no vapor barrier, I have read people doing it both ways.  If I understand this correctly putting plastic is like making a gigantic soggy diaper.

Joe Diyer

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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Joe.

    You do not need a vapor retarder. Detail the rigid foam as an air barrier with sealant around the perimeter of the panels and taped seams to keep warm summer or heated air from reaching potentially cool foundation walls where it can condense. I recommend you read this to make sure that you are getting all of the details right: How to Insulate a Basement Wall

  2. PLIERS | | #2

    Thank you, I’m no longer confused

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