Do I need a poly barrier between concrete and 3″ poly iso foam?
user-231615
| Posted in Energy Efficiency and Durability on
I have an 8″ exterior concrete wall above grade, 3″ polyiso, sheetrock. Concrete will be waterproofed on outside.
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No.
Whether and where a vapor barrier (retarder) is required depends on your climate zone and whether the interior is primarily heated, cooled, or evenly divided between them.
If the foam board is foil-faced and the foil is taped at seams and the foam is sealed at all edges, then the foam/foil is a nearly perfect vapor (and air) barrier.
If the goal is to prevent condensation on the inside of the concrete wall during the heating season, then you do need an air/vapor barrier on the warm side - but you may already have one.