is xps a vapor barrier?


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Old 11-16-19, 04:29 AM
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is xps a vapor barrier?

Is XPS a vapor barrier if a put tuck tape on all the seams and tape up where the xps meets the walls and ceilings?
Everything I'm reading says it is not considered a vapor barrier but a vapor retarder and does actually breathe a bit.
If it is a vapor barrier then why do products like ISOCLAD come with a foil vapor barrier 'built in'?
 
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Old 11-16-19, 06:27 AM
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It is considered a class 1 vapor retarder, allows moisture to pass!

Non faced foam is a class 2!
 
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Old 11-16-19, 10:42 AM
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So then I still need to put plastic on top of it?
 
 

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