[Greenbuilding] XPS perm rating

[Thomas Lewis]

Hello All, 

I'm in the process of insulating my basement.  I'm
gluing  1" xps to my stone and brick foundation. 
Today I found that there is a thin, think 1mil, layer
of plastic on either side of the foam.
  
I've never noticed this before and it made me wonder
if anyone out there knows if the perm of this product
(as found in Lstiburek's books and on
buildingscience.com) was developed with our without
this plastic layer.  Further I wonder what the impact
on perm is when I peel the layer off.

If anyone has a source of data on this then maybe I
could increase the thickness of my insulation without
sacrificing drying ability.


Best,
Tom Lewis


"Time makes more converts than reason."  Thomas Paine, Common Sense


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