XPS is most often used in below grade applications because of its inherent resistance to absorbing water.  XPS falls in the middle of the three types of rigid-foam insulation in R-value (about R-5 per inch). XPS typically comes unfaced. Unfaced 1-in.-thick XPS has a perm rating of around 1, making it semipermeable and is considered a vapor retarder, not a vapor barrier.  The traditional blowing agents used to make XPS have a very high global warming potential. US Manufacturers are currently testing and introducing a new generation of blowing agents that dramatically reduce global warming potential. Thermal drift, the gradual lowering of R-value over time, is a consideration with both XPS and ISO.

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Common Applications:

  • Below Grade Applications: foundation walls, basement walls, basement floors
  • Below Slab: radiant heating systems
  • Walls and Ceilings
  • Low Slope Roofing
  • Pipe and Utility Line
  • Earth Stabilization

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