EPS vs XPS (expanded polystyrene vs extruded polystyrene)
2 lb nominal density EPS (expanded polystyrene) has become a very
popular alternative to extruded polystyrene for under slab and perimeter
foundation wall insulation. The 2 lb EPS is available in any thickness,
not just 1″ increments and is more economical than extruded polystyrene.
It has the same 25 psi compression strength as extruded polystyrene.
Since EPS has a slightly lighter R-Value per inch than XPS, producing
the panels just a little thicker lets you meet any required R-value. For
this particular project an R-10 was specified and met using the EPS at a
substantial cost savings. Read the test results of a study published in
2008 comparing EPS to extruded polystyrene long term insulation values.