I am going to insulate exterior foundation walls and underslab of my new addition slab-on-grade foundation. I will have hydronic heat embedded into the slab so I need good insulation value. Which insulation polyiso or extruded polystyrene is more suitable for this task? 2" polyiso has better R-value (R13 vs. R10 for extruded polystyrene). However, I checked the link
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13 years ago