Creating a Thermal Break With Insulated Slab
I am attempting to build a high performance house for my son. The style could be considered a simple modern raised ranch. It’s a simple 24′ x 36′.
I’m in climate zone 7 and we initially planned on putting the footings at frost line, as per code which is 42″. However, my excavator suggested only going 32″ and backfilling due to a relatively high water table. My lower level is going to be ICF with additional insulation on the exterior. The upper level will be 2×6 advanced framing with two layers of recycled 2″ polyiso.
I plan on putting 4″ of Type IX EPS below the slab. I realize that the insulation should be continuous, so placed on top of the footing so it meets the wall of the ICF. Due to the more conservative depth of the footing, I’m afraid of the upper floor being too high above grade. It sounds a little crazy, but I’m trying to save inches. Could I use one layer of 2″ EPS and another 1″ layer on top of that, between the footings. Then I am considering adding a third layer of 1″ EPS that would go on top of the footing to create a thermal break. So my question is: Would that 1″ layer of EPS create a sufficient thermal break? Or would horizontal below grade insulation help my situation, like that found on a FPSF?
Once again, thank you in advance for your replies. They are very much appreciated.
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