Greg could you please call me. I need more info from you.

gregj: that is a very high price for this type of product! 1.50 a sq ft is more in reality.

Dmaceld: Where in the IRC are you reading this EPS statement? I've never seen it and millions of
ft are sold annually for this purpose. Secondly the 1.5 lb I spoke of would never compress under reg
floor conditions. 1.5 is equivalent to 15# psi under compression (best of my memory) which is
144 sq inches a sq ft x 15# = 2160 # per sq ft. You could drive a car on a 4" slab and never put
this kind of compression on the foam. When you squeez EPS or xps with your fingers you put more
weight per sq inch than a house or car ever could.

Dave

I've attached a PDF of the particular page. See Note e under the table.

After looking at it again it looks like I may over extended the restriction. It looks like the restriction applies specifically to a shallow footing under a slab. The only other reference to under-slab insulation I found states the insulation must have compressive strength adequate to carry the load on it.

Looking at the diagram again it shows the horizontal insulation outside the footing only. Maybe the requirement to use XPS only is because of the propensity of EPS to get water logged if it stays wet for years.

Mac :
If you look around you might find an EPS moulder in your area that makes a Type 2 foamboard.
We have one local to us that makes a board with 25 psi rating, almost equivalent to the Blue boards product.
It is about 65 % of the xps pricing, and works good for residential slabs. Only R4 per inch tho.

We had a customer provide used XPS board that got recycled from a flat roof that was getting refitted.
Better spec than lumber yard stuff and half the money.