[Greenbuilding] Polyurethane door cutouts underslab, and exterior below grade?

[Stewart Abbey]

I have collected about 2000 sq.ft of scrap window cutouts from a door manufacturer who normally throws these in the dumpster. 
Based on this test I am planning to use these steel skinned R 14 1+1/2" panels under my floor slab. 

http://www.blueridgecompany.com/documents/Article_-%20The%20Bubble%20Bursts.pdf
However I have collected enough panels to also use as exterior foundation insulation.
Does anyone know if this type of polyurethane is OK to use below grade?
What about under my footings?  What is the compression specs on this stuff? We are building on a blasted rock pad on top of a hill.  Drainage will not be a problem.  If these panels are not suitable, what type of foam should I use under my footings?  My house will passive solar with radiant floor back-up in the Montreal area.  +- 8700 HDD
Anyones knowledge or experience will be appreciated.
Stewart Abbey




       
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