I am in the planning stages of building a shop with radient heating in the slab.  I do plan on putting down 2" of insulation under the slab before the pour but I heard about thermal barrier's for the outer edges and don't know much about this.  I also plan on using the ICF's for the first 4' above ground will these be sufficient as a thermal barrier is there anything I should know about this transition?

Thanks for your help.