The code is unclear

摘要

Insulation requirements for slab-on-grade floors can be found in section R402.2.9 of the 2012 IECC and section N1102.2.9 of the 2012 IRC. Both codes state, "Slab-edge insulation is not required in jurisdictions designated by the building official as having a very heavy termite infestation." Otherwise, both codes require that "slab-on-grade floors with a floor surface less than 12 in. below grade" need vertical insulation at the slab perimeter. These codes do not require any insulation for slabs that are more than 12 in. below grade. The codes are silent about whether above-grade slabs need to be insulated.