The codes are silent about whether above grade slabs need to be insulated.
Concrete floor slab perimeter insulation.
Below grade need vertical insulation at the slab perimeter.
In order for the slab to be independent of the foundation wall a bond break is needed between the slab which is supported on grade and the foundation wall that supports the exterior wall structure and its loads.
Otherwise both codes require that slab on grade floors with a floor surface less than 12 in.
Perimeter slab insulation heat loss through an insulated slab windows 33 roof ceiling 8 slab 15 6 doors 5 walls 39 insulation and fenestration criteria table 402 1 1.
Floor r value basementc wall r value slabd r value depth crawl spacec wall r value e402 1 1.
However i think by far the best option is one that offers complete insulation from the ground.
Also check the floor for smoothness and level.
If you know you have issues with moisture tend to those problems before installing the insulation.
You may need to grind down significantly high spots to ensure an even surface.
Regarding the rated r value of insulation on slab on grade floors.
For monolithic slab and footing the insulation must extend only to the bottom of the.
Bulletin number 552 edge insulation of concrete floor slabs from branz outlines the accepted solutions for installing edge insulation or a thermal break between the slab and the perimeter wall.
The rated r value of insulation shall be installed around the perimeter of the slab on grade floor to the distance specified.
As clarified in appendix a of standard 90 1 2016.
These codes do not require any insulation for slabs that are more than 12 in.
1 to prepare for insulating the floor first evaluate the condition of the concrete.