Pier on slab

cer2012

Here is my problem.
I have land with a 30 x 40 ft slab on grade. Top is even with soil. I want to use this slab as pier foot pads.
Code guy said I could dig a footer on 2 sides, cut slab and inset the other 2 footers. that woild leave the existing slab floating. Can't find out if wire or rebar is in the old slab.
Slab shows no sign of heaving, but has no footers.
I would also have to pour a stem wall or blocks fill for the plumbing and pour a new slab. [allow for expansion
Don't want the expense. Can I place piers on the slab [in effect using the slab as footer pads] and build a wooden foundation?
I live in N/W Arkansas. Lots of homes are on piers and 16x16 inch pads with blocks atop soil.
Have looked at the IBC and can't figure this out.
If you know this is covered there please site the location.
If I do piers, do I go up 2 blocks or 1?
What would be the best insulation to use on the perimeter and how to do it. Polystyrene, etc requires a ternite shield but the code doesn't explain how.
My thot is to use the space between the floor and old slab as a plenium for HVAC. Will put poly and gravel to block radom and mold etc. I saw this done before and want input on it.
Any help appreciated but has to meet IBC. Tough but fair code guy.
Is there any way, or is it necessary, to fasten the wood foundation down other than thru to footers?