I have an old farm house. Low crawlspace (2-block and SOG) . I was going to demo the crawl and walls and re build with ICF ( I sell ARXX). The main issue is the SOG area is never warm, however, recent research says to insulate on top of slab, install a floating floor. The low crawl area could be insulated from the interior or exterior or both with rigid foam.  Labor would be cheap (me). I was thinking of removing siding and going to the footing with 1" foam in both these areas. Thoughts? Northern Michigan is my address. Thank you

You deal with ICFS so you must be familiar with the bug issue - carpenter ants, termites, rodents and other creatures love to tunnel thru foam. Extending wall foam down to grade means they can chomp their way in at or below grade & head undected up into the house easily. So I'd go with foam on the interior and not the exterior.

What Bob said- keep it on the interior and you'll have fewer issues down the line.

But instead of 1" go with at least 3" of EPS (4" is even better) in your climate. If you want to keep it cheap, seek out reclaimed roofing EPS from commercial demolition/reroofing.

If that's too big a PITA on the SOG section, install copper Z-flashing at the top of the exterior foam as a tunneling-insect deterrent, and finish the exterior of the foam all the way down with the most bug-proof material in our ICF finishing arsenal.