In article , thnewton@nospam-
hotmail.com says...
~ Thanks so much guys for sharing your knowledge. I had a long talk with the
~ contractor today... here's an update. By the way, my location is Long Island
~ NY... average evening temp in Feb about 25 or so, the ground below is dry
~ and densly packed earth with some clay
~
~ We just had a frank talk...
~
Details snipped.

I think your contractor should have consulted you before going ahead
without insulating the slab.

The extra insulation at the edge of the slab will make a significant
difference in the temperature of the ground under the slab because
the "temperature gradient" will be much flatter. That doesn't excuse
the builder, but his offer to install the perimeter insulation at his
expense seems fair.

See: http://tinyurl.com/2au9y

It will explain why insulating the perimeter helps, and will show you
the detail of how it should be done. Ask for the builder's assurance
that he will follow this or something a lot like it.

Rick