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...

1. He explained why the insulation didn't go down (the subconcrete below the
first two inches was too hard and too dense to get any lower... his guys
were jackhammering it for several days... it would have taken TNT to blast
it down any further -- based on what I saw at the time, I take him at his
word.) So, one inch of insulation on top of the slab as it was would have
translated to 2" or more height to the final product... which would
admittedly have been undesireable -- but again -- perhaps baseboard heat
would have been a better reccomendation at that point... even though I did
express distaste for baseboard from the start...;

2. I explained that -- while I did want the end result tile floor to be as
flush as possible as the oak in the main part of the house (he's done a goo
sjob achieving that.. it's only 1/2" higher) -- I didn't feel that he had
educated me to what the ramifications would be by not insulating the slab
(ie heatup time, and heating costs)... but again, he says... Tom, we hooked
this up 24 hours ago, don't freak out yet, it takes a long time to get this
baby up to temp... lets not freak out yet...;

3. We called the heating guy... who helped my contractor (Bill) with the
heat calculations, the pressure tests, the hookups to the boiler, and when I
asked him if putting radiant heat on an uninsulated slab is OK, he says
"optimally no... but does it happen often? yes -- does not having it
insulated mean you're doomed? No.;

4. He had put 6MM plastic below the pex tubing , which sits on a rack of
sorts and then the whole thing gets flooded with the cement etc... 6MM of
plastic seems minor, but the heat guy says that it helps;

5. He has agreed to insulate the exterior perimeter of the foundation (6"
above ground, and 18' below) around the slab "at cost" ... but I'm working
with him on a number as close to free as possible;

6. I explained that the I hear the water temp should be closer to 130 than
180, and he agrees. There was a mixing valve installed to step the water
temp down... but he's had it off so we can heat up the slab.

Anyway, we're continuing to attack the problem --- I haven't told you al
labout my 90 year old boiler! Well, it appears that we're at a crossroads
with this old war horse too. Hopefully we're able to get an acceptable
heating arrangement going shortly.. wish me luck.

Tom

PS. If 130 degree water is going in, and there's 230 ft of pex in the 12x17
area, what's a good target temp for the return water to be? 30 degrees less?
20 degrees less?