One wing of my house is slab-on grade in Northern NH. The area of the first floor is one open room of roughly 1400 sq. ft. The slab is 4" thick but I do not know if the underside is insulated. The floor, right now is bare concrete and there are some pretty uneven spots in it. I have a rinnai tnakless water-heater, as well. I am thinking of laying radiant tubing down on this slab and pouring 2" of fresh concrete over it and finishing the floor with the stamped concrete method. I think this is called a suspended slab? How critical is insulation beneath the original slab? If none, do I need to place insulation on the original slab first? The house was built in 2004. The only heat right now is wood. There are electric baseboards, but I think that was installed by the previous owner (foreclosure) to fool his mortgage company. Does this idea make sense or is it a pipedream (sorry, I couldn't resist). If, by the way, you know any radiant installers/consultants in the Lakes Region, I'm all ears!

insulation between your pours is critical. You could pour a level coat and then do something like Roth panel over it. We know a guy in your area who is good: Mark's Heating and Cooling, 603-452-8120. I don't think he's used Roth before but he's a pretty sharp guy with a lot of experience.

insulation between concrete levels is critical, You can lay down 1 inch CreteHeat panels, tubing goes right into it and then pour. learn more about it at www.barrett-inc.com

Thanks for the information. My wife called Mark today to set up a meeting to figure out the best solution for us. Unfortunately, I have to do this long distance due to work.

She is also going to drill a small hole in the slab and poke around to see if she can find Styrofoam or sand. The rest of the house is easy. The floor above the slab is accessible via suspended ceiling and the floor on the other wing of the house is accessible via the basement.

It looks like the Roth is less than half the thickness of the Crete-Heat, too.

IIRC slab edge insulation wasn't required by code in NH back in 2004, but is now. In northern NH R10 is now down to a depth of 4', R15 if it's a heated slab. If it has insulation under the slab you can get away with less.

Example diagrams of current code-complaint slab edge insulation configurations can be found here, and you might have to poke around a bit to figure it out for sure:

http://www.ossipee.org/departments/zoneenforcement/pdf%20for%20web/express_nh_res_eng_code_app.pdf