Yea, I'd have to throw some calcs in there to see if it would work up North. But, the further South that you go, the warmer the Earth temps. Of course you could really spend some bucks by coupling it with an active solar system.

The continuous circ idea is a good one. Especially if you can power the circulator mostly with PV panels. Insulate the slab really well, and say having 50° water circulating through it all the time. I gota think that would work! And that would cover every place from NE East to PA, and all states South of there(with 50° min ground temps).

well, it's a little more complicated than that: even geothermal systems don't *constantly* emit heat drawn from the ground, and they see a temperature differential in the ground over the course of a heating/cooling season. Then in the summer, you'd need to charge it back up.

But basically with a 24/7/365 pump circulator, you might make a big enough "thermal battery" to never keep allow the surface to stay frozen or cold. I bet it would have to be a pretty big loop field. If I weren't slammed right now I might even do some calcs....

Sorry for the post...I was on meds this weekend and it left me somewhat ...giddy!

Basically, what you are saying is that you can temporarily change the ground temperature(in this case making it colder), despite the mass and inherent constant temperature. I have heard that, but I wondered if it was true. 'Charging' it back up shouldn't be a problem. Just run the circulator during the summer, and put all that heat from the slab back into the ground.