I am building a new house and using GEOTHERMAL as a heat source. I would like to use hydronic heat in my basement but I don't want to heat the entire slab due to cost.
Can I heat only a portion?
Will I need to put a brake in the concrete dividing where I don't want the radiant because of conduction?

Yes, you can just install it in a zone. Concrete has a transmission coefficient of 0.42, similar to earth, so you won't be heating the whole slab. Heat transmission depends on what is called Delta T. In a basement, you have a basic ambient temp and the outflow-Delta T- will not be that great. I don't think a true thermal break is necessary but you could use a fiberboard expansion joint that would do the same thing. Problem with thermal floors in basements, and other areas, is that they need to be uncovered and in basements, people like to put rugs down and that just insulates the floor from transmitting heat to the foot.

Quote:

---

"Will I need to put a brake in the concrete dividing where I don't want the radiant because of conduction?"

---

Yes, you will need to install a thermal break depending upon your local energy code.

Talk to your local code officials to determine what you need.

But generally speaking the 2009 IECC (International Energy Conservation Code ) requires a minimum of R-5 insulation under the entire heated portion of the slab and at least R-10 rigid foam insulation from the top of the heated slab to frost depth along the perimeter of any heated slab.