This is new construction so anything can be done. Do I need to put insulation under the basement slab so that I do not lose heat created by my radiant system? Also, what is preferred, water or electric radiant systems?

Yes and water.

thats what i thought. i just wanted to make sure. sorry bout the dumb question.

Another thing to keep in mind,
2 inch rigid insulation under slab, your ICF blocks may provide horizontal insulation barrier at slabs edge but if not add 2 inch vertical around the perimeter edge of slab.
Staple pex to foam add water.
Good luck,
Dan

i plan on using crete-heat. they offer 2" of insulation that I will probably do.

thanks

I highly recommend create heat. Very simple to install and makes install radiant even easier.

Thanks Angel of debt! CreteHeat is the best to use. Do you have any pics of your install?

Local/regional subsoil temps count- you may want to put down more than R8 (2"). Even the 3" CreteHeat might be worth beefing up in some areas.

If you use the far right column of table 0.2 on p10 of this document as a starting point and adding R5 to those number would be the starting point for a radiant slabs in the respective climate zones:

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

The values in the column are economic even for slabs that aren't being used as radiation for the heating system, using the typical installed cost of XPS and average utility pricing projections. Note that in the discussion starting at the bottom of page 11 the authors suggest fully DOUBLING the R values of the slab may still be economic, but that would depend on a number of other factors- a superinsulated building would run lower average slab temps than a code-min building, etc. Without building the site-specific building-specific heat loss & slab temp model, adding R5 to those numbers are probably economic everywhere, and adding R8-R12 isn't out of the question in buildings where the annualized BTU/square-foot delivered by the slab is high.

It should be possible to just add EPS layers under the CreteHeat to achieve the R-goals.