I plan on building a 2500 sq ft ICF house with timber trusses enclosed with SIPs. The house will be in the hill country of central Texas. I am looking at using in slab radiant heat. Is this practical for the location? While we do not get cold cold weather it can get chilly.

Sure; use reset water temps though, and floor sensors.

that was too quick; the floor sensor will help prevent lead/lag, with reset water temps. Your water temps might be so low though that reset isn't needed, for instance if you only need 90 degree water, reset isn't very helpful. The floor sensors are definitely nice though.

Be aware that your floors won't be roasty warm. But they won't be freezing cold either. Slab radiant is fairly inexpensive though, so go for it!

Thanks Rob,  I am still in the planning stage. As I get closer I will probably ask some more questions.

Enthusiasm among HVAC traditionalists is still low for this, and many are just plain naysayers, but since you're in the planning phase explore the idea of ceiling radiant and using it for cooling also. Humidity control is accomplished by ventilation and dehumidifying the incoming air. If you're planning on using forced air for a/c you can reduce the size of your air handling system significantly. For starters check out these sites.   http://www.bekausa.com & http://doas-radiant.psu.edu/doas.html.