We rented a big house on the slopes at Copper Colorado a couple of years ago and the only heat it had was in floor water.   It was very very comfortable.  Could walk around in socks and your feet were warm.   We found the control room for all the piping and it looked like a nightmare, but this was a 3 story house, it even heated the driveway and sidewalks. 

If I were to build a house I would do it.  I wonder why it hasn't  been done more before now.  It's not popular in this area.