Sounds like the under tile radiant heating. One type I saw on Holmes on Homes show, they weaved plastic tubes under the concrete floor that hot water circulates thru.I know my in-laws had what was referred to as "fussbodenheizung" in the whole house. Under foot heaters. I really liked it, I have no idea how efficient or economical they were since I didn't pay their bills. But it was a nice type of heat.
My wife thinks it weakens your immune system no facts just her experience. But I did like this type of heating.
This was in Weiher, Germany but I did love staying with my in laws just for the fact I could shower without freezing in winter.