This is not entirely up to date but shows part of my system:
Here you can see part of the underfloor heating, before the concrete was applied. Those two wooden square things are actually two of the three openings down to the 290 USG tanks, as they are located below the floor you see here. The light tone is because I used this picture for printing, to see where the tubing is. Carpenter needed to drill fasteners into the floor and it is not really helpful if he perforates the underfloor heating pipe!
And in the existing floor, which was there already, awfully hard concrete had some canals made for the tubing:
I am not sure if this is getting off topic or not, but I really think the actual temperature one keep does depend on how you get the heat. Even if the air is measured at 70F, then cold walls, drafts and even the humidity means something, as well as what activity level is performed. Doing office type work requires more heat than if running around and cleaning the house and so on ...