Hi Greg,
I used hydronic radiant heat in my shop. My Wife and I laid out the tubing ourselves before the slab was poured. I will tell you first off that it is a really nice, comfortable kind of heat. It does not warm up quickly. It really is not difficult to set it up with different zones, so that different rooms are heated separately. Most professionally installed systems use a boiler as a heat source because you can acheive higher continuous temperatures than with a water heater. This means that the heat sours has to run for a shorter period of time, making it more efficient. I used a tankless water heater for my heat source. It works fine, but it is slower and is therefore not as efficient. I pay more to heat my shop than I had anticipated.
A few basics you should know. Radiant heat works by heating the floor - transmitting the heat up through the floor to you. Floor materials that act as insulation are not well suited for this, such as wood and carpet. If you must, wood would still be better than carpet. You can retrofit a house for radiant heat, but the best way to do it is to lay out the tubing on top of the wood subfloor, and then pour a thin layer of cement just to cover the tubing. This would raise your floor by 1" to 1 1/2", but really makes the radiant work for you. The next best option is to use pre-made wood and metal panels with grooves cut in them for the tubing. These are laid down on top of your subfloor, and then your regular flooring over the top of this. The least desirable is to apply the tubing from beneath the subfloor. They make metal panels that fit between the floor joists and have grooves in them for the tubing. You run the tubing in the metal panels, and then staple these up in between the floor joists, then you insulate below these to keep the heat moving upwards.
Please feel free to ask questions.
Scott.