To different animals to consider, Hydronic radiant versus baseboard, in terms of the water temp they circulate. With true hydronic radiant, you want to circulate water that is around 110-120 degrees. The goal is for the finished flooring surface to not exceed around 80-85 degrees. The problem with converting baseboard to radiant hydronic is that baseboard systems typically circulate 180-degree water. Running water that hot through a tight hydronic floor system can result in thermal expansion and contraction issues with the floor. For best performance, it usually results in having to put a the hydronic loop on it's own circuit separate from the the baseboard water. There are a few ways that can be accomplished. You might be able to get away with circulating 180-degree water if you did something like a below-floor suspended PEX system in the joist bays. Not "staple up" with transfer plates, but simply suspending the loop a few inches below the subfloor. For 180-degree temps, I'd prefer to use copper over PEX. But that's a whole new thread in and of itself. If the room is well insulated, or has no exterior walls, in-floor electric mats can provide enough BTUs to heat the room space. You'd need to consider the BTUs per sqft that those systems provide. An alternative would be in-floor electric for simple floor comfort warming, and something along the lines of a Runtal electric or hydronic Omnipanel for room heating. The Omnipanel can put out enough BTUs to heat a room.

I have radiant heat in my addition, forced hot air in the rest of my home. I live in central NJ and you are invited to see hot it works if you would like to come to my home. Yes, it does not respond quickly to temperature changes, thatÂs true, but the pluses make it worth it. I have it in a guest bedroom that is in a "slab on grade", that means a cement slab floor. On the coldest days, that room feels great! There is no sound of hot air blowing around. The air doesnÂt dry out your skin and nose. If the door opens and cold air rushes in, it remains warm. It just feels really nice. I have it in my bathroom. When I redid my bathroom and added stone floors, the room looked good but, was unpleasant to be in. When I added the radiant in the addition, I ran it in my bathroom too. I ran a lot of extra in the shower. It feels beautiful! I ran it under wood floors in my kitchen addition and it doesnÂt work very well there. The company said itÂs about 20% less efficient under wood floors, thatÂs not been my experience. I dealt with radiant tec in Vermont and they were very easy to work with. I dealt with David and I can really recommend him. I had a handyman install it after I figured out what I need done. The company helped a lot with the design. If anyone is thinking of doing it themselves, hereÂs what I recommend. I went through a lot of trouble trying to make a continuous run with the tubing from the water heater, to the whole room, and back to the water heater. That was very hard. Where I couldnÂt do it, my plumber made " joints". If I had known that I could have him do that from the beginning, it would have been so much easier. I thought the joints would be a problem. They are not. You do have to get a plumber to do parts of it, unless you know how to do that type of thing. The part where it was installed in the slab, I did myself. That was EASY. (IÂm a small, middle-aged woman.) As far as the thermostat goes, you can install it anywhere you like. It will read the temperature of where ever you put it. I got creative when installing it under my shower. There is a step up to my shower so there was a space under my shower, (this was not new construction). When I put it in the floor under the shower, the pocket of air under the shower, insulated it from the tubing and the shower was staying cold. HereÂs what I did. I opened the wall next to it. And made three "u" shaped runs of copper pipe and inserted them to the space below the shower. My stone shower feels like heaven on a cold day. It would be too expensive to do whole rooms in copper but it didnÂt run too much to do the shower. ItÂs well worth it!

You'll be needing a console humidifier or two depending on the size of your house. They're sold at Sears and most hardware emporiums. Smaller tabletop units run out of water too fast and are only good for small rooms/areas Here's a link to one at Sears. Here is a link that might be useful: Sears console humidifier

You say that energy efficiency is important to you. Resistive electric heat of any kind is about as INefficient as heat gets. Doesn't matter whether it's radiant panels or baseboard units or a portable space heater or an oil filled radiator or your carpet pads. They all produce heat exactly the same way. They all will cost exactly the same amount to heat a room to the same measured temperature. They all are equally inefficient. Now, the heater manufacturers will tell you that their heaters are 100% efficient. And they are. They turn 100% of the electricity coming into them into heat. However, the process that makes the electricity is not 100% efficient. Many power plants burn coal or natural gas. A coal plant typically converts about 35% of the coal's energy into electricity. Usually the remaining 65% goes up the stack as waste heat - heating the outdoors. A natural gas plant is a bit more efficient, typically 50% IIRC (I'm sure someone will correct me if these numbers are outdated or I'm remembering them wrong). Newer power plants better these numbers, especially cogeneration plants where they make use of the waste heat, but they still don't get to 100% or even 90%. And then there is further loss in the transmission lines to your home. So which would you rather do? Heat your house with half of the energy in a cubic foot of natural gas, or heat it with nine-tenths of that energy? A good forced air gas furnace can easily be 95-96% efficient. Even a cheap one is 80% efficient. No contest. A natural gas fired hydronic heating system is just as cozy on the feet as your carpet pads. It may not be quite as efficient as a forced air system (depends on installation) but will still easily be in the 80% range or better. Circumstances can alter the equation, of course. Maybe your electricity is generated not from coal or gas, but from falling water (hydropower) or even wind or solar sources. (We won't discuss nuclear energy so as to not "generate" controversy over that.) Or maybe you don't have natural gas service where you live. That leaves LP gas, coal, wood, and a few other fuels. In a sunny region, solar heating may even be viable for part of your heating needs. And of course there's electric heat. The most efficient electric heat choice might depend on where you live. In cold climates, the most efficient electric heat system is a ground source heat pump ("geothermal" heat). It draws heat from the earth. By the "100% efficient" standard of a baseboard heater maker, a GSHP is typically 350% efficient! That is, 1 kWh of electricity gives you as much heat as 3.5 kWh in a carpet pad like you are considering. The downside of a GSHP is usually a relatively high cost of installation. In a very mild climate, an air exchange heat pump will have almost as good a coefficient of performance (COP) as the GSHP. The colder it gets, the less efficient a conventional heat pump is. As you get close to 0 deg F an air heat pump drops to about the efficiency of baseboard heat or your carpet pads. A conventional heat pump is more costly to install than baseboards or carpet pads, but less than a GSHP. This is really just a start, and we're getting off topic here. I suggest you take this discussion over to the HVAC forum.