"Theoretical" Question

You have identical homes with identical heat loss.
The homes have identical size and type storage tanks heated to exactly the same temperature throughout.
The boiler type and size are out of the picture!

These homes have different heat emitters.
Standard Fintube, Big old cast iron radiators, Low Temp Panel Radiators, Low Temp Radient in floors.
Will one type of emitter heat the home more efficiently? Will one home cool down faster?
Probable a dumb question but I'm curious.

Conventional wisdom says that the home with radiant floors will use less energy for two reasons:

1) With warm floors, people will be comfortable at lower overall room temperatures. Lower temperatures mean less heat loss through walls, windows, and ceilings.

2) Radiant heat results in much less of a warm air layer at the ceiling, reducing ceiling loss even more.

Ditto to what NoFo said.
I would add that a radiant thin slab would be more efficient than a radiant staple up system since it would allow you to use lower temp water.

I'm in line with Nofossil and Tom.
The concrete slab system is the better system. Thermal mass!
With a staple-up system there are to many "things" that can go wrong when not installed correctly
Also the quality of the Aluminum transfer plates plays an important role. Knowing that most people and installers probably will choose the cheaper ones above the more expensive ones, but guess if the pex doesnt' make good contact with the transfer plate the overall system efficiency drops significantly.

also important to recognize that the radiant system is a low-temperature system so the storage tank can deliver more 'usable' BTU's . When the tank that is supplying the hot water baseboard system gets down to 140 or so, the baseboards will be emitting very little heat into the room, whereas the radiant floor will still be heating the house comfortably with the tank at 120 or even lower. Radiant and storage is an awesome match.

I'm not sure what you mean by more efficiently? Lowest operating cost? Anyone of those choices would heat a properly sealed and insulated space to a given temperature with about the same amount of energy input. The building efficiency and the heater efficiency dictate the cost of maintaining the temperature within.

Radiant floors can be less expensive to operate IF you use lower temperature settings on the thermostat. Poorly installed without proper edge and underslab insulation they can cost more to operate.

Most important is the comfort and controlability. MRT (mean radiant temperature) drives comfort, cast iron rads and panel radiators come close to radiant floors in providing a comfortable MRT.

A radiant slab is also a storage system so it could have more heat "stored" but you had to put it in there first, and it had to be exchanged from somewhere.

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