We are installing three hydronic radiators up stairs, which will be powered by the hot water service (which in turn will be powered by a wetback on the wood fireplace).
I am running the pipework for the hydronics under the upstairs floor (ie in the ceiling of the ground floor). I have chosen not to use the special hydronic insulated tubing, but rather Sharkbite poly tubing with manually fitted foam tube insulation, as the ceiling space is insulated, thus all the pipework is inside an insulated space in an insulated building.
The pipework will poke up through the floor to meet the radiators.