Many years ago I had a rep that promoted ringing the exterior walls with baseboard which allows lower boiler temperature. Of course homeowners weren't keen on the plan but it does work. Unfortunately many see radiant heat and mod con's as a panacea but thermodynamics is thermodynamics regardless of the wiz bang technology. Funny that the Europeans are re thinking high mass cast iron boilers again. Maybe the old timers had it right. I install a lot of mod con's and I'll say right off the bat that sizing the boiler to the load and sizing the load to the envelope is way more critical than running copper fin tube and slapping a C.I. Boiler in ever was. I'd say that 90% of mod con/ radiant problems stem from poor or no calculations being done. Bigger is not better. I have seen far too many oversized boilers feeding insufficient radiant tubing. If the system is close it is possible to tweak thermostats and modulation settings. If it's way far off though, you are screwed.