I am considering an ICF two story with  a combination SIP/cathedral and stick frame over cold attic roof system  ( in Pa.) . For the purposes of my question, accept that I have a free lifetime source of firewood available on-site.  I would like to know what  radiant system or combination of systems would allow me the lowest operating costs. Keep in mind I want a system that I will be able to run  to provide survival - level heat when the grid goes down - frequently but usually not for long- using a back-up generator. Should I avoid radiant panels? What systems will allow the least run-time for such a generator (i.e. - between heat demand cycles.

Now that you have the sixty thousand dollar question, I should add that while I am a builder/ plumber/ DIY 'er,  I will be paying for an intelligent system design by proven providers when the time comes. Hopefully I'll find one among the responders.

Thank You for your time and thoughts.

With an ICF house, hopefully you'll be able to cruise through any short term power failures without need for backup heat by virtue of your house mass and insulation levels, especially if you are charging up a tank with a wood boiler as well. You can manually manage the firing control in that emergency case by turning the heating system off and on with a simple manual switch if you wanted to micromanage energy use; as long as you are below your room setpoints by a few degrees, on would be on and off would be off. If it must be automated, then you need to walk a balancing act between short, higher temperature demands and more room temperature swing vs longer, more frequent low temp demands and less swing.

Any hydronic source off of the wood storage tank could run on two pumps (boiler to tank, tank to radiant), basically, with a few zone valves and some low-draw electronics.

Since you have firewood and are asking about ANY radiant system: Have you considered a masonry heater? They are designed to provide long heat with short, efficient firings, like two firings per day, and they heat up well within a couple of hours - certainly adequate for survival, especially with your insulation level. You can also include a heating loop in the firebox to heat radiators or hydronic systems for areas remote from the masonry heater. The Masonry Heater Association is a good place to get info and has a list of certified heater masons in your area.