When I built my barn I installed radiant hot water floor heat with long term heat storage. Started with a 6 mill vapor barrier, 2" hard foam insulation then 1800' of pex, 8" of sand on top of the pex and 4" of concrete to top it off. The entire structure was spray foamed. I keep the thermostat at 60 and it is a absolute joy to work in. The floor heat and spray foam was the best money I've spent. It has an 18' ceiling peak but it is warm where it counts. Winters here get a wee bit below 0. When I build my home it will have radiant floor heat.

RWebb, you have said that you already heat with wood (at least as a supplement), what about an outdoor wood fired boiler as your heat source? And by the way, the radiant floor heat is far superior to a wood stove as far a comfort goes, no drafts and with the air temp much cooler, the house is more comfortable, feels warmer.