When we first started planning works on the house, we had decided on using pellet heating, as we were told that with all the wood floors, the low-temperature, heat pump alternative would not be possible. Then Sace Bakan showed me wall heating and everything changed. It makes for a lovely room climate without cold spots, and much more efficient. Ok, out with the pellet boiler and all that storage, and instead, use a ground source heat pump with a horizontal collector field to the east of the barn (the green thing in the map to the right). It needs about 500 square metres, with 6 100m-long circuits buried between 1.2 and 1.4m deep (see my first draft below). But it's been tough trying to get someone to help us with digging this, and in the meantime, we've had all sorts of additional ideas from other people, including deep boring (too expensive) and diesel power/heat generators (too radical).
As a result, I've a slight pain in my arse, as I'd hoped we'd have this part done in August. So, now I'm considering one of the new, higher efficiency air-to-water pumps. Good to -20C, they say, but the efficiency varies with the temperature, ranging from 2 to 4.3 at best, the higher of which matches the ground-source heat pump.
It's a tradeoff between a quick, clean installation, with variable energy efficiency, or a longer, dirtier install process with more or less constant energy efficiency (assuming conditions are right underground). In either case, it would be nice to add a wood stove in the living room with a back boiler to help with the hot water supply in deep winter.