Your 8020 design I'm sure has lots more to it, but just talking about the hydronic heating, is way overthinking, too low a flow volume and obviously very expensive.
Technomad said:
The main thing that draws power with forced air heating, in my suspicion, is the motor that has to force air thru a radiator.
Yes there is a need for some air circulation to reduce stratification, but the water-to-air exchangers can just be strategically placed and low down, no forced air blowers needed.
A regular house style baseboard, or old-school radiators are the tried and true and much cheaper templates. But if you want to improve on that, save space and get more flexibility, I'd just enbed into the floor, no reason to go higher.
A square tube set above insulation flush with the floor where it is exposed but won't be stepped on would be enough.
Larger tubing provides some thermal mass buffering, with a higher hysteresis gap would require only periodic cycling of the transfer fluid, more efficient electrically.
In a tight well-insulated space, minimum ventilation just to keep humidity down, you'd be amazed just how little energy is required to stay comfortable, especially with the thermal mass effect allowing you to use lower temps for the transfer fluid.
Now, if the living space is allowed to go very cold, and you want a fast warm up, then a high-temp forced-air blower is appropriate, but only needs to run for the first 15-30 minutes while the slower loop gets going.
But a passive thin-panel radiator pointing right in front of where you're sitting would be almost as good.
A system that allowed you to recirculate the fluid to get it up to very high temp quickly, then scale it down to just periodic cycling once the warm space just needs maintenance, would give the most flexibility.
All of this is independent of the fuel used.
I think heating oil would be great but not available in many places, and even in New England, I'm sure difficult to just roll up in a vehicle and buy, because of that tax issue.
