You could go with hydronic baseboard off your tankless, but you need enough of it to keep it from short-cycling the tankless like crazy on heating calls, and 12-16' probably isn't going to cut it. (The cost/BTU is pretty substantial with propane as a source fuel too.)
The min-output of most LP tankless is ~12-15,000BTU/hr, which would require the radiation to deliver about 1000BTU/foot at domestic hot water temps. Typical baseboard radiators rated at ~600BTU/ft @180F would require something like 220F (or higher) water to deliver that much heat in so short a section! With 120F water out of the tankless you'd need on the order 75' of baseboard to balance at the min-fire output of the tankless. If the min-mod of yours is under 10K you might be able to get away with 50'.
If you cheap out with 75' of fin tube you're still talking about a grand just in baseboard, add it all up with pumps and heat exchangers, expansion tanks, etc it turns into a real project with real expenses. You may get more bang/buck out of a ductless air source heat pump, which would also give you high-efficiency air conditioning, and a much lower per-BTU cost on the heating end.
Ductless heat pumps "play nice" with wood stoves, since they're fully modulating, and you can "set & forget" the temperature. Whenever the wood stove is keeping the temp above the setpoint of the ductless it's just standing-by, but when the room drops even a half-degree below the setpoint it'll start up at it's minimum compressor and blower speeds.
Is there any insulation in this place? Any flashing on the windows & doors (which would be necessary before blowing it full of cellulose or something)? |