Backup heat

Tom,
I respect your opinions on heating solutions within the State, and wantedto run by my situation and feedback. I am in the process of adding on asubstantial addition to our existing home (log home, 970 sq. feet on slab)and am reworking our heating system (currently just a wood stove) as theaddition will have a walk-out basement with a total of 2400 sq. feet. I amconsidering a wood boiler for a heating source. I would like to haveradiant heat in all of the new locations (roughly 1200 square feet), andpipe back hot water baseboard in the old house as well as run domestic hotwater off the system. I was thinking about the low temperature for radiant(roughly 90 degrees) and the jump from that to domestic hot water andbaseboard (which I believe is around 120 or greater?). Would I be betteroff running a dual system? One for the winter and one for the summer? Or,would it make more sense to move away from a boiler and go to a tanklesssystem? Cost of wood is reasonable for me as I get it log length, etc.,but it does not make sense to put in a chimney, boiler and the cost of bothof those if I can maintain a heating system with an on-demand that runsmore efficiently…looking for thoughts, and wondered if you had time topoint me in some directions…Set-ups I was considering:Wood boiler with pellet boiler back-upWood boiler with an on-demand propane or electric tankless back-up and foroff season timesTankless system period, probably propane?Is Geothermal a reasonable option in Maine? I heard contradictoryinformation as to the feasibility in our climate. (I am located in Machias).Any of your thoughts would be very helpful, and I appreciate your time!
Thanks,
Corey

Hi Corey,
I like the concept of a stand alone wood boiler with a tankless backup.Pellet backup is nice, but it is expensive. You could use a unit like aRinnai Continuum for a backup system. Although it is a water heater, youcould interface it with your hydronic loops via a plate heat exchanger. Itis relatively inexpensive and would be a good backup for summertime hotwater. It is, of course, tied to LP gas prices, which are not low, but if ahigh percentage of your heat is coming from a wood stove/boiler, it mightbe a good fit.
Another alternative would be a cold climate heat pump hot water heatingsystem.Only problem is that they are not yet available. And they will cost a lotmore upfront than the Rinnai will.
Tom