Iowa Resident here.
It's cold outside so we got a natural fridge. I also have a couple coleman stoves, gas grill and charcoal grill, so I can cook if needed. Also have a ventless heater in the garage so we can keep warm if needed. I'm going to figure out how to run the furnace off a deep cycle battery and power inverter this winter. I have a few deep cycle from my boat and camper that I bring inside each fall.
You might not need the blower. I wonder if you could take out the filters and see if there's enough heat flow through the building's ducts just from convection. A lot of old-time furnaces used convection, but they had enormous ductwork for the convective flow. Might be enough even with your small forced-air ducts to keep the joint from freezing. Make sure the heat exchanger overtemp thermostat is working, though.
Negative comments and precautions on this idea welcome.Incidentally, as a general factoid, "universal" motors from vacuum cleaners will turn over (with no load) on only 12V DC. I guess at about 36 Volts (three 12V batteries in series) one of those might spin up fast enough to be useful in certain applications.
You realize, of course, that any diddling with that heat system, whether you do it on your own or whatever, will probably void your insurance.
A side note on my old farmhouse, forced air gas, furnace in the basement. Got pretty hot in the two-story brick house in summer. One day I shut off the gas valve and pilot and rigged up the furnace so that the blower would suck in cold air from the basement and push it through the house. Worked pretty good --not quite, but almost like central A/C.
The house burned down.
Oh. I should add that after we moved out, it was scheduled for demolishing, and the local volunteer fire department torched it for a practice excercise.
Had you going there for a second, though, didn't I?
Terry, 230RN