We have found the oil filled radiators work the best. Have wintered in our 40' fifth wheel with out using the furnace. Had 2 in the living room and one small ceramic in the basement on a thermostat set at 50*. While we did not experience the temps you did, we did see 7* with a -22 wind chill.
2021 Ram Limited, 3500, Crew Cab, 1075FTPD of Torque!, Max Tow, Long bed, 4 x 4, Dually,
2006 40' Landmark Mt. Rushmore