The Airhead is a winner for us. Being "dry" we didn't worry about freezing waste water. The installation was accomplished by OEV, running the exhaust fan out the old cassette toilet access door.
The hydronics also worked without any leaks for the first time! OEV reworked the valves so now we have four 2-ways instead of two 3-ways. On the truck circuit, we were able to heat the cabin from the engine while driving, or reverse the flow and heat the truck engine with the Webasto before starting. Once settled, we turned the valves and the Webasto was dedicated to the cabin circuit only. As we were on shore power at the campground, we ran an electric space heater during the day, while we were out, and overnight while sleeping. We fired up the Webasto during the evenings and early mornings. With both sources of heat, we had no trouble maintaining a comfortable inside temperature but moisture was an unavoidable issue. Running the fan while cooking helped a great deal but the large overhead Bomar window had to be wiped free of ice often.
Our plans for post-covid involve winter travel off grid so our take-away from this experience is that a supplemental source of heat will be required when temps drop this low and the electric space heater isn't an option. We have a Mr. Buddy but fear that would introduce too much moisture.
