Camping well below freezing - Sweden over winter

I added a water circulating system to prevent pipes freezing. I believe he may need something of this sort. Also tank heaters and double them up. www.ultraheat.com At -35 I would have a second method to provide at least half the BTU of the main furnace. Could go through a lot of propane so best to have an external connection to a large tank. Propane tank may also need electric heat as it will fail to vaporize fast enough as you get into this temperature zone.