We haven't yet camped in conditions you guys are talking about. My four years at Hill AFB south of Ogden were pre-RV. (I used Utah's winter mountains for skiing back then ... except for hand netting cisco in some high Uinta lake in February!)
However, a lot of the comments above are addressing how to keep the inside of your RV (a trailer in this discussion ... but we have a small Class C) livable and everything as much as possible still working with inside temperatures being low during nights or when absent from the rig during days. We do the opposite when camping in our RV during low outside ambient temperatures. We keep the inside comfortably warm - so freezing pipes/tanks and moisture saturation problems don't become extreme problems.
We set the propane furnace no lower than about 55 degrees during nights. This keeps things simple and problems minimum inside the RV during cold outside temperatures. We find it easier and more comfortable to improve electrical and propane capacity than mope around in chilly interior temps or fix broken stuff from the impact of temperatures inside not being able to adequately counter what's going on outside.
Here are some ways to keep inside temps higher and facility problems lower:
- Plenty of RV battery capacity. We have only 200 amp hours, but in Utah falls and winters probably at least 400 amp hours of capacity would be a minimum so as to provide plenty of propane furnace run time.
- Have a way to maintain this capacity under all conditions, including low-sun conditions. Ensure this by using a high capacity charger with a built-in boost voltage range.
- Power the charger with as small a generator as will power it. (We use only a 650 watt ultra-quiet, gas sipper Honda to power our RV's 45 amp battery charger/converter for 5-6 hours on only one-half gallon of fuel.)
- Do this generator battery charging as much as possible when you're most likely to be using a lot of electrical power ... this probably means in the evenings when you also may want to be comfy before going to bed with the propane furnace cycling so as to maintain, say, 68-70 degrees. This prevents battery power from being used during this time of possibly heavy electrical loading. Save the battery heavy lifting for the rest of the night to keep the inside of the rig at, say, 55 degrees using the propane furnace.
- Use fast charging batteries. Ours are AGM so as to help keep charge times shorter when the generator is running.
- Use heated tanks, so they're kept warm through forced air from propane furnace use or kept warm electrically by large batteries combined with generator charging. Our tanks are electrically heated with 12 volt pads so there's no power conversion losses from an inverter.
- Consider use of a replenishable desiccant stack to absorb moisture continuoulsy inside the RV while camping in cold weather.
- Have a backup way to charge batteries in case of equipment failure. We can idle our main engine and use it's high capacity alternator for emergency battery maintaining or for faster battery charging than the charger/converter and small generator combination. We also have a built-in generator that in an emergency can run at least two electric heaters plus charge batteries in case of furnace system failure. Also carry along a portable battery charger as backup to any built-in battery charger/converter.
- Have plenty of propane capacity onboard. We have 18 gallons for only a 24 foot RV, but many RV's have propane capacity of 23 gallons or more.
- Here's an idea on cold weather ventilation I haven't figured out how to implement yet ... ventilate in cold weather from down low in the interior instead of up higher through open windows or roof vents. Cold outside air should be exchanged with the coldest inside air - not by losing precious already heated interior air through window or roof openings. Perhaps a vent that can be opened/closed and is mounted low in the entrance door could be useful for air exchange without too much impact on interior warmth?