Supplemental heat to "basement"

Heres a kinda of solution that has worked for us and a few others. Very dependant on your situation in regards to where the heat has to go.

We needed to insure some heat in raceways where water lines ran in fairly isolated parts of the coach where although they were heated by the furnace they were marginal when it got down to minus 20 etc. I fisched incandescent rope light through these raceways and areas. Heat tape is 18 watts per foot, much more than I needed or wanted. Not to mention, heat tape should be attached to something like a pipe etc. Incandescent rope light is 6 watts per foot, gets warm, not hot and is easy to fisch. Essentially, every 10 feet is like a 60 watt bulb. This approach worked for our concerns. Maybe it would work for you.

Good luck.

PS, don't get the LED rope lite as it is only 2 watts per foot or less.

I would think about installing about a 1 inch thick foam board. Attach it to under belly with screws so as to be able to remove it. The think underbelly cloth does not offer much insulating value.

All those heating elements would likely require more current so you may have to step up to a site with 50 amp service.

We use heat trace at work but smaller heat tape should work for piping. Just make sure to put insulation around it so the heat is held in. You'll likely have to have a controller to turn the heat trace/tape on and off by temperature.

We used separate Thermal couples at work. Don't know how residential is but Thermal couples placed at different areas on the piping will help the controller turn the heat trace on and off as needed. The control may even be able to control different zones.

Tanks can use heat pads but will need insulation as well.

People who live in mobile home trailers do this every year for their piping.

Also if you are using 120VAC, you'll need to be permanent. Don't know if a 12V system would provide enough wattage.

Good luck.

Ultra Heat has 120V AC heat pads for waste/fresh water tanks.
They also have 'heat insulation' for piping.

Are you opening cabinet doors when temps drop that low so RV furnace air can circulate inside cabinets?

Also check RV Furnace discharge plenum....might be a 'space' opening to add another duct. Route it to area where plumbing lines run (next to outside wall)?

Stationary........skirting around outside of trailer with a 100W light bulb or two under trailer.