How I love a warm floor!
All you need is a supply of hot water, which we all have, in the way of a hot water heater.
Ditching the nasty old Suburban furnace was a delight and warm cozy heat to boot.
I first glued down 1/2" rigid foam, then cut troughs for the 3/8" pex pipe with a modified soldering gun, snapped in the pex, tossed down a laminate floor and presto, warm toes,...
There's also significant foam insulation under the floor.
Now to be fair, this won't fully heat the coach in cold weather, there just isn't enough floor area.
Supplemental heat will be by automotive heater cores and muffin fans.
Water circulation in both the floor and the heaters is by lovely little 12 volt
So that I haven't created a whole new winterizing chore, the in floor loop is isolated from the potable hot water via the engine assist heat exchanger built into select Suburban hot water heaters.
This way I can run antifreeze in that loop and never need to drain.