Hey eamarquardt. No need to get upset. I'm not AT&T. All i did was try to get the correct formulas out there so that others could plug in their own numbers for their own campers with different sizes, number of people, thickness and type of insulation.
BTW, if anyone wants to take windows into account, a single pane of glass has an R value of about .3.
If you run the above formula a second time with the window R value and window area. then add the result of that to the result of your wall formula, you will get a better idea of how much heating/cooling you actually need. (remember to subtract the area covered with windows from your wall area before doing the first calc.
A few years ago i installed a phase change thermal storage unit (that's what these are usually called) into a residence a few miles from my home.
It was a packaged unit about 3ft cubed. The freon coils submerged in the water/ice were made of 3/16" copper separated from each other by only about 3". The inside of the unit looked like it was about half filled with copper!
This guy actually bought the unit to freeze at night when the outdoor temperature was cooler, then thaw during the hottest part of the day when the compressor would have to pump the heat up a higher thermodynamic hill. It didn't save him much money, but he was doing it as a green thing.
The V.A. hospital in downtown Detroit does something similar using a chilled brine reservoir of a little over a million gallons buried under their parking garage. We could chill that down to about 40 degrees overnight when our time of use pricing was close to free, then pump that water through our air handlers until it reached about 60 degrees during the day(any warmer and you lose most of your dehumidification).