Hurrah for insulation!
I can say this here (because we are all Fun Finder Folks, so this is not bragging) -- our trailer was really well insulated. There is a thick layer of styrofoam on all sides and on the roof, and the bottom has a thick layer of fiberglass. So even though it was in the 20s outside at night (and snowing hard), we were quite comfortable inside, even without running the heater. Yes, we dressed warmly, but still -- that is amazing.
I am not sure that all other new trailers are as well insulated.