I never really thought about it in all our old units up through our 2002 class C. If it was cold the furnace ran almost non stop. If warm same for the AC. We thought it was good just to have ducting just to put some temperate air where you wanted it. And the enclosed basement made the floor less cold than our prior units.
But for winter camping we did not even try to use the plumbing. Always kept it winterized until the daytime temps were above freezing at a minimum.
This is a really good trend in RVs, actually having effective insulation.
Jim