You can get the dual pane windows if you order the hauler to your liking. Most dealers will not order them that way. At least out here in CA. As far as the Polar/Arctic packages, they are more of a marketing scheme than anything else. They will throw a little bit more insulation in and maybe a tank heater along with a furnace duct to the underbelly. With the poor quality of construction and all the gaping holes with most major brands, the extra packages probably do very little to nothing to keep you any warmer.
