There is a lot of discussion, not only on this forum, as to what the "thermal" packages consist of. It doesn't matter that they are called Polar, Glacier, Arctic, whatever, this does not mean that you have a four season trailer. Usually a cold weather package from the manufacturer means there is a 2" duct running off of a heater duct going to the tank area. You'll only find this when the bottom of the railer is covered by coroplast. You will unlikely find any type of insulation under the frame, fiberglass or otherwise. You would do well to find out just exactly what kind of cold weather protection your trailer was built with. You may be shocked to the answers you get, but not nearly as surprised as you may be when you wake up on a sub-freezing morning. Your best bet for freeze protection is going to be tank and pipe heaters, and I doubt you are going to find any of that factory installed.
2013 F250 XLT
I now have a Keystone Outback, but I try to help when I can.
Bitter Gun Owner