I'm not sure how they build the trailers. I have owned 2 Bigfoot campers and one 5th wheel, spanning 1986 - 2008. I have looked at the construction of all of them, which was similar.
It is a molded top and bottom half, overlapped and joined at the trim line around the middle. After molding, they glue in sheets of styrofoam insulation using contact cement - 1" for the non-winter versions and 1 1/2" for the versions with the cold weather option in my experience. At many various places, pine or some other softwood is glued in place of the foam, this is for reinforcement or where things will be attached later. On the lower section of the camper, this is replaced by plywood, on my 2008 camper 1 1/2" of plywood. Then luan interior paneling is glued over that. Doors, windows, vents, cabinets are screwed to the pine placed there for that purpose. The cold weather option also included dual pane windows, worth the cost for the noise insulation alone.
This makes them: relatively watertight, as the only leaks are places where a hole has been cut or drilled (unfortunately often too many), there are no long leaking roof and wall joints. It also makes them difficult to modify, unless you are familiar with fiberglass work (then it is pretty easy).
I have said it before and will again: Bigfoot quality sucks, but it sucks less than any other brand. This is the RV industry after all. You will not have ice forming inside (maybe camped at the south pole?) - I've spent many nights in 15 degree weather, perfectly comfortable. I have not seen a more solidly built production camper, and I have looked. Better quality than my Safari motorhome, better than my Airstream trailer. Second hand sales prices are usually an indication. I sold my purchased new 1998 camper in 2012 for about 60% of what I paid for it. Try that with any other 14 year old RV.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear
