More great comments! In no particular order, some thoughts --
I am trying to avoid spray foam because it can't be removed easily in case repairs are needed. But I may have to use some of it for a few of the odd shaped holes.
I like the idea of zip lock bags full of fiberglass. I wonder if there are contractor-tough bags that can be sealed up -- something used for construction debris?
In terms of how cold, I know that no matter what I do, sustained temps below zero are out of the question. My realistic goal is to be able to tolerate nights that drop to about ten degrees, with days in the 30s or 40s. Those are typical late fall and early spring temps for the Eastern Sierra and Southern Utah, places where we often travel.
It won't be a 4 season trailer, but three and a half would be great! ;)
I should add that I recently installed an Ultra Heat heat cable on my water tank outflow line, which is the Achilles heel of the water system. I will be posting a report on that project soon.
