I insulated the inner walls of my older all metal trailer with 1/8"
inch thick foam. Type used underneath automobile headliners. Worked
wonders with condensation issues I had. Delays the cooling at night
and moderates the heat in the daytime. I open it in the morning and
have no moisure to speak of on my glider. It may still sometimes occur
but it has greatly helped. Before, with the bare metal, it was
terrible, like a glass of iced tea in the summer, dripping wet walls.
I am down in Florida though so your milage my vary. Humid for sure,
but not as cold although our low will be in the upper 20's tomorrow
night.
In addition to this foam liner I only have a solar powered vent fan.
Craig