Wool blankets are overlooked far too often as a great source of reliable insulation.
the old surplus blankets are great pure virgin wool.
1 hint:
Wash in cold water with wool detergent.
Then put 3 cups of hair conditioner in the rinse cycle with the liquid fabric softener, your blanket when airdried will be 80% softer and less itchy.
Wool is warm when wet but heavy.
It is naturaly fire resistant.
It is cheap and can be made into other articles.
Good stuff.
I recommed the old military surplus blankets with a tight weave. No particular country they are all good.
Mike