Insulation on the bottom is essential. No sleeping bag will keep you
warm if you don't have a closed cell foam under you. Second, most heat
is lost through the top of your head. If you want to stay warm get a
mummy style sleeping bag and keep the hood on. If you don't have a
mummy bag, wear a wool sock cap and you will be a lot warmer. The third
thing is you want a bag that will pass the vapor from your body. The
worst thing that can happen is it condense in your bag - you will find
out the meaning of cold. So natural materials such as down or the
synthetic insulation designed for the high end bags, hollifill,
thinsulate, etc. will work well for this. Good bags have double
zippers. By opening the zipper at the feet a little to vent the moist
air will also help.
Next, you've got to reduce air flow, including below you. A cot will
freeze you by letting air go under you if you don't have an Insulite matt
or something really warm under you. A folded up horse cooler has worked
in a tight. A metal gooseneck is like laying on a freezer if you don't
get some insulation between you and it.
-- "It is necessary to be noble, and yet take humility as a basis
"It
is necessary to be noble, and yet
take humility as a basis.
It is necessary
to be exalted, and yet take modesty as a foundation."
