[pct-l] To waterproof or not to waterproof (ye old sleeping

[Paint Your Wagon]

Chris,

Thank you for the words of wisdom. After a number of rereads, the light bulb 
came on.

I spent 3 months in IL,
last winter,
camping in my 3 season tent.
I used a Thermarest Ridgerest closed cell foam mattress,
a Thermarest Trail Lite inflatable mattress,
the subject sleeping bag,
a synthetic inner bag liner,
and a fleece outer shell/liner,
which was meant to be used as an inner bag liner for a car camping type 
rectangular bag.
I wore my base layer,
a down vest,
and some times a head cover,
but that was rare.
I was toasty warm.
I repeat- I was toasty warm.
That was the point in me camping in IL,
in the winter for 3 months.
Well, part of the reason anyway.
Everything worked together and breathed.

Fast forward-
I left Mammoth Lakes with a storm inbound.
Andy, the hostel manager,
gave me the mylar bag as he thought I might get into trouble.
It was very cold (I had been off trail for a month),
and, it was late September,
and, I was heading north to Sonora Pass.
As it turned out,
other than the one short weather storm system that I encountered,
the weather was sublime for the rest of my hike.
I bailed at the pass because of a torn tendon.
My fleece outer bag shell/liner, had been sent home in a shake down.
Damn, just damn.

Thanks again,

<>Paint<>

Chris wrote:

>>> Hi Paint,

The source of moisture is YOU, and that moisture needs to escape to the
atmosphere. Any attempt to trap it inside your sleeping bag will soak it
with condensation, rendering it uninsulative. This is especially a problem
with down (synthetic deals with getting wet a bit better).

You basically used the mylar blanket as a vapor barrier, which will
temporarily make things warmer, but not for long as condensation builds up.
A truly waterproof coating on the outside of your bag would do essentially
the same thing. (Incidentally, a DWR (durable water repellent) coating
wouldn't make a difference in this case because it doesn't trap vapor.)

Some folks use a vapor barrier INSIDE the sleeping bag for additional
warmth. It was popular back in decades past (see The Complete Walker by
Colin Fletcher), but not really anymore because all that trapped body sweat
makes you stink. You could use a mylar blanket in this fashion for extra
warmth, but you will wake up sweat-soaked.

I can think of much better ways to sleep warmer. Any combination of these
would help:
- Insulative sleeping bag liner
- Breathable bivy bag over your sleeping bag
- Sleep wearing more layers (down puffy jacket!)
- Additional insulation underneath

That last one is a big deal. A lot of folks overlook how much heat the
ground will conduct away from your body. You can sleep in a 0-degree bag
and still get really cold if your sleeping pad doesn't also insulate well.
Adding a closed-cell foam pad underneath your usual sleeping pad can make a
big difference.

Chris <<<