UKH

Say that I'm camping in cold conditions, consistently -5 to -20. On some days the sun comes out and I can dry my bag, some days are spent tentbound waiting out bad weather and on some days it's good weather and I need to move up to the next camp.

On the days when I move camp, do I want to wake up and immediately compress the down bag into a stuffsack, to expel the humid, warm air? Someone told me that this was the smart thing to do, instead of leaving it in there to condense as the bag cools. I've done this for the last few years but I wouldn't mind heading other people's thoughts/experiences. I found that my sleeping bag seemed to lose loft over a seven day trip in Norway last April, fortunately the nights grew warmer as the trip went on.

Any hints and tips on maintaining loft over a 5 week trip welcome.

Robert

In reply to Roberttaylor:

Use a thin synthetic bag over the down bag.

The theory is that the dew point is then in the synthetic layer and does not dampen the down.

I think some manufacturers make such a system.

In reply to Roberttaylor:

Interesting question. I've also found the bag can lose loft on a long cold trip and in prolonged bad weather its just going to happen. Overall it depends how well you can keep it dry. I've found the main cause of the bag getting damp is from condensation on the tent inner, be it in water or frost form. I sometimes use my goretex jacket to protect it from the tent wall, and having a water resistant outer on the bag helps. Packing it up smartly as you suggest is a good idea, but if its a sunny and dry morning I'd normally have the bag on the tent to dry for a few minutes whilst packing other stuff. Open up the zip, give it a good shake, perhaps turn it inside out and a few minutes in the sun can dry it really quickly, especially at altitude. Having a black inner lining helps as well. After that then taking it out in the sun at any opportunity helps. They can also dry really well inside a tent if you are leaving it whilst out climbing as in powerful sun the tent can get pretty hot.

I think the overbag idea may or may not work, depends on how cold it is and where the dewpoint is. Could still be in the sleeping bag on a cold night.

In reply to Roberttaylor:

In past trips to alaska i have but a cheap thin synthetic bag over my down bag this stops water condensing on the outside of my bag and the bag touching the tent inner wich maybe wet. My friends have also done the same with a bivi bag.

In reply to Roberttaylor:

For those sort of conditions and pushed further in the Polar regions, Vapor Barrier Systems are de rigeur I believe:

http://www.phdesigns.co.uk/vapour-barrier-liners-vbl

In reply to Roberttaylor:

Compressing the warm, damp bag first thing in the morning definitely helps. A vapour barrier would stop it getting damp in the first place, but they're not particularly comfortable to use. You need to keep on top of personal hygeine as you'll be spending basically quite a long time in a warm and wet plastic bag. I use one, but just around my lower legs/feet as I find this is the most damp prone area of my sleeping bag for some reason. Talcum powder on my feet helps hygeine.

In reply to Roberttaylor:

When my brother was in the Army doing lots of ruffy-tuffy stuff he swore by a Goretex bivvy bag over the sleeping bag; said it made a massive difference to warmth and dryness.

In reply to Roberttaylor:

Sounds like a good idea pressing out the still warm humid air out first thing in the morning. I will try that out next time.

To protect my down sleeping bag against condensed water on the inside of the tent, I zip my fiber jacket over the foot end. Adds warmth too.

I have never used vapour barrier bags, and wonder if a large trash plastic bag inside at the foot end would be enough?

In reply to Stefan Jacobsen:

I do the same with a belay jacket thing, chucking it over the feet. Good idea r.e. a bin bag over the feet, might well be worth trying; I'll try a few things out this winter to see what works.

In reply to Roberttaylor:

I would have thought any vapor barrier system would have to be the full length of the bag so any vapor can escape out the opening round you neck and out to the open air. Otherwise its just going to escape from around the feet/middle and into the bag anyway.
I'd be interested to know if it works though, at the moment I think i'd prefer the synthetic light overbag approach!

In reply to pass and peak:

A bin bag over the feet works for me. Worth experimenting with. Wearing thin socks makes the experience less unpleasant. A bin bag with a very thin/non-absorbant fabric lining would be an improvement...

In reply to Roberttaylor:

Vapour barrier. Basically a waterproof sleeping bag liner. Wear long underwear (eg Helly). In the morning you will get out of the bag clammy / bit damp and almost flash dry. Sleeping bag stays dry. Works. You will need vapour barrier socks too to keep your socks and inside of your boots dry. The practice has been around a long time so do some googling - try looking under Alaska expeditions.