Winter/Expedition Sleeping System

I've never been able to avoid frost completely when it's well below freezing but I've got a WM microfiber covered bag and I'm pleased with it so far.

It's been my experience that under those conditions you're going to get frost simply because of your breath condensing in the tent. A well ventilated tent will help minimize that, but it won't eliminate it. The good news is that, since the temperature stays below freezing, you don't need to worry about moisture penetration from the outside, because you can usually just brush it off. Most of the moisture issue will be from the inside, because of body perspiration.

I have several suggestions as to camping in Mt Washington conditions:

– get a VBL liner or clothing. Personally, I use VBL clothing in camp, worn directly over my long underwear. This keeps in my body's perspiration and saves heat and water depletion during the long night. I can't wear VBL when I'm moving as I tend to sweat too much even at 0F. Take a look at RBH Designs for excellent VBL gear (including gloves!).

– seriously consider a much warmer sleeping system. You say you want a 0-5F sleeping bag, but unless you're sleeping in insulating layers conditions in the Mt Washington area can get *well* below that. You should have the ability to go to at least -25F (I've personally been out at -13F in the valleys, and Mt W can be much colder).

Also, take a good look at the MontBell UltraLight SuperStretch bags. I really like their ability to expand when necessary, either when you roll around, or when you're wearing extra layers. I was able to take their 30F bag down to about 10F this winter in Vermont just by wearing some medium weight synthetic jacket and pants.

Hi- I've had many nights that were frost-free-ish, at least as far as on the bag itself. There's frequently at least some frost on the tent wall, or poles on the single wall… But I'd plan on extra moisture. You'll be exhaling and sweating a fair bit of it in a relatively dry environment. Take the time to ventilate as well as you can (realizing that in some environments you'll want to dig in).

My 0F bag for about 10-15 years now has been a WM Antelope w/ Dryloft (now Windstopper, same exact material) and I love it. Still in great shape, never had moisture problems with the bag. I really notice it around the hood/draft collar area where my breaths condense / freeze / soak; Dryloft definitely helps there.

I'd also consider using a vapor barrier liner. One of my favorite items for winter trips. WM's Hotsac is aluminized, weighs about 4 ounces, packs tiny, adds warmth, and keeps your moisture (sensible and insensible sweat) out of your bag and out of your tent.

I think Roger is wearing off on me–I keep wanting to end my posts "Cheers."

Brad

Thanks for your comments everyone! They all make sense. My biggest concern with the sleeping bag is this: after a nights sleep yes I can brush off most of the frost, but there always seems to be a small layer of frost which adheres. Then I stuff the bag into its stuff sack. Given the compressions, the frost/moisture passes into the bag. Obviously if the trip is a short 1-2 days, this is really negligible, but if your one a longer journey then repacking a slightly frosty bag could cause problems. Has anyone used the montbell goretex 2 layer sleeping bag cover?

And to answer a previous question, I always wear my mountain hardwear phatom jacket and some down pants with which I hope to extend the range of the bag down to about -10 degrees.

Thanks again!
Britt

Hey again-
I think one of the important things to remember is that essentially all the moisture in the tent is coming from you. Some of it, yes, will be in the form of snow or damp clothing you bring into the tent (don't wear it to bed!). But much is from your respiration and perspiration (and that of your partner). You could use a full-on goretex bivy/shell, but there are a couple of things to consider. One is that they used to make Goretex sleeping bags, but they don't any more. Why not? Because the goretex wasn't breathable enough, and people were experiencing too much moisture/condensation build-up in their sleeping bags. Basically, I'd think long and hard before putting my bag in there. If the significant weight of the cover doesn't bother you, and you feel like it's necessary (and for you, perhaps it is…), I'll come back to the VBL. VBLs significantly minimize the amount of moisture/potential frost you could experience, and I've found them to drastically reduce the moisture in my bag. Regarding your extra layers, I think you'll find that the VBL will take you down that far. If you still need to use them, just drape them over yourself between the VBL and sleeping bag. Cheers!

Lot of very good advice here.

The DriLoft etc shells were a bit of a failure in the field: they restricted the exit of air and water vapour from the bag too much and you ended up with ice inside the bag : not a good idea. But a breathable shell with a very good DWR is very strongly recommended!

The use of VBL is almost essential at really low temperatures.

Brad suggested:
> damp clothing you bring into the tent (don't wear it to bed!).
Here I have to disagree a bit. We always dry our socks this way! In fact, the amount of water on *slightly* damp clothing is probably small compared to the amount you breathe out during the night, so under some circumstances it does make sense to dry it off overnight. But every situation is different.

We (my wife and I) have had some joy from using a double sleeping bag system. That is, each of us has a light personal bag or quilt, and over the two of us we then put an over-quilt. The over-quilt means we share a lot of warmth which would be otherwise lost. It also means that our personal bags stay very dry: it is only the shell of the over-quilt which gets damp. It works for us.

Cheers

"The use of VBL is almost essential at really low temperatures."

What do you consider really low? I've slept outside down into single digits Fahrenheit, but just layered clothing and a heavy duty sleeping bag. Does a VBL layer make a significant difference or just a minor one?

Someone once wrote: “In cold weather, condensation will tend to collect on the inside of the outer-most layer of fabric where vaporized moisture hits colder temperatures. When using a synthetic outer bag with a down liner bag, moisture will tend to condense on the outside of the synthetic bag with little reduction in loft of the down liner.” It sounds authoritative, and my experience backs it up, but I’m no expert. Re: previous post, “WM's Hotsac keeps your moisture (sensible and insensible sweat) out of your bag and out of your tent,” I’m not sure that all authorities agree that sweat decreases or shuts down when using a VBL. Also, it does not keep your breath from dumping moisture into the tent. A VBL bag prevents using additional clothing inside your bag, except for just putting it on top of the VBL, while VBL clothing allows you to add clothing over the VBL clothing.

Boy, this is all excellent advice! Thanks everyone. Based on everyones advice, I have decided to forego getting a sleeping bag without one of those weather resistant epic or gore barriers. Right now, I am leaning towards a marmot lithium (with my mountain hardwear phantom and down leggings!). I would recommend the mountain hardwear spire, by the way. Ventilation could be better (since there is no high low ventilation), but it is light and boy is this a bomb shelter. The atlass poles and the tent body combine to make a wicked shelter. Thanks again.
Britt

In very cold weatherI always zip up my Gore-Tex shell, cinch down the hood and put the coat over the foot of my sleeping bag. It keeps the frost on the tent walls from melting into the bag when the foot inevitably ends up touching the tent walls by morning.

Plus it adds warmth at the foot of the bag.

Eric

> What do you consider really low?
I have limited experience here; others should be able to give better answers. However, below 10 F seems a bit chilly, while below 0 F seems definitely cool.

Remember the sad experience of the Polar explorers in the early days. They used to end up with totally frozen reindeer hide sleeping bags, from their body moisture. They would simply lay the bags out on their sleds without folding them up for travelling, and shiver for ages when they got into them. keeping your body moisture out of the insulation in your bag is kinda smart.

Cheers

You can also reduce long term moisture build up by hanging your sleeping bag tautly between two skis or poles or trees etc. Doing this right after getting out of the bag, while there is still some stored heat in the insulation, will cause most frost on the bag to sublimate. Because it relys on heat stored in the bags insulation, it can be done in cloudy and even snowy conditions.

"My biggest concern with the sleeping bag is this: after a nights sleep yes I can brush off most of the frost, but there always seems to be a small layer of frost which adheres."

The question here is whether the moisture is coming from the outside or the inside of the bag. If, as I suspect, it's coming from the inside through body perspiration during the night then adding a cover is going to make it worse, not better. I'd suggest starting with either VBL clothing or liner, then see if you still have the problem.

Think of it this way: the inside of the bag is quite warm, and the outside of the bag is around ambient temperature, say 0F. That means the point at which water vapor freezes, 32F, is somewhere *inside* your bag's insulation.
This could explain the frost on the bag's outside shell.

Roger,
I know it sounds funny, but I enjoy winter camping in spite of the fact that I hate the cold.
I agree that keeping moisture out of the insulation is kinda smart, yet I never invested or even put forth any effort into using any VBL strategy. I do make it a point to change into dry clothes and "snap" the bag of outer layer frost and hang up for inner layer to dry immediately after getting out of it in the morning. There's a method to my madness, but I know there's room to improve on the method.
Thanks.
Chris

Roger said Remember the sad experience of the Polar explorers in the early days. They used to end up with totally frozen reindeer hide sleeping bags, from their body moisture.

Indeed, even as early as 1986! IIRC the Steger North Pole expedition's sleeping bags collected so much internal ice that they weighed approx 60lbs by the time they reached to pole. Granted those were not light bags to start with but most of that 60lbs was ice. They reported that it took hours every night to warm them up.

His crew used VBL's on the 1990 Antarctica crossing.

Someone once wrote: “On Denali, one sleeping system used successfully is the down inner bag plus the synthetic outer bag or quilt. (Note that the Mountain Laurel Designs synthetic quilt can expand to fit over even the largest expedition sleeping bag.) Neither bag has a waterproof / breathable shell. Rather, both bags have a water resistant shell similar to the Western Mountaineering micro-fiber shell. A certain amount of sweat will come off the body inside the bags, even if a VBL is used. In cold conditions, most of this sweat will go all the way through the down bag, and most of the way through the synthetic bag. Some of this moisture will turn to ice just below the shell of the outer synthetic bag, and some of this moisture will turn to ice on top of that shell. The ice on top we call frost, and can be brushed off. The ice just below the shell can’t be brushed off. Try to get rid of it by drying both bags outside the tent. But even if it can’t all be gotten rid of, for the same amouht of water in the bag, there is less loss of loft in a synthetic bag. The inner bag stays warmer, and the moinsture that is passing through does not turn to ice until it reaches the synthetice bag. Hence, the down bag is largely protected against losing its loft. Attach strong cords to both bags, and tie those cords down as if your life depended on preventing those bags from blowing away in the wind, because it does.”