/ Sleeping on Snow
I'm forever seeing pics of manly men battling their way up brutal alpine routes or FAs in the Greater Ranges, and they all seem to have closed cell sleeping mats strapped to the outside of their packs. Is this to be used in conjunction with an inflatable for extra warmth, or on its own?
If on its own, is this just a weight saving thing, shaving off the grams in exchange for being a wee bit chilly?
What do you guys do sleeping in these conditions?
You do know that snow is a good insulator?
"Ten inches of fresh snow with a density of 0.07 inches, seven percent water, is approximately equal to a six-inch-layer of fiberglass insulation with an insulation R-value of R-18."
What does that actually mean?
The ratio of water equivalent to snow depth. A US way of determining the density.
I suspect a US source for that quote.
Concentrate on the density of 7% water (density in g/cm^3), meaning the snow pack is mostly air. Air is a good insulator, so a bed of dry snow won't feel that cold. This is one reason why no-one clears their roof in alpine resorts; the snow is good insulation. It's also one reason why melting snow is hard, and why it's best to start with some water in the pot (the energy required to change state from solid to liquid is the other main reason).
Compacted or wet snow will have a higher density, and conduct heat better.
i.e. when you have lain down on it! :) So bury a water bottle in fluffy snow and it will probably not freeze over night, but try lying in snow and you get cold bloody fast.
Alex, I was sleeping out last night at -20: two mats, a Z-rest and 3/4 length ultralight thermarest - empty pack goes under my feet to they have two layers as well. It works well, never any cold from below, and if the thermrest punctured, the z-rest gives quite a lot of insulation on its own although I've never have punctured one.
I recently bought a multimat Exped mat (foam) and it's LOADS warmer than my thermarest. I know you can get warmer thermarests but the multimat is in a different league. I'll use both together when car camping (for extra comfort and luxury!), but will just take foam mat for everything else. I guess having it strapped to the outside of the pack for walk-in's etc is an advantage as well, no need to worry about it getting damaged then either. Also I forgot how nice it was not to have to inflate or pack a thermarest away, and to not slide off the darn thing through the night!
Actually, anyone want a thermarest? Not many holes in it.. :)
Bought a Thermarest Xtherm recently. Amazing. Miles lighter, smaller and warmer than my thermarest prolite 4, comes with free repair patches and isn't that crinkly (like the summer version is famous for. I've used it on snow directly and was toasty.
ideally have a whole arsenal to choose from.
for nasty crazed stuff where a puncture is a game-ender then i take a thermarest with either a slab of z-lite or a sheet of 2mm astro foam with a silver facing if its warmer than about -5c. this system packs tighter and still handles if punctured and combined with a pack and the rope. ropes, when coiled large and laid under other insulation actually insulate really well (on sleepless nights ive contemplated a special bag it would go in to make an intentional system...).
for valley-based stuff or where its just a night or two and/or the chance of puncture is minimal (ie not on cramped ledges etc) then an exped down mat is unbeatable. straight onto snow at -22c is taken for granted, tho a ground sheet or tent floor helps with moisture. only issue is they dont fit inside bivvy bags well. the x-therm does the same job with more noise.
a while back radson mentioned the nemo zor in a similar post. ive got 2 3/4 sized ones that combine well for serious cold, or alone to about -3c. they fold no smaller than an exped tho. for real cold they are a good option as still smaller than a foamy and hopefully less chance of puncturing 2 (...?).
if you do stick with the old school single-big-foamy; rolled up on your pack is a pain in the ass. modify it to fold concertina-style, or roll loose and line your pack with it.
a good system ive seen in japan is a z-lite (made of dimply foam) inside an astro foam sleeve.
another option still is a klymit mat (skeleton of an inflatable) inside the astro foam sleeve.
id keep an eye on that company as i dont doubt sooner or later a down filled version will arise (they are currrently messing about with argon inflation...)
oh yeah, have never punctured a mat but have done tents and drombags - affixing patches in the cold, gloves, cramped tents etc is optimistic.
Before Thermarests were invented I remember spending a very cold night indeed sleeping on a camping mat on a concrete platform in a bothy near Ben Alder.
Before camping mats were invented I remember sleeping on the ground for two weeks in a mess tent in Killarney. After a few days I discovered that sleeping on a towel made the ground much warmer.
Thermarests are the biz, but they weigh about twice as much as camping mats while taking up about half the space.
Think a z-lite or a ridgerest might be the way to go!
> You do know that snow is a good insulator?
> "Ten inches of fresh snow with a density of 0.07 inches, seven percent water, is approximately equal to a six-inch-layer of fiberglass insulation with an insulation R-value of R-18."
But snow is cold, it conducts lots of heat. It would not offer any insulation value by lying on it, surely? Hence the mat.
The mat you carry up in -35° is also cold until you warm it up, itīs a question of how fast it lets the heat escape from your body. Exactly the same as with snow which is infinitely better than rock, earth, metal, concrete, ice, water etc. But you need to ensure the snow doesnīt start melting so something else in between you and the snow is desirable. Even compacted dry snow has a suprisingly high insulation value (ca 0.5W/m/K) which is how Eskimos survive nicely.
Careful with that hyperbole, Eugene...
Snow will be a better insulator than rock, soil, metal, etc, but it will still conduct heat away, so not infinitely better...
I'm not suggesting that sleeping directly on snow is a great idea, just pointing out that it's not as bad as you might think, since even compacted snow is a reasonable insulator compared to other materials you might sleep on at the same temperature.
Fresh snow will compact if you lie on it. Consolidated, re-frozen pack snow won't compact anywhere near as much; that's why you can walk on the stuff without sinking in.
Even lying on compacted re-frozen snow, still over a night and using two mats you sink in quite a lot.
Also, I found it best to use my goretex jacket and down jacket on top of my sleeping bag as another layer. Using a down jacket like this is a lot better than wearing one in a sleeping bag.
I always used to sleep in hat and gloves as well.
Oh yes. But if snow is all there is...
In my experience a normal weight thermarest is inadequate for sleeping on snow, a full weight one is required in order to stay warm.
If you have a decent sleeping bag you can sleep quite well at very low temperatures on snow by putting all your spare clothes and gear, ropes, slings, rucksack, anything soft, and so on under you. Some kind of karrimat (closed cell) is nice but it's a luxury.
Better still is if you can find an area of sandy gravel, on a moraine or ledge. The coldest is on ice as it conducts better. Make sure that if you don't have double boots you don't leave your boots to freeze solid outside your sleeping bag. If you have double boots use the inners as a pillow so they help insulate and don't freeze either. It's quite possible to sleep happily if you are methodical.
So what did everyone use before thermarests? People like Hilary for example.
That was a rhetorical question by the way!
I rarely used any form of mat, simply because of the volume question, and I did a lot of bivouacking up to about 6000 m, often on snow. The coldest was in winter in Bolivia, still just putting clothing, ropes etc under you was all we did. I had a good Point 5 double sleeping bag though but the person I bivouacked with had a fairly light sleeping bag. A decent small tent or double bivvy bag is important too.
I was just reading Murray's book and the experiments with tarry paper but one big difference is that they didn't have modern down gear.
> So what did everyone use before thermarests? People like Hilary for example.
They were made of sterner stuff in those days, genuine comfort probably wasn't an option.
Murray has been mentioned above. He advocated controlled shivering to get through a cold night, a technique he perfected in a POW camp in Poland during WW2.
Decent exped carrimat, much lighter and much more reliable than a thermarest. Also cheaper, the only disadvantage is that they're bulky, I don't find inflatable mats to be comfortable but maybe that's just me. I slept in a ice cave on the mat, in a goretex bivi bag and -20c bag sleeping bag, wearing full clothing and a down jacket inside the bag. I think the down jacket made things worse, I should of put it over my head or something. I wouldn't like to bivi for more than one night in a row in the cold and damp!
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