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Sleeping Sysytem

I can hear him thrashing from here. What's all that nylon rustling about...? Read on and learn how JB sleeps during a winter camping expedition and a bit more about just how anal he is.

By Vincentoli Blanteev, your cybor-spaced mountain correspondent.

Well, well, well....the day is over and now it's time to crash. If there is one thing that HAE receives more questions about, it's our sleeping bag systems. After all, most backpackers have dealt with the other equipment already, but don't regularly spend a week sleeping on a sub-zero wind swept mountain-side. So in this section JB will cover some details about cold weather sleeping systems, developed more or less along theoretical arguments and principles that the reader can adapt to their own situation. And lucky for you the good doctor has decided this time not to inundate the reader with a bunch of Mathcad files modeling Carnot cycles or exult the virtures of three dimensional finite element analysis of the Fourier Heat Conduction equation, as he has been known to do in the past. Here the development here will follow more along qualitative rather than quantitative lines, and we'll toss in some widsom from the school of hard knocks too. In short, no equations, but empirical evidence will be cited.

The fundamentals at work are heat transfer due to conduction and convection, evaporation, and requirements for a comfortable sleeping environment

When sleeping on the ground, first and foremost the largest heat transfer term is the conduction to ground. It stands to reason that the more insulation between the camper and the ground, the lower the majority of heat losses. Unfortunately, only a finite amount of insulation can be expected to be carried in a person's backpack. The choices are rather limited too, insulation between a hiker and the ground generally falls into four categories; foam pads, air mattresss, sleeping bags, and various nylons in the form of tents, tarps, ground clothes, vapor barriers, etc.

JB's 1st supposition of backpacking insulation states that foam is a far more effective insulator than a down bag at the high pressure points found underneath a sleeping hiker. There are two results of significant consequence. First, a lightweight sleeping bag is selected, typically a 26 oz. goose down bag. No use adding goose down underneath just to get more on top, although some manufacturers make bags with more down on top (JB and HAE hikers in general, don't like these kind a bags because that extra down on top is not dual-use). Second, JB uses full-size foam pads both above, and below a full-size air mattresss, the "layers of 3" cliche is validated in the shear comfort of that foam-air-foam stack. Let's take a look at some actual performance results from the great white north.

Back in the eighties, four hikers stood on a frozen pond way up in the green mountains of Vermont. As usual for these guys it was January, and it was hell ass cold. Time to build a shelter, so they did (DAWN OF NEW AGE ARISES). Over the course of two days the four man igloo was constructed. Inside the floor was the shovel scraped bare ice of the pond. The igloo was then used until the trip ended 4 nights later. At the end of the camp the nylon ground clothes were pulled off the ice, and there were four neat human body sized indentations in the ice, corresponding to were each hiker slept.

JB used a foam-air-foam stack with his tent as the ground cloth, so that's two layers of nylon ground cloth to go with his 3 layer stack. After 4 nights the indentation in the ice for his back was maybe one inch deep.

Both Tim and Mark have a foam-air stack, the gortex bivey sack layer and nylon ground cloth underneath. The indentations for these two hikers was on the order of 3 inches into the ice.

Fife had a single thermorest air-mat, a gortex bivey sack layer and nylon ground cloth underneath. No foam. He sank way into the ice, sculpting out more than a half foot deep custom sleeping position.

Even accounting for the discrepancies of weight, size and sleeping times between the hikers, it is clear that JBs foam-air-foam stack is a formidable comfort generator. Essentially no heat is lost downward melting ice, or anything else for that matter.

JB's 1st secret of sub-zero sleeping systems: "foam...air...foam, and you'll be sleeping like at home!"

some common hae expressions of the first law are:
"In foam we trust"
"Better living thru foam"
"Nothin' but foam"

JB rants

JB's second tenant of cold weather camping pertains to using only down insulation inside the down sleeping bag. At 26 onces, the bag is woefully inadequate below 10 oF. So JB stuffs the inside with his down coat that covers the legs and lower torso, a down vest covering the upper torso and head, a down hood around the head, and down boots on the feet. At sub-zero temps it is important that a down vest be used inside the hood directly around the head. Poking ones face through the arm hole puts three layers of down 360 degrees around the campers head, that's counting the down hood and the bag itself. If it looks like it's going to be a whole week of killer sub-zero weather, a second light lightweight vest is stuffed at the trailhead with the sleeping bag to really fill in the mid-torso area between the down coat and the down vest around the head.

All this down on top with the foam-air-foam stack below means that this sleeping system is toasty warm at temperatures below -20 oF. The down stuffing performs two important functions. As an insulator it negates the effect of convection cooling off the top of the sleeping bag. And as a baffle it keeps air from moving in and out of the bag while the sleeper is moving and breathing. There are other ways to keep air from moving inside a sleeping bag, like constrictive drawstrings or vapor barriers, but stuffing a down bag full of down stuff works best for JB. The down on top is lightweight and movable, the sleeper can move around with freedom and lack of weight from above.

And the hiker will sleep well knowing that all the down accessories serve double duty, since the jacket, vest, hood and boots are used both in normal day-to-day camping activities as well as in the sleeping system. That's why JB carries a sub kilo down bag in the first place, with all those down clothes to stuff inside as needed, the total down weight of the sleeping system rivals the heaviest down bags available. But unlike a heavy down bag, which ain't good for much besides sleeping, JB uses all the down clothing for just about everything else. The down jacket is put on under the snow parka at the end of the days hiking, if it's warmer then the down vest is used, and both vest and jacket are used when it's hell ass cold out. The down hood is used around camp when it's to cold for the hiking beenie, and the down boots are the first thing slapped on at the end of a long hard day in the hiking boots.

In fact if anything the biggest issue with the system described is that it is too warm. Any kind of sweating means that layers need to be pulled out of the bag quick. First the long underwear and socks get pulled. The same effect could be achieved by pulling the down coat out of the bag, or maybe the down vest, but removing long underwear and socks is always less restrictive and therefore the first choice. Even once the right combo inside the bag is found, things may still need to be adjusted to make sure moisture does not build up inside due to sweating. Pulling the bag taut or moving the down vest to one side allows ventilation, a subject that will be discussed in exhaustive (...sic) detail shortly.

JB's second postulate: Impeding blood flow is the number one way to freeze your extremities off inside a sleeping bag, use only down clothing items inside a bag for added insulation.

Down accessories insulate and stop air flow without being constrictive. That's because since just about any clothing items put in a sleeping bag tends to restrict movement and increase pressure points, so whatever you have in there, it might as well be down, since that is the most insulation for the least amount of constriction.

For example, let's start by talking about wearing down boots in a sleeping bag. It is an all around good deal, particularly if you make sure that the sole of the down boot is bigger than your foot by a good bit when you buy them. First your foot (no socks!) is insulated by the lightest stuff known to man, down, so your foot is free of the constrictive pressure of wool hiking socks. Second, the sole of the down boot is stiff, protecting your toes from the weight of the bag above, and even more important, floating your heels slightly up in the air, keeping the heels off a high pressure point.....aaahhh.... now that does that feel good after a tough day in the boot! Not having a sock makes it easy to hand warm the foot too, if needed. Don't forget to clean and dry the bottom of the boots with your hands before jumping in.

Next is the down jacket, placed above the legs and lower torso. JB likes to put his water bottle (500 mL), two power bars and two granola bars, a veritable "in-the-bag breakfast" in one arm of the jacket and place between the lower legs. The down jacket arm keeps the cold water bottle away from the legs, and anchors the jacket in place (Tim would be swapping out his plastic for that fancy thermos if things were really getting snappy sub-zero cold). So JB is actually getting three uses out of the down jacket. It's a down jacket (used mostly under the gortex snow parka, the lightweight nylon shell wouldn't handle the abuse of being exposed in the brush or camp for long), it's insulation in the sleeping system, and it's an insulated sack for water and munchies. Start shifting the down jacket to the side or just pull it out of the bag (put the water bottle in a vest pocket) if the temps start going above 15 oF, it is such a thick layer of killer warm insulation that one can start sweating under it real quick.

Next is the down vest, JB usually packs one vest, and pulls it over his head under the down hood, sticking his face out one of the arm holes. On occasion he has carried a second, lighter vest, usually when the weather report is for an extended arctic air cold spell. The second down vest completely fills in the mid-torso area between the down jacket and the primary down vest wrapped around the head and upper body area.

The down hood is detached from the down jacket. It is put on first, probably because it can be worn around camp before lights out.


So the process of getting in the bag involves getting in quickly, because it's a very cold process to get in a bag, and then going back to take care of details once warmed up a bit. The critical task is to get out of your wool clothes and into a zipped up bag as quickly as possible. Get halfway in bag and pull off wool clothes. Fold up put right where your head rests, fat foam on top completes the pillow (avoid put your sleeping bag enclosed head on wool, nylon, gortex, or a Thermorest air-mat, use foam only). In long underwear and socks put on down boots and hood. Climb most of the way in bag and maybe zip up bit.. Pull in down coat and position, don't forget the water bottle and food. Pull in down vest. Lie back and zip up bag.

Now that's much warmer, so slow down, and if you are not holding your breath then you are breathing hard from the effort so make sure that you breath out the exhast port. Try to avoid breathing into the bag as much as possible. Sometimes it can be difficult to tell the difference between breathing through baffling or breathing in the bag, so the best way is expose your face to the ice cold air, and then gently and slowly as you fall asleep move the down vest and hood to baffle that ice cold air, until comfortable breathable air temp is established as you nod off.

In very cold weather, moving around to straighten stuff out really cools off a bag, because the movement ventilates the bag. The classic trick to cope with this is to hold your breath, seal the exhaust port, move around like crazy taking care of whatever needs to get done, like the tasks covered in the next paragraph, and then stop moving when sticking your face out for more air.

Open down hood clasp, pull off beenie hat and flashlight band (oh yeah forgot that you were wearing that stuff, didn't yah? Don't forget to turn off the light). Pull down vest over head, under the down hood, sticking face simultaneously out the concentrically aligned arm hole of the vest and the sleeping bag vent hole. Relax, rest, don't move until you are warmed up. Then increase ventilation to stabilize.

Once warm, it's time to take care of some final housekeeping. Unzip the bag slightly so you can get at your feet. Pull the down boots and the remove the wool socks..ahhh... very nice. Pull the tight long underwear waistband, JB's favorite trick is to pull one leg of the long underwear, and soon he will report back on an investigation to find (or modify) long underwear with buttons or a maybe a zipper. If the remaining underwear briefs have a loose waist band, then you are done, slap on the down boots, zipup and sign off. Otherwise you probably should pull that waistband off also. At temps above 20 oF or so, this two step process can be reduced to one.

Let's talk about a couple of things that the second postulate says should definitely not be worn in a mummy sleeping bag, unless you know it will work for you. The list is long, at the top are tight elastic waistbands in underwear, tight armholes in underwear shirts, and sleeping in bag while wearing...say...heavy wool clothing. Another is any type of inner bag, such as a vapor barrier, cotton or fleece inner bag, etc.

Yes, there are people that don't have problems using inner bags, but JB is not one of those lucky types. JB does not recommend the use an inner bag unless you know that you can handle the increased pressure and movement restriction. Also remember that the slight increase in pressure caused by an inner bag may not be a problem at +5 oF, but could lead to a hell of a cold night at -20 below.

Editor's Warning... It goes on like this for a while. Now you know what we have to put up with. Sleeping Bag system...? More like "Windbag system".

Sleeping on your side is an example of a way to develop very constrictive pressure points. Your arm on the bottom might not be cold, but the reduced blood flow from continuous pressure, if continued over a long period, will result in permanent dehabilitation of that limb. Most hikers sleep on their back, using the side and face positions for short periods of time only.

Corollary to JB's second postulate: Don't be dragging your down bag through the nasty thorns while stumbling around drunk & stoned.

Not that said event has ever occurred on an HAE expedition but the corollary essentially states that if you have not established a shelter sufficient to operate a down sleeping system, then there is a significant probability that it's SOD (shit outta down) time. As one scout master once told my dumb-ass, "your freezing your arse off because you took out your down bag in a rain storm, so now you have a lot of useless wet down!?! hah! hah! hah! (yes, of course he was laughing at me....and, uh... .oh... here's the peanut gallery chiming in too). Don't think a tent or tarp always constitutes a "shelter sufficient to operate a down system," just because it seemed to work fine in the past. Thoughtlessly taking your down out in a tent or a tarp that has been hastely rigged up when it's 35 degrees and blasting rain and sleet, or worse blasting rain and sleet in the forecast, you know, the forecast that you didn't have when the shelter was being built, could be one heck of a big mistake (see HIGH IMPACT CAMPING LOSES IMPACT). Make sure that some effort has been expended before to insure that you don't wake up shivering in the morning with a bag full of water soaked down, or my favorite, water dripping right on you (...thwamp... what was that dripping?... thwamp... hey that's like right on my... thwamp... down bag!) like your in some kind of ancient ritual testing the relative skill level of ones patience. In summary, remember gomerettes, the only dry secure place for a down bag is in a plastic-bag lined heavy-duty nylon stuff sack, unless said dry secure sleeping system has been constructed. Note that if the system integration includes "JB's classic 50 foot clothesline," the letter of the contract does, in fact, state that NO insurance money will be paid to the policy holder if one goes off hiking, singing or a' partying at the campfire whilst said precious down sleeping bag hangs exposed to a lashing rainstorm.

JB's third postulate is all about classical thermodynamics: "A sleeping system in cold temperatures can be modeled as an evaporation-condensation cycle."

Not exactly the piece of the refrigerator cycle one would select for one's own fate is it? This most nasty moisture game goes something along the lines of the following little loop,

JB's winter hiker evaporation call and answer blues
A) a hiker generates moisture in the form of water vapor, and
B) it freezes somewhere so
C) go back to A

The real issue is then focused directly on the exact location of this "freezing" moisture.

A simplified thermal model is as follows: The occupant is at +98 oF and all moisture there is vapor at or near the body temperature. Outside the temp is -20 oF and all moisture is frozen solid. A simulated thermometer is used to take measurements and develop a temperature map as a function of distance and position away from the occupant. Starting from the body core, it would read a constant body temp until the skin surface, but then drop suddenly just outside the hikers last epidermic layer. The temperature reading would decline slowly through the layers of clothes and down insulation to the edge of the sleeping bag, and just outside the bag there would be another significant drop in temperature. A third drop occurs at the shelter walls, the outside being assumed to be at ambient temperature, while the inside could be 10 to 20 degrees warmer (typical for a tent). So somewhere along that temperature profile, in three dimensional time-dependent manifold defined around the hiker, the temperature conditions are right for water vapor to condense into liquid, and a second zone, usually located right at or near the first, for that liquid water to freeze.

Now this is a simple paradigm with a number of technical inaccuracies that any student of thermodynamics could point out, but these simplifications are irrelevant to the model's purpose of explaining a basic corollary of sub-zero sleeping systems.

Corollary to JB's third postulate: Use ventilation, and the right amount of insulation, to keep the frost zone outside the bag.


Successful approaches to the ventilation dilemma, the veritable water is a vapor- water is ice dualality, generally fall into one of three categories.

VENTILATION APPROACH #1: The amount of insulation is adjusted so that the frost zone is at or above the surface of the sleeping bag.

There is the large sleeping comfort zone between having so little insulation and/or so much ventilation that the bag feels cold, and the onslaught of excessive insulation and no ventilation, which can easily bring the condensation and frost zones inside the outermost layers of the bag.

A first assumption is that the correct amount of down is being applied to the conditions. Specifically we are assuming that there is not "too much down," the case when the hiker has stuffed so many down jackets and vests inside the bag that overheating generates sweating, and the moisture generated by that overheating condenses just beyond all that down clothes stuffed in the bag, which happens to be somewhere still within in the bag, resulting in wet down insulation. "Too much down," means that freezing conditions are present somewhere inside the outer layers of down, moisture will condense and freeze in the bag. Eventually this leads to a cold hiker in wet clammy down bag...yuuck!. The trick with the inner down layer is to adjust it so that the dew point is located near, or slightly beyond, the top surface of the bag, not somewhere deep inside the bag (by piling on the insulation).

Of course there is also the very standard and rather trivial problem of having "too little down," as any hiker can sense that insulation layers at the moment is inadequate to protect against those instantaneous conditions. So a combined treatment, too little and/or too much, is generally referred to as "not havin' the right amount of down."


Given that the down bag is being treated properly, and thus "the right amount of down" is employed, then using the bag in a bivey sack will result in frozen moisture at the bivey sack (very cold) and down bag (warm and moist) interface. That is freezing condensation zone JB prefers to have occur way over on the tent walls, not on a piece of cold gortex lying right on top of my down bag! The bag gets wet from the bag-gortex bivey interface inwards toward the down insulation. A very unsurvival like setup with the essentially same result as having too much down. The nasty condensation delivers you a cold wet bag in the morning to go along with the shivering hiker. And after a few nights on the trail, if the bag is not regularly dried out, your are SOD (Shit outta down). So JB's technique is inherently not optimized for use with a bivey sack. "The tent walls are like way over there," JB waves an arm halfway around the room, "the survival tent has a lot of space when the mid-sections are pulled out." But by all means, just throw in any old tent that you have to imagine this scenario. JB has. In the west he often uses a pro looking stand alone or double staker in the "guide size. So from a fancy $600 4-man the manufacturer claims could be used on Denali right down to JBs $65 nylon special, it don't matter, just get in the stinking tent and crash.

But the bivey sack crowd has its answer to all this, it's called the vapor barrier. Now "vapor barrier" is little more than politically correct hiker-jones for the equivalent of cellophane wrapped Chinese handcuffs, according to JB. Since their deployment conflicts directly with the no constrictive restrictions doctrine of the second postulate, not to mention leaving very cold frozen border rings right in front of bare skin, vapor barriers, along with any mid-body sleeping bag drawstrings and other such constrictive techniques, are not used by JB.

VENTILATION APPROACH #2: Use a vapor barrier for ventilation.


The vapor barrier is quite popular because it keeps body moisture out of the down insulation. That is an advantage that can soon be lost however, thru improper use, and more importantly, if it does not work for your sleeping style. Here are some issues that JB has with those stinking vapor barriers.

A) A vapor barrier is very restrictive, a direct violation of the second postulate. Double trouble if you are a restless sleeper, getting tied up from flopping about.

B) The vapor barrier is an inner bag that typically goes around the head so that body moisture ventilates out along with the sleepers respiration. That means no access to the rest of the bag, your arms are stuck inside the vapor liner. To get access, the liner has to be moved back so you can get an arm out, pulling the wet cold edges of the vapor barrier into your down yukiee. So if you need to add extra insulation, where are yah gonna put it? Outside the vapor liner, you can't get at it if it shifts, or if you want to move it a bit. Inside the liner allows you to adjust that extra insulation, but constriction greatly increases. And hold on a second, better not use down in there either because the concentrated body moisture will soon permeate the down, greatly reducing it's effectiveness. I mean heck, that's why the barrier is being used in the first place, to keep all that body moisture away from the down! No comfortable down hood inside means you get to wear that scratchy sweat soaked fleece or wool hat all day, and then you also get to wear one all night itchy!

C) As the night goes by, the vapor barrier edges tend to get pulled into the bag, more wet frozen edges getting onto the bare skin around your neck and face. If the top edge over your forehead falls back a bit, now you have a wet cold vapor condensation zone right around your head...uggh!

None the less, most of these objections can be answered with a little practice. Several other members of the HAE team use vapor barriers with excellent results, I'll leave the excruciating details of operation to their esteemed authorship. The big kicker is objection #1, restriction.

Some hikers can sleep thru anything. If a grenade blew up next to camp, an HAE hiker like Jim Fife would sleep right thru it, even given that he was snoring away only in his bivey sack, without the bag at all. Apparently that bag was left over on the other side of camp when last nights party started, we heard from him the next morning. So a little restriction inside a twisted vapor barrier liner at -20 below is not likely to bother this type of sleeper. While some hikers have all the luck, not JB, even a flapping tent window cover is enough to keep him awake all night, and any kind of restriction or pressure point leading to a cold spot (no threat to life mind you, just an annoying cold foot or hand) will send him into an invective laced rampage to fix the problem.

The bottom line; if you practice using a vapor barrier and it's working for you, then that is definitely the way to go. Otherwise, don't forget to bring along a big heaping summary of how to sleep like a JB in the woods:

JB's three postulates of sub-zero sleeping systems

Foam...air...foam, and you'll be sleeping like at home!

Avoid restricting blood flow by using only down clothing items for insulation inside a sleeping bag.

Adjust ventilation and insulation to keep body moisture from condensing or freezing inside the bag.

VENTILATION APPROACH #3: Ignore everything, just hop in your sleeping bag and crash. Then starting drying out everything the next day or like...whatever. This technique goes along the lines of too tired, too clueless, too wasted, too warm out, or too anything else to care about some stinking body moisture or lack of blood flow. Amazingly, this nonchalant approach does work. At temperatures above 24 degrees or so, even JB will have the bag half unzipped, with arms out and down hood missing, enjoying the balmy conditions. The method is also employed by the vast majority of synthetic bagged hikers who haven't mastered the subtleties of vapor barriers and bivey sacks, or of a down bag stuffed with down insulation inside a tent.

Copyright 2003 John Bellantoni and HAE