Making a sleeping system warmer

[Andy Goodell]

I just got a new montbell alpine down #3 rated to 32F (although reviews called it 38F-40F). I still have an older heavy 0F bag, but I'd rather put money into making the montbell system warmer for the winter months rather than buy another 4 season bag just to be lighter. I've seen silk liners that claim adding 15F for 9oz, and bivy/covers for 6oz that might add more warmth. I've also read that a vapor barrier would greatly increase the warmth, but also makes you sweat a ton. Maybe the best investment is buying a good down jacket. Are they any options I'm missing? What is the best investment for this? Thanks

[Glenn Roberts]

I don't camp much in cold weather anymore, but still get out occassionally in temperatures down to, say, 25. So, my primary bag is a 40 degree Western Mountaineering Mitylite.

When I am going to be out in temperatures below that, I simply sleep in my R.5 longjohn bottoms and top and my Micropuff pullover and pants, and have found that I can extend the range of the Mitylite down to about 20 – 25 degrees (based on what the Weather Channel said the lows were at the state park; I didn't have a thermometer.) I figure that's about as lightweight a system as I can manage, since the R.5 clothing doubles as hiking clothes during the day, and the Micropuff items get worn around camp in the evening. Of course, it doesn't leave any nice, fluffly clothing to use for a pillow, but an air-filled Dromlite works OK there.

I may add some down booties to the system (listening, Santa?) Till now, I've just been drawing my feet up into the Micropuff pants (they're just long enough to do so.) But the booties might be a nice luxury in camp.

I wear a stocking cap over (or under, depending on my whim) an R1 balaclava, and I sleep in a Hubba tent; that seems to keep my head warm enough.

Like I said, don't rely 100% on my opinion; it works in Ohio in late fall and very early spring, but I don't go out at all from December through March any more, and only rarely (usually a state park public campground) when it gets below about 50 at night. But, it does work when I do go out.

[paul johnson]

i seriously doubt a 15F benefit for a silk liner. while i think logically (prob. it's illogically and i'm missing something – yes, i know a bivy sack has no insulation) a bivy sack might help, DrJ corrected me once a couple of yrs ago, when i posted (actually "parroted" info which anyone can read almost anywhere – it's apparently one of those "rural" legends, so to speak) that a bivy sack will add 5deg F warmth to your sleep system. DrJ informed me that a bivy sack's real benefit is in windy conditions, as well as wet conditions. IIRC, he began his corrective post with the word "Nope" (i've gotten this word more than once from him; it makes me chuckle as i appreciate learning the truth so i won't be wrong again).

so, you're absolutely right in considering dual use insulating layers to extend your sleep system (i.e. a jacket and pants, and hood/balaclava that can also be worn around camp or possibly at other periods of low activity).

as far as VBL and/or VBC goes, others have been kind enough to educate me on the theory of use and practical application of using VBC and VBL, but i'll let others far more qualified and experienced than i am address the proper use of such. I've only used VB socks inside of trail runners as "rain gear" to keep my feet dry from the outside.

[Andy Goodell]

I also doubt the 15F from a silk liner, but for 9oz it must do something. I've never understood how a liner would really help, but I guess just having another layer close to the body helps keep the air that your body warms to a minimum volume (although the stretchiness of the montbell already does that to some extent). Would wearing extra clothes be equivalent to using a silk liner? If that's the case, then it would just be best to bring more clothes instead since they have more function. I think a bivy/cover probably wouldn't help me since I always use a full tent, so wind isn't a problem inside of that. Even though the reviews claim the #3 bag to be 38-40F, I think it might be closer to it's actual rating of 32F since the reviews were from tarps and hammocks and therefore had the wind to deal with. I'll be in sunny New Zealand for January, so I still have some time before considering what to buy.

[Frank Ramos]

The simplest way to make any sleep or clothing system warmer is to add insulation to your face, head and torso. In particular, the factor of respiratory warmth is often overlooked. So the first thing I would do is add something to completely cover your face, but which you can breath through, such as a wool scarf. For moderately cold temperatures (above 10 degrees Fahrehnheit), use loosely woven wool. For subzero temperatures, consider a piece of fur instead, or else use tightly woven wool, so you can brush any frost accumulation away.

Next step would be to add a good head covering, such as a Ray Jardine style polarguard bomber hat. The wool scarf used to cover your face can also be wrapped around your head to add more warmth there.

Finally, add a lightweight vest, if you are not carrying one. If you are certain you will never wear the vest under your backpack, then down is clearly better. Otherwise, get the Patagonia micropuff which is made of tightly quilted polarguard, which is much more durable than down for use under a backpack.

[Graeme Finley]

Similarly to Glenn, I use a 40 degree bag (Marmot Atom) and supplement it with additional clothes. I wear Possumdown socks, Sahalie tights, and drape my WM Flight Jacket over me as a torso quilt. That combination has taken me down into the mid 20s quite comfortably.

[Moe Dog]

Ditto on all the comments about adding a good wool hat and/or neck insulation. You would (should) probably be taking those along anyway in colder conditions.

If you are going to add insulative weight to your system, the most 'bang for your buck' will come from increasing the insulation BELOW you – i.e. your pad. A huge portion of your heat loss will be through conduction with the cold ground. Invest in a thicker, higher R-value pad. Compare R-values per ounce. Thermarest Standard (I believe there may be a new name for it though, 2 inches thick, R-value = 5, 3/4 length at only 18 oz) actually has one of the highest ratios of insulative capability to weight. Or, simply add another pad to your existing one. But, again, compare weight to the highest possible R-value and you will be pleasantly rewarded.

In regards to vapor barriers – they DO NOT make you sweat. You sweat from a result of being overheated and that can only be caused by too much insulation (external temperature and exertion aside, seeing that we're dealing with how to be warmer at rest in cold temperatures). Too much insulation is obviously not an issue for you if you're trying to 'add more warmth'. In fact you might actually sweat MORE without a vapor barrier, because your typical high-wicking clothing will quickly draw any sweat off of your body and you no longer notice that you ARE sweating. With a vapor barrier, once you achieve maximum humidity (which isn't long), when you do sweat you know immediately and then it's only a simple matter of venting the warm humid air for cooler dry air and/or possibly removing some insulation – a good sign that you have enough. It's far easier to cool off when you're too warm than vice versa.

I would highly suggest you try the Adventure Medical Kits Heatsheets Emergency Bivy inside your bag. Consider:

– It's cheap (only $13.49 for Members)

– Extremely light at 3 oz (I think mine actually weighs only 2.5 – not sure where they came up with 3.25-?)

– Incredibly small for what it can accomplish

– Much stronger/durable material (and less noisy) than previous mylar version

– Reflects radiant heat (something most will dismiss as inconsequential, although I strongly disagree with them)

– Dual-use as emergency signal (orange side or even the reflective side in strong sunlight) and as emergency shelter (as bivy, or can be cut open and used as a tarp)

– Many other 'dual uses' if you consider the possiblities of a large trash bag.

Just a note on what to wear inside a vapor barrier – thin layer of high-wicking top & bottoms. Bare skin feels sticky and any thick insulating clothing will retain perspiration. Any jacket or other insulation should go on top (outside of) the vapor barrier under the bag if it fits. Only lightweight layers that will not significantly compress your down should be put on top of your bag.

[EndoftheTrail]

Andy:

DON'T believe the hype about adding 15F by use of liner (Sea to Summit's Thermolite is particularly notorious here). I've tried it — and it probably adds around 3-5F (5F being tops).

One arrangement that has worked very well for me is the MontBell Thermal Sheet — a 725fp full-zip, hoodless summer bag. By itself, the Thermal Sheetk makes for a great summer bag, keeping me warm to about 50F. My MB No. 3 bag keeps me warm to about 30F. Used together, they have kept me comfy to 19F (wearing long undies) — and I believe they would be good down to about 15F.

The Thermal Sheet is designed to fit inside any of MB's regular bags — stretch or unstretch versions. I am 5'9" and 150 lbs., and I find the Thermal Sheet perfect in size for me. If you are over 5'10" and, say, heavier than 180 lbs. or so, then the Thermal Sheet may be too snug for you.

Lastly, given that the 725fp Thermal Sheet will boost warmth by 15F — there is JUST NO WAY that any simple liner can do the same.

[Brett .]

Andy, congratulations on your choice of bag; I own a #3 and a #7 and they are the gems of my gear collection. The advertised temperature ratings are spot-on for me; I took the #3 to 0'C with capilene1 and was toasty.

I would like to echo pj and the other posters; FIRST; choose insulating hiking clothing which can be dual-used as an additional sleeping layer. IME this will extend the temperature limit of a MB bag from the bottom of the 'Comfortable' range to the bottom of the 'Minimum' range, as shown in the chart below. Add a bivy sack and tent for a few more degrees each.

SECOND, consider a summer bag to use as a liner. With my setup I could put the #7 inside the #3, or vice versa, creating basically a #2, good down to 5'F.

BTW, I choose Montbell (MB) UL Thermawrap pants and top as my insulation layer (573g set) and a MB goretex bivy as an emergency shelter (225g). My bags and bivy are all 'Long' to fit extra layers or another person in an emergency. I have never tried a VBL and have no desire or need to at this point.

[Andy Goodell]

I spent the night outside in my "grave" as my friend calls it. It's basically a section of a hill that I shoveled dirt to make flat, and made a simple shelter roof with sticks and a sheet of Tyvek. Anyway, it's mostly lacking coverage on the sides, but it was not windy anyway. I used my 1" Thermarest (full length) and MB #3, and the thermometer ranged from 30-35 at night and in the morning, and I was sufficiently warm in just one layer of clothes. I'm thrilled! I think in the cold, in a tent, with another layer, I could possibly be comfortable in 20-25F range.

[Brett .]

Congrats Andy. I see I'm not the only one strange enough to test gear in an urban setting. I usually open all the bedroom windows in winter and sleep on the hardwood floor to test a new layer or pad.. If you like the MB#3, check out their component pad system; lighter than the thermarest which it is pictured with here.. and returning to the subject of the post; it is supposedly warmer too, as indicated in the third picture (MB on left, waffle type on right)
>

[Roman Dial]

My wife is petite and gets cold outdoors easily. She's found that the best way to warm up a sleep system is to change all the clothes she wore hiking during the day and put on "sleep clothes" as soon as we stop for the day. She particulary likes to sleep in cotton so as to feel most comfortable and least clammy.

She wears a camp jacket to trap the heat from teh days hiking as we set up camp.

She claims that sleeping with any clothes damp (i.e. trying to "dry out" hiking clothes) leads to massive heat loss through evaporation. That reduces her bag's "warmth" by wasting heat.

She also insists on a hot drink before bed — at least one liter.

Her startegy to warm up a bag is to prevent heat loss from her little body even before she gets in her bag so as to "warm it up" substantially.

[Roger Caffin]

> I also doubt the 15F from a silk liner,
My wife and I have used silk liners (Sea to Summit) for many years. I would reckon about 3 – 5 F benefit at the most.
But it does block breezes, which can help, and it does keep my SB clean(er), which also helps.

[paul johnson]

>>"She also insists on a hot drink before bed — at least one liter."

Roman,

i don't mean to get into more personal areas here, and there's no need to reply, but your wife must have one HUGE bladder. The nerves in a normal human bladder begin sending signals to the brain when it's about half full. I think i read somewhere (Artic 1000 website maybe???) that you're also a Bio Prof, besides teaching Math at the University level, so, i'm sure that you already know this.

since fuel is being used to heat the water for the drink anyways, why not just heat the water, place it in a Platy, wrap it in a pack towel to insulate it a bit, and place it "hot water bottle style" in the bag.

40min to a couple of hours after consumption at the most, i would guess, based upon my physiology and aged, somewhat non-elastic bladder (sorry for the unsolicited personal info, but i don't think my bladder could even hold 1L), and i don't mean to project such things upon your wife's physiology, i'm going to be drainin' the main, so to speak.

this would involve, waking from the warm, safe "Land of the Sugar Plum Fairy", getting out of the bag (particularly in a female's case), out of the shelter, and entering the cold, cruel world of reality, becoming a bit chilled, returning to the bag, and attempting, without the aid of that hot 1L beverage this time, reheating the cold air in my bag.

in fact, given my age, 1L at bed time will probably do me good for two 'pitstops', so to speak, b/f sunrise.

During the Star Trek Next Generarion years, i once was heard mumbling in the Men's room at work as i stood there ~40min after drinking a cup of hot Earl Grey Tea, "Tea, Earl Grey, body temp" – other STNG fans were immediately identifiable by the raucous laughter which filled the Men's room. I think you get my meaning.

[Andy Goodell]

Sounds like silk is only minimally effective for making it warmer. I bet their +15F is more like making a 60F down to 45F, rather than 30F down to 15F.

I often do the hot water bottle, assuming I have plenty of leftover fuel. I'll often have a 1L platypus bottle with nice hot water insulated in a extra shirt, but I think that only lasts 2 hours at the max.

That one minute of getting out of the bag in the middle of the night for a pit stop is brutal for the next 5. I think I usually fall asleep again before ever feeling warm (I fall asleep incredibly fast)

[Roman Dial]

PJ,

Yep her bladder gets full, and she empties it (she says she drinks 2/3 of a L and gets up twice in the night to pee). We sleep in a Megamid sized shelter so there's plenty of room to pee (agast! they not only eat and often cook in their Mid but they pee in it too!)

Also, my experience is similar to the poster who says that a hot water bottle in the bag lasts max of 2 hours. Putting it in the body before bed heats up the body, which is the goal.

Yes, I have the PhD in biology. Used to teach cold weather physiology and winter ecology, in the field, in the winter, in Alaska, for a number of years.

One "lab" exercise was to have students chill their hands in the snow and then warm them up using one of three methods:

putting on gloves
swinging them hard (full circles) with goves off
drinking warm (subtantially above body temp) water (~1 L)

Of the three, swinging would get them warm fastest but they did not stay warm for long. Drinking warm fluids shoves blood into the extremities, thereby warming them.

On the Arctic 1000 we had a very thin single quilt and slept every night pretty much on ground with permafrost not too far down. We aslo had very small, very thin pads. What I am telling you here, PJ, is that we had a pretty minimal sleeping set up. We needed other ways to bolster its warmth besides liners, over bags, thicker pads, or a car 12 hours away.

I can not speak for Ryan, but Jason and I each consumed about 3 liters of warm fluid before sleeping. We cooked on a fire, but ate in the tent. We each had a full Nalgene Canteen plus split 3 quarts of soupy dinner from our 1 gallon cook pot.

Were our bladders full? Doesn't take a PhD in biology or mathematics to see if you put nearly a gallon of fluid in you you will have to pee. Yes we had to empty our bladders multiple times (we each had our own side of the OWARE pyramid style tent to use for that purpose — one reason we like ) but we were warm.

And that's the message here. Your body is most easily heated from the inside out, not the outside in.

[paul johnson]

Roman, good info. i never would have guessed that. i understand the basic principle that you're speaking of. probably everyone, including myself, have had a hot beverage to warm ourselves. in fact, dieters are often exhorted to drink plenty of COLD water to burn more calories in order to bring their core temp back up.

my reasons (which are apparently faulty based upon your experience which i'll accept over hard numbers – "One test is worth a thousand expert opinions" – J. Rhiele) were:

a) anything you drink will in a short (unquantified in my mind; an hour max??? but, i bet i'm all wet limiting it to an hour – not sure of nominal heat transfer rates in the human body) period of time, relative to how long i'd like to sleep 3-4hrs minimum, have its heating effect dissipated.

b) by the time i get up the first time to make a pitstop, everything i drank earlier before turning in the first time is at or nearly at body temp and not warming me further to any great degree.

c) now i have to heat the cold air that will enter my sleep system using body heat (calories) only.

d) i may be more fatigued after repeated rising to make pitstops, and burn more calories warming cold air each time i return to the quilt/bag to make this approach less optimal than sleeping straight through for 3-4h and getting up and moving on until i need to sleep again (maybe a nap later on???).

Still don't know what i'm missing here, but i obviously am missing something (i'm not the sharpest tool in the shed by any means) since your vast experience dictates otherwise.

Can you help me further to understand please?

[Andy Goodell]

I can't understand why waking up several times in the night helps. Are you emptying bladders while in the sleeping bag? If I got out of the bag, even if still in the tent (too risky for me!) I would think that would negate any hot water benefits. I'd much rather sleep through the night anyway.

[Erin McKittrick]

For external heat, rocks heated in the fire are also nice. And there's usually no limitation to the size and number of them you can have (unlike hot water bottles). The only concern is that you have to be very careful they're not hot enough to melt anything, or delaminate a sleeping pad (I have ended up with thermarest "tumors" when I wasn't careful).

-Erin
http://www.groundtruthtrekking.org/WildCoast.html

[E. A.]

Great website! I checked it out following your post about sending/acquiring food in the Bush. I ended up spending 30 minutes "flying" around Google Earth near Hatcher's pass around Palmer, AK trying to locate by first excursion to week long backpacking (and launching my outdoor addiction).

What subjective measure to do you use to determine how hot is hot enough/not too hot for your rocks(e.g. able to handle for so many seconds, etc.)?

[Roman Dial]

PJ and Andy,

Right. This is all very counterintuitive. However, try a pee bottle if you get too cold getting out of your bag to pee.

Better yet, try it for yourseldf, in the cold. Go for three weekends using the same gear for each if you can't get out for 2-3 weeks, where you really learn how to stay warm.

First weekend eat nothing but cold food.

Second weekend eat warm food but have no hot drink before bed.

Third weekend try the hot drink, too.

Find out what works best for you.

Also in between pick up "Life in the Cold" by Peter Marchand and "Winter Ecology" by James Halfpenny to explore the theory of heat loss and cooling and the behavior animals use to stay warm.

Some more counterintuitive behavior: One thing many of you (us) may have noticed is that when you get cold, you have to pee — also drinking lots of fluid or even small amounts of caffeine or alcohol make you pee — but each of these is for a different reason.

The reason the body wants to pee when it's cold, is that when you get cold, your body shuts off blood to the extremities to reduce the blood's exposure to heat loss by reducing surface area to volume ratio of the vascular system and hence heat loss rate. In other words your hands and feet get cold to save the brain and organs some heat. To bring the heat/blood into the trunk requires that your body make room for the blood. So your body empties the bladder. So, again, counterintuitively, your body is sacrifing immediate heat for longer term warming.

Now, I know what I just described is about why you pee when you get cold and your problem is how in the world it could be better to have a hot drink and get up to pee, rather than no hot drink so you can just get a good night's sleep without getting cold when you squirm out of that nasty, wet, constricting bivy bag encrusted with frost (that's why I don't use a bivy bag and use a floorless megamid and just role over and pee without even getting out of my bag).

This is a classic trade-off in physiological ecology. And in my experience, the trade-off is: sure I pee more because I drink more to stay warm, but the heat loss associated with peeing is less than the heat gain from drinking hot fluids, so the net effect is not "negation" but positive.

[David Olsen]

I echo some stuff already mentioned.

Use extra clothes (I like to pull my jacket or vest upside
down over my feet inside my bag and my rain coat upside down
over my feet outside my bag)

Hot water bottles, one liter (in a sock to prevent burns)
gives me 6 hours of good sleep even with a too light bag
and wet clothes inside.

Lots of ground insulation (I like double pads of closed cell)

VBL's if you will be out more than a couple of nights.

Eat a quarter stick of butter before bedtime (put it in
your dinner and cocoa)

And ones I didn't see mentioned—-Niacin tablet before
you get in your bag for that hot flash to get things warmed
up.
— Cayenne in a gel capsule for long term heat to the extremities.

[Moe Dog]

PJ, one aspect you may not have considered about drinking that much fluid is the level of hydration their bodies achieve (as opposed to how dehydrated most of us probably go to bed). Being well hydrated will thin the blood and allow core body heat to be carried easier to your extremeties. It also aids digestion, which is a huge source of heat generation in the body. There's probably many more benefits that I'm not aware of or hadn't thought of…

[paul johnson]

wrap clean hot rocks in a pack towel, it will prevent burning and also keep them warm a bit longer.

[paul johnson]

Roman,

rolling over to urinate – BRILLIANT!!! (shouted like in those Guiness commercials).

now i know why DrJ slept separately!!!

actually, three in the Mid would've probably had urinary-logistical difficulties with three in there. besides, if you're at all like me, half-awake i wouldn't trust my aim.

ok. for me your "true confession" regarding the Nocturnal Urinary Habits of the UltraLight Alaskan Trekker was the missing piece of the puzzle. i know from being bedridden for so long after a near fatal accident that, post-Foley, i got pretty good at semi-waking to use a 1L urinal (the urinal, after use and resealing, also helped to warm me under those cold hospital sheets).

[Author]

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