“I’m a girl, and I don’t make heat. It sucks.” Sleeping bag opinions for super cold sleepers.

Thanks, Tom, I forgot about vapor barriers! I find a vapor barrier really useful on below-freezing nights to keep body moisture from getting into my sleeping bag. That's one reason I have non-breathable rain gear (the other being that I get just as wet inside expensive "breathable" gear which wets through a lot sooner than coated nylon). Just remember that anything inside the vapor barrier will be damp, so don't wear your down inside. I wear my vapor barrier over my base layer, with my insulating items outside the vapor barrier.

My dog certainly helps, too–I consider him part of my sleep system. There have been a few nights when I would have liked to have three of them! The main precaution is to keep the dog's claws well-trimmed and keeping him off your air pad and lightweight-shelled down sleeping bag. And, of course, lots of obedience training courses for you and your dog before you take him out on the trail.

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Rodger, who told you this stuff or where did you read it? It's not jiving with what I have learned in biology/physiology/nutrition classes and what I and am reading. Here's some research based info…

"Women also regularly lose some iron on the 28 cycle."
An old study came to the conclusion that "There was no decrease in the incidence of iron deficiency following the menopause" (http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2141.1967.tb08846.x/abstract) Sooo, this does happen, but not really statistically common. More period information, yay. Anyone hating me for this too?

"People that have a higher than avg body fat % (women?) get cold faster. Fat is a fuel source, but it is a lousy insulation and retainer of heat."
Look at this scientific study that says the exact opposite: http://www.ncbi.nlm.nih.gov/pubmed/2803162

"People that have a higher than avg iron % (men?) are always heating up. Iron is the body's insulation, like a Thermos or the inside of a kitchen oven."
I've been googling this for the past 15 minutes and I'm coming up with nothing to support that iron insulates people. Nothing to oppose it either, just nothing at all about the insulative properties of iron in people.

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Roger-

FWIW, my experience doesn't jive with your posts at all. I eat exactly the same food (high protein, high (good) fats, low carbs) as my husband. He's a furnace, and I'm cold. I've never tested low on iron, and have been tested multiple times. I do test low on vitamin D if I don't supplement but that has a lot to do with living in Alaska (not enough UV radiation to trigger the natural production of vitamin D 9 months out of the year). I supplement with D daily in the winter months, a couple times a week in the summer, and get my bloodwork done twice a year.

The only food I've found that seems to impact my body temperature is actually a spice- cayenne. I have experimented with some success on drinking a tea with a good dash of cayenne before bed and have found that it helps me to feel warm for quite a while after consumption, in the same way a spicy soup or chile might make you sweat when eating it.

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The FF Spoonbill double bag seems like just the ticket. I thought it looked great, but just to warm for our normal temps, but if you are looking for a warm 20F bag, it seems like it would be the ticket, with it's independent hood/zipper adjusting lettting your sleeping partner air out while you bundle up. Then increase the delta by wearing warm down clothing.

Whether or not iron is an "insulator" I cannot say; however, spinach as a good source of iron is an old wives tale. Yes, it has a high content of iron, but it also has a high content of oxalic acid, which inhibits the body's uptake of the iron. By comparison, the little oysters in a tin of smoked oysters (ummm good!) contain 35% iron…much tastier than liver, and they go quite well with cheese and wine. Happy Trails!

My 92 year old grandma just told me that when she was in girlscouts she put in heated rocks/bricks in her sleeping bag

"Fat is a fuel source, but it is a lousy insulation and retainer of heat. . . Iron is the body's insulation, like a Thermos or the inside of a kitchen oven."

My MD/PE household responds:

Fat on the human body is very much an insulator against conductive heat loss. We've butchered arctic critters including a bowhead whale and the mostly furless ones have their fat concentrated under the skin where it does the most good. A human's coolest skin (given the same exposure) are those areas over the most white adipose fat. (The brown fat in the small of the back is an exception – it is involved in metabolism in both genders).

Iron is used in hemoglobin in our blood to transport oxygen to our cells and carbon dioxide back to our lungs. It is not insulation.

Editted for spelling.

Thanks David. That was the first time I had heard the claim that fat was a " lousy insulator".

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Sounds more like a test of thermal storage, rather than insulation.

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thoughts from yet another one who could've posted the title:

For me, double quilt or sleeping bags zipped together don't work well – because whenever my partner rolls over or gets up to pee (which happens several times a night) I get a blast of cold air that wakes me up. Your experience may not be the same; this is just a cautionary thing you may want to consider. For me, direct access to the heat source is outweighed by the random ventilation occurrences!

My feet are usually a bit chilly by the time I climb in the bag (heck, they're chilly right now in my 70 degree house!), so a hot water bottle by the feet is the best placement for me.

I definitely recommend using a pad long enough to have it extend under your feet, with high enough insulation value (women's neo-air xlite has worked for me so far but I haven't had it in really cold conditions yet; perhaps the xtherm for you?)

I've just changed from an old REI Down Time bag to a WM Versalite 10 degree bag – love it. Have also made myself a sleep hat from heavy windpro fleece.

Really, it seems like a riddle. Starting at body temperature, left with a human all night, both materials will remain very near body temperature. There would be minor effect because human skin and the environment inside a sleeping bag isn't quite 98.6F so the fat will be warmer for longer.

20 pounds of iron would be 1.15 liters (think one liter water bottle) whereas 20 pounds of fat/lard would be 21 liters (think 5 gallon fuel container).

Iron is 335 times as thermally conductive: 80.4 versus 0.24 watts/(meter degreeK).

Fat holds more sensible heat (has a larger heat capacity) by a factor of >4 (0.53 versus 0.12 cal/gram degreeK)

So if you heat each (to 150F, 212F, whatever) the iron holds 1/4 the heat and cools off much faster than the fat.

"Insulation" is simply the reciprocal of thermal conductivity. If that little bit of math is too much, you've waded too deep into technical concepts.

I think one thing that is being misunderstood is that iron is not an insulator in the body but it does play an important role in thermoregulatory system function.

So if you are an extremely cold sleeper it may be worth having your iron levels checked because it could be one cause of the issue.

Roger, taking gender out of the equation, I have the opposite experience. I was always a skinny kid and always froze my butt of on backpacking trips and scouting trips. In my late 20's I got married, took a corporate job, pretty much stopping backpacking and over the next 15 years, frankly, got fat. During this time, I became a HOT sleeper. Could not sleep under anything heavier than a sheet. .

At 40 years old and 40lbs over weight I got back I to camping and backpacking, still a very hot sleeper. I camped out in 25 degre weather with just a 32 degree Mountain HW synthetic bag, and got hot. Carrying a heavy pack on one long weekend trip started my journey into UL backpacking and carrying around 40 lbs of fat motivated me to get back in shape.

I dropped 40 lbs in 6 months and the next fall, on the first semi-cold weather trip, I thought I was going to freeze to death. It never dropped below 40 degrees yet my 30 degree down bag could not keep me warm.

Being fat DOES provide some insulation , but I'd rather carry 2 extra lbs of down in my sleep system than 40 extra lbs of fat.

The hot bottle trick is the way to go. Here is the trick if you are cold before getting into your bag: Put the hot water bottle in your bag for about ten minutes before you get in. durning that time, do some jumping jacks to warm yourself up or jog around the campsite for a bit if possible (and not to dark to hurt yourself). The warmer you are getting into your bag, the better sleep experience you will get. The water bottle will keep you warm all night until the early morning. If you get into a cold bag while your body is cold, you will have at least an hour or two before you will get warm given you have a good enough bag to keep building on the temperature given the temperature outside.
My wife says it makes all the difference in the world to excercise a bit right before getting in to warm up your limbs and the hot water bottle makes the hugest difference in her comfort in the cool weather. I use the same technique for winter backpacking… and I sleep in a hammock which can be harder to keep temps up that way if you are not good at insulating the bottom of your hammock. it keeps you very warm.

One technique that I employ in order to stay warm in the Fall and Winter, using the same summer sleeping bag (a MontBell ultralight super stretch #5 w/o a zipper), is to add a Vapor Barrier Liner. Many campers have remonstrated how they have fallen asleep toasty warm, only to awaken in the hours before dawn freezing. Some even go on to tell how they put on their down jacket, and the process just repeated itself…they woke up freezing again! The reason? Insensible perspiration. It seems the human body is continually releasing water vapor, even when not exercising, as when asleep. Our skin likes to be cloaked in a thin layer of warm, moist air for optimal comfort. On a warm day it keeps us cool as it disperses, as it functions to carry away excess body heat, and on a cold day clothing traps this warm, moist air to insulate us from the cold.

So what happenes when we're sleeping? Well, it disperses, percolating right through the down filling of the sleeping bag we're in and much of it becomes trapped there. Condenses. It's not uncommon for a sleeping bag to weigh a pound or more in the morning from condensed vapor. And all this moisture compromises the thermal effeciency of the sleeping bag. In other words, what started out as a 30F bag is now a 50F bag, and the shivering begins!

A VBL works because it in effect turns off the vapor faucet. Once the optimal humidity level is attained, the skin's pores close and no more insensible perspiration is released. More importantly, there's no vapor to condense inside the down filling of your sleeping bag, which will then not loose its thermal effeciency as the night progresses, and all who use this method will sleep warm and toasty the night long through!

Happy Trails!

I love this discussion – lots of helpful tips and a little amusement. I just wanted to update this thread with my most recent experience.

Over labor day weekend, my husband and I camped in the Holy Cross Wilderness near Leadville, CO. It got fairly cold. I didn't have a thermometer but I could see my breath that night and the low in town was 41. We slept on a pair of full length Thermarest Z-lite Sol's with a piece of flannel sheet on top of those and our big rectangular synthetic bag zipped open on top of us. The manufacturer says it is a 0*F degree bag, but its not EN tested and I think that is an optimistic number. Also, d k is right about the drafts. I thought that since our bag was so wide that drafts wouldn't be an issue because I thought there would be enough material to tuck under our side and enough to push down between our necks – there was but it didn't stay put. I did wear silk long john's, thick wool socks, my fleece and a fleece hat. The verdict: I was not super-comfortable-toasty-warm but warm enough to sleep through the night. Needs a bit of tweaking, but hypothermia didn't get me :)

I haven't tried putting hot water in my Platypus foldable bottle because I'm so scared of it leaking in my down sleeping bag. Is there a reason other than weight that y'all don't use the chemical warmers? Last cold night mine was between my legs or draped over my throat (i'm wearing a cashmere turtleneck sweater so it wasn't on my skin).

Maybe the Grabber brand is better than it used to be. Lots of people used to complain about them.

You can also try the sodium acetate phase change hand warmers. Those start up instantly, but then they run out of warmth after an hour or two. But, they are rechargeable in boiling water.

–B.G.–

Goosefeet down socks were a game changer for me. A long day in the cold wet paramos makes for some very cold feet and big thick wool 'sleeping' socks just wasn't getting it done. Finally went 'soft'and bought me a pair of goosefeet down socks and it lowered my quilt range at least 10 degrees. No x-spert here but it worked for me.

I was always cold until I bought a down pad. I have the Exped and love it to death. I used to have a closed cell pad mated with my Big Agnes insulated pad and it would either slide off, I would slide off…I hated the combo. I also have bags/quilts rated much lower than I need. In a pinch I sometimes have used the 12 hr body heat packs; same as hand warmers but much larger. My hips are the first to get cold.