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"I'm a girl, and I don't make heat. It sucks." Sleeping bag opinions for super cold sleepers.
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David Thomas
(DavidinKenai) - MLife

Locale: North Woods. Far North.
Re: Re: Re: Fat and iron on 09/05/2012 18:52:32 MDT Print View

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.

Greg F
(GregF) - F

Locale: Canadian Rockies
Anemia on 09/05/2012 20:03:30 MDT Print View

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.

Rob Reynolds
(rfreynol) - MLife
Fat helps, but the heat the weight ratio blows. on 09/05/2012 20:13:55 MDT Print View

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.

Devon Cloud

Locale: Southwest
This works great for my wife and she is cold at 70 degrees! on 09/07/2012 10:13:35 MDT Print View

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.

Monty Montana
(TarasBulba) - MLife

Locale: Rocky Mountains
New: What happened to the ol' Vapor Barrier trick? on 09/07/2012 12:42:08 MDT Print View

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!

Heather Toyne
(heathert) - F
Update on 09/11/2012 20:35:43 MDT Print View

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 :)worth it

Texas Chinooks

Locale: DFW
Grabber hand warmers on 03/03/2013 15:29:21 MST Print View

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).

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Grabber hand warmers on 03/03/2013 16:09:39 MST Print View

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.


Clayton Black
(Jivaro) - MLife
Re: "I'm a girl, and I don't make heat. It sucks." Sleeping bag opinions for super cold sleepers. on 03/03/2013 17:39:26 MST Print View

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.

Donna C
(leadfoot) - M

Locale: Middle Virginia
Re: Re: "I'm a girl, and I don't make heat. It sucks." Sleeping bag opinions for super cold sleepers. on 03/03/2013 18:29:03 MST Print View

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.

John Martin
(snapyjohn) - M

Locale: Pacific NW
7 Keto DHEA on 03/03/2013 20:10:16 MST Print View

This is supplement you can purchase that is supposed to increase your metabolism by increasing body temp. Worth a try?

just Justin Whitson
Re: "I'm a girl, and I don't make heat. It sucks." Sleeping bag opinions for super cold sleepers. on 03/03/2013 21:40:51 MST Print View

I seem to run into a percentage of women that have some kind of thyroid issue or imbalance. My wife is one of these, and she also runs fairly cold despite having a curvaceous type body.

She is an egg donor and she had to go through a lot of health screening to do so--they checked out EVERYTHING, and the tests showed that she had an under-active thyroid. The doctor that talked to her told her that she would have be on thyroid hormones for the rest of her life, and specifically that she would have to get her levels up if she wanted to donate (that's standard procedure).

She didn't agree, told him she would fix it on her own, and she decided to consult me since she knows that i know a lot about holistic health (in my case, personal necessity was the mother of invention and research), as well as do her own research. I told her to up her kelp intake (primarily for the high iodine levels--we Americans in particular would do very well to intake much more, and i believe the standard daily recommended is too low), take some good iron (bonded with an amino acid aka "chelated") and co-enzyme form of B12 supplements as well since she tends to be a little anemic also. She did all this, and fairly consistently (she really wanted that 6,000 i guess).

A few weeks or so later, they retested her, and her thyroid and hormone levels were now within the normal range. Needless to say, the good and learned doctor was kind of surprised she proved him wrong, as he made it quite plain beforehand that he didn't believe she could do that by changing her diet and adding certain supplements and nutrient dense foods...

Anyways, when she keeps up certain levels of nutrients, and generally eats better, she tends to not run as cold as when she is slacking off and ignoring. She eats about 99% vegetarian (very occasional fish--mostly wild alaskan salmon) and so it's doubly important for her to get enough of these particular nutrients (well minus the iodine). Phosphorous also helps with the anemic tendencies as well.

From looking at her case and knowing other women with similar issues, my intuitive sense is that there are more women out there have issues with their thyroids than they realize, and that this can really impact the cold feeling issue. Even if you test within "normal" in a standard test, it might be a good idea to go that extra step to help strengthen and balance your thyroid by simple and very safe dietary measures like the above. For example, the Japanese eat many times the upper limit of iodine than do Americans and it only seems to benefit them.

All the other suggestions, eg exercising before sleeping, being well hydrated, eating a lot of fat and/or protein relatively close to bedtime, etc. is excellent advice but if there is a basic body imbalance it's not going to work as well.

And yes, of course body fat generally insulates well, which is why so many Arctic type adapted animals have extra body fat--"blubber" to help keep them warm. But if your thermo-metabolic system is off, then it won't help as much as it normally would.

just Justin Whitson
Re: supplements on 03/03/2013 21:49:12 MST Print View

Re: supplements, no need to spend much money to find something that will help to temporarily raise your metabolism--i've found, and others too, that simple cayenne or ginger will do the trick quite well. They also have other benefits such as aiding digestion. Eating a large, very fatty and/or protein rich meal just before bed may help to keep you warmer, but it's not necessarily the healthiest thing to do in general, and personally gives me really weird, nonsensical dreams or nightmares, and so some ginger or cayenne will help a bit to digest those harder to digest foods. Complete digestion is one of the basic cornerstones of good health, along with good assimilation (very related to the former), good eliminations, and good circulation--all very interrelated in a whole system.

Edited by ArcturusBear on 03/03/2013 21:53:34 MST.