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Sleeping Naked in a Sleeping Bag

Sleeping Naked in a Sleeping Bag
Sleeping Naked in a Sleeping Bag

Contrary to popular myth, sleeping naked in a sleeping bag is not warmer than wearing additional clothing. There are actually many good reasons not to sleep naked in your sleeping bag if you want to stay warm and preserve the investment you’ve made in an expensive bag.

Let’s assume the you have a sleeping bag that is properly rated for the temperatures that you’ll be using it for. The next biggest factor in whether you will be warm or not is the insulation rating of your sleeping pad. Unless, you have the right amount of insulation below you, the ground will absorb most of the radiant heat vented by your sleeping bag and you’ll feel cold at night. You can prevent this by using an insulated sleeping pad like the Big Agnes Air Core or the Exped Downmat 7. These pads contain primaloft and down, which trap the warmth you generate at night and reflect it back at you. This is necessary to compensate for the fact that you are lying on your sleeping bag, which compresses the down or synthetic fill, eliminating most of it’s loft and heat retention capabilities.

The next most important factor in staying warm at night will be a hat, even if you are sleeping in a mummy bag. It is estimated that 20-40% of the your bodyheat is lost through your neck and head, so covering them up can keep you warmer.

Now suppose you’ve taken all these steps and your are still cold. Well, now is the time to start putting on clothes. Start with long underwear, socks, and then a coat with additional insulation. All of these will descrease the amount of room in your sleeping bag taken up by air and increase your warmth level because your body has to heat less air in the sleeping bag around you. If you are still freezing, you can stuff more of your gear inside the bag with you, to further reduce the amount of air in sleeping bag.

More advanced techniques for staying warm utilize vapor barriers. These are primarily used by moutaineers or winter campers in extreme environments.

Finally, if you have invested a lot of money in a sleeping bag and you want to keep it for many years to come, it is advisable that you bring along a pair of long underwear (top and bottom) on backpacking trips, that you only use for sleeping in. These clothes will help keep the inside of your sleeping bag clean and prevent the dirt, oil, or chemicals such as DEET, that have collected on your body after several days, from ruining your bag. These clothes can be used in emergency situations when all of your others are drenched or they can help prevent bugs from biting you if you need to vent your bag in hot weather.

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14 comments

  1. Good post. I've heard good arguments for and against sleeping naked. Personally I sleep hot, so I tend to wear fewer clothes in my bag rather than more.

    My top tips for staying warm (other than the good ones you point out, such as wearing a hat and getting a good sleeping pad) include:

    – eat fats before going to sleep. A handful of peanuts, salami, etc. The slow burn will keep you warm. Garlic tablets (or anything of that family, such as pickled onions) also promote blood circulation.

    – fill your water bottle with hot water, and take it in with you. For extra heat, put it between your thighs where it will heat the blood that passes through the femoral vein.

    – do a few situps or leg-pumps when you first get in (but not so many that you start to sweat!). This gets the blood flowing, warms the muscles and also pumps warm air into the insulation of the bag.

    – place unused clothing (jacket, etc) under your mat.

  2. as an old 11B with more than a few nights spent sleeping outside, i'd suggest that you always orient your sleeping arrangements so that your feet are on the downhill side of your body.

    that way, they get full blood flow, and stay warmer. packing the clothes/uniform you're going to put on in the morning inside means it's much warmer when you have to leave your nice warm bag and venture out into the cold.

  3. The heat loss through the head is a long-standing myth and nothing more than a myth.

  4. I've always thought that the heat loss through the head might be a myth as heat loss occurs through evaporation (sweating) and conduction/convection so it would depend very much on the size of the areas exposed to cooler temperatures and the head is not a particularly large area of the body (there are certainly larger) – I agree with the Guardian and add, to this extent, that a possible reason for the myth is that the head is less likely to be covered than other areas of the body (modesty being a major factor) so heat loss is likely to occur for that reason. Interestingly, a friend of mine raised this point – heat loss can occur through the capillaries near the skin (as in vasodilation) and there is a greater concentration of capillaries in the head so that could influence the speed at which heat is lost through the head area. I'm no doctor, but that sounds accurate…

    Chris' point (and he should know – snow holes being a favourite of his) about some light exercise and eating (especially nuts etc) just before you get into your bag (or whilst in it) is a tried and tested method that most hillwalkers use in the UK as the act of digestion burns calories which, in turn, produces energy and has the effect of heating the body so I agree with that whole-heartedly. Have to say I'd never sleep naked in my bag as I will tend to sweat a little and this would have me sticking to the damned thing all the time! I also found in Sweden a few years ago when the temperature dropped to -6C, which is about as low as I have gone for some time, that my 0C rated bag was fine when I wore all my clothes but there was a substantial difference when I did not wear a hat and socks. I find that a 0C rated bag suits me for a wide-range of temperatures (WM Summerlite, in fact) and can be supplemented in al sorts of ways – silk liner, base layers, down/primaloft jackets, hats etc. This permits me the greatest flexibility with one bag which weighs only 580g (well, mine does, despite the manufacturer's listed weight!)

  5. I always sleep with a hat on. I thought it was to keep warm, but it also blocks out daylight/twilight. As you say, you can easily extend the range of a sleeping bag – I have been thinking about doing this recently with a 40 degree bag I bought this year. Just wearing all of your clothes, especially your rain gear will do the trick. The rain gear acting as an approximation of a vapor barrier.

  6. Didn't know about the vapor barrier so thanks for that. My silk liner has a very nice feel (especially in dortoirs in Alpine refuges) and is also very helpful in increasing the warmth of the bag as well as regulating my sweat. Cannot quite tell you how it does this latter but it's pretty good in winter.

  7. “It is estimated that 20-40% of the your bodyheat is lost through your neck and head – -”

    In my opinion that is just as much a myth as sleeping naked being warmer than sleeping with clothes. It’s really difficult to give a generalized estimation like that and even though it’s very simple thing to do and makes the point clear, should be avoided in my opinion. But otherwise spot on article.

  8. While sleeping in a bag with layers on may be the best way, the description of the physics claiming radiation, reflection, and warming more air are incorrect. I doubt the author has a science/engineering background.

    The most important reason to wear something, as the author states, is to keep your bag from getting funked up with grime. For survival situations where your core may drop to critical levels, having as many layers as possible, without compressing the insulation of the bag or restricting circulation, is best. For situations where there is no danger of hypothermia, wearing the fewest layers possible can help redistribute heat to the extremities (feet). This needs to be tested to back it up, but the reasoning is that circulation alone is not sufficient to keep the feet warm. Allowing the heat from the core to migrate externally (to the body) through the air layer adds additional heat input to the feet, which can keep them warmer. This is strictly a comfort issue, and why in a survival situation more layers are better.

    Factoring in frostbite can further complicate the layers/no layers benefits, since in some situations losing the use of your feet may be just as deadly as becoming hypothermic. Either way, it is best to have an appropriately rated bag for the conditions (with compensation for personal variations in heat needs).

  9. Nice idea, but I think it is not good for storing your sleeping bag

  10. I am a woman. I have been camping and day hiking for 38 years. My first experience was one most people, especially the majority of women/ladies I know, would have left them totally turned off to camping, hiking, sleeping bags and.

    Upper Michigan in late fall. 1978~ Rain began to fall and wind started roaring. Temperatures were not bad by the fire and air temperature was around 20 degrees. A fairly warm night for upper Michigan. My camping partner had given me the best bag (down filled…although I cannot remember the rating) because it was my first experience and didn’t want it to be unpleasant. Best of intentions……

    During the night the rain continued to fall and the wind blew, but shifted directions. We were in a little two man ‘pup tent’ (A frame design) and the wind whipped the rain into the tent on my side somewhere near the ground. Of course, I didn’t know this because I was sleeping, but during the night I started to get cold. I remembered my friend had told me to ‘fluff’ the bag if I got cold. So, I’m fluffing and still I’m getting colder. Finally, I realized that my torso was what was really cold. I had on long johns, no socks and no head covering. When I got so cold I couldn’t stand it anymore and I could not produce heat to keep me warm, I unzipped the bag and thought about trying to fluff the down under me. As soon as I reached my hand down to the mid-section of the bag, I knew why I was cold. My bag and pad were in water. Actually in a slight dip in the ground on my side, so my torso was in icy cold small puddling of water. I got up and out. Lucky for me, there was a heated comfort station with hot water. I took a warm shower and got into dry clothes. Since everyone else in the group was still asleep and apparently dry and warm, I stayed in the comfort station. It took hours for my core body temperature to get comfortable. After it began to get daylight, I went to the van, climbed in and lay on the back seat fully clothed including my ski jacket. Still I felt chilled. When everyone else was up and by the fire, I didn’t even want to venture out to join them. The down sleeping bag was so wet and heavy, we thought it was never going to air dry enough to put it in the van for the long ride home.

    Everyone assumed that since I had such a bad experience, I’d never want to camp again. They were all wrong. I began to camp steadily in the early 80’s, making at least two trips a month. I have learned a lot since that first trip. As for sleeping, I don’t sleep nude, but in winter (night time temps in the 0 to minus 25 range) I sleep in a long john shirt and underwear or light weight 100% cotton sleep shorts. No socks and no hat needed for me. I weigh 98 pounds. I was perfectly comfortable in my -25 degree poly filled bag. Warmer nights…. say around 20 degrees, I’ve actually had to partially unzip my bag because it was too warm for me. The first bag was stolen from my tent. I now have a mummy bag (North Face) rated to -20 degrees. I have slept when it was -25 degrees outside, rainy and wind blowing. I don’t know what the wind chill was. I am perfectly comfortable in minimal clothing, basically same as I sleep in all the time. Long john shirt and cotton shorts. I’m one of those who cannot stand seams and socks when I sleep. I purposely purchased a long mummy bag so I could put my clothes in the bottom of the bag along with a down vest I put on when I wake in the morning.

    There are other things to consider when you buy your bag. In a geo-dome style tent with two bodies (98 lbs and 145 lbs), the inside temperature has close to or hovers close to 32 degrees. It’s comfortable. I’ve slept alone in my tent, but I prefer another body as I think this makes a difference in the temperature on the inside of a tent. My daughter and I have camped together for years and both of us are very small ladies.

    Personally, I don’t see how anyone could sleep with jackets, socks, hats, or fully clothed in a mummy sleeping bag. It’s just too cramped and doesn’t allow you to move around which generates body warmth. Just as wearing warm socks in your hiking shoes loose enough so your toes can move around can make the difference in cold feet or warm, comfy feet when you snow skiing (cross country). I had to learn this the hard way too. But, my advise for anyone is to experiment and find what works for you. Each body is different. This is one reason I suggest to my friends who go with me that if we are going to be camping in cold weather (we always check weather reports daily) and if the expected temperature is say, 20 degrees, that they need a bag that is rated at LEAST 20 to 25 degrees lower than the lowest temperature we expect to encounter. Sadly, I’ve had a couple show up unprepared and ill equipped and lived to regret it. I’ve learned to carry an extra sleeping bag and bag liner just in case.

    For me, the less I wear while sleeping, the warmer I am. I don’t recommend sleeping nude because if there were an emergency and you had to get out quick, this could be embarrassing as well as a make for a very cold experience if you had to leave the tent.

    So, I think it’s also a personal choice as to what you sleep in. As long as you are comfortable, not sleeping in the open, but in a tent, sleep in what you feel most comfortable in.

    Just my opinion.

  11. While searching for ways to keep warm should the electricity & heat in my apartment go out, it occurred to me that those who camp would have valuable suggestions to help me devise a plan, which I hope I won’t have to put into action. This site and the comments have been very helpful and I’ve made copious notes.

    I have a sleeping bag, long silk underwear, Sterno and camping equipment for cooking, water and various types of food; I would be sleeping on a bed.

    Does anyone have any other suggestions as to how I can keep warm in the winter in New Jersey, without heat?

    I admire the fortitude of those who camp and will appreciate any suggestions you can offer. Thank you.

  12. Order a polypropylene suit and a GI ECW
    3 piece sleeping bag from Sportsman Guide and you are ready for anything short of an Ice Age. The poly suit comes with socks and a poly baclava that will insulate even when wet and drys quickly.
    When in wet cold remember: cotton kills. PS:Do avoid the campfire in the poly suit.
    And it is much easier to cool down than to warm up.

    • I’ll tell you a down sleeping bag can do wonders. I live in Arizona and in the summer we go to Long Valley near Flagstaff it gets down to mid forties in the summer at night. But sleeping naked out in the wild is both scary and enticing.

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