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When camping in cold weather, some people say it is actually warmer to sleep naked than to sleep with clothes on.

Is that true, or is it better to leave warm clothes on while in the bag?

  • 22
    The only people I've ever heard this from are people who've never been camping. – Lagerbaer Jan 28 '12 at 22:56
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    It's only warmer if you're not alone... – Jay Bazuzi Jan 29 '12 at 7:41
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    @david - I believe standard accepted practice now is NOT to buddy up to treat hypothermia. Best to construct a 1-person burrito wrap. Should be its own question on here if not already. – Lost Feb 2 '12 at 2:15
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    Lots of good thoughts - but one thing I know is true: if you are cold and want to warm up, try taking off (and putting back on) all of your clothes without getting out of your sleeping bag. Works every time. – Lost Nov 15 '12 at 14:19
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    This seems to have attracted a lot of contradictory answers, none of them containing any solid evidence. This question might be better for skeptics.SE. – Ben Crowell Mar 4 '14 at 4:15

13 Answers 13

96

When talking about fresh, dry clothes then it's not true. More layers definitely equals warmer!

As pointed out in the comments if you really go to extremes then more layers doesn't necessarily equal warmer, but to get to that point you have to really cram yourself in the bag so there's no insulating air between the layers. You could also make yourself so warm you sweat which would make your clothes damp and cool you down again, but if you just wear warm enough clothes to be comfortable, not sweltering (which is surely what you want anyway!) then you shouldn't have an issue.

Where this saying may come into effect (I've heard it branded around before as well) is when you wear clothes to bed that you've already been wearing so they may be damp, or clothes that are next to damp clothes in your rucksack (somewhat surprisingly regular for the more novice hikers!) and so on with similar situations. In those cases, it's probably best to sleep without than put on damp clothes.

Yes, in certain contrived / specialised / odd cases this may be true. But on all practical levels my experiences, and the experiences of those I know suggest that it's a myth with dry clothes and only comes into play with damp clothes, which most seasoned campers (and many other people too) know tend to easily cool you down anyway!

There's no paradox.

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  • 2
    Except for with wool, perhaps. From my understanding, wool will keep you warm when dry or wet. – Liggy Feb 1 '12 at 19:10
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    Clothes insulate body parts from other body parts though, whereas a sleeping bag would not. I have poor circulation in my feet, and wearing socks to bed makes them warm up considerably slower. – nfirvine Feb 11 '12 at 18:10
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    Note though that if you manage to make yourself too warm, you sweat, and then your clothes that were dry turn damp. – Patrick Feb 28 '12 at 18:13
  • Wet wool is still pretty uncomfortable, it's just not nearly as uncomfortable as wet cotton. – Fred the Magic Wonder Dog Mar 24 '15 at 16:40
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    not to speak of a wet sleeping bag, after wet clothes have been inside... – cbeleites unhappy with SX Apr 18 '16 at 20:47
30

Possibly. the reason this is a consideration is best way to stay warm is with loose layers (multiple depending on the temp) that trap air pockets close to the body that are heated BY the body. if you are in your birthday suit you will trap a decent larger pocket of air around you.

BUT a single sleeping bag will NOT keep you warm this way. if you go this route here are a few things to keep in mind

  1. SWEAT is your enemy. I personally would NOT go completely naked but have 1 or 2 layers on. the first would be a wicking layer like under-armor or a polypropylene or silk layer (NOT COTTON)
  2. Being that your don't have as many layers ON you. you will need to re-locate those layers to the other side of the sleeping bag. that may be other sleeping bags, a blanket, a tarp around that, or (most likely a combination there of)
  3. once you get out of your sleeping bag it will get REAL cold REAL quick. therefore I would leave my layers for the next day INSIDE my sleeping bag to warm up with me.
  4. four words. "Bathroom trip ain't fun." you may want to keep a "pee jar" with you so you can avoid this. better yet go BEFORE you strip down. BUT IF YOU HAVE TO GO go. you WILL stay warmer with a empty tank
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  • 3
    A friend of my parents went on a Himalaya expedition a long time ago. During the night, his friend went on a bathroom trip in the storm. His friend was never seen again. – gerrit Nov 2 '12 at 20:52
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    @gerrit, a storm in Himalaya is a very extreme example;) I've made a lot of <0 C bathroom trips, some of them barefoot on the snow, and it's not that awful. Never tried during a heavy storm, though. – Steed Nov 15 '12 at 11:33
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    "some of them barefoot on the snow" : this can actually improve your experience a bit. A few seconds in the snow can improve circulation in lower legs significantly. Of course, YMMV as may the outside temprature. – Erik I Jun 8 '15 at 18:35
20

Two considerations: Layers should be loose and non-constricting so as to allow good circulation. Too many layers can get tight. Also, day clothes will be damp, even if you think they aren't. Air them before bringing them into your bag if it is cold.

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20

My experience tell me this: sleep naked always if there's no sign of a possible avalanche.

I've been in many high altitude expeditions in three Continents and have explored many vertical and horizontal caves and underground systems. Sleeping bags are best when they're good. Don't try to get a cheap offer and trade it for your safety or comfort.

In mountaineering, especially when camping at very high altitudes (5,000 metres or higher) it is recommended to sleep naked.

First, we use only down feathers sleeping bags OR linear single fiber ones -Hollofill is one of the materials made that way. The specs can go from good for 0ºC to -40ºC. Kelty, Big Agnes, Valandre, Marmot... there are many options with high quality standards. Differences are huge in price between a good sleeping bag and a bag for laying down.

One of the main reasons why sleeping naked is more comfortable and safe is that moisture in our clothes stays there for a much longer period of time than on the skin.

Second, the air cushion of warm air that our body produces by means of its own heat, is maintained between the skin and the inner layer of down -or fibers- and these let the moisture pass through their loose structures, then it's evaporated or frozen on the outside shell of the sleeping bag, keeping your body dry.

One should always make sure to undress when already inside the bag. The boots and all layers of socks must be kept inside the sleeping bag as well. This helps to dry them and keep them warm for the next morning. You can leave your parka and windbreakers outside and use them as pillows.

Going to the loo in such situation will take its time. But, if weather is just around -10ºC, you can grab your thermic undies and go outside without much fuss. Just make it fast!

Camping at warm places asks for another layer, if possible: use a light cotton sheet inside the sleeping bag. It will pass the sweat to the outside as vapour and you'll feel that smooth and fresh sensation when in contact with cotton.

Never cover a proper sleeping bag with anything. This will shut the shell's properties of heat exchange and you'll feel colder or smothered.

Try sleeping naked at home. Always take a shower before bedtime and you'll experience why sleeping naked is much better. Keep your pj's under the covers and use them if you have to get out of bed. You'll find yourself rested and fresh in the morning.

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  • 1
    Good answer — shows things are more complicated than they seem. Also agrees with my experience. – gerrit Nov 15 '12 at 21:08
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    I would like to hear the story behind how you got the experience not to sleep naked in avalanche? :D – Ossi Herrala Aug 17 '15 at 15:28
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    This doesn't make any sense to me. Lightweight alpinists are increasingly using sleeping systems which combine clothing and bags to save weight. There is extensive practical experience with this at all altitudes and it works, even on 8000ers. PHD have a whole section of their site on this: phdesigns.co.uk/what-is-sleep-systems – Tullochgorum Sep 16 '17 at 11:51
18

Only in contrived or extreme examples does wearing less clothing about your body in fact make you warmer when camping.

The areas where I might consider it warmer to not wear clothing inside a sleeping bag are:

  • Insufficient ground insulation when sleeping on solid ice or where you have no other viable insulation. In this case, it might make more sense to place the clothes between you and the bag or between the bag and the ground / tarp. This is especially true when the uncompressed side of your sleeping bag is sufficiently lofted but the compressed side is not.
  • Clothes that are wet and will chill you as the water evaporates or interfere with down insulation in the sleeping bag.
  • The obvious case where being naked results in additional heat generation due to companionship or "calisthenics" - especially if your clothes are too plaid for your party.
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16

There is more than one reason, which makes you feel warmer sleeping with less clothes (even if it's perfectly dry):

  1. It's the same deal as with mittens, which are warmer than gloves. When you wear a lot of clothes, there is additional separation between the parts of your body and more exposed surface. More surface means more heat transfer from the body to the environment. And if you share a bag with someone, you get less heat from one another.
  2. What's more, your arms and legs, which produce less heat, get separated by thick clothes from your torso (and from each other). So you end up with uncomfortably (or even painfully) cold toes or arms.
  3. In winter/high altitude you are usually wearing a lot of clothes and it's quite bulky. When you get into your sleeping bag like this, some parts of your body get compressed/clamped (e.g. armpits, elbows, ...). This leads to worse blood circulation and less heat for peripherial parts of your body.

There is some balance, actually: you should wear something, but not too much. I personally prefer sleeping completely naked, but high up or in winter I use Polartec-100 linen, socks and a cap with a scarf (though in these conditions I'm usually sharing the bag).

And all this doesn't mean you have to put your clothes in your backpack. You can use it to insulate your most exposed parts: the one which are closest to the tent and to the earth (actually snow). Just don't put it on but keep it loose between yourself and the sleeping bag, effectively improving bag's thickness.

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13

I generally sleep naked in my sleeping bag. Ive slept nights where I went to sleep in my clothes, and then woke up because my feet were freezing in the middle of the night, so I took off my clothes and when back to bed, and then woke up at dawn toasty warm. And nights where I didn't do that in the same exact conditions, and suffered the night.

And these are dry clean clothes kept away from any moisture.

My theory is that my core produces a lot of heat, but my extremities are always cold. Sleeping naked lets the heat from my core make the whole sleeping bag warmer so my extremities can warm up. Layering up only reflects heat from your body back at that same part of my body, so I end up with an especially warm core, but freezing feet.

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12

I’m not sure where this came from, but I can assure you that on some nights people are glad to put on whatever extra layer of clothes they find in the backpack!

In other words, according to my experience there is no paradox and more clothes equals warm night.

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9

Keep the bag Warm not your clothes!

Both clothes and sleeping bags are insulators, the problem with wearing too many clothes in your sleeping bag is that you will actually insulate yourself independent of the bag, as a result, your bag won't get warm or it will take a long time to warm up. You will eventually have issues with moisture control, as your bag will slowly warm up after you fall asleep as heat escapes your layers and eventually replaces the cold air in the loft of the bag, causing you to sweat. There's nothing worse than waking up with that clammy sleeping bag feel.

The best solution:

Layer your bag! – Fleece, cotton or silk bag liners–although some are not technically designed to add warth to your bag–can actually add close to an extra 10°C to your bag, in addition, adding a vapour barrier keeps warm air next to your skin, and reduces moisture build-up in your bag, keeping your bag dryer and warmer by a few more degrees. Not only will you stay warmer, but you will also be way more comfortable. Overbags add an additional 5-10°C by adding a layer of insulation and by reducing built-up condensation from frost and the sleeper's own perspiration. The result is your sleeping bag's insulation stays drier and more effective. In really cold weather you can even consider layering with a second sleeping bag.

There are multiple benefits to layering your bag:

  • You can stay warmer with fewer layers of clothing on
  • Less moisture condensation in the bag keeps your bag dryer and therefor warmer
  • Better heat distribution prevents cold spots/toes
  • More comfort in bag means a much better nights sleep
  • You protect your bag the same way sheets protect a mattress, keeping your bag cleaner
  • Less time needed to air out your bag/let it dry in the mornings

The best routine: strip down naked and put on a DRY base layer before getting into your bag. I usually sleep with nothing more than a polyester base layer and a pair of wool socks in cold weather (except for a touque and neck-warmer to keep the drafts at bay). In the morning, I change out of my sleeping layer back into my hiking clothes.

This is of course assuming that you already have a good ground sheet and sleeping pad, which are essential components of a warmer sleep system.

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7

From my experience - no way. If the temperature outside is below the comfort range of your sleeping bag, you'll have to put some extra things on you, otherwise you risk hypothermia (in best case - sleepless night). The best things are the fleece ones.

However, when it goes to trousers and jackets (normal or rain-proof, without warming), it's usually a better idea to put them under your sleeping bag or foam-pad, to increase isolation from ground (the most head you loose through ground). So actually it may be a source of that hypothesis - better to sleep without trousers, and sleep on them instead.

However, many people claim that it's warmer to sleep naked. Well, the ones I know have very warm (and expensive) sleeping bags, so the temperatures were above their comfort rage. I have an impression that such rumors are produced by sleeping bag producers, which want people to buy warmer sleeping bags for cold weather, instead of trying to keep them warm in their (cheaper) summer-time sleeping bags with extra layers of clothing.

Note that sleeping bags are relatively new. As a soldier in 1st World War, you had only a blanket to keep you warm and you had to sleep in everything you have on you during winter.

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  • Increasing insulation against the ground = Good. Sleeping on your extra layers = Bad. You risk getting your extra layers wet which could turn into a fatal error the next day. – ShemSeger Nov 7 '14 at 23:41
  • " The best things are the fleece ones.". Not really - the best things are the down ones, followed by anything with synthetic insulation. – Tullochgorum Sep 16 '17 at 11:54
1

Personally I slept with less layers while in the military and sometimes naked and was warmer than I ever was when I slept with layers on. I don't really know if it's dependent upon the type of bag you're in or what, but I have 0 doubt that it worked much better for me personally.

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1

TL;DR: Honest answer: depends on too many things, different situations will be different. Best answer: do what you feel like, whatever makes you feel comfortable.

If you cannot sleep naked in your bag comfortably, you should consider getting a better bag.

If you cannot sleep fully clothed comfortably, you should consider getting better clothes. Note you can get clothes cheaper than sleeping bags.

What you want is insulation to trap warm air.

The more insulation you use the more heat you keep.

If insulations are used the same way all that matters is how insulating it is. For practical purposes, nothing else matters, not even what you call it (bag or clothes).

… but clothes aren't used the same way. They are less efficient.

Worn clothes insulate body parts from other body parts.

This stops them from sharing heat efficiently. For this reason a sleeping bag insulates you more efficiently. This is where the "naked sleeping is warmer" idea comes from.

More insulation or efficient insulation, which do I want?

If your bag barely keeps you warm so the sleeping method matters, then your problem is you need a better bag.

In the end, there's a catch-22 here:

If your bag can't keep you warm, you need to wear clothes.

If it can keep you warm, you don't need clothes so do whatever because it doesn't matter.

If your clothes can keep you warm enough by themselves, then you don't even need a bag.

"Ok fine" you say, "But I still want the answer to which is warmer."

Where is the line? It depends on too many variables, including your own metabolism and recent activity level and comfort preferences. Only you can know this, and only by trying it out. There will be configurations where one is warmer and some where the other is warmer. That's not the answer you want to hear, but it's the truth.

Which is warmer? Option 3!: take your clothes off, wrap them around you like a blanket so they add insulation but not between body parts. This is both warmer and more annoying to do than either option we discussed.

So what should I do!?

If you are like most people and camp above freezing temperatures and without a cold weather bag then you probably want to wear your clothes. If you wear enough clothes to keep yourself warm anyway or have a good enough bag, both of which you should have, then it doesn't really matter.

What do you do?

I've done both under tarps and in hammocks down to about -10F/-25C. My findings are that you do whatever you feel like doing as long as you have good clothes and a good bag. Again: it really doesn't matter.

You get in your sleeping bag to sleep, but other than that the same rules apply as during the day: wear whatever makes you feel warm enough, your body will help you decide.

But why get naked and then redressed in the morning when you don't have to? It's such a hassle. I prefer to sleep in what I will wear the next day, even the jacket. In the morning I just step out and start my day.

I also camped at about 40F/5C with no bag. I gave my bag to someone else who joined last-minute and I wore everything I brought plus their jacket. It was very windy (there was even a high wind weather warning), yet I was still quite comfortable sleeping under the stars, on top of a tarp, in slightly-above-freezing weather with no bag. As I said: with enough insulation, just do whatever you feel like.

Extreme Situation

I've never been to the arctic but been considering it for a couple years. I hope to get some -40 degree nights at least, if not colder. In this situation I would want to use my insulation as efficient as possible, so I plan to use arctic bag inside a good bivy bag, and possibly a very warm blanket inside the arctic bag.

With all that insulation, I plan to strip down to bottom 1 or 2 clothing layers but not naked, and the rest of the clothing layers I would wrap around me to keep them warm for morning. That way my body parts can share some heat hopefully keeping my legs and feet warmer, and there's plenty of insulation around to keep the body as a whole warm.

Summary

Keep clothing in your bag with you and try it out and see how you feel. Listen to your body and adjust as you feel you need it.

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0

I did several (short) winter hikes below zero degrees Celcius (freezing point) while having only a plastic cover and sleeping bag.

I always took of my clothes, especially jacket (since it was slightly wet due to snow), and put ALL clothes inside the sleeping bag but not wearing it.

Because of your body heat the sleeping bag will get warmer and it will dry and keep the clothes warm (relative) so in the morning you don't have cold clothes.

What is important, to keep as much air inside the sleeping bag. I don't mind to sleep with just an inch of gap opening of the sleeping bag, but some feel suffocating. Of course you need a so called 'mummy' type sleeping bag.

The only thing I keep on is (preferably clean) socks; somehow my feet don't get warm otherwise when they are cold.

Also it is important to put a layer under you (like an isolation mat).

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