warmth in your bag...clothes or no clothes?

[David S.]

Growing up, I had always heard that you would stay warmer in your bag if you took most of your clothing off. A few days ago I was out camping with a friend who got cold during the night...she intentionaly wore a few extra layers of clothes to bed to keep her warm. She said she got cold anyway so she decided to test the old theory of taking clothes off in your bag to stay warm...and it worked. She reported staying warm the rest of the night after removing most of the clothing.

While I have found the above to be true, I read stuff all the time that says you can extend the range of your bag by wearing all your clothes to bed.

From my experience, I think both cases are true...but can anyone speculate as to why? I have a suspician that wearing cotton to bed (dry) will cause you to be cold...where as wearing fleece (or some other highly insulating garb) to bed will allow you to stay warmer. But why would dry cotten make you colder? I have a few theories but would be interested to hear from you guys.

[Footslogger]

If you're cold when you first crawl in it might be a good idea to wear some clothing that would trap some body heat. Once you're warmed up and provided your bag is of adequate comfort rating, you might be more comfortable losing some or of all of the clothing.

It's a very individual thing and depends a great deal on whether you're a warm or cold sleeper, the rating of your sleeping bag and the weather conditions.

'Slogger
AT 2003

[cutman11]

Because cotton does not repel water, even if its not rained on it gets damp in humid conditions...... So your cotton stuff gets damp, then you take it in the bag and it gets you cold....... So you take off the cold wet cotton, and get warmer....the conclusion: .....hopefully all the scupted female hikers wear cotton!

[Lone Wolf]

Slogger is right. It also depends if you stay in a shelter, tent, tarp, hammock, etc.

[Fiddleback]

All last year I slept in cold weather, insulated clothing only -- no sleeping bag in the hammock. And I can't think of a single piece of cotton that's ever on me anymore while backpacking. Too risky in winter, to uncomfortable (soggy and heavy) in the summer.

But when using a bag, I've always changed into fresh (dry) polypros and socks. It adds some warmth to the bag, keeps the bag cleaner and just seems more comfortable. If the weather was warm I opened up the bag or used it as a quilt. Clean, dry clothes inside the bag is the key.

FB

[orangebug]

Ditto with FiddleBack. Either wear that spare dry pair of Capilene's or nothing until the bag warms up. Then I'll bring a few pieces of wet gear into the bag to help dry them some, and avoid having to put on frozen clothes in the morning.

Of course, I use a very warm down bag.

[grrickar]

I wonder if some over do it and start to sweat, and then they feel cold in their bag, whereas when they take those clothes off they start to feel warmer.

Damp clothes next to your skin will rob you of heat much faster. When I kayak, I dress for water temperature, not air temp. Water robs the body of heat much more readily than air, which is why I have seen people get borderline hypothermic in the summer months after a protracted swim in cold water. If you happen by the NOC, wade out into the Nantahala and stand there for awhile. You'll know exactly what I am talking about.

[Nightwalker]

I've heard the back and forth on this for years, and I'm going to try a logical argument for clothes over no clothes.

The purpose of your sleeping bag is to keep your body warmth in; to be a shield between you and the big, bad, no-heat outside world. It would help for one to understand that there is no "cold", there is only a lack of heat. Heat is your friend in the cold, cold night. (okay, the no-heat, no-heat night! )

If the loft, or insulation, of your sleeping bag is what is keeping you warm--again, by keeping your body heat inside where it belongs--why would it follow that more loft (again, as insulation) in the form of clothes would make you colder, and less insulation (nekkid!) would make you warmer? Remember, it's all about a heat barrier between you and the outside.

If you climb into a sleeping bag with cold clothes on, it may take you a little longer to get warmed up. You're warming up the clothes too, after all. Climbing into the bag naked lets you get right up next to that soft, snuggly down that you paid so much for, and your maximum warm-up is fast. I believe that is where the mythologizing comes from. Your max warm-up is less however.

The real test, and where I believe that I've found the truth, is when you are sleeping out in weather that is at the edge of your bag rating. I'm now carrying a Mountainsmith Wisp 30 degree down bag, because it only weighs 1.5 pounds and it feels so good. On nights when it gets below 30, and there are many, I layer in the bag just like I would on the trail. I stay very warm in my bag that way. If I were naked, I would be extremely uncomfortable or maybe even in danger of hypothermia.

Layering works in more ways than you might think, and if you're trying to keep your pack light, you can't do without it.

Nekkid in my bag? Well, since Squeaky won't fit in there with me, why bother?

[steve hiker]

I've always felt warmer with no or minimal clothes in my down bag. Body heat just seems to interact better with the down if there's not a lot of clothing to interfere. Don't know if you'd have the same result with a synthetic bag.

[weary]

I've heard the back and forth on this for years, and I'm going to try a logical argument for clothes over no clothes.

The purpose of your sleeping bag is to keep your body warmth in; to be a shield between you and the big, bad, no-heat outside world. It would help for one to understand that there is no "cold", there is only a lack of heat. Heat is your friend in the cold, cold night. (okay, the no-heat, no-heat night! )

If the loft, or insulation, of your sleeping bag is what is keeping you warm--again, by keeping your body heat inside where it belongs--why would it follow that more loft (again, as insulation) in the form of clothes would make you colder, and less insulation (nekkid!) would make you warmer? Remember, it's all about a heat barrier between you and the outside.

If you climb into a sleeping bag with cold clothes on, it may take you a little longer to get warmed up. You're warming up the clothes too, after all. Climbing into the bag naked lets you get right up next to that soft, snuggly down that you paid so much for, and your maximum warm-up is fast. I believe that is where the mythologizing comes from. Your max warm-up is less however.

The real test, and where I believe that I've found the truth, is when you are sleeping out in weather that is at the edge of your bag rating. I'm now carrying a Mountainsmith Wisp 30 degree down bag, because it only weighs 1.5 pounds and it feels so good. On nights when it gets below 30, and there are many, I layer in the bag just like I would on the trail. I stay very warm in my bag that way. If I were naked, I would be extremely uncomfortable or maybe even in danger of hypothermia.
Layering works in more ways than you might think, and if you're trying to keep your pack light, you can't do without it.
Nekkid in my bag? Well, since Squeaky won't fit in there with me, why bother?

I think Frank has it figured out. The only way dry clothing -- including cotton -- in a sleeping bag could make you colder is if the clothing is wet or so tight or bulky that it cuts off circulation. Even the diminished insulation of damp clothing is better than no insulation at all.

I carry a down-filled sleeping bag liner between April and November. When temperatures drop below 45 degrees, I augment the liner with a down jacket, dry socks, and occasionally with insulated long johns.

I expect to be chilly for the first few minutes. Afterall, my body heat has to warm a cold sleeping bag, down jacket and socks. But soon everything equalizes and I sleep comfortably the rest of the night.

Weary

[cutman11]

[QUOTE=weary] The only way dry clothing -- including cotton -- in a sleeping bag could make you colder is if the clothing is wet.....


And that was my point...dry cotton clothing is an oxymoron on the trail. If it isnt wet when you get in your bag, it will be shortly thereafter from the water vapor your body emits to keep the skin at proper humidity. The cotton soaks it up, gets cold, then you get cold trying to evaporate it.

[DebW]

I'll add one thing to this discussion from my experience. You feel warm in your sleeping bag when the microclimate next to your skin is warm. That is a very thin layer of air. That thin layer is disturbed anytime you move around in the bag. Down does a wonderful job of not letting air circulate within the bag, so your body warms the still air within the down. But interior to the bag, the air can circulate. A properly fitting bags helps minimize this air space, and down bags tend to drape around your body, also minimizing air space. But the air space is never eliminated, and therefore air can circulate both passively and dramatically every time you move. This is a noticable effect in many cases. Either you move part of your body to a different part of the bag that you weren't touching before and it feels chilly for awhile, or you feel air pump in and out of the neck opening of your bag and chill you. This is a good reason to wear a thin layer of close-fitting long underwear to sleep in. Then the thin layer of air next to your skin is not disturbed by the air currents sloshing around in the bag, and you can move in the night without feeling a temporary chill. Always best to go to sleep in dry clothing because any dampness will chill you until the moisture is driven off.

[verber]

Growing up, I had always heard that you would stay warmer in your bag if you took most of your clothing off. A few days ago I was out camping with a friend who got cold during the night...she intentionaly wore a few extra layers of clothes to bed to keep her warm. She said she got cold anyway so she decided to test the old theory of taking clothes off in your bag to stay warm...and it worked. She reported staying warm the rest of the night after removing most of the clothing.

Your friend's experience is quite different from mine. I can imagine three explainations. First, the extra clothing were damp and made from a material that didn't dry quickly. Water is much more effective at moving heat than air. The second possibility is that the extra clothing were sufficently bulky that it was compressing the insulation in her sleeping bag producing cold spots. Third, it could be psychological.

While I have found the above to be true, I read stuff all the time that says you can extend the range of your bag by wearing all your clothes to bed.

Yes... I do this all the time. There are two keys. First, you need enough room to wear the extra clothing without compressing your insulation. So if you bag is snug naked, it might be better to lay the clothing over your bag rather than wearing it.

Second, you want your clothing to be dry or too dry quickly. I often bring a base layer to sleep in which is different from what I hike in. I am not doing this so much so I have something dry as much as being able to sleep in something that doesn't smell and will help keep my quilt clean. But sometimes I don't have an extra base layer. I have found that modern synthetic base layers will in most condition be dry in a hour or two after I crawl under my quilt without significant impacting my quilt's performance.

I have a suspician that wearing cotton to bed (dry) will cause you to be cold...where as wearing fleece (or some other highly insulating garb) to bed will allow you to stay warmer. But why would dry cotten make you colder? I have a few theories but would be interested to hear from you guys.

I don't recommend cotton in the backcountry.. but if you had it., and it was dry, then it would help insulate.

[David S.]

Thanks for all the interesting and informative replies. My suspicion regarding those who have been warmer because of removing clothes is that they were probably wearing articles of clothes that were poor insulators, i.e...clothing that retained enough insensible moisture (from perspiration or otherwise) as to act like a heat sink, or clothing that was made in a way that made for poor heat retention.

Pardon the nerd in me...but let me just think out loud here.

Imagine as an extreme example that instead of say jeans (a common article of clothing I have seen worn to bed by many less experienced folks...including myself on some early occasions), you were to wear a steel suit of armor inside your sleeping bag. Your body would have to expend a huge amount of energy just to keep the metal warm...before the down in the bag would begin to receive any amount of heat. In all likely hood, you would never be able to put out enough heat to warm the metal plus your bag.

Though this is an extreme example, I suspect that this might happen on a much more insignificant scale when a person wears certain articles of clothes to bed, particularly cotton or any fabric that is woven in such a way as to make a poor insulator....or rather, a great heat sink. I would say that cotton clothing probably creates some of the best heat sinks just because of (I suspect) cottons ability to hold and trap insensible perspiration inside the fabric...as has already been mentioned.


As an experiment, I think I will take my jeans I am wearing right now and weigh them, then throw them in the dryer and weigh them later and see if they have lost any weight.

Ok...all done.

[Bjorkin]

Good thoughts DavidS. I like the suit of armor analogy. I've never slept that warm in cotton so your theory may hold water. Hardy, har, har.

With regards to your experiment, be sure to scrape the lint filter to add back to the jeans for gram weanies!

[Youngblood]

Another thought to what has already been mentioned. I have noticed that some types of insulation seem 'warm to the touch' while others seem cool at first and then warm up slowly, but do a great job once they do 'warm up'. I don't know exactly what the difference is but sometimes is just seems to be the lining or surface material. Maybe some surfaces are acting a little bit like a conductor, are acting in parallel with the insulating capabilities of the bulk of the material and it is just a time thing until the thin conductor warms up?

I know that if I am cold, that I need to put on more insulating clothing or generate more heat by exercising more and/or eating something to stay warm... and that principle applies whether I am in my sleeping bag or out of it.

[The Solemates]

Growing up, I had always heard that you would stay warmer in your bag if you took most of your clothing off. A few days ago I was out camping with a friend who got cold during the night...she intentionaly wore a few extra layers of clothes to bed to keep her warm. She said she got cold anyway so she decided to test the old theory of taking clothes off in your bag to stay warm...and it worked. She reported staying warm the rest of the night after removing most of the clothing.

While I have found the above to be true, I read stuff all the time that says you can extend the range of your bag by wearing all your clothes to bed.

From my experience, I think both cases are true...but can anyone speculate as to why? I have a suspician that wearing cotton to bed (dry) will cause you to be cold...where as wearing fleece (or some other highly insulating garb) to bed will allow you to stay warmer. But why would dry cotten make you colder? I have a few theories but would be interested to hear from you guys.

the old tale that nekkid in your bag means warmer is nonsense. put clothes on and it will be warmer.

adding clothes means adding more and more trapped air layers between your nekkid body and the ambient temperature. more and more trapped air pockets allows for a more efficient way to warm up.

[David S.]

The difference in the weight of my jeans before and after putting them in the dryer was 780 grams before and 760 grams after coming out of the dryer. These were cotton jeans that I had been wearing all day. I don't know that this is significant but I find it fascinating. One would have to do lots of tests with other materials to see if this is even a contributing factor. It may be very possible that all clothing...synthetic or natural all hold a certain amount of moisture that you aren't aware of. Regardless, it sure is interesting.

[siouxdog]

there is a difference other than the obvious with regards to your question between a down bag and a synthetic bag. a down bag works of course by trapping ones body heat. to do so it must have an adequate amount of "dead" space. if there is little to no "dead" space then the temp rating of the bag is most definitely compromised. in other words if you have on so much clothing that the bag is close fitting then you will most certainly be colder than if you were in the same down bag with no clothes on. that being said you can wear some extra clothes and be warmer than no clothes at all. the key of course is to only have one or two layers and close fitting items like tights and underarmour shirts are best. therein lies the difference-too many clothes actually hinders the bags performance.

[AlphalphaPB]

When you get into the sleeping bag, the warm parts of your body warm up the air inside. Since clothing is an insulator, it will keep the heated air in the sleeping bag from warming up the cold parts of your body, like your feet.

This is why your feet take forever to warm up inside a sleeping bag when you wear socks. To solve this problem, I take off my socks and warm my feet with my hands and by sitting crosslegged before I sleep.