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Myth or fact: You should sleep naked in a sleeping bag to keep warm

Is sleeping naked in a sleeping bag a terrible camping idea or a good one?

There is an age-old theory that if you’re finding yourself getting cold at night in your sleeping bag, you’re better off removing clothes rather than layering up. Talk to any group of avid campers — especially from an older generation — about the fact you’re getting cold at night and at least one of them will suggest you are wearing too many layers. But doesn’t this go against everything we always talk about in the outdoors, about needing to wear layers to stay warm?

Throughout the summer, you can generally get away with being a little less cautious about your clothing. Sure, there are rules to follow — avoid cotton, wear active layers — but as fall comes around and the nights get cooler, you’ll notice the conditions affect you more. So is there any truth in the idea that you should sleep naked in a sleeping bag?

A man lays in a sleeping bag on the grass, looking out over the mountains as the sun sets

How do sleeping bags work?

Sleeping bags are filled with insulation — either down feathers or synthetic fibers — that trap the heat your body generates. This then creates what can be thought of as a micro-climate inside your sleeping bag, where warm air circulates around your body. This circulation is the root of the myth. People believe that if you don’t allow the air to circulate, then your body won’t all be benefiting from the warmth inside the sleeping bag.

There is some truth in this theory, though. If you wear too many clothes, or your clothes are bulky enough that they push against the outside of the sleeping bag, then there isn’t space for that micro-climate to be created. You need your sleeping bag to be able to loft — where the insulation has room to trap the warm air — and your bulky clothes pushing against this can stop this from happening. It’s the same reason that if you have a sleeping bag that is too tight in the toe box and your toes push against the end, you will always wake up with cold feet.

Should you sleep naked in a sleeping bag?

This one is easy: no you shouldn’t. That’s not to say you have to layer up in your sleeping bag, but regardless of temperature, it’s usually a good idea to at least wear a pair of wicking underwear for hygiene reasons. This also means that if you’re caught short in the middle of the night and desperately need to leave your tent to answer nature’s call, you don’t have to scramble around in the dark to find something to throw on.

The only time it’s a good idea to wear nothing in your sleeping bag is when your clothes are all soaked through. In this instance, warmth and comfort trump hygiene and decency — but remember to keep some clothes at hand for midnight trips to the bushes. Wearing clothes in a sleeping bag definitely keeps you warmer, so long as they’re the right clothes, but they also help to regulate temperature and moisture levels.

What should you wear in a sleeping bag?

When you’re looking at clothes to wear in a sleeping bag, it’s a good idea to follow general camping tips and guidelines on clothing. The most important here is not wearing cotton — which holds moisture and doesn’t breathe — and making sure you have a clean and dry set of clothes for sleeping in. The best choice for sleeping clothes when you’re camping is to wear merino wool long underwear and a merino wool base layer. Avoid bulky layers which press against the outside of your sleeping bag, but you can layer up — within reason — if you need extra warmth.

Merino layers don’t just offer excellent warmth for their weight, but they also wick moisture away effectively. Most campers are careful about not getting wet from the outside  (by re-waterproofing their tent and staying away from the sidewalls at night) but without moisture-wicking clothing, you can get just as wet from the inside. Damp air inside your sleeping bag cools down quicker in the early hours of the morning and can leave you feeling cold and uncomfortable.

Don’t forget the hat, too. While the studies that showed we lose the majority of the heat from our heads have been debunked, you should still keep a hat handy for those cold nights. Any exposed area of your body is going to pour heat into the tent, so put the hat on, and if you still get cold, pull the drawstring tight on your sleeping bag’s hood.

Bonus tips for camping comfort

Wearing the right layers unfortunately does not guarantee a warm and comfortable night under the stars. Understanding camping sleep systems will keep you warm. These include everything from getting the right size of tent to avoid having to heat a company’s worth of space, to getting your sleeping bag ratings right. Don’t forget to add a sleeping bag liner too — these keep your sleeping bag clean and can change your sleeping bag from a 2-season to a 3-season bag.

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