You may have heard this one before, or you might have wondered to yourself at night while in your sleeping bag “Is it warmer to sleep naked in a sleeping bag?” regardless of where you heard it from or where you first thought of it. It is just one of those things that you need to know the answer to. I too have heard this before and wondered to myself if it was true or not. So I did some research to find out if the answer is true or not and why.
So, is it warmer to sleep naked in a sleeping bag? In most circumstances, it is not warmer to sleep naked in a sleeping bag. Keeping warm layer clothing will help ensure you stay warm and comfortable.
The primary reason for the answer has to do with how heat is generated by the body and how it is held onto. It is better to wear layers in your sleeping bag, but you don’t want to get too warm to where you start sweating. There are some exceptions to this rule that you must know in order to make the smartest decision for the circumstance that you are in.
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How is heat generated by the body in a sleeping bag?
The answer to this is a little bit sciencey and I am not a scientist, but basically, our bodies partake in a process called thermoregulation. That is our body’s ability to keep itself within certain boundaries even if the ambient temperature is different. You might be familiar with this process by referring to yourself as “warm-blooded”. For generating heat, our bodies are utilizing a chemical reaction where it turns glucose into energy that heats the body.
The same general principle of generating body heat is done inside of a sleeping bag. A sleeping bag acts as a layer of insulation to keep that warmth closer to our bodies. So heat is not generated any differently inside of a sleeping bag than it is outside of it. The rate of heat generation may change however depending on the ambient temperature. The sleeping bag aids us in regulating our body heat just like layers of clothing do in order to help our bodies maintain homeostasis.
How is heat held onto in a sleeping bag?
Sleeping bags come with different ratings. Those ratings are meant to suggest the minimum temperature that a camper could comfortably sleep in the bag. So if the bag says it is rated for 30° then you can reasonably expect to sleep comfortably in weather that is 30° or higher. The ratings are not 100% set in stone however and are just general recommendations. Different people enjoy sleeping at different temperatures. That is why it might be better to get a higher rating sleeping bag and wear more layers, but more on that later.
Sleeping bags are designed to be a barrier to trap the heat that your body is generating and not let it escape. Instead, the heat is supposed to be held in place around your body to maintain a good temperature. The more layers you have between your body and the cold outside ambient temperature, the easier it is for that heat to stay closer to you and the harder it is to escape. Sleeping naked in a sleeping bag would mean that the layer between you and the outside air is only your sleeping bag. Throwing on a layer of clothing would add another layer of protection. It is important, however, not to have too many layers because they can ultimately work against you.
How many layers should I wear in my sleeping bag?
The answer to that question depends entirely on the conditions of which you will be sleeping, however, you want to wear enough layers that will keep you warm enough but not too warm. If you get too warm then you may begin to sweat. Sweating is another way your body attempts to maintain homeostasis. Getting too warm means your body has to thermoregulate itself to cool down and that could end up making you colder by accident.
Sweating in a cold environment is not something you want to do. The moisture will suck heat from your body all night so do not wear too many layers that will cause you to overheat and sweat. Start with fewer layers at first to see if it is eventually enough. Basics like a beanie and socks, and thermals are a good start. Having a good sleeping bag in the first place also goes a long way. If the bag is too hot then you could always unzip it partially to allow enough air to vent out.
By now you should know that is is not warmer to sleep naked in a sleeping bag in most circumstances, especially under normal conditions. There are however a few exceptions to the rule that make sleeping naked worth it oversleeping in layers to stay warm.
What are the exceptions to the rule?
The first exception is if all of your clothing is wet or damp. It then makes more sense to sleep naked than it does to sleep in wet or damp clothing. Assuming your sleeping bag is dry and you have no other dry clothes to slip into, then sleeping naked and dry is better than sleeping layered and wet. The moisture of the clothes would get trapped inside of the sleeping bag and further degrade the effectiveness of keeping you warm throughout the night.
The next exception is if your layers are causing you to sweat. That sweat will do a good job at cooling you down, but it could do too good of a job and then cause your body not to be able to properly warm back up after dampening your clothing. If the ambient temperature isn’t all that cold and wearing layers will make you sweat then it might be better to sleep naked or unzip the sleeping bag. Just don’t get too hot to where you are sweating all night.
The last and probably least likely exception is if the layers you have is too tight for your body and actually cut off blood circulation. This will not help your body maintain proper temperature, and you should have tried on your clothes beforehand. There are some best practices you can take to ensure you can get a good night’s sleep and stay just warm enough.
What are the best choices for me to stay warm?
- Get a good sleeping bag that is properly rated for the kind of weather you will be using it a majority of the time.
- Bring enough clothes so that you can put on and take off layers as you need to in order to maintain the best temperature. Keep the layers inside of your sleeping bag with you if possible.
- Never wear wet or damp clothes and prevent yourself from sweating, it’s even better to keep anything wet or damp outside of your tent altogether if possible.
- If you do end up getting too hot inside of your sleeping bag, unzip it to vent out warm air for as long as you need to.
- Eating a good amount of calories before bed will supply your body with energy to keep in warm.
- Use the restroom before bed to avoid having to leave your sleeping bag in the middle of a cold night, it is also less liquid that your body has to keep warm.
- Use a good sleeping pad to aid you in staying warm.
- Consider a sleeping bag liner if you will be camping somewhere especially chilly.
- Do some light exercise in your tent before bed to warm up your body fast, but not too much to where it will cause you to sweat.
Conclusion
Don’t sleep naked in your sleeping bag if you want to stay warm in cold conditions unless in rare circumstances. With good equipment like your sleeping bag, sleeping pad, and warming layers you should have no issues except in the very coldest conditions. Start out with light layers and adjust as necessary to where you are comfortable, but always try to avoid sweating in a cold environment.
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