How to Choose a Sleeping Bag: Temperature Ratings
How to Choose a Sleeping Bag: Temperature Ratings
Whether you are spending several days in the backcountry, or you’re doing a weekend of car camping, the temperature rating of your sleeping bag is a major consideration for staying warm and having a restful night’s sleep. Keep in mind that you are the source of heat in your sleeping bag, so along with temperature rating, you need to make sure your sleeping bag fits well. If your sleeping bag is too big or too long, you are going to have to heat up more space, and you may sleep colder than the actual temperature rating for the bag. Also, if your bag is too small for you, you are going to overly compress some of the insulation. So, along with temperature rating, the size of the sleeping bag really does matter.
Most sleeping bags will have a temperature rating. Some will just have a flat 20-degree, 15-degree, etc. rating. Some sleeping bags will have a European norm, or “EN” rating, and that typically gives you an upper limit of comfort and a lower limit rating, or risk rating. You want to stay away from that lower limit, because you are definitely going to be cold at that point and you want to be more towards the comfort or the upper level rating.
These temperature ratings are a really good place to start, but they are not the only feature of any given sleeping bag; there are lots of other variables to consider when choosing a bag. The first variable to consider is your sleeping pad. Like sleeping bags, sleeping pads also have temperature ratings. Most of the time these are referred to as an R-value, which indicates the insulation strength of the pad; the lower the R-value of a sleeping pad, the lower the thermo-efficiency it is going to provide. A higher R-value is going to insulate you better from the cold ground. For example, if you have a zero degree sleeping bag, you are going to want to pair it with a four-season sleeping pad with a high R-value. If you have a lighter weight summer sleeping bag, you are going to want to pair it with a sleeping pad that doesn’t necessarily give you a lot of warmth.
The second thing to consider when choosing a sleeping bag is the tent that you are going to be in. Whether you are in a three season or a four season tent, keep in mind that it is going to be a little bit warmer inside the tent because you are trapping the heat your body naturally produces, and if you are sharing the tent with a couple of other people, their body heat will be building up, as well.
The third thing to consider is gender. There are women’s specific sleeping bags that tend to have an EN or a comfort rating for women, which has been determined based on the assumption that women sleep colder and lose heat from different areas of the body than men. There are also sleeping bags that are not gender-specific, and those will have a separate men’s and women’s comfort rating.
The next thing to think about is your metabolism. Some people, regardless of gender, tend to sleep colder and some people sleep warmer than others. If you pick a 20-degree sleeping bag for 3-season camping and you are normally a really cold sleeper, you might want to go down 10 or 15 degrees just to get that comfort rating up a little bit more. If you are a warm sleeper, you can get away with being closer to the lower limit that a sleeping bag is rated for temperature.
Another thing to consider is just the clothing that you will be wearing. For example, if you choose a sleeping bag that doesn’t have a hood, you may need to wear a hat or some type of insulating layer with a hood to prevent heat loss through your head. No matter what you wear to sleep, it should not be constrictive, as too-tight clothing may cause cut-off circulation and sleep-disrupting feelings of being cold in the middle of the night.
Obviously, choosing a specific temperature rating can be a daunting task, but there is a way to improve your bag’s temperature rating if you find that you’ve miscalculated; use a sleeping bag liner. Sleeping bag liners come in different weights, but are all quite packable and can serve a lot of purposes. You can use your liner as just a summer sheet, using it alone if it is really warm outside and you don’t even need your sleeping bag. You can also couple it with your sleeping bag to add warmth. Some sleeping bag liners actually come with temperature ratings of their own, so they will promise to improve the warmth of your bag by 10 or 15 degrees. Others don’t have a temperature rating, so you may have to judge potential warmth by the particular material the liner is made from. Liners also protect the inside of your sleeping bag. For example, if you are sweaty from backpacking all day, you may not want to crawl right into your bag and transfer that sweat to material that’s not necessarily easy-care (such as some down-insulated bags). Sleeping bag liners are easier to wash than many sleeping bags themselves.
One final thing to think about is there are also dual-rated sleeping bags. These bags have a rating of 55 slash 35 or something along those lines. The idea behind a dual temperature-rated sleeping bag is that one side of the bag is more lofty than the other side. If it is 35 degrees outside, you would want to put the more lofty side facing up so it is going to trap in more of your heat from the front side of your body. If it is a warmer night, you can flip the bag to the other side. These bags are usually two different colors so you can tell the difference between the two sides. These bags offer some versatility and are a good option for people who are traveling and may be sleeping outside one night and sleeping inside the next night.
In the end, there are lots of considerations when choosing a temperature rating for your sleeping bag. We hope to have covered many of them here so you can choose confidently and sleep well.