How to Choose The Best Cold Weather Sleeping Bag For Extreme Cold Conditions
Choosing the best cold weather sleeping bag is about more than just Temperature Rating. As you shop for the sleeping bag that’s best for you, consider these 6 factors:
- Temperature Rating
- Insulation Material
- Sleeping Bag Shape
- Zipper Design & Location
- Weight
- Additional Features
Let’s expand upon each.
Related: The Best Sleeping Bags For Camping
Temperature Rating
Sleeping bags are rated for temperature using a standardized process outlined in either EN 13537 orISO23537.
What is this process?
Essentially, a manikin rigged with thermal sensors is used in a controlled environment to rate the insulation power of a sleeping bag. Because a standard process is used every time, sleeping bags rated according to either EN 13537 or ISO 23537 criteria can be compared apples to apples.
Note: ISO 23537 became the standard in 2016. Prior to that, the standard was EN 13537. If you’re researching cold weather sleeping bags and come across EN 13537 ratings, note that it’s a similar and still useful rating.
These processes rate 3 different temperature limits for sleeping bags:
- Comfort Temperature: Lower limit of the comfort range for a sleeper in a relaxed position
- Limit Temperature: Lower limit of comfort range for a curled up sleeper
- Extreme Temperature: Lower limit for survival; the sleeper will feel cold but will survive
When you’re shopping for the best cold weather sleeping bag, you want to make sure the coldest weather you’d likely run into is above the Limit Temperature for the sleeping bag. Ideally it’s above the lower end of the Comfort Temperature range.
If there’s even a remote chance the temperature could drop below the Limit Temperature for a sleeping bag, you don’t want to buy that sleeping bag.
In the event that a sleeping bag doesn’t have a specific temperature rating, it probably has a general classification such as “Summer” or “3-Season.” If that’s the case, REI has a guide that can be used to turn those vague terms into approximate temperature ranges:
- Summer: Above 35°F
- 3-Season: 10°F-35°F
- Winter: Under 10°F
Note that the low end of these ranges is the Limit Temperature as defined above.
Insulation Material
Sleeping bag insulation can be made of two different materials:
- Synthetics, generally polyester
- Down feathers, generally duck or goose (duck is better)
While both are capable of keeping you warm, there are some key differences between the two.
Benefits of Synthetic Sleeping Bags
- Dry more quickly
- Non-allergenic
- Better insulation in wetter conditions (usually)
- Usually less expensive
Benefits of Down Sleeping Bags
- High-quality down bags can be much lighter for the same temperature rating
- Compress more easily
- Better insulation in dry conditions
- Longer lifespan when treated well
For more information, check out our Synthetic vs Down Sleeping Bag comparison.
Sleeping Bag Shape
Sleeping bags come in 4 different shapes:
- Rectangular
- Semi-rectangular (ends taper inwards)
- Mummy
- Double-wide (rectangular for two people)
The first three descend from most comfortable/spacious to least comfortable/spacious. However, spaciousness is inversely proportional to insulation power. That means the best cold weather sleeping bag probably will be a mummy sleeping bag. However, if you’re a big guy be aware that mummy bags can be more restricting.
Zipper Design & Location
The zipper is the weak point in a sleeping bag. That’s where the insulation tapers off, giving way to a potential avenue for warm air to escape. As you look for the best cold weather sleeping bags, take a long look at the zipper. You’ll want to focus on three aspects of the zipper:
- Durability and quality of construction
- Length
- Location
Durability and quality are important (obviously) because a well-designed, well-made zipper will allow less warm air to escape and is much less likely to break. A stuck zipper that won’t properly seal your sleeping bag is a recipe for disaster.
Length is important because shorter zippers reduce the risk of warm air escaping. Many mummy style sleeping bags feature half-zip zippers with fully-enclosed feet. However, the downside to these types of sleeping bags is a lack of temperature regulation in warmer temperatures. You can’t just stick your feet out to cool down.
Location isn’t quite as important on a cold weather sleeping bagunless you want to connect two sleeping bags to make one larger sleeping bag. In this case, you’ll want to choose one left-handed zipper bag and one right-handed zipper bag, making sure the zippers are the same length. Note that the major downside here is you likely lose some insulation power. However, having shared body heat can mitigate that.
Weight
Weight is more about you being able to carry the sleeping bag on your pack if you’re backpacking. Heavier sleeping bags are not warmer by default. Remember that down vs synthetic discussion above? Synthetic sleeping bags actually weigh more for the same insulation power.
If you’re looking to cut weight, mummy sleeping bags should be given strong consideration. They’re narrower and use less material with the trade-off being their restrictiveness. Semi-rectangular sleeping bags will have more weight but also be more comfortable.
7 Additional Features On Cold Weather Sleeping Bags
As you’re shopping for the best cold weather sleeping bag, consider these additional features:
Hood With Drawstring // Extreme cold weather sleeping bags often have a constricting head design with a drawstring, giving you the ability to really seal yourself in.
Baffles // Baffles are designed pockets of insulation and are intended to keep the insulation in specific areas. You can see these as the geometric stitching/seams visible from the outside of the sleeping bag. They’re especially important in down sleeping bags, as down feathers tend to shift more than synthetic polyester.
Face Mufflers // Face mufflers are baffles around the face that localize insulation to keep you warmer.
Pockets // Whether it’s tents, backpacks, or sleeping bags, pockets are ahuge part of your camping and survival gear. Consider the pocket location in your sleeping bag (if applicable). This is more important in restrictive mummy sleeping bags, as pockets near your hands to store your phone or flashlight can be especially helpful.
Footbox Shape // Also more important in mummy sleeping bags, does the footbox round off the end or have a boxier, trapezoidal shape? A trapezoidal footbox provides a more natural shape for your feet, providing more comfort and potentially placing less stress on the sleeping bag material because your feet aren’t abnormally crammed inside. The downside, however, is more material/weight.
Sleeping Pad Compatibility // Some sleeping bags are “bottomless” in design, by which I mean they don’t have insulation on the bottom. Instead, they have either a sleeve or hooks where a sleeping pad slides in or attaches. The major upside to these sleeping bags is they’re lighter and store away more compactly. If you’re bringing a sleeping pad anyway, you may want to consider one of these sleeping bag designs.
My Testing & Review Process
First, I spent 20+ nights camping in the cold weather and nasty conditions. Don’t worry, I loved (almost) every second of it! I’m a fanatic about testing and researching gear and I love to go camping in colder temperatures.
I started with the sleeping bags I already owned. Both my wife and I go camping and being the gear snob that I am, I own multiple sleeping bags already.
Next, I reach out to my many friends who share my passion for the outdoors. If I haven’t used it, there is a darn good chance they have.
Finally, I examined 100’s of verified reviews from other first-hand users.
As always, my goal is to provide you with the most accurate and unbiased review possible.
Features I Considered
I compared each of the sleeping bags by looking at the following list of features:
Shape: The shape of a sleeping bag significantly impacts its ability to keep you warm.
Fill Type: All of the bags on my list are down or premier synthetics designed to mimic and improve upon the characteristics of down.
Fill Power: We’re always looking for the most power at the lowest weight
Low-End Comfort Temp: This is how cold it can get while you still comfortably sleep through the night. Keep in mind this is often a much warmer temp than the survival rating, which is how cold it can get while you shiver away all night but still survive. Don’t get me wrong…survival temp is VERY important. But, always remember that comfort temp is what matters for a good nights sleep.
Outer Shell: The shell protects the bag (and you) from the elements. So it’s design definitely matters.
Inner Shell: The inner shell is what is next to my body and needs to be both moisture-wicking and rugged.
Weight: If you are backpacking, weight is of critical importance. We want maximum warmth with minimal weight.
Fit: One of the best things about humans is that we are all different! As such, what may be a great size for one person may be awful for another. So I try to simply comment on the size and who it is best suited for rather than Iigh it into my scoring criteria.
