Winter is coming… so it’s time to start thinking about winter camping gear. Sleeping bags are part of the “big three” (tent, sleeping bag, and backpack) for any backpacker or survivalist. Whether you’re car camping with your family or backpacking in the Brooks Range, a great sleeping bag is vital which is why, in this article, we’re going to focus on how to choose the best cold weather sleeping bag for you and your adventures.
Consider This Before Choosing a Sleeping Bag
Most have a summer sleeping bag, something that’s good ‘til about 30°F, but there’s really no reason to stop camping once it gets colder. You just have to prepare for it. Before we get into conventional wisdom and what bags are worth checking out, let’s think about what you want this bag for, besides the cold.
If you’re looking to backpack vs. car camp or rent a cabin, the bag’s weight is going to be more or less important to you. However, if you’re doing long backpacking trips with big mile days, weight is going to be a huge factor for you. So, focus in on what you’ll mostly be doing this winter and use that to help guide what weight range you want to stay in.
Since we’re talking about cold weather bags in this article, figure out how cold you’re willing to go and then factor in for slightly colder since you never know what the weather is going to do. It’s easy enough to vent a bag if you’re too hot.
Speaking of temperature, how are sleeping bags rated?
Understanding the European Norm
The European Norm (EN) 13537 is the most objective and widely accepted standard when it comes to rating sleeping bags. A bag’s EN rating comes in the form of two numbers. The comfort limit rating means that the listed temperature, say 20°, is meant to keep the average “cold” sleeper comfortable. The lower limit rating is the lowest temperature that will keep a “warm” sleeper comfortable. These numbers are based off the sleeper wearing long underwear, a hat, and sleeping on a 1” thick sleeping pad.
Concerns with Cold Weather Bags and the EN
Cold weather sleeping bags are those with a temperature rating below 10° F. Makes sense, right? But here’s where it gets tricky. Bags under 10° F aren’t assigned an EN number because manufacturers have realized that this standard isn’t as reliable for cold weather bags. This leaves manufacturers with a problem.
Going back to the old way of doing things, which for manufacturers means rating bags the way they each individually did before the EN. Interestingly enough, it’s been found that before the EN manufacturers overestimated their bags warmth by about ten degrees.
Here are two tips to avoid getting caught in the cold:
- Add ten degrees to what’s advertised if you’re shopping for a bag 10° and under.
- Western Mountaineering and Marmot have shown that they have rated their bags more accurately because of how they fill and how they test their bags.
The Best Styles for Warmth
Sleeping bags keep you warm by trapping a layer of air next to your body and acting as a barrier between you, the outside air, and ground. Your body warms the trapped space of air, also known as ‘dead air’. The less space you have to heat, the faster you can get warm and the longer you stay warm.
Sleeping bags come in four shapes:
- Double Wide
We’re going to focus on semi-rectangular and mummy bags since they perform best in cold weather conditions. Mummy bags are trim fitting. They feature a narrow bottom and wider top. A semi-rectangular bag is, unsurprisingly, semi-rectangular. It’s more ovular than rectangular so you have some space for lying on your side and moving around, but the tapering at the top and bottom cuts down on extra fabric and space.
Breaking down the pros are cons of the two doesn’t need to be complicated:
- For less weight and more warmth: go for a mummy bag.
- For more comfort and weight: go with a semi-rectangular bag.
When Size Does Matter
Sleeping bags typically come in two sizes. Regular and Long. But you can find short and extra–long among certain manufacturers.
So how do you get the right fit?
You want to get a bag that fits you so you’re fully covered but there isn’t extra space for your body to have to try to warm. Look at the product specs and see what it’s “fits up to” measurements are, then try it out in a store. There are a lot of things in life to get cold feet over, a sleeping bag that’s too long is not one of them.
Three Insulation Options
Insulation (also known as fill) doesn’t provide warmth, it minimizes the amount of body heat you lose throughout the night. It traps heat, not creates it like some people commonly misunderstand.
Fill comes in three types:
- Goose or duck
- There’s a water-resistant (or hydrophobic) option as well.
- Usually Polyester
- Down and synthetic are blended together to try to capitalize on the benefits of both and offset the disadvantages.
Synthetic is an appealing choice for most because it’s cheaper than down, quick drying, insulates even when wet, and is hypoallergenic. Down is pricier, packs down smaller than synthetic, excels in cold and dry conditions, and maintains its loft longer than synthetics though.
I want to focus on a word here, loft. It’s very important to understand loft when purchasing a cold weather sleeping bag, even more so than when buying a summer bag because trapping heat is more important in the cold. The loft is what enables a sleeping bag to trap heat and it’s measured in terms of fill power. Fill power is calculated by how many cubic inches one ounce of down can fill in a testing device. Feathers taken from more mature birds require fewer plumes to fill a space and therefore achieve a certain temperature rating. This means that a 700-fill power down bag rated for +20° F will be lighter than a 600-fill power down bag rated for +20° F.
Additional Features to Consider
We’ll start off by going over aspects of the actual cold weather sleeping bag that you have some choice and variability in. Then we’ll move into aspects that are more in the accessory category, things that can be added to your sleeping bag.
Shell and Lining
The outer shell of a sleeping bag is made of either rip-stop nylon or polyester because they are known for their durability. You also might want to consider a bag that’s been treated with a durable water repellant (DWR) finish. DWR prevents water from soaking into the bag and instead allows it to bead up on the surface of the bag. You can easily tell if a bag has been treated by spraying the bag with water, which good retailers will allow you to do and will have a spray bottle on hand.
You’re going to lose a lot of heat out of your head, which is why a semi-rectangular or mummy bag is preferable over a rectangle bag because the come with a built in hood. You can cinch it down tighter or looser around your face to create a warm and comfortable sleeping arrangement with adjustable pull strings.
Pillow pockets are found in some sleeping bag hoods. You can stuff your clothes into it to create a pillow and keep your clothes warm for the morning or insert a camping pillow.
A draft collar is an insulated baffle around your head and neck. It helps to prevent body heat from escaping out of the bag and helps to prevent cold air from seeping in.
The draft tube runs along the inside of the sleeping bag’s zipper. It’s filled with insulation and is designed to keep warmth from escaping through the zipper’s coils. Every little bit helps, right?
If you like to sleep on your back or tend to have cold feet, a foot box might be of interest to you. It’s basically some extra space and insulation around your feet to make you more comfortable and to reduce the tension your feet put on the bag. This helps extend the overall life of the insulation.
Sleeping Pad Sleeve
Some sleeping bags have a sleeve on their underside to slip in a sleeping pad. This is a great option if you roll around while you sleep and it also promotes warmth by keeping you off the ground and on your pad.
Sleeping Pad: Forget the Ground
Now, you’ve probably slept on the ground before with no problem. Maybe it wasn’t comfy but it was do-able. Maybe you’re looking to save some money and pack space by foregoing one again. All I can say is, it’s worth the investment. It’s worth the physical comfort of laying on something soft and it’s worth the extra heat it’ll keep in. There’s a lot of options for this piece of gear too. There’s anything from what mostly resembles a yoga mat to blow up, chambered air mattress. For cold weather, you’ll want to focus on a closed cell foam pad because air mattress models will only insulate down to about 30° F. Therm-A-Rest is one of the best manufacturers in sleeping pads and their Riderest Solar pad is the type you’ll want to get for cold weather sleeping.
A key to saving money here is to look for older models, the newer the more expensive.
Liner: Turn up the Heat
Since you’re cold weather camping, adding a liner to your bag is something you’ll want to consider. Liners are sold separately from sleeping bags and come in a few different fabrics, each having their own pros and cons. Your options range from silk, cotton, fleece/ microfleece, synthetics and insulated. A liner not only keeps your bag clean because it is a barrier between yourself and the bag, but they add anywhere from 8° to 15° F of warmth to your bag. Liners range in price from ~$40 to ~$100. On the lower end, you have blended options, like silk and cotton and the pricier options are 100% merino wool or silk. When you’re ready to go shopping, Sea to Summit and Cocoon are two quality manufacturers for liners.
Budgeting for a Sleeping Bag: Buy Once, Cry Once
When it comes to buying gear as important as a sleeping bag, it’s best just to buy once and cry once. Especially when thinking about camping in cold weather conditions, it’s just not worth it to go cheap and pay with freezer burn. Quality, cold weather bags range from about ~$300 to ~$600. But that doesn’t mean you have to break the bank to stay warm. Many stores like REI have an outlet or garage sale where you can buy gear cheaper and there are off-market stores like Amazon that are definitely worth checking out before you take the plunge.
Popular Options for Cold Weather Bags
We’ve got four solid cold weather sleeping bag options for you to see what a good combination of many of the features we’ve talked about above will look like. They’re ordered from warmest to coolest (rated -50 to 5° F).
Military Issue Modular Sleep System (4 Parts)
This is a flexible four piece (or ‘modular’) sleeping system issued from the U.S. government.
It’s made in the U.S.A and features a waterproof Gore-Tex bivy and carry sack. Each layer can be used separately but when combined, this bag is rated to -50° F and it weighs around nine pounds. Vets who’ve used this tend to love it above all other options.
What it includes:
- Compression sack
- Intermediate sleeping bag
- Patrol sleeping bag
- Bivy cover
Intermediate Sleeping Bag:
- Made of water resistant rip-stop nylon (Black)
- Rated to -10° F
- Additional insulation in foot box
- Quilted chest collar
- Adjustable hood
Patrol Sleeping Bag:
- Made of rip-stop nylon (Olive drab green)
- Rated to 30° F
- Reversible, double pull slider allows for air flow
- Made of 3 layers Gore-Tex (Woodland camo)
This mummy style bag is rated for -40° F and weighs 4lbs. Its sizing is limited to regular and long and comes with its own stuff sack.
- 800+ goose down fill
- 30D rip-stop nylon shell
- Coated with Pertex Shield 2L laminate (breathable and waterproof)
- Nine baffles in the bag’s core
- Head contains six baffles
- Adjustable draw cord hood
- Draft tube along the zipper
- Internal pocket
- Wrap around foot box
Feathered Friends Snowbunting
This bag is rated to 0° F, is lightweight, waterproof and features:
- iPertex Shield EX shell material
- Stuffed with 850 fill down
- Draft tube
- Neck baffle
The hood and neck baffle are closed with snaps instead of Velcro because snaps are stronger and less likely to wear out or come undone. This sleeping bag is a trim cut making it a great option to maximize heat but it might not be the bag for you if you like having a little extra room to move around. Because of its smaller cut, it also means the weight comes in at around 43oz.
This bag is ideal for backcountry skiing, alpine climbing, and mountaineering.
This sleeping bag is rated to 5° F, even more lightweight than the Snowbunting at 39oz, and is highly water resistant. This bag has a similarly trim fit, utilizes Velcro, and has two anti-snag zippers.
It also features:
- MicroLite XP shell material
- 859 fill down
- Continuous baffling from the top to bottom of the bag
- Room for accessories
- Neck baffle
This bag is considered usable for all purposes and year-round.
Warming to a Decision
When you take a piece of gear into the field, you want to be able to trust it completely to do what you need it to do: keep you alive and hopefully keep you comfortable. As veterans, it might be tempting to fall back on old practices and continue to use familiar gear, but with today’s technology you don’t have to sacrifice comfort for durability or effectiveness as much as you may have in the past. With the information we’ve covered from external (shell materials) and internal (types of fill) anatomy of bags, the industry standards and pitfalls of the EN, and all of the accessory options that are available to you, you’re now able to make an informed decision for yourself. Hopefully, the four bags we’ve featured can give you a head start into that.
Semper Paratus! Adventure far!