Product Knowledge: Buying a Cold Weather Sleeping Bag



With warm summer nights fading in the rearview mirror, most outdoor lovers are packing up their camping gear for the year. Fall is here, and thoughts of powder days and cozy evenings spent indoors are once again replacing daydreams of nights spent around the campfire.

But dismiss cold-weather camping as a venture reserved only for those with a few screws loose, and you’d be missing out on one of the best outdoor experience one could have. Think about it: crisp nights with stars and northern lights shining bright, the usual crowds long gone and serene frosty mornings spent sipping hot campfire coffee. If there’s a better way to experience the fall, we’ve yet to find it.

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If prepared and properly equipped, cold-weather camping can be one of life’s true joys. With this in mind, we sat down with outdoor gear manufacturer Big Agnes representative Carl Johnson to get the skinny on buying and caring for a cold-weather sleeping bag.




Many sleeping bags have what’s referred to as an EN Rating, the international standardization of sleeping bag temperature. It’s a relatively expensive process to acquire an EN Rating (only 3-4 labs around the world will certify an EN Rating for all manufacturers), but it’s the only way to know for certain a bag is accurate in its temperature rating. That’s not to say a bag without the EN Rating isn’t worth considering, it’s just not guaranteed to the industry standard.

“Generally speaking, the EN number correlates to the survival rating of the sleeping bag at that temperature,” says Johnson. “Let’s say you get a zero degree bag, and the temperature drops to zero degrees. You’re not going to freeze, but you’re not going to be very comfortable.”

Johnson suggests erring on the side of caution and getting a bag rated at least five degrees less than the minimum temperature you’ll be experiencing.

Some manufacturers, like Big Agnes, offer a modular “sleep system” where multiple bags can be used together to lower the temperature rating. But more important than any EN Rating is the fit and comfort of a sleeping bag.




While shape is more of a comfort thing, fit is crucial to keeping you warm. If the bag is too big, it creates a dead airspace between you and the bag. This dead space takes more energy to heat up and dead air tends to cool off quickly, resulting in a bag that will sleep a lot colder. And if the bag fits too tightly, it’s just not going to be comfortable.

“You don’t want the bag to be snug, but you don’t want too much extra space,” says Johnson. “The rule of thumb for comfort and fit is lay on your back in the sleeping bag, and then lay on your side. As long as it doesn’t feel like it’s constricting you at either of these two points, it’s a good gauge that’s it’s the right fit.”

Johnson adds that sleeping bags are made to fit a wide population, and most average-sized people can feel comfortable buying a sleeping bag online. But for larger or smaller people, Johnson suggests they may want to try out a bag in the store first.




Probably one of the most debated topics when it comes to sleeping bags is natural down versus synthetic fill.

“Down and synthetic each have their own places in the market,” says Johnson. “Synthetic is the less expensive option, and it also performs better than traditional down in wet conditions, but down tends to pack smaller and be lighter.”

Many manufacturers offer both options, and Big Agnes has moved its down line almost exclusively to a product called DownTec, a water-repellent down that doesn’t add weight or cost.

So what about fill level? Down bags have different fill levels, ranging roughly between 600 and 900. A 600-fill bag will be made from coarser feathers. These feathers are bigger, and easier to pluck of the bird. With a 900-fill bag, the feathers are much finer, more efficient and there are less of them on the bird, which makes for a more expensive bag. But you need less 900 fill down to achieve the same warmth, which makes the bag much lighter and compact.




It’s best to think of a good sleeping bag as an investment. Spending more for a quality bag upfront will likely pay off in the long run. And caring for your investment is just as important as the bag you choose.

One thing consumers should look for is a ripstop nylon material for the shell,” says Johnson. “Occasionally bag manufacturers will use a heavier polyester or a cotton for a more value-oriented bag. They can be more durable, because it’s a thicker fabric, but that fabric is generally cheaper to produce and can be heavier. It can get really heavy when wet, and often doesn’t pack very well.”

Price for a sleeping bag is determined by the quality of the nylon itself, says Johnson. “An ultra thin ripstop nylon is going to add a lot of cost to the bag.”

When it comes to caring for a down bag, Johnson stresses the importance of hanging a bag until it’s bone dry after every excursion, typically at least 24 hours.

Also, you should have two stuff sacks, one to pack the bag, and a larger one for when you’re storing the bag. Down bags should never be stored compressed.

“It will add a lot of life to the down if it’s stored not compressed,” says Johnson. “The filaments on the feather itself will break down a lot slower if it’s stored in an expanded way.”

For laundering, there are specific washes for down, and Johnson stresses to only ever wash a bag in a front-loading washing machine. Another trick is to machine dry the bag on low heat, with two tennis balls in the load.

“The tennis balls basically punch the down out, like fluffing a pillow,” says Johnson. “A lot of people complain about down sleeping bags getting flat, that the loft just isn’t there after a handful of years. And a lot of that can be remedied by just throwing it in the dryer with a couple tennis balls. It makes the bag perform better, because it fluffs out the down.

“Also, washing a bag helps remove the oils that a bag collects form your skin,” he adds, “These oils can also contribute to the flattening of the down and the breathability of the liner. So washing a bag can help get rid of the skin oils and actually help fluff the feathers, which will keep you warmer and add to the longevity of the bag.”

Caring for a synthetic fill bag is primarily the same, but the tennis ball trick doesn’t work as well.



We touched on breathability, but how important is it really? Turns out, it’s crucial.

“You want a highly breathable shell and liner,” says Johnson. “Because just like a baselayer, you want to the perspiration to wick away from your body and exit the bag. Even in cold weather, everybody sweats a little bit when they sleep, even if you don’t feel it. You want that sweat to leave the sleeping bag, or your going to feel clammy.”

And as with most cold weather gear, layering is your friend.

“I personally think that a sleeping bag needs to be bought so that you can sleep in it with a baselayer or nothing on; it should be warm enough for the coldest conditions, and you can add on from there,” says Johnson. “If you reach the lower extreme of the temperature rating, it’s not a bad thing to wear a down puffy or down pants a that point.”

Another thing to consider is the zipper. Bags come in different configurations: 1/4 zip, 1/2 zip and fill head-to-toe zip. If you’re looking to shave ounces, a 1/4 zip is going to be lighter and more compressible, but a full zip allows you to unzip and cool down without exiting the bag.



The old adage within the outdoor community—you’re bag is only as warm as your sleeping pad—definitely rings true.

An ingenious feature on many Big Agnes bags is the Big Agnes Sleep System. Opting to remove the fill from the bottom of the bag for a sleeve to insert a sleeping pad, not only shaves weight and compressed size, but also keeps you from sliding off your pad in the middle of the night.

You might be asking, wouldn’t removing the bottom layer of insulation make the bag colder? The short answer is no.

“Insulation traps air, and this loft actually stores warmth,” says Johnson. “So when you crush that insulation by laying on it, it actually doesn’t provide any insulation value. At that point, the pad is providing all the insulation.”

Like we said, ingenious.

So there you have it. Now you’re equipped with all you need to know about purchasing your next sleeping bag. Because let’s face it, life’s too short to only sleep outside during the warmer months.

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