Down or synthetic? Mummy or rectangular? Such existential questions have been plaguing outdoorsmen and women since the beginning of time, especially when lying awake in an ill-fitting or poorly insulated sleeping bag on an extremely cold night. If this has happened to you, don’t fret – you’re in good company. We’ve all been there. It doesn’t have to be this way, though. With the help of our insightful buyer’s guide to sleeping bags, you’ll have all the info you need to sleep comfortably outdoors. In this post, we’re going to go over the following:
- Sleeping bags and area of use.
- Sleeping bag shapes
- Sleeping bags and temperature
- Down vs. synthetic
- Characteristics of a “good sleeping bag”
- Sleeping bag care
Area of use
There are several reasons for buying the wrong sleeping bag, including asking the wrong questions or just getting poor advice in your local shop. The first question a customer will usually ask is: “What kind of sleeping bag do I need?” A good salesman would then answer the customer with another question, like: “Well, where do you plan on going?” This is an extremely important question to ask because it will narrow down the possibilities by focussing on sleeping bags made for a particular area of use or purpose. After all, you would need an entirely different bag for Mexico than you would for the Alps, long distance hiking or a trip to Norway. Unfortunately, when it comes to sleeping bags, you’ll never find “the one” that can do it all.
Other questions a salesman might ask would be the following:
“What is most important to you? Warmth? Weight? Comfort and space? Susceptibility to moisture? Packability? Or maybe even several of these things?
Finding a sleeping bag that has many of the above-mentioned characteristics is not impossible, but it does have its price. Let’s face it: you won’t get both sophisticated technology and quality craftsmanship at some discount retailer. So, if the last question is something along the lines of “How much are you willing to spend?”, then you know you have a good chance of sifting out the ideal sleeping bag for your individual needs.
If you know where you’re going to use your sleeping, the question of “down or synthetic?” usually answers itself. However, the decision is further complicated by the fact that there is a wide variety of down and synthetic bags of varying quality. This means that the best synthetic fibres can actually trump the seemingly more powerful, “higher-quality” down in a less than optimal model. This is also reflected in the price of high-end synthetic sleeping bags, which can be even more expensive than simpler down models.
That being said, the best thing to do would be to go over a list of criteria and rank them according to importance. So, that’s what we’re going to do now! Here are the criteria that most outdoorsmen and women would deem important:
Shape is usually the easiest criterion to tick off. When it comes to pack size, weight and warmth, mummy bags (a snug-fitting bag that tapers toward the feet) are basically the only viable option, with the occasional exception of some eggshell bags, which are wider at the hip and knees. The blanket shape (rectangular) is more intended for indoor use – for motorhomes, holiday homes or at home as a guest bed.
The mummy shape is the narrowest, so not only does it have less material as a whole, but the interior warms up the fastest as well. The eggshell may be more spacious and comfortable, but you pay for it with more weight and volume and poorer insulation. However, for outdoorsmen and women with a larger build, the eggshell shape can often be the best option in terms of function.
“How warm is it?”, “How warm does it have to be?” This is a concern for many an outdoorsman. Coincidentally, we have already written an article with the answer, which you can find right here. Instead of forcing you to read the entire article, allow me to summarise it, with the assumption that you are a person with an average sensitivity to cold:
Think about the lowest night-time temperatures you’re expecting to encounter on your trip and choose a sleeping bag that has this temperature as the comfort temperature. Make sure it’s not the comfort limit or the extreme temperature rating. You’ll find all of these three ratings on each sleeping bag. Although the comfort limit temperature is often referred to as the “area of use”, the limit describes the lower threshold. Only under the very best conditions will it feel “comfortable”. If you find yourself in the extreme temperature range, it’ll be quite the epic night – and I don’t mean that in a good way.
Since there is an EU standard temperature rating system for sleeping bags used by almost all manufacturers worldwide, they are relatively comparable and reliable. For you, this means: Only if the air temperature is no colder than the comfort temperature will you be able to get a good night’s sleep in the sleeping bag, even in suboptimal conditions.
The categories are divided up according to the temperature range:
- Summer sleeping bags: Comfort temperature above 12°C
- Three-season sleeping bags: Comfort temperature up to about 0°C
- Winter sleeping bags: Comfort temperature significantly below 0°C
Keep in mind that the temperatures are only estimates because the three sleeping bag categories are not clearly defined. Also: the category ”three seasons” covers the majority of an outdoorsman’s needs, as it is suitable for such activities as summer hill walks and alpine mountaineering as well as summer treks in Norway and Lapland.
Those of you looking for something significantly warmer have probably noticed that such bags either have temperature ratings from the manufacturer or none at all. This is due to the fact that the testing methods employed for the EU standard only work up to a certain fill weight. If a sleeping bag has a high fill weight, it is not possible to determine a comfort temperature, so you have to rely on the information provided by the manufacturer. Fortunately, this is rarely an issue, since only reputable manufacturers produce sleeping bags of this calibre and have a reputation to lose!
Weight and pack size
Another important aspect to consider along with the temperature ratings is weight, which can be lower or higher depending on the fill material, shell material and size of the bag, among other things. Since most of the material used is for the insulation, down and synthetic fibres will dominate the discussion here. We’re not going to go into too much detail, seeing as the topic of insulation material is intricate enough to fill an entire book, but what we will do is summarise two articles we have already written for purposes of comparison (the links to the articles are coming soon):
The fluffier or loftier down is, the higher its fill power. And the higher the fill power, the more air down can trap and the warmer it will be for its weight. The fill power of down is measured by placing a set mass of down into a cylinder, lowering a disc onto it in order to compress it and subsequently releasing it. The volume of the space the down fills after expanding is called fill power.
It’s measured in cubic inches, which is why “cuin” is used to indicate fill power. Down with a fill power of 600 cuin or more is considered good. 700 cuin is really high quality, and 800 cuin is regarded as extremely high quality. Although the measurement with cuin is standardised like the temperature ratings, there are differences between Europe and North America.
For example, a rating of 650 cuin in Europe would be at least 700 cuin in North America. For this reason, two sleeping bags with the same fill power value can differ in their “plumpness” or “firmness”. The sleeping bag with less will probably bear a North American logo. However, this difference does not mean that North American sleeping bags have down of “poorer quality”. You might just want to go for a higher value.
Another important value is the down-to-feather ratio. It is extremely rare to find a sleeping bag filled with pure down and no “supporting feathers”. However, in contrast to popular belief, mixing feathers in with down has little to do with reinforcing the down and much more to do with making production more economical. In fact, when it comes to large goose down, feathers actually have a negative effect on both loft and weight, increasing the latter and hindering the former. However, since hardly anybody can afford pure down, almost all down sleeping bags you’ll find on the market have a down-to-feather ratio. The first number in the ratio indicates the percentage of down, the second the percentage of feathers: there are ratios of 70/30; 80/20; 90/10 or, for high-end sleeping bags, values of 95/5. The more down, the better!
Now let’s move on to the pros and cons:
The small pack size and low weight will be something you’ll definitely appreciate when you’re lugging it around all day. The softness and balance temperature inside a down sleeping bag will keep you nice and comfortable at night. If you care for your down sleeping bag properly, it will last you a long time, even if you use it on a regular basis.
Down is more susceptible to water and moisture and when wet will lose its loft and insulating properties. Do keep in mind that the effect moisture has on down is often exaggerated, almost as if down were as sensitive as cotton candy. Your sleeping bag would have to get directly rained on or there would have to be some major dew for the down to lose its insulating properties. If airing out and drying your bag proves difficult, you can always opt for a sleeping bag with water-repellent down and a waterproof and breathable shell. But, these, of course, have their price.
You can find out more about these kinds of sleeping bags in Buyer’s Guide to Down Sleeping Bags.
As with down sleeping bags, synthetic sleeping bags should trap as much air as possible with as little material as possible. The more complex constructions (such as the shingle construction) usually achieve better warmth-to-weight ratios than the simpler constructions (such as the simple quilted through layers).
Because synthetic fillers insulate when wet, it’s always a good idea to opt for a synthetic bag for adventures in wet conditions. The lower price tag is another advantage synthetic bags have over their down counterparts, but in the end, this is usually offset by their lower durability.
In the short term, synthetic material is actually more resistant to wear and tear (e.g. spilled drinks or people constantly walking on their sleeping bag at festivals). Plus, in contrast to down, synthetic materials also hardly ever cause allergic reactions. And, last but not least, there is no direct link between synthetic insulation and maltreatment of animals, which is music to the ears of vegans and animal lovers. But, there are ethical downsides too, one being the petrochemical industry…
Even though synthetic fillers may have the same temperature ratings, they do tend to weigh more and have a larger pack size than down. Their long-term durability pales in comparison as well. Whilst down can be “like new” when properly or even professionally cleaned, any damage to your synthetic bag will really destroy it. Cleaning and caring for synthetic material is much easier and quicker than down. However, unlike down, synthetic fills cannot be refilled or replaced.
Down vs. synthetic in warm sleeping bags
Here’s something a lot of people don’t know: The weight and pack size of synthetic sleeping bags goes through the roof in the “warmer” versions. Whilst there are synthetic bags with a zero-degree comfort temperature and a backpack-compatible weight and pack size, the very same model with a -10-degree comfort rating suddenly becomes a 2-kilogram monster. Why? Well, the additional amount of synthetic fibres – even the best fibres – does not result in the corresponding amount of warmth. Therefore, in order to tack on just a few more degrees of extra warmth, you’d need a lot more insulation material.
When it comes to down, it’s a completely different story: Much less additional material is needed for the same increase in insulation. Thus, you can easily find a backpack-compatible down sleeping bag with a -10 comfort rating. Another point for down.
Comfort depends not only on the fill material and its insulating properties but also the interior space and the material used for the lining. The latter also has an effect on how dry/wet it feels and, to a lesser degree, the perceived temperature. Personal preferences play a role here as well. Some like a silky feel, whilst others prefer a more “cotton-like” feel. Obviously, cotton is unsuitable as an a lining in an outdoor sleeping bag due to its lack of functional features.
Another important factor when it comes to comfort is the length and fit of the sleeping bag. As mentioned earlier, the mummy bag is probably the best choice for mountaineers and outdoorsman when it comes to fit. Although it is the narrowest, it can be quite comfortable, provided you choose wisely! It’s always better to choose a sleeping bag that is a few centimetres “too long” instead of trying to save weight by taking a shorter version. Also: A shaped foot box is a great thing to have as well and even works well for those who sleep on their sides because the bag moves with you when you roll over in your sleep.
Whether there is a right or wrong side for the zip to be on is a purely subjective question and only plays a role if you’re planning on connecting two sleeping bags. When it comes to “warm” sleeping bags, make sure yours has a a draught tube along the zip to prevent cold draughts getting in and warm air getting out.
Since we’re on the subject of zips: Make sure they have an anti-snag guard (usually just a small, slightly stiffer strip of fabric) in addition to the already-mentioned draught tube so that they run smoothly. As for the length, a shortened zip that only goes down to the knees may make it less comfortable to get in and out of the sleeping bag, but it improves thermal performance and simultaneously reduces weight. It’s a great option for those who need something lighter and packable with good insulation.
- Hood: A sleeping bag suitable for the mountains and the outdoors must have a contoured hood that can be tightened all the way, leaving a little opening to breathe out of without pressing down on your head.
- Draught collar: Very useful when sleeping in temperatures below about 5 degrees. It is better to have to carry a few extra grams than not being able to fall asleep. A cold draught on your neck and chest can be pretty annoying. And, if there’s a big difference between the inside and outside temperature, your collar only has to be open a few centimetres to create such a draught.
- Inside pockets: A very convenient way to keep your socks dry or your camera battery warm. There’s even room to put a small heating pad in the inside pocket, which is often located at the foot of the bag.
How to identify a good sleeping bag when you see one
What are “good” values when it comes to weight, pack size, etc.? When choosing between two sleeping bags with a comfort temperature of zero degrees, the one with the smaller pack size and lower weight is the better one. If it is made of strong ripstop nylon and other high-quality (brand) materials, all the better. If you want synthetic insulation of the highest quality, brand-made fibres are the way to go. Primaloft, Thermo ProLoft from Deuter, Spirafil from Marmot or MTI 13 from Mammut are some well-known examples. They’re also known to have a good silicone coating, something that you can’t really verify by looking at them. This coating is extremely important, as it significantly increases the durability of synthetic sleeping bags.
High-quality techniques are the material-saving shingle construction or the one-sided lamination to prevent cold spots. An example of an excellent synthetic sleeping bag is the Hyperlamina Spark from Mountain Hardwear.
As mentioned above, the cuin value and the down-to-feather ratio are the most important aspects in assessing the quality of down. Examples of high-end, do-anything down sleeping bags are the Neutrino series from Rab or the sleeping bags from Sir Joseph.
Inexpensive synthetic sleeping bags are the best option for those of you who aren’t great at giving your sleeping bag the love and care it needs. They can take the wear and tear that comes with camping in damp places, but they won’t hold up for long. Because once synthetic fibres start to “fatigue”, they just give up. The insulation is nowhere near what it was when it was new. Down, on the other hand, can be reanimated if you wash it properly – yep, even down sleeping bags you’ve repeatedly stuffed in your stuff sack over the years.
Washing and caring for your sleeping bag
Contrary to popular belief, caring for your sleeping bag is pretty easy. The easiest way to start is on your trips by shaking it and airing it out in the morning before packing up. You can leave it out in the sun for a few minutes, too, but not too long – the UV rays will ruin the material.
When it comes to packing, do NOT fold or roll up the bag. It is designed to be stuffed. If you roll it up, you’ll damage the baffles. Unfortunately, some manufacturers ignore this fact and roll them up anyway, contributing to the false belief that you should roll your sleeping bag…
Stuff it when you’re on the move, but when you get home, store it in a large cotton or mesh sack. The more space the fill has, the longer it will last you.
Wash your sleeping bag as rarely as possible. When sleeping in your bag, you should wear long clothes or thermal underwear to make sure that as little sweat and dirt gets into the sleeping bag as possible. When it comes time to wash it, our Care Instructions for Sleeping Bags will help.
Unfortunately, washing sleeping bags can be very time-consuming, especially when it comes to down sleeping bags, so it’s easy to make a mistake. If you have a very expensive sleeping bag, we recommend getting it professionally cleaned. Professional cleaners would wash the down and shell separately, since down has to be washed at different temperatures than the technical fabric used for the shell. When you get your sleeping bag back, both the down and the shell will be like brand-new. Of course, it’s far from being cheap, but given the amount of time and energy you save, it’s definitely a viable option.
Finding the “the right sleeping bag” can be almost as complicated as finding “the right car”. But, we hope with our instructions, you’ll be able to find the sleeping bag that suits your needs. Then, before falling asleep, you can philosophise about existential questions instead of being distressed with existential struggle against the cold.