There are lots of different types of sleeping bags out there, with lots of different name brands stitched to them. Until I got into backpacking, my idea of a sleeping bag was the rectangular sleeping bags we used to go car camping, and that was it. I didn’t think about temperature ratings, or cuts, or draft collars, or any of this stuff. But I found out quick, there’s a lot to think about. So, I will try to break it down and hopefully make it a little easier to you. (But again, you go research, don’t rely on my word alone. Sleeping bags are a very personal matter.)
All sleeping bags do the same thing, they trap body heat in the insulation fibers that are between the top and bottom liners. It is the insulation between these liners that is what makes the difference. So I will start with fill. Basically, you have two types. Down and synthetic.
I’ll start with down. Down is mainly from geese but is sometimes collected from ducks. Down is graded by fill power. You may see some sleeping bags with things like this: 550 Down Fill, 650 Down Fill, 800 Down Fill, 850+ Down Fill, etc. These are down fills. Basically the higher the fill, the better, both in terms of weight as well in the down’s ability to retain heat. However, the higher the number, the higher the $$$.
So, what do the numbers mean? Well basically the numbers represent how many cubic inches 1 oz of down will occupy when the down is lofted. So, it is obvious that 900 cubic inches (900 down fill) is more than 550 cubic inches (550 down fill), so it now makes sense that the higher the down fill rating, the more space is occupied. This means that less of the higher grade down is needed to fill a space, so the overall weight is less with higher down fills.
Now, this explains the weight savings, but how about the ability to retain warmth better? The higher fill power down is collected from the more matured geese. This means bigger down clusters and more of them. These bigger, more abundant clusters equals more insulating air pockets, which equals more retained warmth. 900 fill power is about the most that will be had with down and this is pretty expensive to have.
One thing to take into consideration with down is that when down is wet (completely) it offers no thermal insulation, and it weighs a lot more than it did to begin with. The difference between down and synthetic when wet is that the actual down is saturated and needs to be dried out, whereas with synthetic, the insulation is not saturated, but rather the spaces (air pockets) in between is filled with water. With this in mind, synthetic can still offer some thermal insulation when wet (theoretically), whereas with down there are no pockets to trap heat in. So, if you go for down, get a good waterproof stuff sack to keep it in, and keep it dry as your life could depend on it. (However, why wouldn’t you do the same with your synthetic bag? From what I’ve heard they are both miserable to be in when that wet.)
As for synthetic, I am not real familiar with all the different types. All I really know about synthetics is that there are a few different types. Some is heavier than others, and some will compress better than others (although none is as light as down, compresses as well as down, or insulates as well as down). My suggestion is to really look into the type of synthetic fill when buying a synthetic bag. Research it.
Another thing to consider with sleeping bags is the cut. Basically there are three cuts:
Traditionally, the rectangular are reserved for car-camping and the mummy cut are for backpacking. Why? Because of weight, and even insulating factors. Basically, the less air space inside the sleeping bag to heat the better, however, if there is none, then there is no space to heat. This is why it is not recommended to wear too much clothing while inside the sleeping bag. If the clothing actually compresses the insulation provided by the sleeping bag, the clothing is actually counter-productive and you will be colder. What keeps you warm is air pockets, this is why a few layers inside a well lofted sleeping bag will work wonders.
The rectangular sleeping bag offers a large air pocket because of all the room inside, however this is not the main reason backpackers don’t (typically) pack these bags for their trips. Weight is the biggest reason. These bags can weigh a lot, It is nothing for a 0* F sleeping bag to weigh nearly 10 pounds. However, you can get a mummy cut 0* F sleeping bag for around 3 pounds or less.
Some companies offer semi-rectangular cut bags. These bags are good for people with a larger build, or simply for people who don’t like the tight fit of a mummy bag. These are obviously slightly heavier than mummy cut bags, and depending on the size of the person inside the bag, could provide less warmth than a smaller cut bag. Again, this all comes down to the amount of air space inside the bag.
There are other things to take into consideration on sleeping bags, such as hoods. Pretty much all mummy cut sleeping bags have these, and they can be a great thing to have in the colder weather for its added warmth, and can be bundled underneath your head during the summer for more “pillow.” Other things such as zipper length can be an issue. Some bags are made with zippers that only go half way down, which does allow for a lighter weight sleeping bag. while others go all the way down and allows the bag to be opened up and used more like a blanket or a quilt. Using the bag opened up allows the bag to be used in a wider range of temperatures, because of the ability to vent.
There are still other features to consider to, such as a draft tube, which is a tube that runs the length of the zipper to keep cold air from seeping in, or warm air from seeping out. A draft collar, which is a collar of fill that runs over your chest or neck and keeps air from exchanging when moving around inside your bag. Also, consider the way that the bag is sewn; is it sewn through or is it comprised of baffles. A sewn through bag is fine for temps above thirty, however, in temps less than this you will feel the cold air seep through where the bag is sewn due to a lack of insulation. This is where the baffles come in. A baffle is a solid chamber of fill that completely covers you, leaving no areas for cold air to seep in.
There are other little things to look into such as pockets on the sleeping bag, usually at chest level, zippered foot boxes for venting options, and the ability for sleeping bags to be zipped together so that you can share a sleeping bag with that special someone. Also, does the bag come with both a stuff sack and a cotton storage sack? No matter if the bag is synthetic or down filled, the sleeping bag should not be in the stuff sack unless it needs to be, such as when you are hiking. For storage, the bag should be stored either loosely inside a cotton storage bag, opened up and laid out somewhere flat, or even hanging from the hang loops on the bag.
One other thing to take into consideration when choosing a sleeping bag is the material it is made of. This is more of a personal thing as well, since the type of material depends on the person using the bag, and the conditions in which it will be used. Some materials are more waterproof while others are more breathable. Some are more durable than others where as some need more special attention because they may sacrifice some of the durability for the purpose of a ultra-light weight bag. Again, these all depend on the conditions in which you intend on using your sleeping bag.
And then there are temperature ratings. These can be a bit, well, overrated. Most sleeping bag companies have their own idea of how to determine the temperature ratings, which makes it hard to compare bags, sometimes even by the same company, let alone two different companies. There are a couple of manufactures that are pretty spot on for what they claim their bags to be. (Two of them are Feathered Friends and Western Mountaineering. In my opinion – and many others, but maybe not necessarily to you.)
However, there is a rating system that is slowly starting to draw in more manufacturers so that there can be a more realistic way to compare sleeping bags. The system is called the European Norm, or the EN ratings. This system comes up with four readings, three of which are typically listed:
- EN Comfort Rating. This number represents to what temperature a “standard” woman can sleep comfortably in a relaxed position in the bag.
- EN Lower Limit Rating. This number represents to what temperature a “standard” man can sleep in a curled position for 8 hours without waking in the bag.
- EN Extreme Rating. This number represents the minimum temperature a “standard” woman can survive for 6 hours without the risk of dying in the bag, however frostbite is a possibility at this point.
Some of the manufacturers have gone to the EN rating system (The North Face, REI, and Marmot to name a few). These ratings are usually listed on the hang tags on the bag, or on the manufacturer’s website. It’s also never a bad idea to ask a sales rep. There are also CLO values that can also help determine a more accurate temperature rating of a bag, but I am not familiar with it, so I won’t try to act like it!However, these are great things to study up on for your own personal knowledge (and then you can let me know!)
There is a way to get a pretty good estimate of temperature rating for down bags just by letting the sleeping bag lie out and loft up. Just measure the thickness of it (keeping in mind that half the thickness is from the bottom half of the bag and will be compressed underneath you, however to keep confusion down these estimates are based on total loft of top and bottom together.)
- 3 inches equals 40* F
- 4 inches equals 30* F
- 5 inches equals 20* F
- 6 inches equals 10* F
- 7 inches equals 0* F
- 8 inches equals -10* F
- 9 inches equals -25* F
- 10 inches equals -40* F
Again, these are just rough estimates. There are a few things to take into consideration when doing this, such as size of bag and the size of the person going in it. Also, the construction and quality of materials of the bag must be taken into consideration.
On another note, another general rule of thumb is to buy a bag 10 degrees lower than what you are expecting to need it for. (If you are expecting to use the bag in 20* weather, look at some 10* bags.) This will help to take into consideration the possibility of an overrated bag. But also try to know what kind of sleeper you are: Do you sleep cold? Do you sleep hot? Just by knowing these things can also help you in making a wise choice in which sleeping bag to buy. And it is never a bad idea to test the bag at home, outside in the back yard or even on the porch one night before relying on the bag, especially in extreme situations, or even just for comfort purposes is never a bad idea.
A liner is an option for some people. Liners are made of a few different materials and serve two main purposes. 1 Extra warmth, and 2. they help to keep your sleeping bag cleaner. I have read that some liners will add anywhere from 9 – 25 degrees of extra warmth to your sleep system (bag and pad). I have read that a simple thin silk liner can add up to around 10 extra degrees of warmth, while there are others of course thicker that really add-on the extra warmth. Of course this all comes down to you though. Just because it says so, don’t necessarily mean it. The only way o know for sure is to try it out for yourself.
One thing to think about though is will you like a thin sheet inside your already snug mummy bag. Some people can’t stand it, while others love it. A good way to try it out is to get some cheap material and make a homemade liner to see how it feels for you. And then if you do like it the homemade liner may be all you need.
Another good reason is to keep your sleeping bag clean. If you have a down sleeping bag (or even a synthetic one for this matter) you will not want to throw the bag in the wash every time you get back from a trip. A liner will help to keep the oils and dirt from your body from getting all up inside that high dollar material and clogging it up. Of course, another option for this is to always use a designated set of sleep clothes. But even going this course, the oils and dirt can still come from your arms and legs.
So, these are just a few things on sleeping bags, quilts and liners. Again, do not take my word on any of these things. Go out and do the research for yourself. Things change every day and I don’t claim to know that much about any of it. I have had a very limited experience with all of this, and most of this information has been given to me second-hand or is my interpretations from the research I have done. I am only trying to help out by making things aware, so that you can dig a little too. Besides this is part of the fun. Good luck, and I hope that I have at least helped you to get started.