Beginner's Guide to Sleeping Bags
Sleeping bags, like many areas of outdoor equipment, can cause a lot of confusion. There's a lot of choice, and construction methods which can often make choosing one seem over-complicated. It is however, deceptively simple if you know what to look for and in this guide we'll give you a very brief run-down on how to pick a bag, and what some of the terms you'll see mean.
How to Choose a Bag
Although there's a huge variety of sleeping bags around, it's quite simple to choose one if you ignore all the features, and concentrate on the end-use...basically you need to work out what you want it for, and where you want to use it. One thing you will probably not get a choice about is the colour, most bags come in one colour only...so ideally hang up any reservations you have in advance..colour may be an important factor in jacket choice, but in sleeping bags you'll just limit yourself.
The first thing to decide on, is what temperatures you need it to cover. There's no 'catch-all' bag, you won't be able to buy one for every use, a dedicated mountaineering bag will be far too warm/heavy for tropical travel, so put some thought into the primary use, or more importantly, the temperatures where you intend to use it.
This is often a confusing area, although the most important to get the right, and is not simplified by manufacturers all having their own methods of testing and rating sleeping bags.
As a rule of thumb, the more specialist brands like Rab & Mammut will give a more accurate rating due to better testing than cheaper brands. To counter this, the cheaper brands don't make bags rated to -40°C; where the bag not performing can be lethal, as opposed to uncomfortable!
There's a few ratings around, but the most common are variations on the following set-up.
At around or above this temperature you will find the bag becomes too warm to sleep in comfortably.
You can however, open the bag up and use it like a duvet, which will often extend this limit.
This is usually the most useful statistic of a bag, and is generally expressed as either a temperature range, or a single figure. (e.g. 0°C to 10°c , or 5°C)
Simply put, it's the temperatures which the bag is designed for, and most people will experience a good night's sleep between this range.
Work out the average temperature you expect to use the bag in, and then match it to this figure.
This is the minimum figure you should use the bag in, although if temperatures begin to get this cold then you will probably have a very uncomfortable night's sleep, and in some cases, be so cold you can't sleep at all.
Try and ensure you don't use your bag in conditions approaching this temperature if you can help it. In very cold sub-zero conditions, you may be at risk of hypothermia. You can extend this limit slightly but using a liner, which we'll discuss later.
Your Own Body
You're the only person who can answer this one, but also worth bearing in mind is that when calculating ratings, manufacturers use an average. Of course people can vary widely depending on metabolism, circulation and whether they've eaten or not!
If you're the kind of person who usually feels cold, then it might be worth considering getting a bag with a few extra degrees warmth; if you're always hot, you may not need such a warm bag.
Women may also want a slightly warmer bag than men for the same end use, however specialist brands like Rab or Mammut often make women's specific bags (different proportions, fill areas & temperatures), or at least rate them for gender.
Remember to use a roll mat, and ideally eat a good meal before going to sleep, you'd be amazed at how much warmer and more comfortable your night is! Socks, thermals and hats can all be used if you find yourself too cold, don't be afraid to put them on if you feel the need to. As an example, I estimate that there's roughly a 3°C difference between my partner and I in terms of our 'comfort' temperature.
Down or Synthetic?
Once you've worked out what temperature you need to use the bag in, you'll probably have narrowed your choices down a lot. You will normally have one more important choice though...do you chose Down, or Synthetic as your insulation?
One of nature's finest insulators, down is usually from geese or ducks. You will usually see two values expressed with down; fill power (700, 800, etc.), and quality (e.g. 80/20, 90/10).
Fill power is, simply put, a measure of how much down is in the bag...the higher the fill, the more down and the warmer it will be, which is ideal to know when comparing mountain bags.
Quality is the ratio of down to feathers, the higher the ratio the 'better' the down, and the more effectively it works.
- Best for Warmth-to-Weight ratio
- Best for compressibility
- Best for comfort across extremes of temperature
- Best for lifespan (assuming care is taken)
- Will not work when wet
- More complicated cleaning/drying process
Ideal for cold, dry environments, mountaineering or winter use, travel in temperate regions.
The work-horse of insulation, synthetic bags are usually filled with a hollow-fibre which traps air for warmth.
There are many different types of fibre available, from cheap and cheerful, to the more expensive which are often very close to down in performance (and price unfortunately!)
The major advantage of synthetic fills, other than price, is that they will still work when they're wet (although it might not be hugely comfortable). This means they're the ideal choice for use in the UK or similar temperate regions.
- Best for cost
- Best for low maintenance or casual users
- Best for use in damp conditions
- Can feel uncomfortable at upper limits of temperature range
- Cheaper synthetics can have large pack-size
- May not perform as long as down. (depending on care taken)
Ideal for UK 3 spring-autumn use, general purpose camping, leisure camping, spares for guests etc. Travel in a range of regions.
By considering the above two points hopefully you've narrowed the massive choice to something more manageable...this is where comparing features can help settle the issue.
Anatomy of a Sleeping Bag
>> Mummy or Rectangular
You may not actually get a choice in this, any bag that's approaching 0ºC will usually be mummy-shaped.
If you do have a choice however, the differences are that mummy shaped bags eliminate 'cold spots' and minimise weight and pack-size...ideal for cooler conditions. Rectangular bags can feel less restrictive, especially on hot nights, and are usually used in warm weather bags.
>> Zips & Zip baffles
Zips are a major factor in heat loss, especially on cold weather bags, therefore they need to 'baffled', which prevents too much heat escaping. Zips & baffles also add extra weight.
For very cold condition use, or extremely lightweight travel you may wish to find a sleeping bag with either no zip (very hard), or a ½ - ¾ zip.
The advantage zips provide is ease of entry/exit, and more controlled ventilation, allowing use of the bag in a wider range of conditions.
Again, most zips & baffles scale with the bag's intended use, a lightweight summer bag will usually have a zip allowing it to open up fully, and minimal baffles, whereas a mountain bag will have as smaller length zip as possible, with more advanced baffling.
>> Left/Right hand Zip
As a rule of thumb, left-handed people find right handed bags easier to open/close, and vice versa. It's not actually a deal-breaker, but if there's a choice then it's worth thinking about.
You can also sometimes use a left hand & right hand model to zip together to form a double bag (not on all models!)
>> Two-Way Zip
Pretty much de facto for sleeping bags, a two way zip will help you ventilate the bag, allowing for a more comfortable night's sleep.
Like most things, you'll find the hood is suitable for the temperature range, warm weather bags have loose hoods designed for a little extra warmth on cooler nights. Cold weather bags will have much more technical hood, designed to eliminate as much heat-loss as possible.
>> Neck baffles
Many bags have a neck baffle for creating a seal to stop body heat escaping from the torso area. All cold weather bags will have this feature so again, it's not really something you'll chose a bag for, but if you've got the temperature range correct, the attached baffle will be fine. Some do have elasticated cords to allow for quick escapes should you wake up upside down in your bag.
Many bags will have a top pocket for keys, medication etc. Sometimes it's zipped, sometimes it's Velcro.
This is a guide to itself really, but at a most basic level, entry-level/warm weather bags tend to have a 'stitch-through' construction, which is easy to achieve and cheap. It will cause cold-spots across the seams, but you probably won't be using the bag in conditions where you'll notice.
The more technical method of constructing a bag basically consists of making Box, or Trapezoid baffles (compartments) for the insulation (especially down) to live in, which prevents it from migrating to your feet. It also helps to ensure that there are no cold-spots. There are many variations on the above methods including shingle and V-Shaped baffles, but the pictured ones are the 'usual suspects'.
Sometimes different combinations of baffles and/or fill are used on different areas of the bag, so you may have different fill over the feet, legs and torso areas. This helps save weight and keep insulation distribution where it's need most.
For a beginner's guide it's acceptable to say that, if you've chosen the correct temperature range for the bag (especially if it's from a well-respected supplier like Rab or Mammut), then the construction will be suited to purpose.
>> Sleeping Bag Liners
A very useful addition to any bag is a sleeping bag liner. Commonly available in cotton, silk or fleece, liners have two main benefits.
- They increase the lower temperature range, so you can eek out a few more degrees, making your sleeping bag more versatile!
- They reduce the need to wash you bag, thus improving the lifespan.
Cotton is the cheap option, and is very reasonably priced. Silk is the luxurious option, feeling nice against the skin, weight roughly a third less, taking up roughly a third of the space, but cost roughly three times more. Silk will not get infested with, but cotton can. Anti-bedbug/anti-microbial treatments are available, which is useful for extended, or tropical use.
Rectangular liners are ideal for warm weather travel, mummy shaped are ideal for actually lining a bag as it decreases bunching around the feet and feels less rumpled.
Up to 80% of your body heat is lost to the ground when sleeping, a decent sleeping or roll-mat like a Therm-a-Rest can make a huge amount of difference to your night. As a minimum sleeping bag manufacturers expect you to on a foam roll mat when calculating temperatures.
Never roll your sleeping bag to fit in into its stuff-sack...it's both really hard to do, and will also reduce the lifespan of the bag by pulling fibres. (This applies to waterproof/down jackets as well)
Just stuff in the feet and continue, it's much easier, and better for the bag!
Don't store sleeping bags in their stuff-sacks, it reduces their lifespan and temperature rating if done long enough...try and store hanging in a wardrobe, or even loosely packed into a bin-bag or similar.
Washing sleeping bags will reduce their lifespan slightly, try not to wash them too often (which means try not to get them too dirty! A liner can help you out here as you'll generally only need to wash that, and air the sleeping bag instead. If you do need to wash it, be sure to follow the manufacturer's instructions and use suitable cleaning products.