Sleeping Bags - The Basics

A good sleeping bag is the difference between a good night’s sleep after a day of fun in the sun, hiking or any other crazy hobby that you can dream up, and a horrible cold night dreaming of being at home in your bed. If there is anything that can ruin a holiday faster, it’s a bad night’s sleep.  

The aim of a sleeping bag is to trap the warm air, heated by your body inside the sleeping bag, and the cold air outside. In emergency situations the right sleeping bag is the difference between life and death.

Remember that you are the heat source in a sleeping bag, the sleeping bag is just there to keep the heat trapped around your body. Ideally when you go to sleep you should be warm, dry and well fed, and not had too much alcohol. Go to the toilet before getting into your bag, once you get out most of that heat will be lost. Wear light but warm clothes like a base layer and socks and a knitted hat if you think you might be cold. Draping your jacket over you, or adding more insulation underneath you will help if you still feel cold.  

Buying a sleeping bag seems to need a degree in sleeping bag labels. Follow our quick guide to what the labels mean, and what to look for when buying your new sleeping bag.


Comfort /Warmth ratings

Seasons:

1 and 2 season sleeping bags are great for use indoors or camping on warm summers evenings, normally the lower limit is about 5 degrees at the coldest, were as 3 season sleeping bags are designed for when the nights get a little chillier in spring and autumn, maybe when temps get close to freezing, but without frost. 4 season sleeping bags should keep you toasty warm all year round. But always read the comfort temperature range, as some bags even within the same season have different ranges.

Recently a European wide system for measuring and assessing the warmth and comfort of a sleeping bag came into play. This covers the comfort range and the extremes that a sleeping bag can handle. The testing is done using a computer controlled dummy placed in a carefully controlled climate chamber and monitored to see how the sleeping bag controls the temperature around the dummy.

 It is worth noting that women need a comfort level approximately 5 degrees warmer than men. This is a general guide line and there are a large number of other factors to consider.

The Upper/Lower Limits:

these are the practical limits, you might not be comfortable, but bag should keep you warm/cool enough to sleep and be not be in extreme discomfort. At the upper end the assumption is that you’d have the bag unzipped and the hood down if you have one.

The extreme lower limit is what you will be able to survive in. Frost bite might still occur, but you should stay alive.  

Comfort level:

this is the temperature range that you should be able to be comfortable at. It’s based on a 25 years old man or woman, and you should aim for the widest range so that your bag should be as comfortable as possible, in the widest range of conditions. Normally they have two ratings, so -4/1 would mean that the bag will be comfortable for men at -4 degrees and women at 1 degree.  

Whilst it may seem simplest to buy the warmest bag possible this presents two possible issues. A sleeping bag designed for camping in the deepest snow and winter storms will be too warm to sleep in during the summer and the extra weight and bulk will make it more difficult to carry around.  

How do you handle the cold?

Some people start to shiver long before others, if you’re that person who’s putting on a jumper whilst everyone else is still in t-shirts, or turning on the heater weeks before everyone else, then remove about 5°C from the lower comfort temperature. For example, a bag with a comfort rating of 0°C might be better, if you are susceptible to the cold, than a bag that has a comfort rating of 5°C. 

The factors that influence how cold you feel include:

  • Age brings wisdom and the tendency to feel the cold more than younger people, remember the bags are tested by a pretend 25 year old. If you’re older and know you start shivering before anyone else it’s worth adding 5 degrees to those comfort ratings.
  • Women feel the cold more than men. This is scientific fact, not just a stupid statement around the camp fire by the lads bragging, sorry ladies.
  • You get used to the cold, and the warmth, occasional campers feel the cold more than regular campers, if this is your first time camping it’s worth buying the best bag you can afford, or this may be your last time camping after a cold miserable night.
  • Being hungry and thirsty can upset your body’s natural systems. Meaning you’ll feel the cold more, your body stays warm by burning calories, and after a day of hiking, or running round after the kids there is a chance your body might be low on fuel anyway.
  • It is a myth that alcohol warms you up, in fact it can make things worse, alcohol makes the blood vessels near the surface of your skin dilate, hence why drunk people get red in the face. This blood flowing to the surface of the skin means you lose heat faster and your core body temperature drops.
  • The larger you are the less you feel the cold, and by larger this works in every way, more muscle means your body burns more calories, and so produces more heat and fat is a good insulator. 

There are other things which can make you feel cold.

  • Being exposed to the wind.
  • If it’s wet and humid.
  • Not being insulated from the ground, in fact insulation from the ground is one of the most important factors. Always have a sleeping mat, air bed or camping bed. Not only can you lose heat directly into the ground, but the insulation underneath you is the most compressed, and so can lose the heat the fastest.
  • The higher up a mountain or hill you are the colder it will get, as well as being more exposed to the wind and more extreme weather conditions. As an estimate the temperature gets 1 degree colder per 150 m of altitude. 

If in doubt always buy a bag with a comfort level lower than you expect to be sleeping in, so if you think 10 degree is going to be the lowest, go for 5 degree, you can always sleep with the zip open and the hood down.

Down vs synthetic sleeping bags

This may seem like an argument between people who can afford expensive down sleeping bags and equally expensive synthetic technical sleeping bags. But the down vs. synthetic fibres debate is a bit more than that.

Down is a layer of fine feathers found under the tougher exterior feathers of birds, most down comes from water fowl, specifically geese and ducks. Down is a great thermal insulator and padding, used in jackets, bedding, pillows and sleeping bags.

 Various types of down exist. Goose down from older bird, generally from Eastern Europe is the most expensive, whilst duck down from young birds is the cheapest.

 When down is compressed the fibres create small air pockets to trap air in the filling of the sleeping bag, this pockets of air trap heat. The proof is in birds themselves, even in the depths of winter they do fine with their feathers to keep them warm

 Synthetic insulation is designed to replicate natural down. Made from pure polyfibres, synthetic fibres are general considered to be the cheaper option when it comes to sleeping bags.

 Both types of fillings have a price range and various qualities, cheap down vs. expensive synthetics may not be a fair comparison. But in general…

Down sleeping bags: the positives

 Keeping you warm; as a rule of thumb down gives twice the insulation for the same weight of synthetic fibres.

 Durability; down tends to last longer than synthetic fibres. Some sources say two to three times as long.

Down sleeping bags: the negatives

  • Getting wet; down is a really poor performer once it gets wet, and takes ages to get dry. If your sleeping bag is at any risk of getting wet then down is the wrong choice. Having said that there are very few situations where you plan to have a wet sleeping bag at the end of the day.
  • Cost; short term down is a lot more expensive, but when you factor in the long term savings down works out to be cheaper, if you take care of the sleeping bag.  

Synthetics sleeping bags: the positives

  • Getting wet; synthetics will perform quite well when wet (up to 50% as effectively as dry) and they dry a lot quicker than down.
  • Cost; if you tend to damage sleeping bags, or only plan to use it for a short period synthetics are much more cost effective.
  • Allergies: some people are allergic to dust mites and their faeces, down is generally considered to be a better environment for dust mites to live. But there are plenty of ways to keep down sleeping bags clean and dust free. Airing the bag regularly and using a silk liner are ways to reduce the allergens in the sleeping bag.

Synthetics sleeping bags: the negatives

  • Weight and Bulk; to provide the same amount of warmth synthetics can be twice as heavy, and if you’re carrying it around all day ever gram of weight will count.
  •  Durability: synthetic won’t last as long as down, but they do require less care, and can be discarded and replaced and still be cost effective.

Overall

 Down would seem to be the clear winner, but there are a number of reasons that synthetic fillings are a valid choice.

  • If you think the sleeping bag might get wet.
  • If the bag is only to be used for a short amount of time, such as children’s sleeping bags or only occasional camping.
  • If immediate cost is important.
  • If you know you won’t have the time to wash and care for your sleeping bag.

If the use is going to be long term, weight and bulk are important, and you want the warmest sleeping bag possible, go for down every time.

Weight and Size

Weight is only really a concern if you have to carry your bag for long distances, such as when you’re backpacking or even cycling or kayaking. If you do have to carry your bag then every gram will count.

Packed size is important if you need to fit your bag inside a backpack cycle pannier or kayak hatch, the list goes on, often you can strap your sleeping bag on the outside of other bags with your tent. Generally it’s possible to compress a sleeping bag more than the packed size states, but compressing your sleeping bag flattens the fibres and reduces the insulation effectiveness.

Shape

You might think a sleeping bag is just a rectangle that you can climb into, but the shape can really influence how comfortable you are. The more space inside the sleeping, the more space you need to heat, but too tight and you might feel constricted.

Rectangular sleeping bags

A basic shape, which is great for indoor use, or on very mild summer camping trips, but the extra room means extra heating, and lack of hood and open neck means that heat escapes easily.


Double sleeping bags

Double sleeping bags are normally rectangular bags with opposite zips, i.e. one left handed and one right hand zip. Even a double can be a bit small with two people wriggling round in it.


Mummy sleeping bags

One of the more common designs in sleeping bags the mummy sleeping bag is tailored to be as well shaped as possible, narrower at the feet, and tapering up to be wider through the hips and the shoulders. A hood with a draw string around the face will keep all the heat loss around your head to a minimum and the space that you need to heat is at a minimum.

Generally these bags take up less space when packed and weigh less, if you plan on camping in anything but the mildest weather then you’ll need a mummy sleeping bag.

The hood on a mummy sleeping bag should fit to your head with a series of panels designed to curve around and cover as much of your head as possible. On winter camping trips don’t be surprised to see the hood done up so tight that only a tiny gap remains for the sleepers nose to poke out of and allow them to breath.

Draft collars are at the base of the hood, allowing you to pull the collar tight over your shoulders and leave the hood to cover your neck, adding an extra layer of insulation. These again normally have drawstrings to tighten them.


Pockets

Some sleeping bags have inner pockets for a small amount of valuables, such as wallets, purses and mobile phones. Be aware that if you roll over in your sleep you may roll on top of your phone. It may be worth investing in some form of protective case to stop you damaging our phone in your sleep.

The second type of pocket is sometimes in the hood, this allows you to put something in the hood to use as a pillow. Normally this is in sleeping bags where weight is an issue and this pocket is often used for clothes, as the extra weight and space taken up by a dedicated pillow isn’t worth it on a long hike.

The lining and outer shell

If the sleeping bag warmth comes from the filling, then the outer shell and the lining are also important. The liner should absorb sweat and other moisture without feeling clammy or uncomfortable, some liners have a reflective liner to reflect heat back towards your body. As these tend to reduce breathability they are better on sleeping bags designed for colder temperatures.

The outer shell should be treated to dirt and water are repelled, meaning that moisture will bead off the outer shell, or even a wind proofing treatment to make the outer shell and impenetrable membrane.

The outer shell is commonly made from rip stop nylon and the inner liner a brushed polyester.

Right or left handed

There is nothing worse than waking up in the morning, needing to get out of your sleeping bag to go the toilet, and finding you can’t get the zip to move, and the hand nearest the zip has no leverage, so choose a zip on the side away from your dominant hand.

If you are right handed you need a left zipped sleeping bag and visa-versa, most sleeping bags have the zip on the left side to make it easier for the right handed population. 

Some sleeping bags have zips that go all the way around and across the bottom. This has two advantages, the first being you can unzip the bag all the way round and lay it flat for drying out or spreading over the top of a bed or similar. The second being that you can unzip the bottom if you need to walk around and are too comfy to get out of your sleeping bag, although there are some health and safety implications of stumbling around the camp site with your arms trapped in a sleeping bag. Zips can be single or double, a double zip can be opened from either end, great if you need extra ventilation.

Size and gender specific shape

Length; it is possible to get sleeping bags that are shorter or longer than average, the closer the sleeping bag is to your body size then the less it will take to keep you warm.  

Women’s sleeping bags

are different in they have more space in the hip area, rather than the shoulders. Whilst women can be comfortable in unisex bags if you’re shopping for a woman with wider hips and/or narrower shoulders then it may be well worth investing in a woman specific bag.

Children’s sleeping bags;

as well as being smaller and normally more brightly coloured there are plenty of technical sleeping bags for children. Price can be a consideration with children’s bags as they might outgrow them rapidly, but you also don’t want to put them off camping by buying a cheaper sleeping bag and leaving them cold and uncomfortable of a night.

Sleeping bags construction

Most of the time the manufacturer will try and keep you as warm as possible, constructing the bag to make the most of the insulative properties of the filling. But it’s worth knowing the different types and how this can impact on how warm you stay.

Sleeping bags are constructed by creating a series of internal baffles, these are the sections created between the inner and outer lining. These baffles mean the insulation is distributed evenly across the sleeping bag.

  • Stitch-through construction - this simple method is where the shell and lining are stitched together to create a line of baffles. This system is really only used on 1 season sleeping bags as it only allows a small area for the down or synthetic fibre to lift in, meaning the insulation is not as effective, and cold spots can occur.
  • Box wall - a simple method with vertical side walls to keep the insulation in place, the clue in in the name, in that each of these baffles is like a box. It does not hold the insulation down as effectively as trapezoidal or shingle construction, leading to the possibility of cold spots.
  • V system - a more complex method in which each baffle wall is inclined at an angle to form a series of ‘V’ shapes to obtain the great number of baffles in a single layer construction.
  • Trapezoidal - a very popular ‘in between’ design that provides more baffles than a box wall construction but less than a V construction.
  • Shingle - a more advanced version of trapezoidal baffle construction which offers excellent cushioning, heat retention and loft. However, it is more complex and therefore expensive to manufacture.
  • Two layer offset stitch construction - a system with two box wall layers with seams in the middle that are sewn on top of each other. The baffle walls are offset relative to each other, creating a similar appearance to that of a brick wall. It provides a high level of insulation, required for sleeping bags that are designed to cope with colder temperatures.

Caring for your sleeping bag

When arriving at camp it’s worth getting your sleeping bag out a few hours before you go to bed if possible. Shake out the bag to allow the down of synthetic fibres to expand and recover its isolative properties.

Packing your sleeping bag:

if you were ever in Scouts or Guides you may have been taught to pack you sleeping bag away by rolling it very tight and then carefully sliding it into the carry bag before carefully compressing the last bits of air out of the bag. Well after years of camping, search and rescue training and packing more sleeping bags than I can remember there is one piece of advice I can give.Stuff it in the sack.

Release the compression straps as much as you can, and pack your sleeping bag in by stuffing in from the bottom, once it’s in carefully go round the compression straps working them down one by one, working from opposite sides can help, so tighten one strap and then the opposite strap, then moving round the circle carefully. Always shake out your bag before packing it away, there is nothing worse than finding a mouldy bit of the midnight snack from camping when you unpack your sleeping bag.

Stuffing it in also means that you won’t be compressing the same part every time, rolling can mean that you flatten the same point of the sleeping bag every time.  

Carrying your sleeping bag:

your bag needs to be kept dry, especially if it’s down filled, you can buy waterproof bags for your sleeping bag so that you can tie the sleeping bag to the outside of your pack, as one of the bulkiest pieces of kit that you’ll carry its often worth carrying it on the outside of your bag.

Caring for your sleeping bag:

This is intended as a guide only, check the wash and care instructions on your sleeping bag before washing or cleaning.

  • Air your sleeping bag as soon as you can, clean any stains on the outside with a damp cloth, if you’ve been using a liner its probable that your bag will be clean inside.
  • If you need to clean it properly then getting it professionally cleaned is always recommended. The use of a large front loading washing machine and a large tumble drier will keep the down of synthetic lofted and means it won’t be compressed. Many local laundrettes will offer this service.
  • If you do wash it at home you can hand wash, but it’s better to use the bath, and be aware this can take a long time. Fill the bath with luke-warm water and about a third of the usual amount of soap you use. Again check the care instructions on your bag, leave to soak for an hour or so, and then start rinsing. Key here is not to wring or squeeze your sleeping bag as this can damage the down or fibres.
  • If your washing machine is large enough you can machine wash it, avoid very warm temperatures and select the cycle based on your sleeping bag.
  • If you machine wash, either at home or a Laundrette then you can use this chance to add a waterproofing, these are available at most camping stores, and online retailers.
  • Drying is the most important step, remember that bag is wet, and will be heavy, if you have a big tumble drier, and your sleeping bag is tumble drier safe then use it, but pick a low heat setting. It might be worth throwing in a few tennis balls to break up the clumps of feathers as they dry. Also be careful that if you are using a laundrette their driers can get extremely hot. If you do get it through a nice warm tumble drier cycle or two this should leave you with a dry fluffy sleeping bag. If you don’t have a suitable tumble drier then lay the bag flat to dry. Every few hours give the bag a bit of massage and shake to break up the clumps of feathers of fibres.

What you need from your sleeping bag.

Before buying your sleeping bag there are a few things you need to consider.

When are you going to be camping?

If you’re only going to be out in the summer, then you don’t need to buy a sleeping bag that will cope with -10°C, but remember that it can get chilly on a summer night.

Likewise if you are camping close to your transport and won’t need to carry a sleeping bag for miles on your back weight is less of an issue.

Size is a compromise, the larger the bag the more space your body needs to heat up, but the smaller the bag the more constricted you’ll be.

If the sleeping bag is for use indoors for children’s sleep overs, or use in a hostel then you may be as well getting a simple bag, but for camping purposes in a tent or bivouac then you’ll need to select a more technical sleeping bag. 

What else you need to buy with a sleeping bag

Liners; just like with your bed at home you have sheets and duvet covers, they make it easier to keep your bedding clean, a sleeping bag liner does the same thing. Easy to take out and wash clean, and can be used to make a sleeping bag more suitable for slightly colder conditions.

Liners

come in various shapes, so buy one to match the shape of your bag e.g. mummy, long, rectangular etc. Silk liners are lightweight, easy to wash and dry and a total bit of luxury in your camping gear.  Silk does tend to be the preferred option for serious campers.

Polycotton and cotton are the cost effective option, just as easy to wash and dry the only disadvantage over silk is they are slightly heavier, and maybe don’t feel as luxurious.

Fleece liners are also available these are said to add a full season to a sleeping bags comfort rating.

Mats

insulation underneath is more important that insulation above in many conditions, mats are light weight and easy to pack away, they also add a layer of comfort between you and the hard ground. Normally these are closed cell foam and come in single of double thickness, whilst double thickness is normally more expensive and slightly heavier, it’s well worth the extras to get a thicker barrier between you and the ground.

Inflatable mats

these are inflated by mouth and so need a bit of puff to blow them up, as well as being heavier you’ll need to have a puncture repair kit in case of emergencies. 

Air beds

Serve a similar purpose, but need to be inflated using a pump, they tend to be heavier to carry around, even without the pump needed to blow them up, but they are drastically more comfortable. The weight does mean that they’re really only an option for camping close to transport rather than being carried around.

Stuff sacks

are a key piece of kit with any sleeping bag. Designed to hold and compress your sleeping bag, most come with the sleeping bag, but if yours goes missing or rips then its well worth buying a new one. Sometimes it is recommended to fold the sleeping bag before putting it in the stuff sack, but the name implies the normal way of putting the bag away, by stuffing in and packing tight using the compression straps.                 

Compression straps

if your stuff sack doesn’t have compression straps, or you need extra straps to allow you to attach the bag to something else, such as a backpack or bike rack then these are vital.

Camping can be a great way to have fun, get away for a few days and get back to nature.  But with the wrong equipment it can be cold frustrating and end with everyone huddling in the car to try and stay warm. Instead choose the right sleeping bag so that you don’t get cold, and don’t overheat. Make sure you’re going to be comfortable and get a great night’s sleep, so you can enjoy the next day of your holiday refreshed and ready.