Choosing your sleeping bag
“The very definition of beauty is outside.” Adam Carolla
When selecting a sleeping bag, the temperature rating, shape, insulation type and additional features such as hoods and zippers are key considerations as well as the price.
Another option for ultra lightweight bushwalkers is the overquilt or integrated sleeping bag/mat system – more details below.
Temperature Rating Selecting the appropriate sleeping bag temperature range
Sleeping bags come with a temperature rating that is a guideline for what conditions the bag is most suitable for. However, everyone is different, and some people feel the hot/cold more than others, so be prepared to adjust accordingly to find something that best suits your needs.
The temperature rating is a guideline for what temperatures the manufacturers suggest that the bag can be used in. Manufacturers generally do in-house evaluations to find the ‘R-value’ that represents the insulative properties of the bag. Some manufacturer’s use the EN 13537, which is an European standard that aims to standardize sleeping bags manufactured and sold in Europe. No such standard exists in Australia, but many sleeping bags sold in Australia do follow this EN rating system.
The EN 13537 standard rating system tests sleeping bags using a manikin. The manikin is dressed up in a layer of thermal underwear and is resting upon a sleeping pad. The testers record heat loss by the manikin to determine the extreme and comfort limits of the bag. There is a surprising amount of detail that goes into ensuring accurate thermal measurements, everything from arm positions, through to weight of the manikin [note]Kuklane, Kalev, and Valter Dejke. “Testing sleeping bags according to EN 13537: 2002: details that make the difference.” International Journal of Occupational Safety and Ergonomics 16.2 (2010): 199-216[/note].
Sleeping bags often visually depict their thermal limits. Examples include Columbus, Mont and Sea to Summit:
The three measurements listed as part of the rating are [note]European Committee for Standardization (CEN). Requirements for sleeping bags (Standard No. EN 13537:2002). Brussells, Belgium: CEN; 2002[/note]:
- Comfort rating: Defined as the lowest temperature that a standard woman can get a comfortable night’s sleep.
- Lower limit temperature: Defined as the lowest temperature that a standard man can still sleep throughout the night in a curled position.
- Extreme limit temperature: Defined as the lowest temperature that a standard woman can still survive for 6 hours without risk of death (but with a risk of hypothermia and frostbite). This is intended to be an extreme scenario where you can survive but probably will not sleep.
Sometimes a fourth temperature rating is also given – maximum temperature – that is, the hottest conditions that the bag can be used in.
Men can generally get a comfortable night’s sleep at lower temperatures than women, so the comfort rating is based on a more conservative rating for women (unless explicitly stated as ‘men’s comfort’ or ‘women’s comfort’).
For the thermal testing process, a standard man is defined as 25 years of age, weighing 73kg and at a height of 173cm. A standard women is defined as: 25 years of age, 60kg, 160cm [note]European Committee for Standardization (CEN). Requirements for sleeping bags (Standard No. EN 13537:2002). Brussells, Belgium: CEN; 2002[/note]. However, none of us are standard! Temperature is a very personal thing, and it’s important to take into account personal factors that might affect how warm or cool you sleep.
Sleeping bag rating and general fitness level can affect how warm you sleep in general, but more subtle changes such as how tired you are at the end of the day or whether or not you’ve eaten well on a trip (going to bed hungry may leave you colder than if you’ve eaten well as your metabolism is a significant source of heat production overnight) can change your sleep patterns also.
Bushwalkers that walk in NSW all year round tend to have two sleeping bags: a summer bag and a winter bag – although this will vary greatly depending on the location of the walk and the forecast. This gives them the option to use the one that is most appropriate for the conditions.
|Sleeping bag||Approximate months||Comments|
|Summer||October-March||On cooler summer days, or autumn/spring period, consider carrying additional layers.|
|Winter||April - September||On hotter winter days, use a liner only and put your sleeping bag on top of you as a throw over (rather than wrapped tightly).|
A good rule of thumb is to select a bag with a comfort rating that is 10 degrees below the ambient temperature you expect on the trip.
- Weather patterns can bring unpredictable cold spells, so it’s important to check weather conditions relative to where you plan to walk before decided on the appropriate sleeping bag. If unsure, take a warmer sleeping bag and additional warm layers.
- At altitude (e.g. Snowy Mountains), conditions are cooler and can change rapidly. Remnant snow patches from winter time can still be seen on Mt Kosciuszko during summer months, and cold windy weather patterns can persist. Take into account these highly variable and cold temperatures when selecting a suitable sleeping bag for an alpine trip.
A last word of warning: cheaper bags may not have undergone laboratory testing, and ratings may not be accurate.
Shape Selecting the appropriate sleeping bag shape
Similar to sleeping bag liners, sleeping bags come in a few different shapes.
- Lots of room to move around
|- Works best in warmer conditions because of loose material
- Generally heavier and bulkier because of additional material so less suited for overnight bushwalking
|Semi-rectangular (or barrel-shaped)||Summer example|
|- This type of bag is inbetween a rectangular and mummy, so it is still quite roomy while at the same time having less air pockets to heat so is a good insulator.|
- Comfortable, lots of room for shoulders and hips.
|- Warm, body-hugging|
- Very effective at insulating
- Lightweight and small volume due to less material
- Some people find them very restrictive and uncomfortable to sleep in
- Generally pricey
|Double-wide||Example||n/a||- Efficient option for couples||- You probably need another single sleeping bag for trips without your partner|
length Selecting the appropriate sleeping bag length
Regular and long
Sleeping bags generally come in two lengths: regular and long. It’s worth getting the right length as a bag that’s too short will leave you cold at the shoulders and neck, whereas a bag that is too big will leave your feet cold.
Check the specifications to decide on the right size by matching your height to the bag length.
Some manufacturer’s sell female bags that are designed to fit women better than the standard mummy or barrel shapes due to their shorter length, narrower shoulders and broader hips.
For ultra lightweight camping, half-bags are coming back into fashion (e.g. Hispar Half Bag). The logic is that the user already has enough clothing to keep their upper half warm (down jacket, thermals), so the sleeping bag only needs to be long enough to cover legs.
Kids sleeping bags
For people with petite build, it may be suitable to use a children’s sized sleeping bag (e.g. Coleman Kid’s Firefly Sleeping Bag). However, take care to examine temperature ratings and bag weights carefully as materials used in children’s sleeping bags are generally lower quality (and hence heavier and less insulating).
insulation Selecting the appropriate sleeping bag insulation
The insulation in a sleeping bag traps the heat your body produces while you sleep and keeps you warm.
Synthetic material and down feathers are the two main types of insulation used. For down insulation, duck or goose down (or a mix) are most common, although pure duck down is most abundant because more ducks than geese are manufactured and sold as meat, and so duck feathers are cheaper and more plentiful.
|Hybrid synthetic-down||These hybrid bags contain a blend of synthetic and down feathers, with pros and cons from both materials. Sometimes they are blended, in others, they are layered with synthetic materials on the bottom and down feathers on top.||These hybrid bags contain a blend of synthetic and down feathers, with pros and cons from both materials. Sometimes they are blended, in others, they are layered with synthetic materials on the bottom and down feathers on top.|
Down feathers are generally treated to become somewhat water resistant to some moisture, but not effective if fully immersed or soaked (i.e. down is water resistant not waterproof).
Some companies are moving towards ethically sourcing down in response to a number of issues but in particular live plucking. A few companies such as North face have put in place policies to ethically sourced down insulation and responsible auditing of all manufacturing steps including production and collection of feathers to ensure humane treatment of animals. Price alone does not tell you if the material is ethically sourced or the workers treated well.
The fill power describes the insulation properties of the bag, or the down’s ability to loft (i.e. trap heat). It is a measure of how much air the insulating down can trap (i.e. its ‘fluffiness’), and generally speaking the higher the fill power, the more insulated the bag is. The fill power is a factor of how many cubic inches the insulation takes for each ounce. 300 is a low end feather an 900 a high end down.
Sleeping bags with a higher fill power rating are more fluffy and better insulators than lower fill power bags. For instance, the insulation in a 600 fill power sleeping bag is more fluffy and effective at trapping air than the insulation in a 400 fill power sleeping bag. Since high power insulation is a more effective insulator, manufacturers need to use less volume and thus can create lighter weight bags (including ultralight gear).
Fill power reduces over time as the bag ages and gets dirty. That’s why it pays to look after your sleeping bag to keep it as effective as possible!
Features Selecting additional sleeping bag features
At its most basic, a sleeping bag comprise of an outer layer, insulation and an inner lining, however, sleeping bags and stuff sacks do have a few additional features to consider which we’ll work through here.
Hoods provide additional warmth and comfort and help retain insulation across the body. However, in warmer conditions, a hood may be overkill. Some sleeping bags come with a detachable hood (e.g. Black Wolf Zambezie King -5ºc Hood Removable Sleeping Bag) giving users the option to carry it in cooler conditions, or remove it for warmer trips. Some ultralight bags do not have a hood at all (e.g. Feathered Friends Vireo Sleeping Bag)
Some hoods offer a pillow pocket where you can put your pillow securely inside. Others come with ‘clinch-able’ contour hood allowing users to wrap their head thoroughly (great for cold weather conditions) in the sleeping bag (or around your entire pillow also).
Most sleeping bags have one side with a zipper to provide easy access into and out of the bag. For some bags, you can specify which side you prefer the zipper on (perhaps you find it easier to exit on the left than the right): e.g. Sea To Summit Trek 2 TKII Down Sleeping Bag – Regular.
For couples, it’s possible to zip up compatible bags to create a double bag. For rectangular sleeping bags, unzip the bags, lay them together with the insulation facing inwards and zip up corresponding zippers. See this video. For joining mummy-shaped sleeping bags, you must join a right hand zipper sleeping bag with a left hand zipper sleeping bag.
Some sleeping bag designs include pockets for valuables such as money, passports or phones. Internal pockets are preferable so that you can grab items without opening the bag and losing all the nice trapped warm air.
Some sleeping bags have loops that can be used to connect the sleeping bag to sleeping pad. Also handy for hanging up sleeping bag to air.
- Neck baffles
Additional insulation around the neck area to prevent warm air escaping (usually only on bags designed for cool conditions).
- Draft tube
This is a thin insulated tube that surrounds the zipper area and prevents warm air escaping through the zip system.
- Trapezoidal footbox
This design adds additional space around the feet for more natural comfort during the night (particularly for those people that sleep on their back).
Alternative Designs Overquilt and integrate sleeping pad
The sleeping bag, sleeping bag liner and sleeping pad system has been around for a long time with little change to the core principles: create warm space by insulating heat loss from body, particularly loss through the ground.
Recently, there have been a few new designs suggested for sleep systems that aim to optimise this setup, and ultimately save on weight.
An overquilt is a blanket style sleeping bag. It keeps users warm by covering the upper side of the sleeping, but not the underside (which gets compressed when you sleep on it and reduces insulation). Overquilts are often used by ultralight hikers or by hikers that use a hammock.
They are lightweight and versatile, enabling the user to adapt the bag to best suit conditions and some users report to use them exclusively over a sleeping bag. Take care when selecting an overquilt to match it to your needs, checking that there is enough insulation around the neck and head.
‘Integrated sleeping pad’, ‘pad sleeve’ or ‘hybrid sleeping bag/pads’
Another design is to integrate the sleeping pad into the sleeping bag system, creating one unit. The idea again here is to save on the weight and material of the underside of the sleeping bag that gets compressed and insulates poorly. Since the sleeping pad is doing most of the insulating anyway, this design does away with the underside of the sleeping bag altogether.