The temperature rating is a guide for manufacturers assessment of temperatures where the bag can be used. Manufacturers generally do in-house evaluations to find the "R-value" that represents the insulative properties of the bag. Some manufacturers such as Mont™ have a clear label showing the temperature rating.

EN 13537 is an European standard for sleeping bags manufactured and sold in Europe. No such standard exists in Australia, but many sleeping bags sold in Australia follow EN 13587.

The EN 13537 standard rating system tests sleeping bags using a manikin dressed in thermal underwear and resting on a sleeping mat. Heat loss by the manikin determines 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 the weight of the manikin.

Sleeping bags often visually depict their thermal limits. Examples include Columbus™, Mont™ and Sea to Summit™.

The three ratings1 are:

Comfort: 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 six hours without risk of death (but with a risk of hypothermia and frostbite). This is intended to be an extreme scenario where you will most likely survive, but it will be a very ugly night.

Sometimes a fourth temperature rating is also given, maximum temperature, 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

BWA April 2018 | 51

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.

CautionWeather 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, additional warm layers, or both.

At altitude and southern latitudes, conditions are cooler and can change rapidly. Remnant snow patches from winter can be seen on the Main Range at Kosciuszko National Park during summer, and cold windy weather patterns can persist in Tassie. Snow has fallen in alpine Australia and Tassie at all times of the year, so be ready for cold nights. 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.

ANATOMY OF A SLEEPING BAG

LengthRegular and longSleeping 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, and 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 bags are designed to fit women better than the standard mummy or barrel sleeping bag shapes. Don’t be shy about asking in the store to climb into a sleeping bag and testing it out.

Half-bagsFor 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 such as a down jacket and thermals to keep their upper half warm, so the sleeping bag only needs to be long enough to cover the legs. However, there's a often a gap between the two parts of the sleeping arrangement, which lets cold air in and warm air out.

52 | BWA April 2018

Kid's sleeping bagsFor people with a small 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 of a lower quality compared to adult bags, and hence may be heavier and less insulating.

Alternative designsThe sleeping bag, sleeping bag liner and sleeping mat system has been around for a long time with little change to the core principles: create a comfortable sleeping environment with ground insulation that is soft and a sleeping bag that keeps the cold out and warmth in.

Recently, new, lighter sleep systems have been designed.

Top quiltA top quilt is like an unzipped sleeping bag, keeping users warm by covering the top, and with a pocket for you feet. The reason that it does not go underneath is because this is compressed, reducing insulation. Top quilts are often used by ultralight bushwalkers or by people using a hammock. Top quilts are often referred to as quilts.

Top quilts are lightweight and versatile, enabling the user to adapt the top quilt to best suit conditions and some users report

to use them exclusively instead of a sleeping bag. Take care when selecting a top quilt to match it to your needs, checking that there is enough insulation around the neck and head.

Integrated sleeping bag and matAnother design is to integrate the sleeping mat into the sleeping bag system, creating one unit. This saves weight and material of the bottom of the sleeping bag that gets compressed and insulates poorly. Since the sleeping mat is doing most of the insulating anyway, this design does away with the bottom of the sleeping bag altogether.

Half-bagSource: phdesigns.co.uk

Quenda Quilt. The opening goes underneath.Source: tiergear.com.au

BWA April 2018 | 53

MaterialsSynthetic material and down 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 bred and sold as meat, and so duck feathers are cheaper and more plentiful.

Down is generally treated to become somewhat water resistant to some moisture, but is not effective if fully immersed or soaked. That is, down is water resistant not waterproof.

Some companies are moving towards ethically sourcing down in response to ethic issues including live plucking. A few companies such as North Face have policies to ethically source down insulation. They have 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 if the workers are treated well.

Pros and cons of different sleeping bag shapes

Horizontal baffels on a sleeping bag

pronounced cut as one gets lower.

54 | BWA April 2018

Fill powerThe fill power describes the insulation properties of the bag, or the down’s ability to loft, which is related to how well the down traps heat. Loft 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 better the insulation. The fill power is a factor of how many cubic inches the insulation takes for each ounce: a 300 rating is at the low-end, whereas a 900 grade is 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 efficient insulator, manufacturers need to use less fill 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.

FeaturesAt its most basic, a sleeping bag has insulation in pockets separated by baffles between two layers of material. The baffles may be one of several kinds and the material is usually a synthetic, similar to nylon. One side usually has a zip with a draft tube to stop heat escaping.

HoodHoods provide additional warmth and comfort. However, in warmer conditions, a hood may be overkill. Some sleeping bags come with a detachable hood (e.g. Black Wolf Zambezie King 5oc sleeping bag)

Properties of insulation materials used in sleeping bags

BWA April 2018 | 55

giving users the option to carry it in cooler conditions or remove it for warmer trips. Check that the detachable hood or sleeping bag has a draft tube to eliminate drafts to maintain comfort and warmth. Some ultralight bags do not have a hood at all (e.g. feathered friends vireo ultralight sleeping bag review).

Some hoods have a pillow pocket where you can put your pillow securely inside. Some come with drawstrings or other methods of allowing users to enclose their head thoroughly in cold weather, or around the entire pillow.

ZippersMost sleeping bags have one side with a zipper to provide easy access into and out of the bag. Some bags have zippers on either side, making it easier to exit on the side you prefer, e.g. ATK2-R500. That is, the sleeping bag may have a left or a right zipper, but not both on one bag.

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 inside of the bags facing each other and zip the bags together. See this video on youtube. For joining mummy sleeping bags, you must join a right-hand zipper sleeping bag with a left-hand zipper sleeping bag.

PocketsSome sleeping bags have 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.

LoopsSome sleeping bags have loops that can be used to connect the sleeping bag to a sleeping mat. The loops are also handy for hanging up the sleeping bag to air.

Neck draft tubeA neck-shoulder draft tube keeps warm air in. Unless you are a cold sleeper and/or camp in cold places, a neck-shoulder draft tube is probably unnecessary.

Detachable hood draft tubeThis is a thin insulated tube on the inside and adjacent to the zip or detachable hood to prevent warm air escaping through the zip or hood gap.

Foot box A foot box adds additional space around the feet for more natural comfort during the night, particularly for people that sleep on their back. Also, for taller people, all other things being equal, for two sleeping bags the

Sunrise from a rock bivouacBrent Hall

56 | BWA April 2018

Although a plastic bag is a bit fiddly it is a cheap, light and effective solution.

Compression strapsCompression straps may make a significant difference to reduce the packed volume of a sleeping bag. They work by compressing evenly around the stuff sack by drawing the straps downward and in some cases may reduce the volume by more than 50%.

Checking and packing

Sleeping bags are relatively quick to check and pack. First, make sure that your sleeping bag is clean and dry and doesn’t have any damage to the material. Check by running your hands over the material and doing a visual inspection. Also, check that the zippers open and close smoothly, and toggles or clips are working.

Check that the sleeping bag rating is suitable for your trip.

Next, find a clean open area at home to pack your sleeping bag. Some people find sitting or kneeling is a comfortable position to pack the bag, but the most important thing is to be relaxed and not straining shoulders or arms.

Some sleeping bags have a stuff sack or compression sack that makes it easy to reduce the sleeping bag volume with drawcords on the side. Generally, sleeping bags made with down compress into a smaller volume than synthetic bags. However, sleeping bag technology has been steadily improving with new materials on the market each year, so it’s worth keeping an eye out for new products.

Compression straps may halve the size of your packed sleeping bag

BWA April 2018 | 57

58 | BWA April 2018

dust that gets onto the bag. Air your bag out after each use, in the morning or when you get into camp in the afternoon. Avoid direct exposure with UV light for extended periods of time, but an hour of sunlight can help kill smell causing bacterial and fungal growth.

Treat your sleeping bag gently! Bags that are well cared for will stay warm for longer. Do not use a good sleeping bag near the fire. All it takes is a single glowing ember from the fire to create a hole and damage the bag, with dirt, dusk and smoky smell that the bag will pick up. If you like having something to wrap around you at the fire, consider a lightweight fireproof thermal shawl or throw-over instead.

A sleeping bag liner is a very worthwhile investment. Not only does it keep your sleeping bag clean and dry, but it provides extra warmth. Avoid sleeping in your bushwalking clothes. Instead, change into night camp clothes. This minimises body odour, oils and sweat transferring to the sleeping bag.

A few extra tips

Give your bag a chance to fluff up especially on colder nights.

If you are too hot in the bag, try unzipping it part way, take your head out of the hood or shake the bag to force out the warmer air.

If sleeping in the open, use a groundsheet to protect the sleeping mat and bag. Avoid direct contact with the sleeping mat with the ground, which can have small sharps that may puncture the sleeping mat.

When airing out your sleeping bag, hang it high off the ground, to reduce the chance of the bag getting dirty.

Never force any zippers or buckles if they get stuck. Instead, be gentle and slowly undo any caught fabric.

If using a sleeping bag without a hood, wear a hat or hoodie to keep warm and reduce the chance of being bitten by mozzies. This applies if the shelter does not have a flyscreen. A head covering keeps hair oil from the hood.

Wear clean clothes and be clean when getting into your sleeping bag.

BWA April 2018 | 59

Use a sleeping bag liner as this can increase temperature by up to 5ºC.

Wear a beanie to keep the head warm and loose-fitting layer of warm clothes.

Place your head inside your sleeping bag and breathe inside the bag for about half a minute to warm up the air. Be mindful that your breathe is also humid, so avoid doing this for long stretches as condensation inside your sleeping bag can be counterproductive.

In an emergency you can use a foil wrap from your first aid kit for warmth. Be mindful of condensation and water collecting on the foil and wetting your bag.

Sleeping with or without clothesThere’s a lot of debate around whether or not wearing additional layers of clothing adds more warmth to the sleep system or detracts, with strong advocates on both sides and surprisingly little research on the topic.

Frustrated by the lack of information, a blogger called onlinecaveman carried out his own DIY experiment to test the difference between heat loss wearing a layer of clothing versus not wearing a layer of clothing. He found that the system with a layer of clothing lost less heat than the one with no clothing.

The main purpose of a sleeping bag is to create a layer of warm air around the body by trapping body heat, so any additional layers may enhance this effect. Sleep systems work best when the insulation is allowed to do its job, that is, the insulation in the bag isn’t overly compressed by too many clothes).

It seems the clothing layering method used during the day also works in the sleeping bag. However, avoid tight-fitting clothes (these can restrict circulation), and ensure that night clothing is clean and dry. Also, stay away from clothes with zippers or other hard or patterned sections that may cause pressure sores.

60 | BWA April 2018

Sleeping bags can be used for several years before they need a wash. Washing tends to add wear and tear to the bag and reduces the loft (i.e. insulation), so if you can delay the need for washing by caring for the bag, this is the best long-term option.

Check your sleeping bag regularly to make sure that the zippers are working and the seams are intact. Check that the insulation is evenly distributed as over time the insulation can clump unevenly, suggesting that a wash might be advisable.

Carry out small spot-cleaning jobs on areas such as the hood that are likely to accumulate sweat and dirt. Mix a little water with non-detergent soap to create a paste. Hold the shell away from the filling and use a toothbrush to clean and rinse the shell. By keeping the shell away from the filling you can clean the area without getting the inside wet.

Follow the manufacturer’s instructions when washing. As most sleeping bags are similar, washing instructions from a similar manufacturer should suffice.

If possible, follow specific manufacturer’s instructions. In general, the process for washing a sleeping bag is as follows.

Do up all zippers before washing to protect them. Most manufacturers suggest zipping the bag closed for washing. This seems to be to give a stronger bag, especially with newer materials.

If hand washing, fill up a wash trough or bathtub with warm water. Add a small amount of pure soap. Gently massage material and leave to soak (but no more than one hour). Gently squeeze the sleeping bag to remove any water and let the water drain. Refill with clean water, massage the material to remove suds, and let the bag sit for 15 minutes. Repeat until all suds are gone.

Many sleeping bags can be machine washed in a front-loader or a top-loader without an agitator. Add a small amount of appropriate soap (to ensure that no suds are left over, do not over-soap). Consider adding a few additional wet garments to balance out the spin of the machine (e.g. T-shirt). Consider running a rinse cycle with no soap to remove all soap residue).

Take care when handling your wet sleeping bag so as not to damage the baffles and visible fabric. When the down is wet and heavy, it is particularly vulnerable to

Hawks, Leona K., "Care of Down and Synthetic Sleeping Bags", 1990, provides this table as a guideline

BWA April 2018 | 61

Once most of the water is out of your bag place it in the dryer and use a low heat to ensure that synthetic materials do not melt. As the bag dries, the insulation tends to clump together. This can be avoided by placing objects (tennis balls or other soft but firm objects) into the dryer during the final stages of drying to displace the clumps. Once dry, air the bag out overnight to make sure there is no residual moisture before storing.

Another way is to place the sleeping bag on a clean surface outside in partial shade as UV rays can degrade synthetic materials. A clothes line is ideal. Peg a sheet between

two adjacent lines and place the sleeping bag on top, with the carrying sheet underneath. Drape a sheet over the top to protect the sleeping bag from direct sunlight. As the bag dries, the insulation tends to clump together, so check the bag periodically and manually break up the clumps. It will take several days to dry on a clothes line.

CAUTION - What not to do!Never dry-clean your bag. The chemicals used in the dry-cleaning process can damage the bag fabric.

Avoid using fabric softeners or bleaching chemicals on your bag. Follow manufacturer’s instructions for what soap to use (usually a non-detergent soap).

Do NOT try this! Using a top loading washing with a central agitator may rip your sleeping bag

62 | BWA April 2018

Other maintenance jobsRips to fabric: If the outer layer of fabric is damaged in the field, to prevent loss of insulation, consider doing a small repair job by sewing or using an adhesive dressing from your first aid kit. At home, remove stitching and do a more thorough job using a gear repair tape.

Leaking down feathers: Over time, a few down feathers may work their way through the outer shell fabric and poke out. Work the feathers back into the insulation layer by gently massaging the surface and pushing the feather back in.

Waterproofing: Some sleeping bags have a water-resistant outer layer which helps protects the bag from water damage and dirt, but eventually wears off. Consider reapplying the durable water repellent using a suitable product (check with your manufacturer).

StorageStore your sleeping bag in a cool dry area away from direct sunlight. The bag is best stored fluffed up. Many sleeping bags come with a large breathable storage bag us this otherwise a cloth bag like a pillow case or larger is ideal.

For more information and other articles on bushwalking checkout the NPA Bushwalking101.org website.

Have fun and stay warm out there.

Helen is a passionate conservationist who is always planning her next escape into the bush. In early 2015 she completed a PhD at The University of Sydney studying the impacts of exotic and native rodents in Australia and New Zealand. Helen works at the National Parks Association NSW developing information to help bushwalkers build their confidence and bushcraft skills.

BWA April 2018 | 63