Author: Lutz Otto
Should your ambition be to spend time hiking in diverse terrain types, through the different seasons of the year, and in varying weather conditions, your working through that which follows will allow you to make better decisions in choosing the bag RIGHT FOR YOU.
Quality sleep is incredibly important to maintain good energy levels, and to recover from any physical activity. Further this neuroscience proves, how even one bad night's sleep, can seriously affect your memory, concentration, decision-making ability, thinking clarity and emotional stability/ resilience. Fundamentally, when we are tired, the way we engage with the world, and what we are busy with, is just not the same.
Not only is choosing the right sleeping bag very important to your getting a good night’s rest, it is also alongside your boots, rain gear, backpack and tent, one of your bigger ticket hiking equipment investments. With all of this in mind, it is a really good idea to spend some researching brands and models, and as with all of these processes, not to leave it until the last minute.
So let’s jump straight into it.
When undertaking the research to buy a new sleeping bag, what are the first questions that I should be asking myself?
To ultimately create a better purchase outcome, you should spend a little time thinking about, and answering, each of the following questions:
What are my short and longer-term hiking ambitions? Should I be thinking of buying or hiring? Even if your decision is to hire, you should make your choice based on what you read in the below.
In terms of the trails I have walked, and hope to walk, and the terrain that these are found in, what night-time temperature ranges can I expect to encounter. Remember that the temperatures encountered in the South African lowveld are substantially milder to those which we experience when hiking in most other terrain types, especially when moving into the mountains.
What seasons do I expect my hiking activities to take place in? Will I walk through the year? Will I focus on the warmer months, or is my preference for the cooler winter months? Is it likely that I will be exposed to wet conditions at this time?
On an individual physiological, and metabolic level, we have vastly differing abilities to tolerate cold, and to generate heat. In normal sleeping conditions, do I class myself as a cold, or a warm sleeper?
How much weight am I willing to carry? Also, what is the packed size of the target sleeping bag?
What is my realistic budget?
How do our bodies cool, and what is a good sleeping bags function?
Our bodies lose heat through evaporation, respiration, radiation, convection, and conduction. In terms of the sleeping bag discussion, the latter three are important. Briefly:
Through our normal bodily function, we radiate heat, and our heads, necks, hands, wrists, ankles, and feet, loose heat faster.
Cold air, or water, moving over the skin, speeds heat loss through the process of convection.
Heat transfers to colder matter until both are the same temperature. This means that without insulation between us and cold ground, our radiative heat transfers into the ground through conduction [more about this later].
A good sleeping bag:
slows, or even stops radiative, and convective heat loss.
contains our radiated heat within the loft of the bag [this is what keep us warm].
insulates us from the external environment.
Now that we have worked though the above, let’s look more specially at sleeping bag construction and different bag types.
As a starting point, it is important to accept that that not all sleeping bags are equal in design, nor in their ability to insulate. So, let’s climb straight into the important points associated to bag construction:
The choice of insulation material is very important. Weight for weight, down sleeping bags always pack smaller, are lighter than hollowfibre bags, and well contained goose, or duck down, provide the best insulation values. It is very important to note the following though:
Down is fairly much useless as an insulator once wet. It takes a very long time to dry, and if it is not dried according to a specific process, it is prone to clumping.
Hollowfibre will retain some of its insulation ability if wet, and it dries much quicker than down. This is a very important consideration if walking in very wet, or high humidity, regions.
Regardless of whether down or hollowfibre, it is important to look at the fill power of the insulation material. Fill power is a measure of the lofting ability of the insulating material of the bag. Without going into the technical detail, the higher the fill power, the more heat can be trapped, and the warmer your bag will feel.
A sleeping bag that has the inner and outer shells sewn through, will see you sleeping cold. To allow insulation materials to perform at their best, and to distribute them equally, a high-quality bag will have the insulation material contained in chambers known as baffles. The better baffle systems are constructed as slant box walls, trapezoidal box wall and V-tubes. When trying to save on weight, some sleeping bags employ a system known as differential fill; The baffles on such bags take into account that the insulation material which we lie on will be compressed, and those on the base of the bag are thus smaller and contain less insulation material.
A good sleeping bags inner and outer shell, the material containing the insulation, will be strong, super lightweight and fast drying. On some of the alpine bags, the outer shell material has a water-resistant film - Although useful, be mindful that this can cause higher levels of natural condensation within the bag.
It is very important to understand the difference between a sleeping bag’s comfort, transition and extreme temperature ratings. All good sleeping bags will show these ratings, and the best manufacturers will be open in how they were calculated. Remembering your answers to the questions at the beginning of this article, narrow your choices according to the comfort rating, and at a maximum consideration, the transition rating.
In the pursuit of light, we can, within reasonable parameters, extend these ratings through wearing quality thermal underwear and additional layering. We will unpack this in a little more detail further into the article.
If you walk trails often, as well as in different terrain types, there are substantial weight losses/ gains that can be made in sleeping bag weight as we move through the seasons. This is one of the reasons why frequent hikers always consider using different summer and winter sleeping bags. A good summer sleeping bag could weigh as little as 450 grams, and an equivalently good a winter bag will start at around +/- 1600 grams. In the context of seasons, two additional points are:
To be mindful that when packing for an autumn or spring trip, that a cold snap can produce winter temperatures.
Sleeping bag fit is often not given enough attention.
Too much space in a bag requires our bodies to work harder for the bag to retain our radiating heat [too much interior volume].
Too little space in the bag means that we will stretch the bag tight, and thus it cannot loft properly. If going into cold areas, tall people should always test a bags fit, and if it is to small, rather purchase or hire, a longer bag that caters for your length.
Before moving onto bags planned to be used in winter, a mention must be made of quilts, and bivvy bags.
Not unlike a duvet, quilts are very popular with sleepers in warmer conditions as they offer tremendous freedom, and are lighter than a traditional sleeping bag. They have a number of strengths and weaknesses, that are the subject of another blog.
For those unfamiliar with a bivvy bag, they are a lightweight, waterproof and breathable bag, that is pulled over a sleeping bag when choosing to sleep under the stars without a tent. In the context of sleeping bags, be mindful that when bivvy'ing, otherwise known as cowboy camping, you will lose the insulation benefits gained from staying in a tent. As with the previous point, they have a number of strengths and weaknesses, which are the subject of another blog.
What about cold areas in winter?
It was the world-famous explorer, Sir Ranulph Fiennes, who was quoted saying “there's no such thing as bad weather, only inappropriate clothing and equipment”. If winter hiking in colder areas is on your agenda, we could not agree with this more. Having a fair amount of spent time on some very cold mountains, I can say from experience that good equipment makes the difference between a great time, versus being extremely uncomfortable, or even facing the possibility of hypothermia.
Back in July 1992, we were camped in Nkosozana Cave at the top of Greys Pass. We had a fair bit of winter experience under our belts, and had developed a system to comfortably manage night-time temperatures to about -8’c. At the time we were using Backpacker Benedorm sleeping bags, we had cotton hand-made inners and slept with reasonable quality thermals. That particular day the temperatures never rose above zero, and by mid-afternoon the temperature started plummeting. We formulated a reasonable plan to get through the night, but even though we wore our full winter down jackets, and all the clothing we had, we hardly slept from feeling the -17'c cold to our very core. Over the years the Natal Drakensberg has taught us many hard lessons. Although still students, the three of us who continued mountaineering, saved like crazy to buy the first [literally], First Ascent, Artic Wolf’s from BergSport in Braamfontein. As a note I have subsequently slept warm many times at equivalent temperatures, including -26’celcius in the Swiss Alps. Mountaineer friends of mine have slept at temperatures of -40’c in the Karakorum and on Alaska’s Denali.
If venturing onto the plateau of South Africa’s Natal Drakensberg in winter, average July night-time temperatures are usually somewhere between -6’celcius and -12'c ; And if a deep cold front moves through it can drop a further 10 degrees. Although you might get lucky a few times with good weather, do not be fooled by what the dragon mountain can produce.
If part of your hiking ambition is to spend time in the high mountains in winter, the following high-level learnings will serve you well.
Sleeping bags designed for such conditions must have a cowl to cover your head, a neck baffle, and side baffles along all of the zips. As the temperature drops, these baffles are critical to containing heat within the bag. A mummy bag with a box foot is by far the best shape in terms of insulation ability for these environments. As a rule-of-thumb I advise clients going to the Berg in the deep winter months to bring a sleeping bag with a comfort rating of -8’c or less.
Manage your temperature inside your sleeping wisely - If you feel too hot, or too cold, it is time to make an adjustment. Let’s start on the high end of temperature. Although it sounds counter intuitive, you do not want to be so warm that you start to sweat. Once you have created moisture inside your bag, you will need to evaporate it with your body heat - This takes time and metabolic energy, and when the temperature drops in the pre-dawn hours, you will not be happy. To reduce the temperature, use your bags zips. Bi-directional zips are found on all good bags; These allow you to create airflow at the top and/ or the bottom of the bag, whilst keeping the center closed.
In winter, regardless of the sleeping bag type, standard practice is to go to bed with a good set of moisture-wicking thermal tops and bottoms. As it gets colder, it is common practice to further extend the range of your sleeping bag by wearing your beanie, and a fresh clean pair of sleeping socks. Should the temperature really drop, and you are on the edge of your sleeping bags rating, utilize a layering system by putting on a quality fleece, or a puffer jacket. Again, and not to sound repetitive, remember that too many layers of tight clothing is not only uncomfortable, but it reduces the space to trap radiating heat.
Do not fall into the trap that a sleeping liner can shift a sleeping bag rating by 10 degrees Celsius – At the very best a good quality sleeping bag inner, adds a few degrees of warmth. To achieve this type of shift, without using a better bag, you need to use a second lighter weight sleeping bag as an inner. If your plan is to do this, it is important to remember the lessons with regards loft compression, and also accept that you will be carrying heavier. Almost all people who regularly undertake activities of this nature, eventually purchase a second mountain specific sleeping bag.
Getting into a sleeping bag when physically cold, will require much more metabolic energy to warm the bag than an already warm body. To this point here are four great tips for camping in very cold conditions.
Eating a good supper will make a substantial difference in your body’s ability to generate heat whilst sleeping. This point is so important that high altitude mountaineers have learned that even eating a snack in the middle of a very cold night, can allow you to sleep warmer a little longer.
If possible, try to generate radiative body heat through movement, without starting to sweat, just before getting into your sleeping bag. If holed up in tent in stormy conditions, you could even consider doing planks, or push ups, to achieve this. Your bag will work faster and keep you warmer if your body is already warm.
If you have fuel to spare, and you use a Nalgene bottle, consider boiling some water prior going to bed. Pour this into the Nalgene, and use it as a hot water bottle. You will be surprised how well this works.
Always try empty your bladder before going to bed, and if your bladder is not as strong as it used to be, and you don’t want to get out of your tent, consider taking along a pee bottle. If the decision is to climb out of the tent, make sure that you put on your puffer jacket as you extract from the bag, close your sleeping bag so that it retains the heat and don't hang around - You cannot believe how quickly the body can super-cool in the middle of the night.
What else should I be thinking about once I have acquired my new sleeping bag?
Important points that are addressed less seldom are:
Sleeping bags compress underneath our bodies, and are thus not able to loft, and consequently cannot trap our radiating heat. With no insulation barrier underneath us, the heat coming from our body will transfer into the colder ground through a process known as conductive heat loss. Our bodies will continue doing this until the ground and the body are the same temperature. The ground will win. To ensure a good night’s rest, you need to sleep on an insulating mat.
All good purpose made hiking mattresses should fulfil four criteria. They should be ¹ lightweight, ² compact when packed, ³ reasonably comfortable, and create a ⁴ good insulation barrier.
Good, purpose designed, inflatable mattress, further need to be ⁶ robust in construction, and if used in winter should have a decent winter rated ⁷ R-value [resistance to heat loss value].
An inflatable without an R-value, and particularly simple blow-up mattresses, do not stop heat loss. Such inflatables must be placed on top of a closed foam mattress.
If using an inflatable, you should seriously consider taking along an 8mm closed foam pad as it adds a serious layer of puncture protection from small thorns, sharp grasses, etc. Should your inflatable have an RV value, doing this will also increase this value.
At the simplest level a 10 to 12mm closed foam mattress is an excellent insulator. These are also the most durable and affordable option. If going into colder environments, those with a reflective shield further improve their insulation value.
Regardless of sleeping bag choice or quality, never store them in their stuff sacks when at home. If you want any sleeping bag to last, it must be uncompacted and either hung up, or stored loosely in a giant pillowcase.
As with all of your equipment, after every trail, check that everything is still in working order, spot clean any dirt, and don’t store the sleeping bag until it is absolutely dry.
Although with care and the right equipment it is possible to wash sleeping bags at home, we do not recommend washing down sleeping bags. If in South Africa, rather send your investment to one of the specialist down manufacturers in the Western Cape. If you decide that you want to wash a hollow fibre bag, follow the manufacturer’s instructions to the tee, and always use a specialist product such as NikWax.
Coming full circle.
Hiking and backpacking are incredibly rewarding experiences. Whether you choose to pursue this frequently, or if it is only for one trip, a good trail will imprint memories into heart that last for your lifetime. A good tent is an equipment investment that will bring you many years of fulfilment. Packing the right stuff will allow you to enjoy the experience to its fullest.
We hope that working through this has helped. We look forward to spending time with you, and creating active, exciting, immersive, connective, safe and impactful experiences, that will result in your eagerly planning your next adventure on your journey home.
About this articles author: 🐾 Lutz Otto is the founder of Spirited Adventures and Consulting. He is a safari trails guide, a mountain guide, coach and leadership consultant. You can explore his bio here.
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