Choosing a Sleeping Bag

We get asked a lot about sleeping bags especially in the winter.  Having just spent the weekend camping on the Long Mynd in the snow, we know a bit about keeping warm.

Whilst we camp the year through, often wild camping in the winter so no EHU (Electric Hook Up) therefore no heater, we don't often have a campfire. We rely solely on what we're carrying with us. Due to these factors our sleeping equipment is very important and we have researched and tried out many mats and bags. This is what we have found and this is the best advice we can give.

We cannot give you a concrete, set in stone answer because it’s not a case of one bag will suit all.  People are very different, some have a quick metabolism and run hot, some have a slow metabolism and run cold.  Some carry more weight and might not get cold easily, and some don’t, and they feel the cold.  Fitness levels play a part, people that are relatively fit and healthy tend to feel the cold less.

Temperatures in winter vary from place to place some hardly reach freezing and some places drop to -50ºC that is Oymyakon in Russia average winter temperature and Dome Fuji, Antarctica recorded a temperature of -93.2°C in August 2010. It's important that you know what the temperatures will be where you're using the bag.

Please Note 🙂

The higher up you go, the colder it gets, so if you’re camping up a hill, Wainwright, Munro or mountain check the mountain weather, it’s not the same as the weather at ground level.  You may of  checked the weather for the area you're visiting, this information shouldn’t be used for mountains.  It can be somewhat cooler on the peak of mountain compared to bottom of it, think snow covered peaks.  We use the Mountain Weather Information Service (


Keeping Warm

Have you eaten? When I'm camping in the cold, I find that a full belly before sleep helps no end.

There is a scientific reason for this, being cold speeds up your metabolism, it’s known as thermogenesis. Firstly, Non-Shivering Thermogenesis, we release norephedrine and ephedrine this increases the metabolism the reaction makes heat.  Brown Adipose Tissue (BAT) also known as brown or beige fat is thought to play a part in keeping us warm when cold. Brown fat have more mitochondria, which turn food into energy also brown fat uses up energy by giving out heat when the body is cold.

Secondly, Shivering increases the bodies metabolic rate also. When the bodies metabolic rate increases it burns calories more quickly, it’s important to eat to keep warm. Nuts like almonds are good they have a high good fat content and they take longer to digest, however if your cold and hunger a honey flapjack containing some dark chocolate and dried red berries, could do you the world of good. There’s a reason the Scottish eat porridge.

I’ve just given you a good reason to get out in the cold...........theoretically you could lose a few pounds.


The clothes that you sleep in can make a difference, and you should always make sure they're dry. I always put fresh socks on for bed, I wear thick hiking socks for bed nearly the year through, I suffer from cold feet.  In the winter along with my socks, I slept in thermal leggings, thermal long sleeved top and a hat. If it's particularly cold I will put on a fleece jumper and a neck warmer.

I have recently purchased a tiny hot water bottle that I take with me on a cold wild camp, it's only the size of my hand and with the likes of the Jetboil stoves you have hot water in a minutes. It's great if you have joints that ache when they're cold.  A tip I've learnt over the years, if you have cold feet and hands don't warm your feet, warm your core, a hot water bottle on the belly will help restore blood flow to your extremities.

Keep yourself covered and away from draughts, don't breath into your bag though, you'll end up damp.

The fit of your sleeping bag is also important, I like bags with a thicker foot box, for extra warmth around my feet.  It also important that your bag isn't to lose, I have a women specific bag for very cold temperatures, it's shaped for wider hips and is more filled around the stomach. Are you tall? You can get many bags different lengths, saving your shoulders from the cold, also stopping the sleeping bag from becoming to stretched. Bags are less effective when stretched, due to less loft which traps warm air around you.

You can Dehydrate in Cold Temperatures

Stay hydrated, when cold we don't feel so thirsty, this happens because our blood vessels constrict when we’re cold to prevent blood from flowing freely to the extremities. Our body restricts the flow of blood to our arms and legs in order to keep our core warm, hence cold hands and feet. This is because it's more important in survival terms to keep the main organs warm and functioning than to keep your hands and feet warm. Whilst keeping the core warm and functioning, the body is fooled into thinking it’s properly hydrated.

The process of fluid retention in the bodies core increases blood pressure, this is because you have more fluid in a smaller area, our kidneys start filtering and removing excess fluid from the blood. The fluid then needs to be got rid of so we pee and pee. Most people will experience this at sometime or another some more the others. If you find yourself peeing more in the cold this is why, it's called Cold Diuresis.

Our bodies will be working harder if we have added extra weight to it by layering up the clothing. If we add to this sweating, we tend not to notice how much we sweat in the cold because the sweat evaporates more quickly, believing think we don't need to replace the moisture that we would be covered in if we were in warm weather.  The colder the temperature and the more intense the exercise, the more vapour you lose when you breathe, that pretty pattern your breath is making is water evaporating from your mouth.

Cold Diuresis is technically a warning sign of your body sensing hypothermia, so you should pay attention and make sure you enjoy the cold weather safely.

Another thing that springs to mind having slept in the cold a lot, is that we might not want to drink because of getting cold when nature calls. Removing a warm body from a sleeping bag when it's freezing outside isn't the attractive proposition, so we might think that if we drink less then no nature calling and no blue nose and toes. It's not the best idea not to drink, just keep yourself hydrated.


Our Advice From Experience

I tend to feel the cold not excessively, but more when I’m inactive (so laying down/sleep time).  I take time release morphine this slows my metabolism, thus I feel the cold, I’m also getting older, if my joints get cold they become very painful.  When choosing a sleeping bag, I’m wanting a comfort level rating that is better than the temperature I’m going to sleep in. An example is if it’s going to be -2ºC, I want at least a comfort of -5ºC/-7ºC.

Our advice is firstly look at your mat, a good insulated mat will provide you with protection from the ground. When you awaken on a cold morning it’s the ground that is white over with frost, you’re sleeping on that. A bag can only do so much, if you’re sleeping on a mat filled only with air the cold will travel through that, leaving you laying on a freezing cold mat. Here is a simple analogy - If you take your roast meat out of the oven and you rap it in foil to keep it warm, however if you then place the rapped-up roast on cold marble or a slate cutting board it will cool a lot more quickly than if you place it on wood or a thick plastic chopping board.

I have camped out in lows of -6°c mainly using insulated Exped Mats, during my cold camps I have placed my hand on the surface of the mat and then on the tent floor and the difference is something else. In temperatures of -6°c I have awoken to sweat on my mat so camping in cold temperatures doesn’t have to mean a night of teeth chattering. However sweating isn't ideal in winter because your bag gets damp it doesn't dry and ends up not working properly, which ends with you cold. Insulated mats might be more expensive than standard ones but when compared to the price of a decent sleeping bag they are less expensive

There isn’t an industry standard that’s been adopted across mat manufacturers, many of the more established companies use R-rating

Sleeping Bag Filling

A decent down bag with ethically sourced down with a comfort of -6ºC is around £250 plus, synthetic are cheaper, but they come with more weight and a larger pack size which is a problem if you're backpacking or short on space. Down is still the best insulator but they’re affected by damp and moisture which is always a problem during wet or cold weather because of condensation that accumulates inside tents, when down becomes damp it can no longer hold its loft which means it can’t trap warmth air. A damp synthetic bag with perform better than a damp down bag.

When choosing a Down bag the higher the fill power the warmer it will be, however do check the weight because if its 800 fill power but only 100g of feathers then 500 fill power with 200g will be warmer. Check your fill to weight ratio on sleeping bag and jackets!

A lot of manufacturers now use water repellent down, you may see Hydrophobic Down in the description, this is the NikWax version, I have a Marmot Angelfire Treadlight Sleeping Bag their variant is called Down Defender. Down is feathers from goose and ducks, so clearly ethics play a part, I'm not here to be all holier than thou, I eat meat, that's raised locally and organically fed, I also don't buy products that contain Palm Oil. Unfortunately some companies down sources have come from suppliers that live pluck,  it's terribly painful, cruel practice that is torturous. Many companies are now very upfront about where their Down is sourced from, the European Down and Feather Association only take feathers from birds that have been slaughtered or feathers lost through moulting. Its been reported that some of the Down from China isn't so ethically sourced and live plucking is still happening. So check with the manufacturers, but like I said most are proud to display that they use ethical Down.

My Winter Bag

The reason I'm mentioning my bag is its hybrid containing both Down and synthetic filling, my bag is made from recycled filling, so good for the environment and the animals. It's also nice and warm with a comfort level of -6ºC and it's a women's bag, with a longer length and a shorter extra zip on the opposite shoulder that allows you to keep the closed if you want to free your arms. Great for shooting pictures on a Sub Zero, clear evening.

Sleeping Bag Ratings,  The Facts...


What do all these number mean, here's a breakdown for you.

Comfort Range
A Standard women should be comfortable in this sleeping bag, if the bag says 4ºC, according to EN/ISO standards then a standard women should be comfortable down to 4ºC in a relaxed position and not feel any cold.

Transition Range
Here, a standard man is will be curled up inside the sleeping bag trying to fight off the cold, and stay warm but he shouldn't be shivering. Within the Transition Range is the performance limit of the bag.

Extreme Range
In this range, the sleeping bag should only be used in an emergency, you're really going to feel the cold, whilst risking your health from hypothermia.  In EN/ISO standard’s language

The EN 13537 Standard was introduced in 2005, this was to help consumers, so they could make fair comparisons between different makes of sleeping bags.  Sleeping bags are now independently tested, comfort and limit ratings are now provided.  In April 2017, the new ISO standard was introduced as an updated version of the EN ratings. The ISO is the updated testing protocol for all sleeping bags now. Although the test was updated, the end results of the tests will remain consistent.

What Happens During the Test

The test is conducted using a heated manikin that is covered in sensors wearing some specific base layers, this is to mimic a human (although the job title sleeping bag tester appeals to me). The manikin is put in the sleeping bag that is to be tested, the sleeping bag is put on top of a foam mat in a cold chamber.

Whilst the temperature drops, the sensor reading are taken, the test is looks for key points like when the manikin’s heat accumulates in the sleeping bag, the range where its temperature remains relatively steady. It also looks for when the manikin begins to lose heat and then when the heat loss is that great, the sleeping bag is no longer effective and if use was continued the user would be putting themselves at risk.

The results are recorded and the ranges of Comfort, Transition and Risk are established, along with the defining limits of these ranges, Comfort, Limit and Extreme.



Spring, Summer, Autumn and Winter bags also have Season ratings, I prefer to use the the scientific ratings personally.

A Quick Recap

Granted there is a lot to take in so here's a quick list for you to keep in mind

1 What Temperatures will the bag be used in, that's the comfort level you will need.

2. What Filling do you want in your bag

3. Size and Shape of bag

4. Pack size, some bags can take up a lot of space.

5. What will you be sleeping on


Hopefully you have found this interesting and helpful and now choosing a sleeping won't be a minefield, I've found writing it interesting but like I've already mentioned, testing them is much more fun.........Try It!

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