For various reasons I recently found myself on an overnight camping trip with a group of people some of whom hadn’t done a lot of camping before. Despite it being a warm day, the temperature dropped significantly at night and some people were extremely cold and uncomfortable. In the morning, amidst cheerfully-shared stories about lying awake shivering all night, a few people expressed surprise that their seemingly warm sleeping bag wasn’t up to the job on what was, after all, just a chilly spring night in Southern England.
There were lots of reasons, and in some cases people just had rubbish or inadequate sleeping bags, but if you’ve ever found yourself in a similar position of being far colder at night than you expected to be, here are a few pointers.
Make sure your sleeping bag fits
This is most relevant to the taller amongst you, as having a sleeping bag that is too large is generally not an issue. Having a sleeping bag that is too small, however, is. If bits of you (most likely your feet) are pressed against the sleeping bag, stretching it out, then you will be compressing the filling and essentially exposing that part of your body to the cold air outside.
Use a liner
Liners aren’t a must-have, and their purpose is more to make cleaning the sleeping bag easier, but if you suspect you are using your bag at something approaching its temperature limit, you could consider a lightweight fleece liner which, for a very small amount of added weight and bulk, will give you a little extra buffer.
Check the comfort temperature, not the minimum temperature
Make sure you are aware of what your bags temperature rating and what that really means. Some sleeping bags will publicise minimum temperature ratings that are, essentially, that temperature at which someone in the bag will not get hypothermia. That is clearly not a suitable temperature to use it for a comfortable night’s sleep.
Fortunately there is a European standard for temperature ratings, and if your bag advertises these, they are a better guide so long as you understand what they mean. They will have three temperatures – the first is the temperature where an average woman lying flat will not wake up during the night, the second is where an average man lying curled up will not wake up, and the last is the temperature where a person will not get hypothermic. Since being warm enough to not wake up is probably your main goal, the first two ratings are a far more useful guide.
Wear a hat
Even in a sleeping bag with a hood, drawcords pulled tight, your head is often the bit that most sticks out, and can be a serious source of heat loss. On any night that is even slightly cold, I’d strongly suggest wearing a hat to sleep, it makes an enormous difference to how warm and comfortable you will be, and you’ll value it even more in the morning as you start to get out of your bag and sort your kit out.
Have a decent sleeping mat
This is perhaps the most important and easily overlooked point. A sleeping mat is not really about comfort, it’s about warmth. If you’ve ever tried sleeping on bare ground, or even, I’ve discovered, directly on a camp cot, you’ll know how quickly warmth is sapped out of the part of you in contact with the ground. The reason is two-fold, firstly the ground actually conducts heat much better than air. But, more importantly, lying on anything crushes the filling in the part of your sleeping bag between you and the ground, making it practically useless. That is why sleeping on a camp cot without a sleeping mat can also be a surprisingly cold experience. It’s also why some hikers, concerned about weight, use a quilt instead of a bag, on the basis that all the part of their bag that is underneath them is wasted anyway.
So, a decent mat which traps plenty of air is vital, and no matter how good you think you are at being comfortable on hard surfaces, it’s important to get a mat suitable to the conditions, simply to keep you warm. The colder it is likely to be, the thicker your want your sleeping mat to be.
Be prepared to wear clothes
The European standard assumes a layer of thermal underwear as a minimum and many sleeping bags, especially serious expedition ones, are oversized specifically to allow clothes to be worn. That’s partly because it’s simply not realistic to expect people in extremely cold conditions to strip most of their clothes off for even the short time it takes to get into a sleeping bag, and it’s partly because it just makes sense from a weight and efficiency point of view. When weight is a concern, it doesn’t make sense to be packing all of your insulating layers in your backpack at night, and climbing mostly naked into an extremely heavy and warm sleeping bag, when you could just take one that’s a bit lighter, and be prepared to wear your down jacket to sleep.