How to

5 May 2016

Sleeping Bag Insulation – How it Works and What it Means

Choosing the right sleeping bag might seem simple, but there’s a lot more to it than you might think. A lot depends on the kind of weather you’ll be camping in, since the level of insulation varies dramatically between bags. Picking a winter bag for a summer trip will make your life unpleasant, but if you pick a thinner one for cold weather, you could well be putting yourself in harm’s way.

For this reason, the most important thing to bear in mind is how your bag is insulated, and where it lands on the temperature chart. It was legally introduced by the European advisory in 2005, and it ranges from "optimal comfort" all the way down to "extreme survival". "Comfort" and "Extreme" are also applicable separately, as one refers to the optimal temperature to use the bag, and the other refers to the lowest possible temperature to use it in.

As a rule of thumb, you always want to get a bag that’s suited to slightly colder temperatures than you’re expecting. The insulation itself is typically either synthetic or down. Synthetic insulation is made up of poly-fibres which trap warm air in pockets. If you’re in a moist or humid environment, it’s by far the better option, since it’s not anywhere near as susceptible to damp as the alternative. It’s also cheaper.

The alternative is down, taken from either ducks or geese. It does the same job, only better. It’s naturally lighter than synthetics, and is able to be layered to trap much more heat. When you get towards the more extreme end of requirements, you’ll see much more down bags than synthetic ones.

There are downsides, other than that terrible pun, the main one being the aforementioned expense and lack of damp resistance. Another thing worth noting is that if you’re a vegan or a vegetarian, you may be motivated to steer clear; the process of gathering feathers for down insulation is fairly gruesome, and almost never occurs without distressing, injuring or even killing the birds. If that doesn’t bother you, fine, but it’s worth knowing where the down came from.

If you’re camping in extreme cold, be sure to wear all your clothes in the bag, the notion of stripping down and placing them over the top is a myth, you should be doing both if it comes to that. Filling up a heat-proof bottle with hot water and sleeping with it is also advisable. 

Callum Davies

Callum is a film school graduate who is now making a name for himself as a journalist and content writer. His vices include flat whites and 90s hip-hop.