Let’s talk about sleeping bags!

This is a subject that I wanted to treat since a long time: Sleeping bags!
What are the different types? What are the meaning of the informations on it? How it works? How to choose one? etc.
(This is my first post in english, so please be nice if I made some mistakes on words haha)

#1 What is it ? What are the different types?

A sleeping bag is a bag packed with insulating material in which one get in to sleep and to fight against the weather and the cold. The main difference between sleeping bags is the temperature resistance (logic!) and it’s most of the time, classified by seasons.

This next picture is a short brief about the main “class” of sleeping bags…
(But there are other kind of course, I don’t want to list every types)

Those sleeping bags are the both I use since few years, so from the image above you can understand which class they belong to:
– Millet Baïkal 750: Class 2
– Lestra Meije 300: Class 3

#2 What are the meaning of the informations on it?

Like tents (You can read my old post about tents here – In french) there a different shapes, materials, uses, prices… depending on what you need to do and where you need to go.

Most of sleeping bags are classified by seasons:
1 season = Summer
2 seasons = Summer + Spring
3 seasons = Summer + spring + Autumn
4 seasons = Summer + spring + Autumn + Winter
Survival = Summer + spring + Autumn + Winter + Hard winter

Another important parameter to understand is the temperature written on it.
There are 3 different temperature: Comfort, Limit and Extrem/Risk
The temperatures indicated are the outside air temperatures in situation.

Comfort (C):
Up to this temperature, you are in a relaxed position on the back, there is a perfect thermal balance and you do not feel any cold.

Limit (L):
Curled up on yourself in the sleeping bag, is at the limit of the sensation of cold.
This position is adopted in order to minimize the surface of the body which loses heat.

Extrem/Risk (E or R):
The risk of hypothermia (leading to death) appears, even curled on yourself.
You can’t stay on “extrem” more than 2 hours: That is unsafe!

But everybody have a different resistance to cold.
For example, I used my “Meije 300” (C+7, L+2, E-12) in the Annapurna while camping outsite by -5°C and I was totally ok.
So if you don’t feel usually cold while sleeping outside, your temperature comfort reference will be between “comfort” and “Limit” and your limit will be between “limit” and “Extrem”.

In any case, trying to go under “Extrem” is too risky!
(Even if you are an inuit!)

I slept over 30 nights under 0°C outside, so based on my experiences I know what are my limits.
But don’t play with that!!
If you didn’t slept often outside: You can’t know what temperature you need to refer.
So choose “comfort” to avoid any risk!

If you need to sleep outside on really low temperatures and if you already own an advanced sleeping bag…
What you can do is to mix different sleeping bags and layers, like this:

#3 How a sleeping bag works?

The principle of the sleeping bag consists in trapping in its envelope a large quantity of air which will act as an insulator, allowing the body to preserve the heat inside of it.
The human body is warm (36°C to 27°C) and ejects heat through the skin, breathing etc.
So the goal of the sleeping bag is to keep that heat inside the sleeping bag and use it!


I give you an example with a “0°C Comfort Sleeping bag” during a night between 5°C and -5°C.

It’s 8pm, you just had warm dinner, it’s 0°C outside: Time to sleep!
So, you get naked (or with underwear) and go inside the sleeping bag :

The first 30mn, you will feel cold a bit, but meanwhile, your sleeping bag is warming up:

30mn later, you will reach the comfort temperature:

The night will be ok, but on early morning:

There is something to understand, Here’s the detail of a sleeping bag build:

The closure system is important, depending how it is made, it will give you a temperature bonus 😉
Most of sleeping bags are reinforced on the bottom, in order to fight against ground cold.
In winter, you need to sleep above an Inflatable mattress (not self-inflating: at least 6cm of air)

IMPORTANT:
While you sleep inside your sleeping bag, you will loose water (By skin and by mouth).
Human body loose 1 liter of water by night!

Inside the bag, water can’t escape and sometimes you get wet.
That’s risky because water can become ice when it’s cold you know…
so to avoid that, some sleeping bags are made in absorbent fabrics, but not all.
Also, it’s better to breathe out the air through a small hole (the “mouth hole”) in contact with the outside.
Only your mouth is outside, all the rest of your body is inside!
It helps to avoid wet during night!

A small advise for the end, because I’m getting tired to explain that to beginners:

The best shop/prices I know in Europe about outdoor equipment and sleeping bags:
https://en.aventurenordique.com

And well… that’s it for now 😉
Feel free to comment or correct me if you want 🙂

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