So you’ve decided to buy a new sleeping bag, but just one glance at all the different types and choices available on the market can leave you feeling overwhelmed. Not only are there many designs, materials, and shapes, but you also have to consider the temperature rating on the bag!
In years before the EN (European Norm) testing standard for sleeping bags, manufacturers had to conduct their testing to assign temperature ratings for their sleeping bags. In 2005 the EN 13537 was introduced, a European standard design used to institutionalize the temperature ratings on sleeping bags. In 2016, an updated version known as the new ISO standard (International Organization for Standardization) was issued, which is what you will notice if you are purchasing a new sleeping bag.
So, now you may be wondering how to determine sleeping bag ratings. Keep reading to discover what the EN/ISO test methods are, how to understand the results, what sleeping bag seasons are and how to choose the right sleeping bag for you.
Sleeping Bag Ratings Test
EN/ISO testing methods were developed in Europe as a European standard for all sleeping bag ratings. The point of the ratings from this scientific test was to help consumers compare the different bags available on the market and choose one that best suited their traveling needs.
Although it started in Europe, many outdoor companies outside of Europe use the criterion. Both the EN and ISO tests use a thermal manikin wearing a long top, bottom, a hat, and a closed-cell foam sleeping pad.
Whereas the old sleeping bag rating of a single temperature only applies to some people, the EN/ISO sleeping bag standard rating is provided for ranges of temperatures, which means it’s useful for a wide range of body types and sizes.
These tests produce four temperature results. Upper Limit, Comfort, Lower Limit, and Extreme. These ratings use the assumption that the user is using a sleeping pad under their body, in a tent, and is wearing at least one base layer of thermal undergarment.
To explain the ratings, you must understand that it references a standard man and a standard woman. The EN/ISO testing specifies a standard man to be 1.73 m in height and 73 kg in weight. A standard woman is assumed to be 1.60 m in height and 60 kg in weight. And it’s important to note that comfort is for cold sleepers, and limit is for warm sleepers.
So without further ado, let’s dive into the explanations of the temperature ratings.
Sleeping Bag Temperature Rating Explained
- Upper Limit
This is the temperature that a standard man can sleep without too much perspiration.
This is the temperature that a standard woman can expect to sleep comfortably in any position easily.
- Lower Limit
This is the temperature that standard man can sleep for eight hours comfortably without waking.
This is the minimum temperature that a standard woman can remain for six hours without risk of death from hypothermia.
As you can tell from the rating scale, the tests produce a lower rating for male sleepers and a comfort rating for female sleepers. Since sleeping bags are largely unisex, you can use the temperature rating chart as a baseline before making your purchase.
The comfort level is the temperature at which a sleeping bag will be comfortable without needing extra blankets or outerwear.
The upper limit is the temperature when you will start to feel slightly warm in a sleeping bag.
The lower limit is the temperature that a sleeping bag will start to feel cold in.
The extreme level (which is the temperature at which a standard woman can remain for 6 hours without the risk of death) is a lesser-referenced rating, but it is an EN standard for range. It’s best to ignore this rating because this is the temperature that the sleeping bag becomes unusable and will most likely result in hypothermia.
So how exactly do you put these temperature rating ranges into real examples?
For example, say the temperature rating on a sleeping bag says lit has a lower limit of -10°C, which means a man should be comfortable down to air temperatures of -10°C. The bag will also have a comfort level on the rating scale, for example, a comfort limit of -3°C, which means a woman would be comfortable down to an air temperature of -3°C.
Keep in mind that these ratings were accrued with a sleeping mat under a thermal manikin, which means you need to sleep with a sleeping mat under you for accurate results. A sleeping bag itself will not keep you warm enough.
The EN/ISO standards are the best way to help you determine a guideline performance level for a sleeping bag. It provides a range scientifically backed up by trials that accounts for one’s body size, giving you a glimpse of how any bag on the market will function.
Sleeping Bag Seasons
There are four sleeping bag seasons to help make the process easier to choose the right bag for your camping/hiking/adventure needs. Contrary to what the name might suggest, sleeping bag seasons don’t neatly fit into our actual seasons of the year. Take a look at the fur sleeping bag seasons here:
- Season 1: 10°C or higher – warm summer nights only.
These sleeping bags are best used when summer camping. A children’s sleeping bag is made for only this season.
- Season 2: 5°C or higher – cool and breezy nights
These sleeping bags are ideal for late spring and early autumn. Your nights should not be reaching 0°C or else it’s recommended to get a season 3 sleeping bag. Also, if you get cold easily, it’s best to opt for a season 3 bag.
- Season 3: 0°C or higher – cold nights but not too chilly
These sleeping bags are ideal for early spring and late autumn. These sleeping bags will keep you warm on cold nights and not too hot on cool nights. The lower limit ranges from 0 to -5 degrees, and if it goes any lower, you will start to feel cold and should consider season 4 sleeping bags if you’re going on brink-of-winter camping trips!
- Season 4: -5°C or higher – frost and snowy nights
These winter sleeping bags are suitable for very cold nights. They are designed to keep you warm even when the temperature goes down to -10°C
As you can probably guess, Season 1 sleeping bags are the cheapest options, but they are only good for summer nights. The higher up in seasons you go, the bigger the sleeping bag gets, so make sure you have enough space to pack it.
One tip when buying a sleeping bag based on seasons is that if you get cold easily, even if you’re going for a cool (5°C or higher) kind of night, it’s probably best that you purchase a season 4 to assure warmth.
Choosing the Right Sleeping Bag
The reality is that we live in such a diverse, grand world, and standards just don’t fit for all of us. Like the places that we decide to visit and camp, our bodies come in different shapes and sizes.
Using the temperature ratings as a guide to choose an approximate sleeping bag is recommended, but don’t worry about not fitting the exact standard of the bag. What feels warm to one person may feel very different to another. As a unique individual, you have to make sure you feel good in your sleeping bag and how comfortable the fit is – because that will be the deciding factor on if you get a comfortable night’s sleep.
Sleeping bag temperature ratings standardize the method for rating the warmth of sleeping bags. This criterion was so successful that it expanded from Europe to all over the world. Most sleeping bag manufacturers use this testing method to provide the most accurate results to their customers.
Although sleeping bag temperature ratings come in four categories, most of them will show just comfort level, lower limit, and extreme level. The optimal category to look at when making your purchase for men and women is the comfort level, even though it is for a standard woman. It’s important to understand that the sleeping bag rating is merely a rough guide. It’s not easy with the abundance of sleeping bags available on the market, but we hope with this handy information, you have the knowledge to make the right decision for your camping needs!