Gina Johnson
Sleeping bag temperature ratings are a complicated topic. They are assigned through standardized testing, such as the ISO test, which involves placing a thermal mannequin, dressed in long underwear, inside the sleeping bag and measuring the amount of electrical energy needed to maintain the mannequin's temperature as the air temperature is lowered. This test produces a range of temperature ratings, including comfort, limit, and extreme. The comfort rating indicates the minimum temperature at which an individual can sleep comfortably, the limit rating is the temperature at which an individual can sleep without shivering, and the extreme rating is for emergency scenarios. However, it's important to note that these ratings are just estimates, and real-world comfort may differ due to various factors such as clothing, body type, and weather conditions. Additionally, there can be variations between brands and individuals, so it's always good to prepare for colder temperatures and use a properly insulated sleeping pad.
Sleeping Bag Temperature Rating Characteristics
| Characteristics | Values |
|---|---|
| Standardized Testing | ISO Test |
| Temperature Thresholds | Comfort, Limit, Extreme |
| Comfort Rating | Minimum temperature where an individual can sleep comfortably in a relaxed position |
| Limit of Comfort Rating | Temperature range where an individual sleeping in a curled position and fighting the cold can still sleep through the night |
| Extreme Rating | Emergency scenario – Minimum temperature a person can remain in the sleeping bag for up to six hours in a curled position while fighting the cold |
| Upper Limit | Temperature at which a standard male can sleep without excessive perspiration with hood and zippers open and arms outside of the bag |
| Comfort | Temperature at which a standard female can expect to sleep comfortably in a relaxed position |
| Lower Limit | Temperature at which a standard male can sleep for eight hours in a curled position without waking |
| Test Setup | Heavily instrumented electronic manikin, clad in long underwear, inside the sleeping bag in question, and positioned on a foam sleeping pad |
| Test Procedure | Temperature of the air is cooled, and the amount of electrical energy needed to maintain the manikin's initial temperature is measured |
| Limitations | Doesn't account for variations in people's clothing, gear, body types, weather conditions, etc. |
| Additional Considerations | Check the weather and leave a safe margin between expected nighttime lows and the bag's rating; consider the R-value of the sleeping pad |
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What You'll Learn
Lab testing
The EN and ISO tests are the standard methods for lab-testing sleeping bags. These tests involve placing a heated or thermal mannequin, dressed in a base layer, inside the sleeping bag, which itself is placed on a closed-cell foam sleeping mat inside a cold chamber. The mannequin is fitted with 15 temperature sensors to represent a sleeping person. As the ambient temperature drops, measurements are recorded via the sensors on the mannequin. The results are used to calculate the EN or ISO temperature ranges and limits.
The EN test produces a Lower rating (for male sleepers) and a Comfort rating (for female sleepers). The Comfort rating indicates the minimum temperature at which an individual can sleep in a relaxed position and get a good night's sleep. The Limit of Comfort Rating is the temperature range where an individual sleeping in a curled position can still sleep through the night. The Extreme Rating is for emergency scenarios, indicating the minimum temperature a person can remain in the sleeping bag for up to six hours without a serious risk of death from hypothermia.
The ISO test provides three temperature thresholds: Comfort, Limit, and Extreme. The Comfort rating is based on the air temperature at which the "average female" can sleep comfortably through the night. The Limit rating is based on the temperature at which the "average man" can maintain his thermal equilibrium in a curled-up position without shivering or danger of hypothermia.
It is important to note that these ratings are based on "average" users and should be used as a guide. Individual factors such as metabolism, age, clothing, gear, and sleeping location can affect how warm a person sleeps. Therefore, real-world comfort may differ from the lab-tested temperature ratings.
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EN standards
EN, short for European Norm, was the original standard adopted by the sleeping bag industry. EN 13537 offers four different temperature ratings to help guide users as to the warmth of a sleeping bag. These are:
- EN Upper Comfort: the highest temperature at which an average 70 kg man should feel comfortable.
- EN Comfort: the temperature at which an average 60 kg female can sleep comfortably through the night.
- EN Lower Limit: the temperature at which a standard 70 kg male can sleep for eight hours without waking.
- EN Extreme: a woman won't die of hypothermia within six hours at that temperature.
The EN and ISO standards use a controlled environment to test sleeping bags, taking into account factors like heat retention and insulation. The tests use a heated mannequin fitted with 15 temperature sensors to represent a sleeping person. The mannequin is dressed in a baselayer top, tights, long socks and a hat, then placed inside the sleeping bag on top of a closed-cell foam sleeping mat, inside a cold chamber.
It's important to note that the above temperatures are merely guidelines, not guarantees. Sleeping bag temperature ratings are based on standardised tests, but the numbers can be presented in different ways by brands, too.
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ISO standards
The ISO (International Standards Organization) oversees the testing of sleeping bags, using a method almost identical to the original EN (European Norm) bag test. The ISO test, known as ISO 23537, is an international standard for testing the warmth of sleeping bags, replacing the compulsory EN 13537 standard introduced in the early 2000s.
The ISO test involves placing a heated, sensor-rich mannequin, dressed in a base layer, inside the sleeping bag on a sleeping mat inside a cold chamber. As the temperature drops, measurements are taken from the mannequin. This process is repeated in rounds of experimentation, and the results are used to calculate temperature ranges and limits.
The ISO test provides three temperature thresholds: a comfort rating, a limit rating, and an extreme rating. The comfort rating indicates the temperature at which a cold sleeper might feel comfortable, and is the temperature rating used for women's bags. The limit rating, which is always lower than the comfort rating, indicates the temperature at which a warm sleeper might still feel comfortable, and is the temperature rating used for men's bags. The extreme rating states that "a strong sensation of cold has to be expected" and that "there is a risk of health damage by hypothermia".
It is important to note that ISO testing does not account for all variables, such as differences in people's clothing, gear, body types, and weather conditions. Therefore, the real-world comfort of a sleeping bag may differ from its lab-tested temperature rating. Additionally, not all sleeping bags have an ISO rating, as the test standard is not valid for bags designed for extreme cold or children's bags.
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Comfort ratings
Sleeping bag temperature ratings are a complex topic, and it's important to understand the limitations of lab testing when choosing a bag. Lab-tested temperature ratings, such as the EN (European Norm) or ISO (International Standards Organization) ratings, provide a standardised way to compare different sleeping bags. However, real-world comfort may differ from lab-tested ratings due to various factors that labs cannot simulate.
Now, let's delve into the details of comfort ratings:
The comfort rating is an important aspect of sleeping bag temperature ratings. It indicates the temperature at which a typical female sleeper can expect to sleep comfortably throughout the night without feeling too cold. This rating is based on the assumption that the sleeper is in a relaxed posture and not curled up for warmth. The comfort rating is typically used for women's sleeping bags, as women tend to sleep colder than men on average. Therefore, women's bags usually have more insulation, making them warmer than similarly rated men's bags.
The comfort rating is determined through standardised laboratory tests, such as the ISO 23537 test. This test involves placing a thermal mannequin, dressed in standard clothing, inside the sleeping bag and measuring the amount of electrical energy or power required to maintain its initial temperature as the air temperature is lowered. This process helps determine the sleeping bag's thermal resistance and predict the level of comfort a person can expect.
It's worth noting that the comfort rating is just an estimate, and individual experiences may vary. Factors such as body type, clothing, gear, weather conditions, and personal preferences can all influence how comfortable someone feels in a sleeping bag. Therefore, it's always a good idea to prepare properly for outdoor sleeping and choose a bag with a comfort rating slightly lower than the expected nighttime lows.
When choosing a sleeping bag based on comfort ratings, consider the following:
- Check the expected nighttime temperatures and select a bag with a comfort rating slightly lower than the lowest expected temperature.
- If you tend to sleep cold, opt for a warmer bag with a higher comfort rating.
- Pay attention to the insulation and weight of the bag, especially if you're considering a women's bag, as more insulation may be needed to match the comfort rating.
- Ensure you have a suitable sleeping pad or mat with an appropriate R-value to complement your sleeping bag and provide additional warmth.
- Remember that comfort ratings are just estimates, and your real-world experience may vary. Always prepare accordingly and consider additional layers or liners if needed.
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Limit ratings
Sleeping bag temperature ratings are a complex topic, and it's important to understand the limitations of these ratings when choosing a bag. The limit rating, also known as the lower limit rating, is one of the key ratings provided by standardized tests like the EN (European Norm) and ISO (International Standards Organization) tests. This rating indicates the lowest temperature at which the average warm sleeper, typically a man, can sleep without feeling uncomfortably cold. It's important to note that the bag may not feel cozy at this temperature, but it should allow for a full night's sleep without significant discomfort.
The limit rating is based on the idea of thermal equilibrium, where the sleeper can maintain their body temperature without shivering or expending extra energy to stay warm. This rating is particularly relevant for warm sleepers or more experienced campers who tend to sleep warm. It is also a consideration for hikers and backpackers who want to reduce weight by choosing a lighter bag.
It's worth mentioning that the limit rating is not a guarantee of comfort. Individual factors such as metabolism, age, clothing, gear, and environmental conditions can significantly impact the actual comfort level of the sleeper. Therefore, it is recommended to give yourself a buffer of a few degrees Celsius when choosing a bag based on the limit rating.
The limit rating is always lower than the comfort rating, which is typically used for women's bags or cold sleepers. The comfort rating indicates the temperature at which a cold sleeper can expect a comfortable night's sleep without shivering or needing extra layers. It's important to consider both the limit and comfort ratings when choosing a sleeping bag to ensure you have a pleasant and safe outdoor experience.
In conclusion, while the limit rating provides valuable guidance, it should not be solely relied upon. It is important to consider individual differences, prepare properly for outdoor adventures, and always leave a safe margin between expected temperatures and your bag's rating.
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Frequently asked questions
A sleeping bag temperature rating is an estimate of how warm the bag will keep you.
Sleeping bags are tested in labs using a thermal mannequin or dummy, dressed in base layers and placed on a sleeping pad. The temperature of the air is then lowered, and the amount of electrical energy needed to maintain the dummy's temperature is measured.
The ISO test provides three temperature thresholds: Comfort, Limit, and Extreme. The EN standard also includes an Upper Limit rating.
The Comfort rating indicates the temperature at which a standard woman or female can sleep comfortably through the night without curling up for warmth. This is typically used for women's bags.
The Limit rating, often referred to as the Lower Limit rating, indicates the temperature at which a standard man can sleep for eight hours in a curled-up position without shivering. This rating is typically used for men's bags.
