Gina Johnson
Sleeping bag ratings are designed to give consumers a baseline for comparison when shopping for a sleeping bag. The ratings indicate a bag's warmth and suitability for different conditions. The current ISO 23537 sleeping bag test standard is recognised globally and uses a heated mannequin with multiple temperature sensors inside a climate-controlled room on a standardised mat. The mannequin, wearing standard pyjamas and a cold-weather mask, measures the power needed to maintain warmth in a cold room, determining the sleeping bag's thermal resistance. However, it's important to remember that these ratings are estimates and not absolute guarantees of warmth. Real-world comfort will depend on various factors, including an individual's body type, metabolism, clothing, gear, and sleeping environment.
| Characteristics | Values |
|---|---|
| Purpose of rating | To provide a baseline for comparison and help users choose the right sleeping bag |
| Lab testing | A sleeping pad is placed under the bag, and a test dummy/manikin is dressed in base layers/long underwear. The temperature of the air is then cooled, and the amount of electrical energy needed to maintain the manikin’s initial temperature is measured. |
| Limitations of lab testing | Real-world comfort probably won't match lab-tested temperature ratings because of all the variables that a lab can't simulate, such as differences in people's clothing, gear, body types, changing weather conditions, etc. |
| Types of ratings | Comfort rating, Limit/Lower limit rating, Extreme rating |
| Comfort rating | Indicates the temperature at which a cold sleeper might feel comfortable. This is the temperature rating used for women's bags. |
| Limit/Lower limit rating | Indicates the temperature at which a warm sleeper might still feel comfortable. This is the temperature rating used for men's bags. |
| Extreme rating | Refers to a woman not dying of hypothermia within 6 hours at that temperature |
| Season rating | Indicates the time of year for which a sleeping bag is most suitable, corresponding to the four seasons |
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What You'll Learn
Lab testing
Sleeping bag ratings are determined through standardised laboratory tests that produce a rating range for each sleeping bag. The ISO (International Standards Organization) oversees bag testing, which is similar to the EN bag test. The EN and ISO tests use a heated mannequin with 15 temperature sensors to represent a sleeping person. The mannequin is dressed in a base layer 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. As the temperature drops, measurements are recorded via the sensors on the mannequin to calculate the temperature ranges and limits.
The EN ISO 23537 standard is used to rate most sleeping bags and provides three temperature thresholds: Comfort Rating, Limit of Comfort Rating, and Extreme Rating. 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, where an individual can remain in the sleeping bag for up to six hours in a curled position while fighting against the cold.
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, body type, and weather conditions can affect the comfort level of a sleeping bag in real-world use. Therefore, lab-tested temperature ratings provide a baseline for comparison, but the actual comfort may vary in outdoor conditions.
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Limitations of lab testing
The limitations of lab testing for sleeping bag temperature ratings are important to understand when using these ratings to shop for a sleeping bag. Here are some key limitations to consider:
Variability in Testing Conditions
Different labs may use varying test conditions, such as different types of mannequins, tracksuits, socks, hats, and sleeping pads. This can lead to significant variability in the results between different testing centers, making it challenging to compare temperature ratings from different sources.
Lack of Movement
The mannequin used in the test remains stationary, which means it does not compress areas of insulation with its knees or hips, creating cold spots. Its lack of movement also means it does not draw cold air into the bag at the shoulders or affect the draft tube near a zipper. Therefore, features like a draft collar, hood, or draft tube design may not be adequately evaluated during the test.
Standardized Clothing and Gear
The tests use standardized base layers, but they cannot account for variations in people's clothing choices and gear in real-world conditions. Different individuals may wear varying layers of clothing to bed or use different sleeping pads, which can impact their comfort levels.
Individual Differences
The ratings are based on "average" users, but individual differences, such as metabolism, age, and personal preferences, can significantly impact how a person experiences temperature. Some people may sleep warm or cold, affecting their comfort levels at the same temperature.
Environmental Factors
Lab testing cannot simulate all real-world environmental factors, such as changing weather conditions, altitude, and windchill. These factors can significantly impact the performance of a sleeping bag in the field.
Extreme Conditions
The test standard is not valid for bags designed for extreme cold conditions or children's bags. Therefore, the ratings for these types of bags may not be as reliable or comparable to those for standard adult sleeping bags.
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EN and ISO ratings
EN (European Norm) was the original standard for testing the warmth of sleeping bags. It was introduced in 2005 to ensure that consumers could make 'like-for-like' comparisons between sleeping bags. The EN test uses a heated mannequin fitted with 15 temperature sensors to represent a sleeping person. The mannequin is dressed in a base layer and placed inside the sleeping bag on top of a closed-cell foam sleeping mat inside a cold chamber. As the temperature drops, measurements are taken from the mannequin, and the results are used to calculate temperature ranges and limits. EN 13537 offers four different temperature ratings: Upper Comfort, Comfort, Lower Limit, and Extreme.
In 2017, an updated standard was introduced, called ISO 23537. The ISO test is very similar to the EN test, and both systems are still in use. The ISO test also uses a heated mannequin dressed in a base layer and placed inside a sleeping bag in a cold chamber. The ISO standard gives three different temperature ranges: Comfort, Transition, and Extreme. The Comfort Range is defined as the temperature range at which a standard woman is "not feeling cold," while sleeping in a relaxed posture. The Transition Range is where a standard man is "in a situation of fighting against cold (posture is curled up inside the sleeping bag), but in thermal equilibrium" and not shivering. The Extreme Range 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 lab-tested temperature ratings are estimates and may not match the real-world comfort of a sleeping bag. The tests cannot account for variations in people's clothing and gear, differences in body types, changing weather conditions, and other factors. Therefore, when choosing a sleeping bag, it is vital to consider the coldest conditions in which it will be used and to sleep on an insulated surface.
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Comfort and limit ratings
Sleeping bag temperature ratings are based on the results of standardised laboratory tests. The ISO 23537 test, also known as "the ISO Test", is the most widely recognised standard. It involves placing a heavily instrumented electronic mannequin, dressed in long underwear, inside the sleeping bag in question, and positioning both on top of a foam sleeping pad. The temperature of the air is then lowered, and the amount of electrical energy needed to maintain the mannequin’s initial temperature is measured.
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 "standard woman" can sleep comfortably through the night without curling up in a ball for warmth. The limit rating is based on the temperature at which a "standard man" can maintain his thermal equilibrium in a curled-up position. He may not be comfortable at this temperature, but he is not shivering and is not in danger of hypothermia.
The comfort rating is the temperature at which a cold sleeper might feel comfortable, while the lower limit rating (always lower than the comfort rating) indicates the temperature at which a warm sleeper might still be comfortable. The comfort rating is typically used for women's bags, while the lower limit rating is used for men's bags. However, these are just general guidelines, and individual preferences and needs may vary.
It's important to note that temperature ratings are estimates and may not perfectly match real-world comfort levels. Lab testing can't account for all variables, such as differences in clothing, gear, body types, and weather conditions. Additionally, the ISO test may not represent all sleep patterns or sleeping environments. Therefore, it is recommended to use the ratings as a baseline and choose a sleeping bag with a lower comfort rating than the coldest expected temperature.
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Suitability for different conditions
Sleeping bag ratings are a complicated topic, and it's important to remember that they are estimates and not exact temperatures. The ratings are based on standardised laboratory tests, such as the ISO 23537 standard, which involve placing a heavily instrumented electronic mannequin, dressed in long underwear, inside the sleeping bag. The temperature of the air is then lowered, and the amount of electrical energy needed to maintain the mannequin's initial temperature is measured. This process helps determine the sleeping bag's thermal resistance.
However, these tests have limitations and may not perfectly represent real-world conditions. For example, they don't account for individual differences in body types, clothing, gear, and sleeping environments. Therefore, it's essential to consider your personal preferences and needs when choosing a sleeping bag.
Seasonal Ratings: Sleeping bags are often rated according to the seasons they are most suitable for. A three-season bag, for instance, would be appropriate for spring, summer, and autumn, while a winter bag would be designed for colder temperatures. Warmer sleeping bags tend to be heavier, more expensive, and bulkier, so consider the trade-off between warmth and portability.
Temperature Ratings: Sleeping bags typically have temperature ratings, such as a "comfort rating" and a "lower limit rating." The comfort rating indicates the temperature at which a cold sleeper might feel comfortable, while the lower limit rating is the temperature at which a warm sleeper could still be comfortable. Women's bags usually have higher temperature ratings than men's bags, as women generally sleep colder due to differences in metabolic rate and muscle mass. It is recommended to choose a bag with a comfort rating that is significantly lower than the coldest expected temperature.
Personal Factors: Keep in mind that everyone's experience with a sleeping bag can vary due to individual differences. Factors such as your body type, metabolism, how accustomed you are to sleeping outdoors, and your clothing and gear can all impact how warm you feel in a sleeping bag. Consider your own "internal thermostat" and whether you tend to feel hot or cold. Additionally, the fit of the sleeping bag and the warmth of your sleeping mat can also significantly impact your comfort.
Environmental Conditions: The actual environmental conditions you'll be sleeping in can vary from your expectations. It's a good idea to prepare for unexpected temperature drops by bringing a sleeping bag that can handle temperatures lower than what you anticipate. Additionally, consider the airflow in your sleeping environment, as this can affect the warmth of your bag, especially if it is made with very air-permeable fabrics.
Other Considerations: Apart from temperature ratings, there are other factors to think about when choosing a sleeping bag. Cost, pack size, and the type of filling (down or synthetic) are all important considerations. Synthetic bags, for example, tend to be heavier, while down bags can provide better warmth-to-weight ratios.
In conclusion, when choosing a sleeping bag, it's essential to consider various factors, including temperature ratings, personal preferences, environmental conditions, and other practical considerations. Remember that sleeping bag ratings are just estimates, and your individual experience may vary. It's always better to err on the side of caution and choose a bag that provides more warmth than you think you'll need.
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Frequently asked questions
Sleeping bag ratings indicate their warmth and suitability for different conditions. The current ISO 23537 sleeping bag test standard is recognised globally and uses a heated manikin with multiple temperature sensors to determine the bag's thermal resistance.
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, while the limit rating is the temperature at which a warm sleeper might still be comfortable. The extreme rating indicates a potentially dangerous situation where a woman could die of hypothermia within 6 hours at that temperature.
First, consider the lowest temperature you're likely to encounter. Then, think about your personal internal thermostat—whether you tend to feel cold or hot. If you often feel cold, opt for a bag with a comfort rating that is significantly lower than the coldest expected temperature. If you usually run hot, you may rely on the lower limit rating, but still give yourself a buffer of a few degrees Celsius.
Yes, it's important to remember that sleeping bag ratings are just estimates, and real-world comfort may differ due to various variables such as clothing, gear, body type, weather conditions, and more. Additionally, consider factors such as cost, pack size, and fill material (down or synthetic).
Sleeping bag ratings provide a baseline for comparison and help ensure you stay warm enough in various conditions. By understanding the ratings, you can choose a bag that matches your comfort preferences and safety needs.
