Miya Pearson
Sleeping bag ratings indicate their warmth and suitability for different conditions. They can be confusing, as they are based on a variety of factors, including the season, the type of sleeper, and the temperature. The most common rating system is the ISO 23537 standard, which bases its comfort rating on a standard woman and its lower limit rating on a standard man. The comfort rating indicates the temperature at which a cold sleeper might feel comfortable, while the lower limit rating indicates the temperature at which a warm sleeper might still be comfortable. These ratings are useful for making comparisons between sleeping bags from different brands, but they are only estimates, and real-world comfort may differ due to various variables.
| Characteristics | Values |
|---|---|
| Standard | EN (European Norm) or ISO (International Standards Organization) |
| Purpose of standard | To provide a basis for comparison between sleeping bags from different brands |
| Test procedure | Place a heavily instrumented electronic manikin, dressed in long underwear, inside the sleeping bag, and position both on top of a foam sleeping pad. Cool the air temperature and measure the amount of electrical energy needed to maintain the manikin's initial temperature. |
| Types of ratings | Comfort rating, lower limit rating, extreme rating |
| Comfort rating | Indicates the temperature at which a cold sleeper might feel comfortable; typically used for women's bags |
| Lower limit rating | Indicates the temperature at which a warm sleeper might still feel comfortable; typically used for men's bags |
| Extreme rating | Indicates the temperature at which there is a serious risk of death from hypothermia |
| Limitations | Real-world comfort may differ from lab-tested ratings due to variations in individuals, clothing, gear, body types, weather conditions, etc. |
| Seasonality | Sleeping bags are also rated by the season(s) they are suitable for (e.g., one-season bags for summer, two-season bags for spring and summer, three-season bags for spring, summer, and autumn) |
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What You'll Learn
Sleeping bag temperature ratings can be estimates
Sleeping bag temperature ratings are based on lab tests that simulate how a sleeping bag is used. A sleeping pad is placed under the bag, and a test dummy is dressed in base layers and placed inside the bag. While this standard protocol ensures that all bag tests are done the same way, it does not account for several variables that can affect an individual's experience. These variables include differences in body types, clothing, gear, and sleeping patterns, as well as changing weather conditions. Therefore, it is important to remember that temperature ratings are estimates and may not perfectly match your real-world experience.
The ISO 23537 standard, also known as "the ISO Test," is the most widely accepted testing method for sleeping bags. It bases the Comfort rating on a "standard woman" who is not shivering in a relaxed posture. The Lower Limit rating is based on a "standard man" who is not shivering in a curled-up position. These ratings are useful for making comparisons between sleeping bags from different brands. However, it's important to note that not all sleeping bags have an ISO or EN rating, and brands might not choose to get ISO testing on bags intended for mild conditions or casual use.
The numbers on bag names may not always match the exact temperature ratings. For example, a bag named the "Men's Snugglebuggle 15 Bag" might have an ISO lower-limit rating of 18 degrees Fahrenheit. Brands often round up or down to a number ending in 0 or 5 for simplicity. Additionally, some companies use their own rating systems, which may be based on comfort rather than standardized tests.
When choosing a sleeping bag, it's essential to consider various factors beyond temperature ratings. Individual characteristics, such as metabolism, muscle mass, diet, and sleep patterns, can affect how warm or cold you feel. The conditions in which you'll be using the sleeping bag, such as the outdoor temperature, shelter, and sleeping mat, will also impact your comfort. It's recommended to choose a bag with a temperature rating at least 20 degrees lower than the lowest expected temperature to ensure comfort.
In summary, sleeping bag temperature ratings are estimates that provide a general guideline for choosing the right bag. However, they may not perfectly predict your comfort in all situations. It's important to consider your individual needs and preferences, as well as the specific conditions in which you'll be using the sleeping bag, to make an informed decision.
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EN and ISO ratings
The EN/ISO testing protocols involve placing a sensor-rich, heated mannequin (known as a thermal manikin) dressed in a base layer into a sleeping bag, which is then placed on a basic foam mat inside a climate-controlled room. As the temperature in the room drops, corresponding measurements are taken from the mannequin to determine key benchmarks such as when the mannequin's heat accumulates in the sleeping bag, the range where its temperature remains relatively steady, and the point at which heat begins to be lost. The results of these tests are used to establish ranges of Comfort, Transition, and Risk, which are then published as temperature ratings. It is important to note that these ratings are not exact temperature ratings but rather ranges of temperatures that reflect the subjective nature of warmth for different individuals.
The Comfort rating, also known as the lower limit rating, indicates the temperature at which a cold sleeper might feel comfortable. This rating is typically used for women's sleeping bags, as women tend to sleep colder than men. The Limit rating, or upper limit rating, indicates the temperature at which a warm sleeper might still be comfortable. This rating is usually applied to men's sleeping bags. The Extreme rating gives an indication of the risk of hypothermia and is based on the temperature at which a person could suffer serious health damage or death from hypothermia.
It is worth noting that not all sleeping bags have an ISO or EN rating. These ratings do not apply to bags designed for extreme cold or children's bags. Additionally, brands may choose not to obtain ISO testing for bags intended for mild conditions or casual use. While these ratings provide a useful comparison between sleeping bags, they may not accurately reflect real-world comfort due to various factors that cannot be simulated in a lab, such as differences in clothing, gear, body types, and weather conditions.
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Comfort and lower limit ratings
Sleeping bag temperature ratings are based on lab tests that measure the amount of electrical energy needed to maintain a manikin's initial temperature when placed inside a sleeping bag. The ISO 23537 standard bases the Comfort rating on a "standard woman" who isn't shivering "in a relaxed posture." This indicates the temperature at which a cold sleeper might feel comfortable and is the rating typically used for women's bags. The Comfort rating assumes that the sleeper will not be curled up in a ball for warmth and takes into account the fact that women generally sleep colder than men due to their lower metabolic rate and muscle mass.
The Lower Limit rating, on the other hand, is based on a "standard man" who is curled up inside the sleeping bag and not shivering. This rating indicates the temperature at which a warm sleeper might still feel comfortable and is typically used for men's bags. The Lower Limit assumes a sleeper who is in a curled-up position, which reduces the amount of body surface area exposed to the cold.
It's important to note that these ratings are estimates and may not perfectly match real-world comfort levels due to individual variations in factors such as clothing, body type, weather conditions, diet, and sleeping environment. Additionally, the manikin used in the ISO test may not represent individual sleep patterns or body sizes, so it's recommended to try out a sleeping bag for fit before purchasing.
When choosing a sleeping bag, it's essential to consider your own comfort needs and preferences. Factors such as your metabolism, muscle mass, diet, and sleeping environment can all impact how warm you sleep. It's also worth noting that the same sleeping bag can feel warmer or colder depending on your physical activity levels, what you eat and when, what you wear, and how accustomed you are to sleeping outdoors.
To ensure a cozy night's sleep, it's recommended to choose a bag with a Comfort rating that matches the expected nighttime air temperature. For example, if you plan on sleeping in 27ºF air temperature, choose a bag with a Comfort rating of 27ºF or higher. Additionally, consider using a sleeping mat with an appropriate R-Value to further enhance the insulating properties of your sleeping setup.
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The effect of face fabrics
Sleeping bag temperature ratings are a complex topic. Lab-tested ratings, indicated by "EN" or "ISO", are useful for comparing bags from different brands. However, real-world comfort may differ from lab-tested ratings due to various factors, such as clothing, gear, body type, weather conditions, and food intake.
Now, let's delve into the effect of face fabrics on sleeping bag ratings:
The impact of a sleeping bag's face fabric on its warmth depends on the environment in which it is used. In huts or sheltered tents, the face fabric has minimal impact on warmth due to limited airflow. In contrast, when exposed to the elements without shelter, airflow becomes a crucial factor.
The ISO 23537 test, considered the best rating system for sleeping bags, simulates a 1 kmph airflow. While this test helps identify bags that deviate significantly from their advertised ratings, it may not precisely differentiate between bags within a few degrees of each other. Additionally, very air-permeable fabrics may perform poorly in the test despite their advantages in practical use. These fabrics are breathable, comfortable, fast-drying, and lightweight, making them ideal for multi-day trips.
The face fabric's impact on airflow and, consequently, the sleeping bag's warmth, is crucial in understanding the interplay between lab-tested ratings and real-world performance. While the ISO 23537 test provides valuable insights, it's essential to recognize that practical considerations may lead professionals to prefer certain fabrics despite their lower test ratings.
Overall, when selecting a sleeping bag, it's important to consider various factors, including the face fabric, lab-tested ratings, and real-world performance, to ensure a comfortable and practical choice.
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Season ratings
Sleeping bags are rated according to the International Organization for Standardization standard, using ISO 23537 (the ISO Test). The ISO test is almost identical to the EN (European Norm) test, which was the original standard adopted by the sleeping bag industry. The ISO test involves placing a heavily instrumented electronic mannequin, dressed in long underwear, inside the sleeping bag, and positioning it 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.
One-season sleeping bags are designed for summer camping and backpacking, where nighttime temperatures will stay above +5° Celsius/Centigrade (approximately 40° Fahrenheit). Two-season sleeping bags are designed for slightly cooler nights in spring and summer, with a temperature range of 0 to +5°C (approximately +30 to +40°F). Three-season sleeping bags are designed for colder nights throughout spring, summer, and autumn, when overnight temperatures might dip just below freezing (down to -5°C or approximately 20°F). They are considered very versatile, offering a good balance between warmth, weight, and bulk. For winter camping and mountaineering (below 20°F), a true winter bag is a necessity. Expedition bags can run all the way down to -40°F or lower.
It is important to note that temperature ratings are estimates, and real-world comfort may differ from lab-tested temperature ratings due to various factors such as clothing, gear, body type, weather conditions, and food intake. Additionally, the comfort rating and lower limit rating should be considered when choosing a sleeping bag. The comfort rating indicates the temperature at which a cold sleeper might feel comfortable, while the lower limit 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.
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Frequently asked questions
Sleeping bag temperature ratings are estimates based on lab testing. The rating indicates the lowest temperature at which the bag is likely to provide a comfortable night's sleep.
The ISO 23537 test involves placing an electronic mannequin, dressed in long underwear, inside the sleeping bag, which is placed on a foam sleeping pad. The temperature of the air is then lowered, and the electrical energy needed to maintain the mannequin's temperature is measured.
There are three main types of ratings: Comfort, Limit, and Extreme. The Comfort rating is based on the temperature at which the average woman can sleep comfortably. The Limit rating is based on the temperature at which the average man can maintain thermal equilibrium without shivering. The Extreme rating indicates the risk of hypothermia.
When choosing a sleeping bag, consider the seasonality and your individual needs. One-season bags are for summer, two-season bags for spring and summer, and three-season bags for spring, summer, and autumn. If you feel colder than others, choose a bag with a higher rating.
Sleeping bag ratings are just estimates, and real-world comfort may differ. Consider the brand, the fit, and the sleeping environment. Try to test out the bag before purchasing, and remember to check the R-value of the sleeping pad you'll be using with the bag.
