Gina Johnson
Sleeping bag temperature ratings are often inaccurate due to the limitations of the testing process. Standardized tests, such as the EN and ISO methods, involve placing a heated mannequin inside a sleeping bag and measuring the amount of electrical energy required to maintain its temperature as the surrounding air cools. However, these tests cannot account for various factors that influence real-world comfort, including individual differences in body type, clothing, gear, metabolism, age, and sleeping environment. Additionally, the mannequins used in tests may not represent all body sizes, and the simulated airflow may not accurately reflect real-world conditions, particularly for highly breathable fabrics. Therefore, it is recommended to use temperature ratings as a guide and consider other factors when choosing a suitable sleeping bag.
| Characteristics | Values |
|---|---|
| Standardized testing | ISO (International Standards Organization) |
| EN (European) | |
| Limitations of standardized testing | Doesn't account for individual sleep patterns, clothing, gear, body types, weather conditions, diet, etc. |
| Simulates airflow of 1 kmph, which may negatively affect results for very air-permeable fabrics | |
| Excludes "extreme climate zone expedition" sleeping bags | |
| May not represent individual size and fit | |
| Rating categories | Comfort rating (for women or cold sleepers) |
| Lower limit rating (for men or warm sleepers) | |
| Extreme rating (minimum temperature to avoid serious risk of hypothermia or frostbite) | |
| Tips for buyers | Check the actual test rating, not the number in the bag's name |
| Choose a bag with a comfort temperature lower than the lowest expected temperature | |
| Try the bag for fit |
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What You'll Learn
- Individual differences: physiology, sleep patterns, clothing, gear, and body type
- Limitations of lab testing: variables like weather, diet, and environment
- Misleading names: comfort, limit, and extreme ratings are not precise
- Manufacturing differences: materials, insulation, and fabric airflow
- Rating systems: EN, ISO, and homebrew ratings
Individual differences: physiology, sleep patterns, clothing, gear, and body type
Sleeping bag temperature ratings are based on standardised laboratory tests that produce a rating range for each sleeping bag. However, these ratings do not account for individual differences, such as physiology, sleep patterns, clothing, gear, and body type.
Physiological differences can affect how individuals experience temperature. For example, data shows that, on average, women tend to sleep colder than men, leading to women's sleeping bags typically having more insulation. However, not everyone fits within these gender stereotypes, and individual variations in metabolism and age can also impact temperature perception.
Sleep patterns also play a role. A person who sleeps soundly through the night will experience temperatures differently from someone who frequently wakes up. Additionally, some people may move around a lot in their sleep, affecting how the sleeping bag retains warmth.
The clothing and gear used in conjunction with a sleeping bag can also impact temperature ratings. For example, wearing excessive clothing can lead to overheating and sweating, which can result in feeling colder. Similarly, the type of sleeping pad used can affect temperature regulation, with higher-quality pads providing better insulation.
Body type is another factor that influences temperature perception. A sleeping bag that is too tight or too loose may not provide accurate temperature ratings, as the bag's insulation can be compressed differently, affecting its ability to retain warmth.
While laboratory tests provide a standardised way to rate sleeping bags, it's important to remember that individual differences can significantly impact how a person experiences temperature. Considering these factors can help individuals make more informed decisions when choosing a sleeping bag that suits their specific needs.
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Limitations of lab testing: variables like weather, diet, and environment
Lab-tested temperature ratings are useful for making comparisons between sleeping bags from different brands. However, real-world comfort may differ from lab-tested ratings due to various factors that a lab cannot simulate.
Firstly, lab testing does not account for differences in people's clothing, gear, and body types. For example, the amount of clothing worn to bed can significantly impact warmth, with some people preferring to sleep in base layers or underwear, while others may prefer long johns and multiple layers of socks and shirts. Additionally, individual metabolism and age can also affect comfort levels.
Secondly, external factors such as changing weather conditions and diet can influence how warm or cold one feels. The temperature rating on a sleeping bag assumes ideal conditions and does not account for weather variations like wind chill or humidity, which can significantly impact how warm the bag feels. Diet can also play a role, as the food we eat can affect our body's ability to generate and retain heat.
Another factor is the sleeping pad used in conjunction with the bag. Sleeping pads provide insulation from the ground, and the R-value of the pad can vary significantly between different products. A low-quality pad with poor insulation can make a person feel colder, even if the bag itself is rated for the temperature.
Lastly, lab testing assumes that people fall into distinct categories of "warm" or "cold" sleepers, based primarily on gender. However, individual variations exist, and not everyone fits neatly into these categories. Some people may be more sensitive to temperature changes or have medical conditions that affect their circulation or temperature regulation.
While lab testing provides a standardized way to compare sleeping bags, it is important to remember that it cannot account for all the variables that affect comfort in the real world. Therefore, it is always a good idea to prepare for a range of temperatures and bring extra layers when sleeping outdoors.
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Misleading names: comfort, limit, and extreme ratings are not precise
Sleeping bag temperature ratings are assigned based on standardized testing, which provides three temperature thresholds: comfort, limit, and extreme ratings. However, the names of these categories can be misleading as they don't precisely reflect the actual experience of sleeping in the bag.
The "comfort" rating indicates the minimum temperature at which an individual can expect to sleep comfortably in a relaxed position. This rating is typically used for women's bags, as data suggests that women tend to sleep colder than men. However, this is just a generalization, and individual differences, such as metabolism and age, can also affect comfort levels.
The "limit" or "lower limit" rating is the temperature at which a warm sleeper (typically a man) can still sleep comfortably. This rating assumes that the sleeper will be in a curled position and may be fighting against the cold to some extent.
The "extreme" rating is the most severe and indicates the minimum temperature at which a person can survive for up to six hours without serious risk of death from hypothermia. However, it's important to note that frostbite is still possible at these temperatures, and additional layers or sources of warmth may be necessary.
While these ratings provide a helpful guide, they don't account for all variables that can affect an individual's comfort. For example, factors such as clothing, gear (including the type of sleeping pad), body type, weather conditions, and diet can all impact how warm or cold a person feels. Therefore, it's always a good idea to prepare accordingly and bring extra layers when sleeping outdoors.
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Manufacturing differences: materials, insulation, and fabric airflow
Sleeping bag temperature ratings are assigned through standardized testing, which provides three temperature thresholds: comfort, limit, and extreme. The comfort rating indicates the minimum temperature at which an individual can sleep comfortably in a relaxed position. The limit of comfort rating is the temperature range where one sleeps in a curled position and fights the cold but can still sleep through the night. The extreme rating is the minimum temperature a person can remain in the sleeping bag for up to six hours without risking hypothermia.
However, these ratings are not always accurate due to manufacturing differences in materials, insulation, and fabric airflow. Firstly, the materials used can vary between brands, affecting the bag's warmth. For example, a bag with more insulation will be warmer than one with less. Women's sleeping bags typically have more insulation, making them warmer than similarly rated men's bags.
Secondly, the type of insulation used can impact the bag's effectiveness. For instance, down insulation provides more warmth with less weight, while synthetic insulation is better at retaining warmth when wet.
Lastly, the fabric airflow of a sleeping bag can affect its performance. The ISO 23537 test, which is widely used, simulates a 1 kmph airflow. While this test is useful for comparing bags, it may not accurately represent the performance of very air-permeable fabrics, which are breathable, comfortable, and lightweight, making them ideal for multi-day trips. Therefore, professionals often prefer these fabrics despite their lower test ratings.
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Rating systems: EN, ISO, and homebrew ratings
Sleeping bag temperature ratings are assigned through standardized testing. The EN (European Norm) rating was the original standard adopted by the sleeping bag industry. Today, the ISO (International Standards Organization) oversees bag testing, using ISO 23537, which is similar to the EN test. The ISO test involves placing a heated, sensor-rich manikin, wearing a base layer, inside the sleeping bag, and positioning it on a foam sleeping pad. Measurements are taken as the temperature in the cold chamber drops.
The ISO test provides three temperature thresholds: a comfort rating, a limit rating, and an extreme rating. The comfort rating is the temperature at which a cold sleeper might feel comfortable, and is typically used for women's bags. The lower limit rating is always lower than the comfort rating and indicates the temperature at which a warm sleeper might still be comfortable; this is the rating used for men's bags. The extreme rating gives an idea of the risk of death from hypothermia in a matter of hours.
While the EN/ISO protocol ensures that all bag tests are done the same way, it cannot account for all variables, such as differences in clothing, gear, body types, weather conditions, and food. Therefore, a bag's comfort level will probably differ from its tested temperature rating. It is worth noting that not all sleeping bags have an ISO or EN rating. These ratings are not valid for bags designed for extreme cold or for children.
In addition to the EN/ISO standards, there are also "homebrew ratings," which are trustworthy ratings typically from cottage companies.
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Frequently asked questions
Women's sleeping bags are usually designed with more insulation, making them 10–15 degrees Fahrenheit warmer than similarly rated men's bags. However, this is based on the premise that the average woman sleeps colder than the average man, which may not always be the case. Therefore, it is recommended to add about 10 degrees for women or cold sleepers.
Lab-tested temperature ratings provide a standardised way to compare different sleeping bags. However, they may not always match real-world comfort due to various factors that labs cannot simulate, such as clothing, gear, body types, weather conditions, and individual preferences.
The ISO test uses a thermal mannequin to measure the insulating properties of a sleeping bag. However, it does not account for individual sleep patterns, real sleeping environments, or variations in mannequin shape across labs, which can affect the accuracy of the ratings.
