top of page

Forum Posts

Keith
Feb 11, 2023
In Temperature Ratings & Testing
This is also an excellent presentation on temerature ratings, testing, and staying warm by Kelly Florogear published online in May of 2020. I have misplaced the actual link but I will try to locate it. Again, Kelly lacked information about our technology, but there presentation is otherwise exceptional. MAY 25, 2020 : KELLY FLOROGEAR The Ultimate Guide to Backpacking Sleeping Bags and Quilts for All Budgets A bad night’s sleep is the quickest way to ruin a camping trip. At best, you’re guaranteed to be sore, miserable, and exhausted by morning. At worst, you’re putting yourself in danger of hypothermia. That’s why it’s so crucial to choose the best backpacking sleeping bag. I know, I know. Easier said than done. There are so many variables at play with sleep gear, and it’s also pricey as shit. That’s probably why you’re reading this post. You don’t want to end up saddled with an expensive, crappy sleep system that doesn’t work. That’s where we come in. This guide exists to answer all of your most pressing questions about sleeping bags—including tips to get the most bang for your buck—so you can get it right the first time and buy the best backpacking sleeping bag for your needs. Understanding Sleeping Bag Temperature Ratings Most manufacturers use a standardized temperature rating system known variously as “EN,” ‘”EN13537,” or “EN/ISO.” So how does it work? Basically, by popping a sleeping bag-equipped thermal mannequin inside a controlled testing chamber (at an independent laboratory) and measuring its response to different air temperatures. The mannequin simulates an adult human, complete with sensors to measure heat gain and loss. It always wears synthetic base layers and a beanie, and “sleeps” on a one-inch foam pad. Comfort, Limit, Extreme Three numbers are generated from this test: “Comfort,” “Limit,” and “Extreme.” Usually, you’ll be able to find all three printed somewhere on the bag itself. Only one of them is featured as the primary rating, though. Comfort is the lowest temperature at which a typical cold sleeper can stay warm in a relaxed position. Women tend to sleep colder than men, so Comfort is usually the primary temperature rating for women’s bags. Limit is the lowest temperature at which a warm sleeper maintains thermal equilibrium while curled up to conserve heat. This number is used to rate men’s bags. If you’re shopping for a men’s bag, bear in mind that Limit describes the temperature at which warm sleepers are supposedly right on the edge of being too cold. It’s not the lowest temperature at which they’ll be comfortable, like with women’s bags. Finally, extreme is the lowest temperature at which a typical cold sleeper can survive for six hours without getting life-threatening hypothermia. Obviously, we all hope never to test this number, but it’s a good one to know in case of an emergency. How Accurate are Sleeping Bag Temperature Ratings? Standardization is a great thing for consumers: it makes it way easier to compare different brands and instills a degree of confidence in the accuracy of the numbers. … But still. You probably run hotter or colder than the physiological averages used to calibrate some random mannequin in a laboratory. You also probably use different gear, and conditions in the backcountry are persistently unpredictable. So while standardized ratings are useful, remember to take them with a grain of salt. That’s why, if you want the best backpacking sleeping bag for your personal needs, you should always pick one that’s rated at least 10˚F below the lowest temperature you expect to encounter when backpacking. Temperature Ratings by Brand Not every major brand uses the EN/ISO rating, and there are some that use the system but don’t rate everything the conventional way. For instance: Therm-a-Rest uses EN/ISO, but doesn’t have female-specific models. All of their bags use the Limit temperature as their rating. Rab uses EN/ISO, but they use the Limit temperature for both men’s and women’s bags. Big Agnes does not use EN/ISO. Their in-house temperature ratings are less conservative than EN/ISO’s standards. Feathered Friends and Western Mountaineering do not use EN/ISO. Their in-house temperature ratings are considered more conservative than EN/ISO. REI, Nemo, The North Face, Marmot, Mountain Hardwear, and Kelty (basically all brands sold at REI other than Big Agnes) all use the EN/ISO system in the usual way (men’s bags advertising the Limit rating, women’s using Comfort). Even within brands that use EN/ISO, the standard doesn’t apply to quilts, kids’ bags, or extreme cold bags (bags comfort-rated below -13˚F). Temperature Ratings By Season The bag you trust in four-season conditions will be beyond overkill for your balmy weekend getaway next August. What temperature rating should you target for each backpacking season? This is highly dependent on individual physiology, but here are some broad guidelines: Winter (non-mountaineering): 0˚to 15˚F Shoulder seasons: 15˚to 25˚F Summer: 25˚to 35˚F As a reminder, always go for a bag 10 degrees lower than the lowest temperature you expect to encounter on your trip. If you’re just a three-season backpacker, you can probably get away with one middle-of-the-road bag (25˚ seems right on the money to this cold sleeper) rather than spending out the ass to get a dedicated bag for each hiking season. Just use a sleeping bag liner to extend the bag’s temperature range even further. How to Make your Bag Warmer without Blowing the Budget Buy a women’s bag. You can sometimes get more insulation for the same price by opting for the women’s version of a given bag (provided it fits). Women’s bags are rated more conservatively than men’s, so they usually contain more insulation. But for some brands, they still cost about the same as their male counterparts. For example: the women’s version of the REI Magma 15 bag contains an incredible 47% more fill than the men’s, but the price tags are identical. Marmot’s Trestles 15˚ women’s bag has about 50% more insulation than the men’s for just $10 more. And it’s a similar story with the NEMO Riff men’s and women’s bags. Use a liner. If you want to extend the temperature range of your sleep system, try getting a sleeping bag liner. Liners like the Sea to Summit Reactor Extreme only cost around $70. For not much money, these bad boys can add a surprising amount of warmth to your existing system. As a bonus, a liner will keep your bag cleaner and protect it from damaging body oils. Trust me… liners are so much easier to wash than bulky-ass sleeping bags. Make sure you get one with a drawstring if you want maximum warmth. Eat a hot meal just before bed. Even a cold sleeper like me can stay toasty by eating hot, fatty food just before bed to supercharge my metabolism. My personal favorite calorie/heat delivery system is a Mountain House Mac ‘n’ Cheese with plenty of extra cheese and butter mixed in. I’ve ended up overheating on single-digit nights in my REI Magma 15 thanks to this trick. Sleep with a hot water bottle. Pour hot water into a Nalgene bottle and stick it in your footbox to inject extra warmth into your bag. Pro tip: Overheating in your sleeping bag? You can do the opposite (put an ice-cold water bottle in your bag) to cool off. That way, you can bank excess body heat and end up with warm drinking water by morning. Layer up. There’s a myth out there that your sleeping bag will work better if you’re naked inside it. In reality, quality sleep clothes will actually help keep you warm in your bag (as long as they’re not so bulky that they compress the sleeping bag insulation). Here are some examples: Base layers: REI’s synthetic top and bottom are plenty warm and about half the price of wool Sleep socks like Darn Tough’s Mountaineering socks Down booties (if you have literal cold feet, I can’t over-emphasize how crucial this is) Hat: if your mummy hood isn’t cutting it, a simple beanie can help warm you up Differences between Men’s and Women’s Bags Men’s and women’s bags are insulated differently. Women generally lose more heat through their feet and hips, so those parts of a woman’s bag are usually overstuffed with insulation. The other difference is in the cut of the bag. Women’s bags are shorter on average, and are narrower in the shoulder area but wider in the hips. The Importance of Sleeping Bag Fit If you want to maximize warmth, weight, and comfort, it’s important to make sure your bag fits you right. It should feel snug, without much dead air space (you’ll end up wasting energy keeping that air warm). You’ll want a close fit around your shoulders and neck in particular. That way you won’t catch a draft through the opening. On the other hand, if your sleeping bag is too tight you’ll end up compressing the insulation. Whether it’s down or synthetic, compressed insulation doesn’t perform well. That’s why it’s important—especially if you’re extra big or extra small—to try bags on for fit before purchasing. Down Insulation Ever seen a flock of geese or ducks tooling around in a tiny, unfrozen patch of lake on a frigid winter morning? Birds have a layer of soft, insulating “fuzz” called down beneath their feathers that keeps them warm in incredible conditions. Humans harvest that delightful fluff for use in insulating products like comforters, puffy jackets, and sleeping bags. Down makes some of the best backpacking sleeping bags because it’s warm, light, compressible, and feels pretty damned cuddly. Sleeping bags can use either goose or duck down. Goose down is harder to come by, and therefore more expensive. There’s not much difference in quality between goose and duck down of similar loft (fill power). If you’re comparing two bags of similar fill power and one uses duck down, you may as well go with that one. It will be cheaper and perform just as well. That said, goose down is available in higher fill powers than duck down (which pretty much maxes out at 650-fill). High-end, super lofty bags therefore usually use goose down. Fill Power The quality of down is functionally equivalent to its loft, or puffiness. That’s because down insulates by creating air pockets that trap heat. Loftier down has more air pockets and therefore insulates better. Fill power is the number of cubic inches of loft generated by an ounce of down. You can use this number to assess the quality of down. 650-fill is decent quality for backpacking gear and is a good budget option (especially if you go with duck down). In contrast, high-end products might use 800 or even 900-fill goose down. Compared to 650, it takes fewer ounces of 900-fill down to produce the same level of insulation. That means you can get a bag with the same temperature rating that weighs a lot less. Fill power is a warmth-to-weight ratio, not an absolute measure of warmth. A tiny amount of 900-fill down (the best quality money can buy) still won’t generate enough loft to keep you warm. That’s why, as a consumer, it’s important to pay attention to other factors like the temperature rating and fill weight, too. Responsible Down Standard Animal-based products always raise certain ethical concerns. Today, companies use the Responsible Down Standard to let consumers know that their down is sourced from humanely raised ducks and geese. The best backpacking sleeping bags all use this standard. Downsides to Down Down is widely considered the best insulation material for sleeping bags, but that doesn’t mean it’s perfect. One of its biggest drawbacks is that it’s useless when wet. The feathers compress down to virtually nothing, and no loft means no warmth. This sucks because it’s pretty tough to keep anything dry in the backcountry. This is especially true in especially rainy and/or humid environments. These days you can find hydrophobic (aka water-resistant) down that retains loft when wet. But in general, it’s still important to protect your down bag from water at all costs. A 20L waterproof dry sack is a good investment in your future if you own a down sleeping bag. If your bag does get wet, whether from condensation in your tent or if rain permeates your protective layerings (which it shouldn’t with a waterproof sac), dry it out in the sun as soon as possible. Enough direct light and heat will restore life into your loft. Down’s excellent warmth-to-weight ratio comes with a high price tag. There’s no denying that down bags are more expensive than synthetic ones. If you’re reading this post because you’re broke AF but still want to go backpacking, you’ll probably (rightly) view this fact as down’s biggest drawback. Just note that, while down is pricier upfront, it may still be a better long-term investment for those who can swing it. Down bags can last significantly longer than synthetics because they can survive more cycles of compression and expansion. … Synthetic Insulation Synthetic sleeping bags are stuffed with highly engineered polyester fuzz under brand names such like PrimaLoft® and PolarGuard®. These materials mimic the lightweight warmth, compressibility, and softness of down as closely as possible—all at a much lower upfront cost. Unlike down, there’s no industry-wide equivalent to fill power for synthetic insulation. Without a consistent way to measure the loft or loft-to-weight ratio of synthetic fill across brands, consumers must base comparisons mainly on temperature ratings and brand reputations. On one hand, synthetic bags generally weigh more than down and aren’t as deliciously floofy feeling when you snuggle into them. They’re bulky and don’t compress well. But on the other hand, compared to down they retain a decent amount of loft and warmth when wet. Synthetic bags are great for trips where you’re likely to get soaked. For instance: a synthetic sleeping bag was likely the difference between life and death for my boyfriend on an ill-fated, rain-sodden trip to the redwoods one frigid November. Even if you’re not planning to get drenched, synthetic bags are a budget-friendly choice. At perhaps half the price of a down bag, its synthetic equivalent is undoubtedly so much more affordable. Yes, they’re heavier, but you may be able to make up for that by shaving ounces somewhere else in your pack. In any case, as sleep system technology continues to evolve, the weight (and floof) disparity between down and synthetic will likely continue to shrink. … The Best Backpacking Sleeping Bag Designs Mummy Bags Mummies are the most popular design on the market, and they’re definitely the warmest. They’re cut to fit very snugly, hugging the shoulders and tapering toward the feet. This design cuts airflow and uses as little material as possible. Mummies also have close-fitting hoods that you can cinch down tight around your face, minimizing air gaps and exposed skin. This design takes some getting used to; that tight fit can be kind of claustrophobia-inducing, especially if you’re new to the experience. It’s good to practice sleeping in your mummy at home to adjust to this sensation before you take it out camping for the first time. If you just can’t get used to it, you might like the generous cut of NEMO Equipment mummy bags. Double Bags If you hike with your significant other, you might want a couple’s sleep system so that you can get freaky in the tent without freezing your sensitive bits off. The market for double bags is pretty slim, but they do exist—check out the Cabin Creek model from Big Agnes. Double bags are typically more rectangular than mummy-shaped. This cut makes them roomy enough for two, but it’s also draftier and less weight-efficient than a mummy design. A couples’ system is less versatile if you sometimes plan solo trips. A compromise solution is to zip two single bags together. Men’s bags usually zip on the left, while women’s zip on the right. If you and your beau each get bags from the same manufacturer, they’ll probably have compatible zippers. The zipped-together setup can be a little awkward, but it’s a great way to retain the versatility of your single bag while reaping the benefits of a double. Quilts Backpacking quilts eliminate the hood, zipper, and entire bottom half of the sleeping bag. You’ll be sleeping on an insulated pad anyway, and the sleeping bag insulation won’t do much good all crushed up underneath you—right? So why even bother with all that extra material? As for the hood, you can always throw on a wearable insulated hood or a beanie if needed. As a result, quilts are lighter, cheaper, and more compact than regular sleeping bags—all while being just as roomy as your comforter back home. Even minimalist quilts usually have some form of sewn footbox you can tuck your tootsies into. Some quilts also have features like drawstrings, draft collars, and pad attachment sleeves. Quilts have some advantages over traditional systems, but they’ll never be as warm as mummy bags: they’re just too drafty. At the end of the day, you’re unlikely to see four-season backpackers venturing out in frigid alpine conditions with anything less than full mummy bags. For more temperate adventures, though, quilts are a great option. … Features to look for in the best backpacking sleeping bags Worth noting that there’s often a trade-off between features and weight. More of one typically translates to more of the other. If you’re planning for an especially long distance trek, you may want to forgo some of the below features in favor of weight savings. Two-way zipper: Half zippers save weight, but they’re not versatile. With two-way full-length zippers, you can open up the bottom to vent heat on warm nights. Draft collar: The best backpacking sleeping bag in the world won’t do you much good if cold air can seep in through the giant hole at the top of the bag. So make sure you get an insulated draft collar that hangs around your neck and shoulders to cut airflow. Stash pocket: In cold weather, you’ll want to sleep with your electronics, water filter, and maybe a few other things. An internal pocket goes a long way toward maintaining order in your bag once you move all your random shit inside. Water resistance: DWR shell fabrics, water-resistant down, waterproof footboxes… you get the picture. Anything you can do to avoid a sodden sleep system is a win. And on that note… Dark colors: Despite your best efforts, your sleeping bag is going to get wet at some point. When it does, you’ll need to find a sunny patch of trail and dry that sucker out ASAP. That’s why the best backpacking sleeping bags are dark-colored. Black/dark-colored bags absorb heat and dry faster than lighter colors. This one simple feature will save you time and keep your bag in tip-top shape. Pad sleeve: Some models from Big Agnes swap the bottom insulation for a stretchy fabric sleeve designed to hold an inflatable pad. This is great if you’re sick of sleeping on what feels like the world’s most boring Slip ‘N Slide. Pro tip: The low-budget solution to the slippery pad problem is a few strategically placed dots of silicone seam sealer on your pad to create extra friction. Caring for your sleeping bag (without ruining it!) Even if you use a liner, eventually any well-loved bag will start to look (and smell) its age. In time, your body oils will weigh down the insulation and reduce its performance. Knowing how to wash and store your bag can extend its life. Washing Washing your sleeping bag can be an arduous process, but every now and then it’s gotta get done. Because sleeping bags are bulky, it’s best to either hand-wash them or use an extra-large machine at a laundromat. The agitators in top-loading machines don’t always play nice with delicate backpacking gear. With that in mind, be sure to use a front loader or a top loader sans-agitator. Start by zipping the bag up to minimize the potential for damage. You’ll need to use special soap because regular detergent can ruin the insulation. Use tech wash for synthetic and down wash for down. After washing, you can optionally treat the bag’s shell fabric with spray-on Durable Water Repellent to help the material bead and repel water. Don’t use the wash-in kind unless it’s formulated for use with insulation. Drying Be careful when drying down bags, because down forms clumps when it gets wet. You definitely don’t want to let it dry that way. The best way to combat clumping is to add three or four tennis balls to the dryer with your bag on low or no heat. The balls will pummel the insulation, breaking up clumps. Don’t love the tennis ball solution? You can also pause the dryer every half hour and use your fingers to break up clumps manually. Remember to dry both down and synthetic bags on the lowest setting possible. It might take three or four hours for your bag to get totally dry. Storing Don’t compress your down or synthetic bag for long-term storage. Doing so will reduce its ability to loft over time. Instead, hang your bag from the loop at the bottom or use the mesh storage sack most bags come with. What Have We Learned? A good sleeping bag is one of the most critical aspects of your backpacking kit. It typically accounts for a big chunk of the weight and price of your setup. Plus, it has an outsized effect on your comfort and safety in the backcountry. That’s why it’s so valuable to have a deep understanding of sleeping bag standards and designs before you buy. When it comes time to take the plunge and invest in the best backpacking sleeping bag for your needs, we hope this guide helps you get it right the first time. Do you have a tried and true sleep system that you love? Tell us about your setup in the comments below.
0
0
86
Keith
Feb 11, 2023
In Temperature Ratings & Testing
The best explaination about sleeping bag temerature ratings that I have seen so far was presented by Rex Sanders at I have included the text of his presentation here. While he didn't have access to our technology, his presentation is otherwise exceptional. I was greatly impressed with his list of things that can affect a persons ability to stay warm . Standards Watch: Sleeping Bag Temperature Ratings In this installment of Standards Watch, Rex Sanders tackles sleeping bag ratings: the standard, the pros, and the cons. Dec 22, 2020 https://backpackinglight.com/standards-watch-sleeping-bag-temperature-ratings/ Introduction You’ve probably seen sleeping bags advertised as good to “32 degrees” (Fahrenheit) or “0 degrees” (Celsius) and wondered how they came up with that number. Thanks to measurements using the ISO 23537 standard, commonly known as the EN rating, we have a consistent but imperfect way to measure and report those values. In this column, I’ll review the standard in detail and cover its pros and cons. In a future installment of Standards Watch, we’ll hear from some sleeping bag and quilt designers, and look at how companies use, abuse, or ignore standard temperature ratings. You should keep in mind a few facts barely discussed in the standard. Sleeping bags or quilts are just one part of a system to keep you warm at night. Other gear includes a warm enough sleeping pad, sleeping clothes, and a shelter. Essential skills include going to bed warm, well-fed, and hydrated in a location protected from the wind. Your sleeping system doesn’t generate warmth – it just traps the heat your body gives off, like a thermos keeping coffee warm. And just because your younger, fitter, and trimmer hiking buddy slept warm in a particular sleeping bag doesn’t mean that you will too. Overview of the Standard You will see sleeping bag “EN” ratings or “EN 13537” ratings far more often than “ISO 23537” ratings. “European Norm” 13537 was the first widely used international standard for measuring sleeping bag temperature ratings. In 2016, the International Standards Organization published ISO 23537 to replace that standard and make it more consistent. For consumers, the difference between EN and ISO ratings isn’t relevant. Most backpackers and retailers still refer to the EN rating of a bag, whether it’s measured under ISO or EN. The standard defines a test procedure, using a calibrated manikin in a climate-controlled room on a well-insulated sleeping pad, for measuring a sleeping bag’s Maximum temperature, Comfort temperature, Limit temperature, and Extreme or Survival temperature. Most bag makers publish just the Limit temperature, or the Comfort temperature, or sometimes both. ISO 23537 bases the Comfort rating on a “standard woman” who isn’t shivering “in a relaxed posture.” The lower Limit rating is based on a “standard man” who’s “curled up inside the sleeping bag” and not shivering. Regardless of your gender identity, I’ll go into more detail below, and in a later article, help you decide which rating might fit best. There are a few other ways to measure insulation. R-values in U.S. traditional units come from construction, and are now widely used (for better or worse) to measure sleeping pad insulation. RSI or m2*K/w is the metric equivalent and used throughout ISO 23537. You can measure clothing insulation in international tog units or U.S. clo units, but sleeping bags rarely feature them. Testing Process Before testing begins, a climate-controlled room is set up to meet the standard. The sleeping bag and manikin lie on an R 4.8 (RSI 0.85) pad, placed on a large-enough, about 3/4 inch (20 mm) thick wooden board. The whole apparatus is at least 3.9 inches (100 mm) above the floor, with air circulation underneath. Sleeping bag preparations typically start the day before the test, with the bag tumbled for 15 minutes without heat in a large, laundromat-sized dryer. Then the bag goes into the climate-controlled room for at least 12 hours. Yes, even sleeping bags need to acclimate! The real action starts on the day of the test. The tester lays the sleeping bag on top of the pad and board. If the bag’s hood closes small enough, a cold-weather mask goes onto the manikin’s face. Then the tester places the manikin inside the sleeping bag and completely closes the zippers and hood, if appropriate. The manikin has both electric heaters and an array of thermometers connected to test equipment. While monitoring the temperatures, the tester slowly increases and measures the electric power heating the manikin. The rarely-seen Maximum temperature test uses a manikin with arms out, no face mask, a flat hood, and an open zipper. Five pages of mathematical formulas in ISO 23537 can compute sleeping bag insulation in RSI and the four rated temperatures. The equations reflect human heat production; dry, evaporative, and respiratory heat loss; body temperature changes; and sleeping bag breathability. In practice, shortcut formulas and tables in the standard make the job much simpler. Example of an ISO 23537 standard compliant sleeping bag graphic label. The temperatures left to right are Maximum, Comfort, Limit, and Extreme. Credit: Rex Sanders ISO 23537 also requires specific consumer labeling on each sleeping bag, including a graphic based on the four calculated temperatures. Bag makers may be creative if they include all the required elements. Good Stuff Testing most sleeping bags to the same standard makes for easier and more trustworthy consumer comparisons. Before standardized testing, you had to rely on the inconsistent temperature or “season” ratings of bag makers. Moreover, some manufacturers had a much better reputation than others. Despite using a motionless manikin lying on its back, standard developers used extensive human research to calibrate their mathematical models. Also, the standard explicitly allows for testing of hoodless sleeping bags, and by extension, quilts. However, the manikin would lose a lot of heat through its uncovered head, resulting in a more flawed temperature rating. Oddities ISO 23537 has a few quirks. One part of the standard requires testing in a room with a temperature that could range from 41 F to 59 F (5 C to 15 C). A later section specifies calibration using 58.8 F to 59.2 F (14.9 C to 15.1 C). Yet, Amendment 1 requires testing in the same conditions as calibration. The standard has specific but confusing language describing when tests should include a military-grade extreme cold weather mask. In brief, the tester must put that mask on the manikin for sleeping bags with hoods that can close to less than 4.7 inches (120 mm) across the face. That would barely expose the eyes, nose, and lips. For sleeping bags with larger openings or no hoods, or for quilts, tests must not include a mask. That seems like the opposite of what most people would do. The standard says it works like this: in cold air, most sleepers turn their face into the cinched-up hood of their sleeping bag. But the available instrumented manikin’s neck can’t rotate. So to simulate a turned head in a closed hood, the standard requires a mask but prohibits it when there’s no suitable head covering. Test Issues The standard has many limitations that can reduce its accuracy when compared to the real world. For example, all tests use just one manikin that must stand in for humans with a range of heights, widths, weights, and total heat production. This can be a real testing problem for bags much smaller or larger than the manikin. And during testing, the manikin wears a relatively warm long-sleeved top, long underwear, knee socks, and usually a cold weather mask. The standard developers calibrated the test using numbers from a so-called “standard man,” who was 25 years old, 154 lbs (70 kgs), and 5 ft 8 in (1.73 m). And the so-called “standard woman” was also 25 years but with a height of 5 ft 3 in (1.6 m), 132 lb (60 kg) weight, and 25 years old. The standard also warns that it might not work for children, temperatures below -4 F (-20 C), or sleeping bags with “local extra insulation.” Sleeping Bag Design Issues Note that the ISO 23537 test does not cover other features that can affect your warmth. A dummy that never stirs won’t thoroughly test draft-prevention features that can move a little or a lot, like hoods, neck collars, and zipper draft tubes. Real-world tests of bags with identical ratings but different draft-prevention features often discover these differences. Other design issues can make a sleeping bag feel warmer or colder, including: insulation movement and clumping, especially with down; overstuffing that doesn’t add significant insulation, but can stop shifting and delay decay; compressing insulation, especially down, as you move and extend feet, knees, hips, shoulders, and elbows; and balancing between enough room inside for comfort versus heating more air that escapes when you gyrate. Designs that create cold spots, particularly for hands and feet, can make an otherwise warm sleeping bag feel miserable. Environmental Issues A variety of environmental issues can turn any sleeping bag colder or warmer than the controlled environment specified in ISO 23537. Wind through your shelter is very efficient at removing warmth. Low humidity can make a cold night feel colder through skin evaporation. Excess condensation can reduce the insulating power of down. You’re unlikely to stay warm if rain or snow falls on your unprotected sleeping bag. High altitude can lead to more heat loss. But clouds overhead act like another blanket, keeping you warmer. Unexpected temperature drops through the night, like a cold front moving in or camping at the bottom of a drainage, can refrigerate you. A sloping campsite can make you slip out of your bag, or make you and the bag slide into damp shelter walls. And going to bed early on long winter nights allows more heat loss before the warming rays of dawn. Individual Issues Everyone’s different, and everyone changes. Sleeping bag tests based on a theoretical average human can mismatch your camping experience in many ways; to hijack a common BPL acronym, YMWAV – Your Mileage Will Always Vary. Here are some examples. Cold, Wet, Tired, Hungry, or Thirsty If you are suffering from the usual suspects, don’t be surprised if you have trouble sleeping warm enough. Traditional Gender Differences In general, women tend to sleep colder than men, often due to smaller bodies and different circulation patterns. And hormone changes can have a significant effect on perceived warmth. And if your gender identity is non-traditional, some of these factors might not apply. Age Most people lose some heat-generating muscle mass as they age, so older people often sleep colder than younger people. Circulation Some people have better circulation in their feet and hands than others. You won’t be happy if your feet are ice cold, but the rest of your body is warm. Acclimation When you fly from your home in coastal Hawaii straight to a winter trek in central Alaska – watch out! Attitude If you are convinced that you’ll sleep cold, you will. Tossing and Turning Some people rotate and rearrange their bodies throughout the night, pushing out a lot of warm air and pulling in too much cold air. Health Issues and Medications If you’re sick, or have chronic health issues, or take traditional or non-traditional medicines, your body can run much colder or warmer than usual. Personal Thermostat Some people just run hotter or colder than others. Gear Issues Your gear and its condition can assist or obstruct a comfortable night’s sleep. Some people cuddle with hot water bottles for added warmth. Others keep cold water bottles, electronics, gas canisters, and other stuff in their sleeping bag to prevent freezing. Those items are also heat sinks with only one source of warmth – you! Your sleep system may have been a faithful companion on many adventures over the last 20 years. But now the insulation has broken down, the foam in your sleeping pad is noticeably thinner, and your long johns have holes with names. Or maybe you’ve borrowed a bag that’s too big or too small. Don’t be surprised if you wake up colder than expected. Many sleeping bag makers assign the lower Limit temperature to “men’s” and “unisex” bags, and the higher Comfort temperature to “women’s” bags.” If you buy a bag based on the headline number, you could be in for an unpleasant surprise. Pushing Test Limits for Better Ratings Sleeping bag testers could push certain parameters to the boundaries allowed in the standard to get better temperature ratings. I’ve seen no evidence that this is happening. Yet, pushing limits might be in the best short-term interest of well-funded sleeping bag and quilt makers with their own test equipment. ISO 23537 calls for a small range of sleeping pad insulation values. The standard also allows for slight variations in the manikin’s clothing insulation, electric heating power measurement, wooden board thickness, air speed in the test room, and other parameters. Pushed in the right direction, small changes like these can add up to measurable differences in ratings – and price. Conclusion ISO 23537 isn’t perfect, but all similar standards are flawed, since they substitute laboratory measurements for individual real-world experience. Still, widespread use of the standard was a big leap forward for consumers. Now we can compare sleeping bags between most manufacturers more reliably. However, we must keep in mind all the other variables that go into sleeping warm in the backcountry. And high-quality gear reviews will continue to play an important role in sleeping bag and quilt selection. Because as REI emphasized in one blog post: “A temperature rating is not a guarantee of warmth for any bag.”
Sleeping Bag Temperature Ratings
 content media
0
0
107

Keith

More actions
bottom of page