What do temperature ratings for sleeping bags and pads actually mean?

[William S.]

This has sort of been addressed in some older posts, but I'm still in doubt about the various factors involved in calculating the temperature rating. I presume it applies to "the average person's average metabolism"; no problem there. But does it mean "fully comfortable" or "barely tolerable" if the temperature is the stated number? Stark nekkid, or wearing long-johns & fleece & wool socks & a beanie, or something in between? Is there anything resembling an actual industry standard, or is it whatever each company wants to label its products?

[Greg Mihalik]

"Is there anything resembling an actual industry standard, or is it whatever each company wants to label its products?"

In the USA there is no standard. In Europe things are rated against "European Norm" protocol. There protocols for many items. For sleeping bags it is "EN 13537". (Google is your friend.) Some in the US do test and post their EN ratings – Marmot is one.

What it really comes down to is testing the gear in the field, against your personal metabolism.

[And E]

EN tested ratings are a good place to start. They're done by independent labs. Comfort testing is the limit for women, lower limit is the rating for men (getting 6-8 hours of sleep) and extreme is the survival rating. Most bags go by the men's (lower limit) rating.

Now, these are standardized tests done with dummies wearing appropriate base layers (tights, shirt, beanie, socks) and a sleeping pad (r of 5, i believe) and the dummies have a series of sensors and tubes/plates to keep it at human body temp. I think, as the testing chamber temperature is brought down, they measure how long/what temp it takes before the warming system can no longer keep the dummies at normal body temps while in the sleeping bag.

This only provides a general starting point when considering bag temps for real world tests since people have different metabolisms, toss and turn, big meal or not, what kind of shelter you're using, etc. Usually, most people find the EN rating to be off a few degrees (a 20 will feel like a 25 or 30 bag, etc). However, I myself find them pretty accurate since I'm a warm bodied sleeper, so your mileage may vary.

Also, all the independent quilt/bag makers don't use EN testing (expensive), but their ratings tend to be conservative (meaning you can take a given rated bag into lower temps) according to many reviewers on this site.

[Greg F]

EN rating assumes a sufficient sleeping pad and a thin base layer. It then gives an extreme, Limit, and Comfort rating which is usually advertised as Comfort = Womens and Limit = Mens. No reputable compant refers to their extreme rankings.

Now all ths info allows you to do is compare bags it doesnt tell youhow warm of a bag you need for speciic conditions but does provide a good starting point.

[Jerry Adams]

And, if you determine that an EN rated bag at 40 F allows you to go down to 30 F, for example, then you could assume that any other bags rating will also be 10 degrees warmer than your reality.

Like Greg said, EN has four ratings:
upper limit that standard man will start sweating at
comfort rating that standard woman will sleep comfortable down to
lower limit that standard man will sleep confortab;e down to
extreme rating where standard woman will survive down to

If you sleep in just base layer then you could choose comfort or lower depending whether you're a man or woman, but people's metabolisms vary. If you sleep in your insulated garments you wear around camp, you could go 10 or 20 F colder.

Mammut has good document describing EN rating http://www.mammut.ch/images/Mammut_Sleep_well_pt1_E.pdf

[William S.]

Thanks for the good info. Unfortunately for me, I just bought a Big Agnes bag (haven't used it yet), and BA apparently doesn't subject its bags to the EN rating process.

My particular bag – the Lost Ranger +15F, bought as an REI close-out – is said by some on-line reviewers to be inaccurately rated.

[Mary D]

Here's a good article on EN13537 standards for sleeping bags:
http://sectionhiker.com/deciphering-en13537-sleeping-bag-temperature-ratings/

And R values for sleeping pads (no standard testing so we're at the mercy of the manufacturers' marketing departments):
http://sectionhiker.com/sleeping-pad-r-values/

The dummies in the EN13537 tests are dressed in base layer top and bottoms and wear a knit cap. I've read (but didn't bookmark the reference so now don't know where it was) that the tests for 20*F (-7*C) sleeping bags use a pad with an R rating of 5. I note that An-D has also stated that above.

As mentioned there are three ratings (other than the "too hot" (my term) rating, something I'ver never experienced as long as the bag has a full length zipper): the "Comfort" rating, for women/cold sleepers, the "Lower Limit" for men/warm sleepers and the "Extreme," meaning the temperature at which you may not be dead of hypothermia by morning. Watch the ratings carefully, because firms that don't sell their sleeping bags in the EU and therefore don't have to abide by the regulations are liable to confuse the different ratings. This is more of a problem with retailers than with manufacturers. Make sure you (and they) know which rating is being discussed. Look at the manufacturer's website, not the retailer's. It should show all three ratings with at least a graphical explanation.

I personally have found the "Comfort" rating (about 9-10*F higher than the "Lower Limit" rating) about right for me. (I'm female and older than most.) While Western Mountaineering doesn't publish their EN13537 ratings on their website, they do sell their bags in Europe and their EN ratings can be found on UK retailers' websites. For my Ultralite, I found that the "lower limit" rating is 17*F and the "Comfort" rating is 27* F (converted from Celsius and rounded to the nearest whole number–and no, I didn't write down the C number). I have to start adding insulating clothing when the temp drops to 26-27*F, which bears this out. With a sufficiently warm pad, I'm fine at 15*F with all my insulating clothing on. Your mileage, of course, may vary–we all differ in how much cold we can tolerate, as in many other areas.

The dummies are supposed to represent the "typical" man or "typical" woman, whatever that is! Some of the testing procedures have been a bit suspect (different ratings from different labs). However, it's the closest anyone has gotten to a standardized temperature rating system, as opposed to the fictional ratings provided by marketing departments.

Generally, the high end ($$$) bags from firms with an excellent reputation, such as Western Mountaineering and Feathered Friends, are quite accurately and usually conservatively rated. Do note, though, that for those that don't test their bags, their reported temps are probably closer to a "lower limit" rating than to the "comfort" rating.

[Stuart .]

The EN rating only covers traditional hooded sleeping bags, not quilts, hoodless bags or top bags that lack an insulation layer underneath (eg Big Agnes). It's also an extremely expensive certification process, that isn't economically viable for smaller companies with a broad model range (eg Western Mountaineering, Feathered Friends). The net result is a real hodge-podge of numbers that arguably make it harder, not easier, to make direct comparisons based on temperature ratings.

Last year I went into REI just after they introduced EN ratings. Some bags were comfort rated, others were limit rated, and others had the traditional subjective ratings. I was told that for 2013 REI would no longer carry bags that weren't EN certified. That's why, for example, Big Agnes, had to introduce new products with full insulation, and get them EN rated so that one of their biggest retail customers would continue to stock them.

WM's descriptions include a temperature rating, inches of loft, dimensions, and ounces of down fill. Over time I've come to trust that breadth of information more than an arbitrary or 'certified' temperature rating alone.

[Jerry Adams]

"It's also an extremely expensive certification process, that isn't economically viable for smaller companies with a broad model range (eg Western Mountaineering, Feathered Friends)."

Yeah!

It used to be that manufactures rated differently, so 5 oz Climashield bag would be rated differently by different manufacturers – just marketing hype.

EN rating for each model is overkill

They should just use an EN type measurement to determine that so many inches of down or oz of synthetic are good for a particular temperature, then all manufacturers use that same rule.

And it gets further complicated by difference between mummy bag, ractangular bag, quilt, etc. but you could factor that in also.

[Mary D]

As I mentioned, Western Mountaineering bags definitely are EN13537 tested; otherwise they couldn't be sold in the EU. WM just doesn't publish the info on their website. It may be that their European retailers or distributors have the testing done. I've found WM's EN ratings on several UK websites. It appears that the "lower limit" rating for the WM bags I've looked at is several degrees F colder than WM's own rating. Do remember, though, that for us women/cold sleepers who need the "comfort" rating, that will definitely be a higher temp than the manufacturer rating.

I suspect that pressure from both customers and large retailers like REI will lead to most US firms adopting the EN standards. The exception would be the really small firms that have high reputations and the manufacturers of cheap sleeping bags sold in discount stores only in the US.

More interesting, on REI's website I've found that most EN ratings, even "lower limit," are several degrees higher than the manufacturer's ratings.

[William S.]

Stuart D writes: "The EN rating only covers traditional hooded sleeping bags, not quilts, hoodless bags or top bags that lack an insulation layer underneath (eg Big Agnes)."

I wonder why that would be the case. Shouldn't the use of the same R-5 pad underneath be the equalizer for comparison purposes?

[Jerry Adams]

"Stuart D writes: "The EN rating only covers traditional hooded sleeping bags, not quilts, hoodless bags or top bags that lack an insulation layer underneath (eg Big Agnes)."

I wonder why that would be the case. Shouldn't the use of the same R-5 pad underneath be the equalizer for comparison purposes?"

I think EN is (arbitrarily?) defined as only for sleeping bags.

Doesn't mean you couldn't use the same instrumentation to measure top bag or quilt, but then it wouldn't (legally) be EN rating.

Maybe top bags and quilts are such a niche market, especially in Europe?

[Roger Caffin]

There's a PDF by Mammut which covers this. You should find it (on their web site) and read it.

Summary:
In Europe bag testing must be done to the EN standard, and the results are reliable.
In America the manufacturers usually habve the marketing department guess at a rating.
Testing to EN standard found some USA bags were up to 15 degrees out in their ratings.

Cheers

[Jerry Adams]

"There's a PDF by Mammut which covers this. You should find it (on their web site) and read it."

http://www.mammut.ch/images/Mammut_Sleep_well_pt1_E.pdf

[James holden]

unless its EN rated … theres a good chance that its marketing hype … even then dont look at the "ratings" which can still be hype … ask for the actual en-ratings …

read and understand the pdf above … and itll become clear

and WM en-rates their bags … for some reason they dont publicize it in the US, only in euroland

[Kate Magill]

In trying to determine temp ratings on US bags and quilts, I keep an eye on the amount of fill used. All other factors being equal (ie bag dimensions and fill power), a bag with 27 oz of a given insualtion should be warmer than a bag with 24 oz, even though their manufacturers may both claim that they're good down to 20 degrees. Shell fabric and design elements such as draft collars will have something of an impact too. Sme manufacturers, like WM, list expected loft/baffle height, which can help give you a relative sense as well.

However, I don't know any formula to determine how much warmth one ounce of down adds, or the difference in warmth between, say, an ounce of 800 fp down and and ounce of 900 fp down. I'm sure someone out there does, though.

[Anonymous]

A polyester lining vs a nylon "may" be a couple or few degrees warmer, if everything else is similar (including fiber size), since polyester is significantly more thermally efficient/less conductive than nylon. Course, the poly lining bag will be a bit heavier too, and that weight would be better offset and warmer by more fill (in the nylon bag).

[Dena Kelley]

I think the EN is a good starting point, but for me I still know that I'm going to need to get a bag with an EN temp rating at least 20 degrees colder than the lowest temperature I expect. I am a super cold sleeper, and have had to develop my sleeping strategy based on that. If you know you're a hot sleeper or a cold sleeper, then you should factor that in when making your bag purchase.

[Stephen M]

I sleep very cold also so always factor in I will need a bag/quilt that's 15f warmer.

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