View Full Version : Sleeping Bag Temperature rating
Doughnut
05-30-2008, 09:03
I could research this myself but it seems so mauch easier to ask the wise people on WB.
How does a company establish the "temperature rating" for a sleeping bag, and what exactly does it mean? Does it mean I should sleep comfortably or that I will not (or should not) get hypothermic? Ans since some people sleep hot and some people sleep cold, what is used to establish the "norm"?
I have a zero degree, a 20 degree, and a 30 degree bag, each is heavier as the rating decreases (duh..).
I slept in the 30 degree bag when the temp dropped to 40 and I froze my hiney off (that's why I have no hiney anymore).
Thanks for shedding light on this,
Dough Nut
Back a few months I read of European standards being developed. Any news of this? (Hope the piggyback is ok.)
There are no standards for temperature rating.
Some companies, like Western Mountaineering, have pretty accurate ratings. Others, as you found, appear to use temperature ratings as something with which to attract customers.
The main cost of bags is construction and fill material.
People talk about loft, and it is important, but the way the baffles are sewn and the edge rolls are equally important.
Two ways to do it:
1. Buy an expensive bag (WM, FF, etc) and get a fair rating.
2. Buy a cheap bag but get one rated 15-20* colder than you actually need.
3. (Yeah, I know.) Buy a bag locally during cold weather, and sleep in it in your back yard. If it ain't up to snuff, return it.
Doughnut
05-30-2008, 20:24
[quote=Frosty;633252]There are no standards for temperature rating.
Some companies, like Western Mountaineering, have pretty accurate ratings. Others, as you found, appear to use temperature ratings as something with which to attract customers.
The main cost of bags is construction and fill material.
That's what I was thinking, however, it seem sto me if some dummy bought a zero degree bag and went camping in 5 - 10 degrees, and got frostbite or hypothermic, they'd have a huge settlement against some company.
I have a 30 degree bag and one night it was probably 37 or so, and I froze!
I have a new to me campmor 20 degree down bag that I have fallen I love with (don't tell my wife), It's more than I need but plenty of loft and comfortable.
Mrs Baggins
05-30-2008, 20:58
I was told once to think of the degree rating as the survival rating - not the comfort rating. If you're bag is rated at 30 you'll survive at that temp but you will probably be cold all night. I have a 20 degree down bag and get very cold at temps below the upper 30's. I bought a -5 degree down bag for temps below 40 and am quite cozy in it in the 30's. But I'm certain that if I was out in temps in the 20's or lower I'd be cold - I'd live but I'd be miserable all night.
Back a few months I read of European standards being developed. Any news of this? (Hope the piggyback is ok.)
Seriously. Industry standards. European manufacturers. Hoped it would spread this way. Some science types would have fun devising "thermal retention" formulas.
Western Mountaineering's website discusses ratings some, and explains bag construction and how they test fill power & such. Fashionatin'!
Wise Old Owl
05-30-2008, 21:46
3. (Yeah, I know.) Buy a bag locally during cold weather, and sleep in it in your back yard. If it ain't up to snuff, return it....??????
And your trail Name is Frosty....Hmmm Coincidence? Good Advice Frosty!:-?
I read somewhere that this stuff is different, that poly sleepbags with dupont Halofill are overrated and Down bags (in the past) should be dead on, perhaps that was then. Now when I walk into the stores, I think China sews all sorts of lies into the bag tag. And if they are making them why are we still spending $350 per bag?
I've read that a simple way to measure temperature rating is to measure the loft of the bag. How many inches thick is the thinnest part of the bag when you're in it?
If the bag is 6" thick in spots, but 1/32nd of an inch where the baffles are sewn, you're going to lose a lot of warmth through those thin spots. Similarly, if the bag is too short or too tight for you, you'll effectively make it thinner, and it will not be as warm as the rating.
There are also all the bells and whistles--the hood, the draft collar, and the insulation over the zipper. A big, thick bag that doesn't have those will leak away all your warmth when the temperature drops.
Another really, really important thing is to make sure you don't get chilled before you get in the bag. Sleeping bags don't generate heat--you generate the heat. If you start off cold, you'll never warm up, no matter how nice a bag you're in. But that's another subject...
Doughnut
05-31-2008, 08:30
Just found this, it says the same thing, (best guess) Impossible to account for body size, density and sleeping habits.
http://www.adventuresportsonline.com/sleepingtemp.htm
thanks to all,
DoughNut
modiyooch
05-31-2008, 12:52
I have a 40 degree down bag and was in NY last week. The temps must have been in the 30's. I was cold, but more on the uncomfortable side than the threatening side. I had the option of throwing on more clothing. I'm going to invest in a 20 degree bag for the rest of my journey north.
Appalachian Tater
05-31-2008, 13:00
Temperature ratings are most useful when used to compare within a manufacturer's line, slightly less useful when comparing between a manufacturer's lines, even less useful when comparing bags of similar quality by different manufacturers, and of even less use when comparing bags of different quality by different manufacturers.
Comfort and even survival would depend on many other factors including your size, weight, health, personal comfort range, hydration and nutrition, wind chill, humidity, etc. Only if you think of the temperature rating as a comparison tool and not an absolute it is truly useful.
Looking at fill-power and fill weight is a good measure if it is one of the top manufacturers using quality down. Even the amount of "fluff" a bag has is a useful measure. Is the bag sewn-through or baffled? Does it have a well-insulated hood that fits well? There are many useful factors to take into consideration.
saimyoji
05-31-2008, 14:08
http://www.whiteblaze.net/forum/showpost.php?p=448347&postcount=15
shelterbuilder
05-31-2008, 23:44
I know that this isn't the answer that you're looking for, but in the end, the only temperature rating that matters is the one that YOU give the bag. If you buy a bag that's "rated" for 10* and you go out in 10* weather and are comfortable, then the bag is rated for 10*. Some people sleep warm, others sleep cold, so what's a 10* bag for you may not be a 10* bag for your buddy. I tend to sleep cold, so I use this formula: if I think that I migh EVER use the bag in 10* weather, I'll buy a bag that's rated for 0* or even -10*. That way, I know that I'll be warm. If I can't get a good night's sleep because I'm cold, then it's going to be a miserable trip.
Tater's correct: within a company's lines, the ratings will probably be fairly close because they are probably using the same methods to rate their bags. At least we hope so. But between companies, the ratings are meaningless. Always go for quality construction and materials, and don't worry too much about what the ratings say.
Mrs Baggins
06-01-2008, 05:27
I know that this isn't the answer that you're looking for, but in the end, the only temperature rating that matters is the one that YOU give the bag. If you buy a bag that's "rated" for 10* and you go out in 10* weather and are comfortable, then the bag is rated for 10*. Some people sleep warm, others sleep cold, so what's a 10* bag for you may not be a 10* bag for your buddy. I tend to sleep cold, so I use this formula: if I think that I migh EVER use the bag in 10* weather, I'll buy a bag that's rated for 0* or even -10*. That way, I know that I'll be warm. If I can't get a good night's sleep because I'm cold, then it's going to be a miserable trip.
Tater's correct: within a company's lines, the ratings will probably be fairly close because they are probably using the same methods to rate their bags. At least we hope so. But between companies, the ratings are meaningless. Always go for quality construction and materials, and don't worry too much about what the ratings say.
You're right. My husband always sleeps warm and will have his arms out of the bag (same 20 degree bag I have) on a night when I'm fully zipped and as snugged inside the bag as I can get - and I'm still cold. He usually gets down to just a t shirt and underwear while I'm wearing nylon long pants and a long sleeved poly shirt. On a night that was in the upper 20's I was shivering so hard we finally had to leave the shelter with a trail angel that happened to come along to see if anyone needed anything. Now I have a -5 bag for nights like that.