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View Full Version : What the degree rating of a bag really means...



SGTdirtman
03-05-2006, 01:16
Kind of a dumb question but is there any real science behind the temp ratings they put on sleeping bags? I've slept in bags -20 degree bags that are colder than some 0 degree bags... How do you actually tell if the temp rating on a sleeping bag is correct for the climate you intend to use it in? :confused:

jaywalke
03-05-2006, 01:44
The only good gauge is the depth of loft, fill type and the relative reputation of the company, because there is no standard. Temp ratings on sleeping bags are as silly as temp ratings on clothing (which LLBean used to give, just to drive those of us who worked in gear shops mad) because of vast differences in physiology, fat, age, activity, etc. One man's 5 degree bag is another's -10, and so on, and so forth. Stacked on top of the personal factors are the environment, like how much you had to eat that day and the relative humidity.

All you can really do is collect a lot of opinions. In my opinion, Western Mounatineering bags are rated conservatively, meaning you will be warm at the rated temp and lower. Kelty, on the other hand, seems to be wildly optimistic about their ratings, and only the warmest sleepers will reach their low ratings in comfort. REI and EMS house brands are okay, but still a little optimistic. Sierra Designs and Mountain Hardware are fairly trustworthy (FOR ME), while North Face bags run a crazy spectrum depending upon which sub-contractor they are using this month.

verber
03-05-2006, 01:47
There are some standards for testing sleeping bags, but in the USA there is no requirement to use one of the standard protocols when listing a bag temp, ratings. As a result many manufacturers rate their bags for "survival" (e.g. you won't be comfortable, but you won't freeze to death). A few manufacturers like Western Mountaineering tend to be conservative (e.g. all but the coolest sleepers will be comfortable if not warm at the rated temp).

In Europe there is a much more rigerous temp rating system. To read a good description of the european system (as well as other standards used for rating bags) check out:

http://www.mammut.ch/mammut/uploadedFiles/Sleep%20Well_Pt1_e.pdf

saimyoji
03-05-2006, 11:22
Wow, that article is certainly informative. Copperman rules. It makes you wonder what other research the army has done that remains secret.

Thanks for the link.

Just Jeff
03-05-2006, 11:30
You mean like the internet? Shh...don't tell anyone.

Well, it was the military and Al Gore, I guess...

saimyoji
03-05-2006, 11:38
Nah, we all know Algore invented the net, thats not secret. I'm thinking of more mundane things, like inkless pens, solar powered radios that work in the dark, dehydrated water.....

vipahman
03-05-2006, 12:47
For a good degree rating, look for the higher numbers on these 3 points:-
1. Fill power - The amount of cubic inches that 1 oz of down will occupy. 600 fill is less fluffy than 800 fill resulting in more fill being used and that adds to the weight of the bag.
2. Fill weight - The weight of the down used. 15 oz will be warmer than 25 oz meaning that more weight will generally translate to a lower temp bag.
3. Loft - The uncompressed range of the down in the bag. Down does not warm you unless it is allowed to loft/fluff. Good 0 degree bags have about 7" of loft.

And once again, it's not just these 3 factors. It's how they all come together in a bag with the right size for you, good baffles, draft collar, neck drawcord, good stitching, etc. Marmot and Western Mountaineering are among the best brands.

betic4lyf
03-05-2006, 14:40
gore didn't invent the internet, but he did have a large hand in devoloping legislation to govern it and make it applicable for regular people to use.that is what he said, in context, that he had a large part in its devolopment

awol
03-05-2006, 14:59
I stealthed around last week in the ga mtns along the AT. Two nites where I was at it hit 23, one nite it was 18. My Marmot Sawtooth 15 wasn,t as warm as I would of liked and I have the sniffles now, but am here typing now and suffered no signs og hypothermia on the trail so I reckon it worked. Saw lots of NOBOS, drove one out from Three Forks.

neo
03-05-2006, 15:04
Kind of a dumb question but is there any real science behind the temp ratings they put on sleeping bags? I've slept in bags -20 degree bags that are colder than some 0 degree bags... How do you actually tell if the temp rating on a sleeping bag is correct for the climate you intend to use it in? :confused:

regardless degree rating is different for different people with same bag or quilt for us hammockers,i am one that sleep well below the rating of a bag,
last sunday night i stayed warm at 18 degrees in a 30 degree ed speer lite loft sleep quilt,most people would have been very cold in same situation.:cool: neo

irritable_badger
03-05-2006, 15:34
Standards make things very expensive. As a rule they are only financially viable in fairly horizontal industries where the standardized "widget" is a component in a larger system. The outdoor equipment industry is pretty much direct to consumer, there are no intermediary parties involved in manufacturing the products so there is no business need for standardization.

While I understand why there are no standards the lack of them sucks. The market is large enough to benefit from standardization, someone just has to develop the standards and the compliance tests and get buy in from the big manufacturers like TNF, Marmot, etc... If the big players in the industry don't support the standard it will not last. The politics of standardization make it highly unlikely that the US will ever see standardized bag ratings. No one wants to put up the money for developing/marketing the standard and the big manufacturers don't want to retool their manufacturing processes.

SGTdirtman
03-05-2006, 16:01
So what I gather is... I have to take every bag out and try it to see if its actually warm

irritable_badger
03-05-2006, 16:13
So what I gather is... I have to take every bag out and try it to see if its actually warm

That's the conclusion I came to. I just picked one that I knew would be too warm (0* bag) and I unzip it to regulate the temperature. Sure it weighs a bit more than a 20* bag and takes up a bit more room but I'm warm.

Seeker
03-05-2006, 16:28
So what I gather is... I have to take every bag out and try it to see if its actually warm

or buy something from WM, and trust it...