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Old 06-18-2009, 11:40 PM   #1
John T OP
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Sleeping bag testing - how?

I have read many posts on sleeping bags and have yet to get an understanding of how they are rated.

Years ago, I slept in a bag rated for 30-degrees. In 20-degree weather, I felt like I was over heating. A few months later, I tried a friend’s sleeping bag, also rated for 30-degrees. This time I froze my butt off at 25 degrees.

How does a company rate their bags? Do they just stick Joe Smo in a bag and toss him in a freezer? Is Joe Smo a skinny twig with not body fat? Maybe, Joe Smo is the size of a bear, all muscle, no body fat. Or, just maybe, Joe Smo carries around a lot of extra insulation.

How long was Joe Smo stuck in the freezer? An hour or two, or longer?

Did a computer or geek with a calculator perform a algebraic equation to come up with the number?

What happens if Joe Smo, the computer, or the geek comes of with a golden number to be comfortable of 25-degrees? Do they round the rating to 20 or 30-degrees?

I am in the market for a new sleeping bag, but want to make sure I am not buying a toaster over to melt away my extra insulation.
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Old 06-19-2009, 01:03 AM   #2
Cam
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To my knowledge there is no standard and each company is different in how they measure. Ultimately there is no easy way to judge how one bag will work for person A versus person B since bag fit is a key criteria. The larger the space around a person the longer it takes to heat and the more the body has to work to keep it heated. I am a big fan of "hugger" style bags for that reason. They allow the bag to stretch but they keep it close to your body as they have stretch panels built in. They don't need nearly the same insulation level and they perform fairly uniform from one person to the next.
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Old 06-19-2009, 10:23 AM   #3
T O Double D
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Yeah, there's no regulation on bag ratings, therefore they very wildly. I would buy one from REI that way you can return the bag if you find you don't like it.
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Old 06-19-2009, 10:45 AM   #4
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Thoughts...

1) Buy from a source with a good return policy in case you make a mistake you can't deal with - REI has been mentioned and check out Sierra Trading Post for another

2) 2-way zipper lets you dump some heat from the foot area if you overheat or just unzip from the top a bit to dump some heat.

3) Your own internal temp gauge plays a part. Figure out if you are a warmer or colder person in general. This might be good for about 5-10 degrees of swing.

4) Can always boil up some water and pour it into a Nalgene. That Nalgene bottle then goes into your bag (foot area for most) to offer some additional heat for awhile.

5) A pad underneath helps add a few degrees as well (I assume you will be using one anyway).

In my experience (outdoor retail, gear testing, overall getting out there), the larger brands do a decent job of staying close to rating #s for the majority of folks.

Remember too that with use, performance does go down (as in how warm the bag continues to keep you). But it does take awhile to go down. Always store the bag in a LARGE mesh bag or lay it out under a bed (assuming you have no pets ) - this helps maintain warmth factor longer as well.

I wouldn't over think this purchase too much. Odds are you will purchase a good bag & will figure out ways to adapt when pushing it's use.
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Old 06-19-2009, 10:49 AM   #5
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Ask that question to these guys. There hasn't been a single issue that I didn't get something worth while out of it.

The last issue covered getting a 'GOOD' nights sleep while camping. Sleeping style at home and body weight play a role in bag and pad selection.

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Old 06-19-2009, 11:02 AM   #6
Wuwei
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In my opinion, and lots of sleeping bag use, the typical bag, even labeled "summer weight," is way too hot for when most of us go camping, the summer! Even for upstate NY camping in the summer a cheapo bag rated to about 40 degrees is all you'll need. Keep a light fleece jacket, some wool socks, and maybe even a light fleece hat handy and you can go down below freezing in that summer bag. I usually have the opposite problem--how to stay cool enough while covered enough to keep any bugs off. Sleeping bag liners are good but another thing to carry. For summer use a light fleece blanket or fleece bag is actually pretty nice (fold the blanket so it goes underneath you too). It has the advantage that you can just throw it into any old washer and dryer and it offers pretty good warmth even if soaking wet--dries fast too! Of course, winter camping is another story--get the 20-below down bag!
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Old 06-19-2009, 03:45 PM   #7
OuttaHere
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I remember reading somewhere that the rating number is based on the use of a good sleeping pad as well, it insulates you from the cold ground.
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Old 06-19-2009, 03:57 PM   #8
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Quote:
Originally Posted by OuttaHere
I remember reading somewhere that the rating number is based on the use of a good sleeping pad as well, it insulates you from the cold ground.
Yep, and there are many other variables that can't be agreed upon let alone their implementation & usage in testing. This is why it can be kind of confusing.

Get close & folks will generally be fine
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Old 06-19-2009, 04:02 PM   #9
CBACH
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Quote:
Originally Posted by John T
Years ago, I slept in a bag rated for 30-degrees. In 20-degree weather, I felt like I was over heating. A few months later, I tried a friend’s sleeping bag, also rated for 30-degrees. This time I froze my butt off at 25 degrees.


Could be Menopause
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Old 06-19-2009, 04:26 PM   #10
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bag testing will change

Right now, temp testing is all 'wild west' in North America and manufacturers can claim whatever they want. In Europe, there IS a standard, the EN 13537 test (read about it here). Its a pretty well thought out test, standardizes many of the variables, and brings science to an area where it was lacking.

While a bag that is rated for 27 degrees may not mean 27 degrees everyone, at least you can compare bags to each other.

How does this affect you? Well, some euro bag manufacturers that sell in the US already use (and usually market) these temp ratings. And REI, the industry's 800 lb gorilla, is moving to adopt these test standards as well and already includes some of them on their website. Hopefully, everyone else will come along...
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Old 06-19-2009, 04:31 PM   #11
jet123
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Now get to asking us what bag(s) we like! That's never been asked before

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Old 06-19-2009, 11:10 PM   #12
MMcnamara
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Marmot and REI bags are now tested using the EN rating system.
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Old 06-20-2009, 12:29 AM   #13
ak bike
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sleeping bags

I ended up with two bags , one 45 degree and one 40 degree bag , both zip open on the side and bottom. Trips out and back from alaska in the spring and fall end up with temps from frost to 75 degrees at night . Just use both open or one closed and one open or stuff one inside the other. if it gets too cold throw on the one set of long johns and knit cap. Ratings don't seem to be to benificial. Both bags are pretty small in their compression sacks . I don't sleep well in mummy bags so both are rectangular. Have a friend that says all you need is a Debit card and your sleeping problems are solved. Flawed thinking forces me into trying to beat the elements. :0)
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Old 06-20-2009, 04:04 PM   #14
HaChayalBoded
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I read somewhere thats its a pretty silly rating. It doesn't mean you will be comfortable at that temperature, it means something lik eyou will not die of hypothermia at those temps but may very well be miserable. But like all things, that variable changes depending on the person in the bag. I have a 40 degree bag thats too hot in 15-20 degree temps and a 20 degree bag that I get cold in in 50 degree temps.

The type and fill weight of the insulation is also a contributing factor, as is whether or not its been sitting stuffed in its stuff sack for the past 3 years or if its new. The same exact make and model can provide different levels of warmth and comfort depending on how its been stored.
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Old 06-20-2009, 08:08 PM   #15
iLander
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survival...

most bags are rated according to a "survival rating" which means that you won't die at the minimum stated temperature..."you" being an average person weight/body fat wise. Surviving and being comfortable are two different things altogether.

Use the temp rating as a baseline & go from there: do you sleep hot or cold regularly? What's the coldest you expect to encounter? Will you be sleeping in PJs, long underwear or ???? A sleeping pad (good one) will add 5-10 degrees (centigrade) to your warmth; covering your head or keeping it inside a mummy bag, ditto. If you generally are someone who sleeps cold, buy a bag at least 5 - 10 degrees warmer than you expect to encounter or you will be shivering all night!
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