Bag temp ratings

[maddawgg]

Newb question! I was discussing hiking with a friend who has some expierience hiking and the subject of bags and temp ratings came up. I said I was looking at a 20 degree bag because of it's light weight he said that you always add 20 degrees to stated temps and the bag I was going to buy would only be good for nights around 40 degrees. Does he know what he is talking about?

Thanks
Maddawgg

[Pacific Tortuga]

Always, is not a good rule of thumb for anything.
My F.F's is right on for me, a warm sleeper.
There will be many good answers here. Bag quality plays the biggest part IMO as well as the quality of the shell.
Your doing your homework on them and that, well, is always best.

[Toolshed]

Maybe if it was a synth bag that was overstock from 3 years ago and still pack tight from the day it was made, or perhaps it is a very low end bag, but I have never really had a problem with a bag not living up to its ratings, except for one time - but it was my fault - Winter with my Clip Flash in high winds that kept moving through the tent.
But your friend's rule would not be a rule of thumb that I would ever use on any gear I gravitate towards.

[Tinker]

If it's a non name brand synthetic filled bag, your friend is probably pretty close to being on the money, however how warm a bag is may have as much to do with how warm you are at any given time. If you're dehydrated, tired, and hungry, a )-50 degree bag may not be warm in 30 degree temps.
Give us a list of bags you're considering and you may find folks here who have used that very item. This may save you a lot of time.

[bigcranky]

That might be a good rule in WalMart or Dick's Sporting Goods. Maybe. But it's not a good rule for high-end down bags.

[Franco]

The rule of thumb with sleeping bags is about the same as with most gear :the cheaper the item, the more inflated the figures are.
So what your friend tells you may be true for particularly the cheaper synthetic types but does not apply to the better brands and in particular to top of the line down bags.
As an example you will find that most will comment that Slumberjack's are overrated (in temps...) but Western Mountaineering are somewhat conservative with their ratings.
Franco

[Cool AT Breeze]

I know of 3 companies that rate their bags true. Western Mountaineering, Featherd Freinds and Montbell. Most other manufacturers are off by 10 20 deg. You wont be dead but you will be pissed off.

[Spirit Walker]

A lot depends on the brand, whether you actually make your mummy bag into a mummy (my husband gets claustrophobic if his bag is snug around his face), what kind of sleeping pad you are using, and your personal metabolism. The US does not have good standards for sleeping bag ratings. There is a lot of difference between the brands. Most assume that you will use the bag inside a tent, with a pad, and totally snugged down. If you are cowboy camping, not using a good full length pad, and sleeping with your head exposed - the ratings even of the good brands will not apply. If you naturally sleep warm or cold - the ratings may be off as well.

[JustaTouron]

It varies on a lot of factors......

* what you are wearing
* the type of pad you have under you (if any)
* quality of tent
* wind
* and the biggy how warm you sleep.

At home in bed in the winter my wife has on significant clothes I have on just boxers. We share the same blanket. Yet I am often too warm while she is often too cold.

I am pretty sure a bag I would find comfortable in 20 degree weather, she would find inadequate in 40 degrees.

The cheaper brands use members of the polarbear club for testing.

[BrianLe]

I'm sure that someone will get around to mentioning the ~new European standardized sleeping bag rating system (EN13537), so I may as well do it ...
Not clear how much this will impact us here in the long term, as there are some questions about how consistent that system is.

Still, I like the overall idea, and hope that ultimately this results in more consistent ratings across manufacturers. For now the three that Cool AT Breeze lists as having good ratings sounds good to me; there are no doubt others, perhaps nunatakusa.com
or JRB for example (actually, I'm not sure JRB even offers a temp rating, but instead just a measure of loft ...).

[johnnybgood]

Not the case at all- all bags are not equal. There are high end bags from the likes of WM , Montbell and Marmot that are spot on for their advertised rating.

Also I might say - No two people are exactly alike in the same environment -i.e. I may sleep warmer than you in a bag rated 15* higher and with less loft because I'm a warm natured person and that will always be the case . I am miserable during the summer months here.

Anyway,I bought a cheap snyth bag from a dime store retailer with a impresive 0* rating which is freaking like "liar liar pants on fire " NOT true and is only tolerable to about 40* .
And this coming from someone that is a warm sleeper. It'll work fine for me but probably not for 50% of those who are cold sleepers or just typically normal.

Botton line- Buy a quality bag and the rating will hold true .

[buz]

Jonny's last line is the right approach, spend good money, get nice down bag, you will have it for 20+ years easily if you take care of it.

[DrRichardCranium]

My bag had two ratings, one for a man and one for a woman. Men tend to sleep "warmer" than women, ie, men can tolerate colder temperatures & still be comfortable.

On the other side of the spectrum, I have also noticed that women can tolerate warmer temperatures than men can, & still be comfortable while the man is sweating & miserable.

[Gray Blazer]

At home in bed in the winter my wife has on significant clothes I have on just boxers.

I hate it when that happens.

I was talking with some gearheads this weekend and it appears that some of the inexpensive bags are rated to a temp you can survive at (as opposed to being warm).

[Doooglas]

The problem with sleeping bag ratings, IMNSHO, is they don't take in account relative humidity.
I can take you up into the cloud forest and have you shaking uncontrollably at 50 degrees.

[Cuffs]

This very thing was just recently discussed (if anyone would search for it...)
http://www.whiteblaze.net/forum/showthread.php?t=57323

News flash! As of right now, any maufacturer can slap on a stamp with any degree rating they want. there is no standard for testing these ratings (in the US). (that's why some of us may have been freezing our tails off in so-called 20* bags in 40* weather!)

The European nations DO have standardized testing and bags must meet them to be labeled with specific degree rating info. This testing is called EN13537.

Recently, many large retailers took a position and stated to the manufacturers that if they want their bag sold in their stores, they will have to meet this EN13537 testing standard.

That being said, new bags being sold in the US are clearly tagged with this info. You will see many of the old standard bags that we all know by brand and model either get revamped to meet this standard or disappear altogether.

Marmot and a couple other major makers are already meeting this and their bags are clearly marked.

If you can wait a bit, wait til all the new bags hit the market over the next 6 months or so...
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