Sleeping Bag Ratings?

What has been your experience for sleeping bag temp actual rating vs. its advertised rating? Any brands way off the mark?

I've found Western Mountaineering bags are conservativly rated.

onestep said:

I've found Western Mountaineering bags are conservativly rated.

Click to expand...

Onestep what's behind you on the avatar?

I don't know how they come up with the ratings.
I have a winter tent, 2 pads, capilene long johns, fleece, balaclava and a light bivy sack in addition to the bag when it's cold.
Do the ratings assume you're in a snowbank in your birthday suit or acting a little more rationally ?

Having said that; my Downright Voyager is rated 0. I'd rate it to 25 or 30.
My Valandre Nuptse is rated to minus 45 and I have no intention of testing that rating.

Chip said:

I don't know how they come up with the ratings.
I have a winter tent, 2 pads, capilene long johns, fleece, balaclava and a light bivy sack in addition to the bag when it's cold.
Do the ratings assume you're in a snowbank in your birthday suit or acting a little more rationally ?

Having said that; my Downright Voyager is rated 0. I'd rate it to 25 or 30.
My Valandre Nuptse is rated to minus 45 and I have no intention of testing that rating.

Click to expand...

I have a 0 deg Bean down. The coldest temp I used it was 10-14F. Very toasty.

VFTTop'r said:

Onestep what's behind you on the avatar?

Click to expand...

The pic was taken on top of West Bond. Thats Bondcliff behind me.

rating are all over the place - good question

I have 2 bags - right - a minus 40 north face darkstar that I have been chily in in minus 5. I have an old 0 rated LL bean bag about 7 years old that almost works better than the north face one. go figure.

I am in the market for a 15 degree rated bag myself. the llbean is decent - but want something a bit lighter.

One way is to check the loft.

Lay the bag out on a flat surface and let it loft fully. Then measure--top loft is half the total loft. (Note: many bags for cold weather have differential loft: ie more on top than on the bottom, so you may have to measure the top and bottom separately.)

Air Temp......insulation (top loft)
40F...........1.5in
20F...........2.0in
0F..............2.5in
-20F...........3.0in
-40F...........3.5in
-60F...........4.0in

Based upon US Army Quartermaster Research Data quoted in an early 70s EMS catalog.

Of course heat is also lost through warm air leakage and through the insulating pad below you. And of course individual's sleeping metabolisms vary. Women supposedly sleep 5-10F colder than men, on the average.

Features like draft tubes and collars (hopefully ) make a difference.

So treat the above numbers as a minimum.

Lofts I have measured on some mummy bags:
20F........... 5in (3in/2in)
0F............. 6in (4in/2in)
-20F.......... 8in (5in/3in)
-40F........... 10in (6in/4in)
-40F............ 12in

Doug

I usually ignore the printed numbers. (Mountain Hardwear seems conservative in its ratings, North Face looks about right to me through most of their range.) As Justice Powell might have said, I know a 0 degree bag when I see it.

First I find out where and when the bag will be used. Then I look at the type of insulation, the loft, the fit around the individual user, and the ways in which the bag's construction impedes or allows air flow. Finally, I ask the crucial question: Do you sleep warmly or cold? Then I walk over and point to the bag(s) that fit(s) the bill of particulars. So far, nobody has come back to complain, and no heirs have started any postmortem actions.

I think this is one of those things that people have to test personally over several seasons and in different conditions to know more precisely what's best for them individually. It ain't cheap to own several bags, so I'd recommend that folks try to rent and/or borrow when possible while picking.