Range of comfort in WM bags

This is maybe a stupid question, but your input will strongly influence my purchasing...

I'm looking for a midwest shoulder season and 3 season alpine bag. I'm all set for 40 deg F and above. I want to be comfortable in baselayers from 40 to 20 degrees F. I'm fairly certain that I'll get at least a WM alpenlite bag, but I'm wondering if I should go for the versalite which is an ounce and 10 degrees warmer... but I don't want to sweat when it's 35 degrees.

I have no concerns about opening bags to vent, but I have had the experience of sleeping in a 0 degree bag during a windy 40 degree night and it was very hard to balance venting and staying warm.

Using WM bags as a standard, what would be the "comfortable" range for a twenty degree bag? How about the ten degree bag? I'm thinking that a 20 degree bag would be not quite comfy at 20 degrees but quite fine at 40. Whereas the 10 degree bag would be comfy at 20 and just a little warm at 40, but easy to slightly vent and be comfortable. Is that about right?

I'm an average sleeper. If a loft is rated to a lower limit of X degrees, I usually find that I'm catching some sleep at X degrees and comfortable at X+10 degrees.

A long post, but any thoughts?

Believe it or not, Western Mountaineering bags do have EN13537 ratings, but WM doesn't publicize them. Their bags are sold in Europe, where the ratings are required, but it may be that the European wholesalers, rather than WM, have the testing done.

Several years ago, I looked up my bag, the WM Ultralite, on a UK website. Unfortunately I didn't bookmark the site so I can't document this without searching all over again. The comfort rating (for female cold sleepers like me) is 24*F. (I used a conversion table since of course the UK site used degrees Celcius.) The lower limit (for male warm sleepers) is 17*F. I suspect that's pretty accurate, since I've found I have to add insulating clothing at around 24*F . With all my insulating clothing on, a vapor barrier suit underneath (but over my base layer) and a warm enough sleeping pad, I've been cozy at 15*F. As mentioned, I'm female and a very cold sleeper.

For the conditions you describe, the Versalite would be overkill. You always have the option of adding insulating clothing layers if it gets colder. That's your safety margin!

Do remember that the EN13537 testing conditions have the dummy wearing a base layer and a knit cap. For testing 20*F bags the sleeping pad has an R rating of 5.

Thanks for the reply! I've done some searching on EN13537 found those european sites. I also came across this thread, which speaks to the same points I asked about:

http://www.backpacking.net/forum/ubbthreads.php?ubb=showflat&Number=172301

My biggest unknown to me is still the alpine side of things. I agree a true 20 degree bag that has room for layers (like the alpinlite) will work fine for midwest shoulder seasons into the mid teens. I have no experience for what temperature to expect in spring/fall alpine situations. I've found people talking about using everything from 30 degree to 0 degree bags.

...adding on:

What temperatures do you find your ultralite simply too warm? I.e., About what temps do you start venting it ? What temp would you unzip it and use it as a quilt? What temps would you say, "ugh, I wish I brought a different bag!"?

You seem to have a good grasp on what you are comfortable with. For what it is worth here is my perspective. I was fairly sure i could get by with one bag for winter, spring and fall. I used weight as a criteria. I felt a good quality bag with 800 or 850 fill down that was less than 2.2 pounds (kilo) would be sufficient. I purchased the NF Hightailit 3S with a comfort rating at 27F. It weighs exactly 32 ounces, has tons of loft and has worked well. I was comfortably warm at 30F with just a t-shirt and underpants. I'm sure it will be perfectly fine at 27F with long johns and a base layer top. That said, I consider the manufacturer's temp ratings as only one of many factors when purchasing a new sleeping bag.

That's true; girth is important, too, so you can layer up inside the bag without compressing your insulation when the temps drop lower than expected.

It also depends on where and when. I don't backpack past the first week in October (the nights get too long for me at my latitude) and at least through September, even at high altitudes 15*F is the worst I've encountered. Then this year my eldest son in SW Ohio reported 0*F temps in November. It got pretty cold out here then, too, with wind chills in the single digits at my house!

I have a Kelty 20º 800 fill down bag that has a comfort rating of 32º. For me, those EN13537 ratings on that bag are very accurate and it's the first bag I've had I can say that about, so I'll blabber on a bit about it...

I've spent a lot of 30º-40º nights in it and have been very comfortable in just long johns and a light shirt. I've spent quite a few 20º nights in it too, and for those I got chilly until I layered up.

The coldest nights I've spent were below 20º and I put my down jacket over the bag. That kept me comfortable to probably down near 15º. I've also used one of those emergency blankets over it on cold nights and they work very good to add a few degrees of warmth too. I did get a thin layer of frost on my bag doing once that, but it never got wet and I just brushed it off in the morning when I found it. With that and my jacket and layered up with everything I brought I was probably good to near 0º. I know I was warm while everyone else with me wasn't, but they didn't have down bags or jackets or SOL blankets.

I've also spent a few 50º or so nights in it, and mine isn't easy to vent so I didn't stay so comfortable on those warm nights. My bag has a 3/4 length single zipper and I was sweating a bit, or chilled. I really didn't like sweating in my down bag so that alone kept me up at night wondering if I was going to stink it up forever. So far I haven't, but I lost sleep over it.

I don't see how the ratings on a WM bag should be any different. The weight, materials, design and craftsmanship may be, but not the warmth you'll get out of it.

In my experience an EN13537 20º rated bag works perfect for the temps you're wanting it for. If venting it is something you'll be wanting as a feature I'd look into designs that offer that and if WM has that, great, if not, I might look around some more before clicking the buy button.

In my case, I was looking for value and comfort at 20º-40º, and the Kelty I got was a very good one when I got it. I really shouldn't expect it to be comfortable at +45º, or even +40º considering the design, and I was thrilled at being able to make it work at below 20º. The biggest downside is it's a bit tight, and I'm not a big guy. I'm about 5'9 and 140 with a full belly.

I have to think WM bags in the same range would be impressively better.

Just to add, I have a WM bag that weighs one pound and is rated, I believe, at 40F (maybe 35). One day in Maine I forgot to bring in my water bottle. I was wearing everything in my pack, but I was toasty warm when I woke up and found there was ice in my water bottle. Didn't have the thermometer that day, but it takes more than just 32F to freeze a water bottle, so I'd say it had to be at least 30F. best, jcp,

Regardless of numerical ratings, staying warm in a sleeping bag has a lot to do with things other than the sleeping bag brand and model. First, the bag has to fit you, too large and you get drafts, too small and you squish the loft. You have to be willing to use the hood system to stay warm at the lowest rated temperature. If the hood and draft collar are poorly designed or do not fit your body type, then you do not get maximum warmth. Women and men are shaped differently - large shoulders vs small shoulders make a difference on how the hood fits. And as others have said, for warm nights, a full zipper vs half or 3/4 zipper makes a difference.

Non-sleeping bag issues -- being hydrated, a good lasting high fat/protein meal before bed, getting into the sleeping bag when you are warm vs chilled, quality of sleeping pad, other clothing, humidity inside the tent, wind if sleeping under a tarp only, on and on!!

I would rather error a bit on the "too warm" side. I have never liked regarding my extra clothing as part of my sleeping system. Usually cases where I am dangerously cold, are cases where I have had to resort to using my insulating clothing to stay warm during backpacking (getting caught in a storm on a pass, for example) in really poor conditions, where sometimes they have gotten wet as a result. My sleeping bag is always my "last resort" - kept dry. In fact, in severe storms when I worry about tent failure, I pack up my sleeping bag in a waterproof bag and put on all clothes and sit inside the tent on my sleeping pad, waiting out the storm. Also, ounce-for-ounce, a slightly colder rated sleeping bag is a more efficient way to add warmth than added clothing.

I have always had a 0-5 degree bag, weighing just under 3 pounds total. I am much more minimal on clothing. I now use a WM Super Antelope (very old bag, 750 down). When it is hot, I simply throw it over me as a blanket. If I could afford many bags I certainly would buy a 30-degree bag. But for a "do-it-all" bag, I would not consider anything rated less than 10-degres. (I do mainly high altitude, Sierra and Wind Rivers).

This has been a really helpful conversation. Thanks WD for adding in the high alpine experience!

Leaning versalite... but not quite sold yet Very very close though.

This is a very interesting graph from the Mammut catalog. I darkened the EN lines to make it more readable. Of particular interest to me is the maximum comfort lines, which I think are an overestimate, but seems to suggest that a 10dF/-12dC bag isn't horrable at 40dF/7dC.



Here's the publication:

http://www.mammut.ch/images/Mammut_Sleep_well_pt1_E.pdf

Oooh la la! Got a Versalite in the mail yesterday. A great fit for my 6 foot, 195 pound body. Can't wait to test it out in the backyard.

Thanks again everyone!