Any guesses at how low a temp I could push the following to:

W.M. Summerlite
Eddie Bauer First Ascent Down sweater
MEC lightweight merino wool long underwear and matching long sleeve top
teko midweight wool socks
Eddie Bauer First Ascent wool toque

Note that I find the 0/32 degree rating of the Summerlite to be pretty accurate with just it a pair of boxers and a the MEC merino wool long sleeve top.

Thanks.

What's your pad? Last spring I took my Lafuma Pro Down 650 to 27 degrees sleeping on a Thermarest Trail Lite. When I awoke the next morning, the eggs I brought for breakfast were mostly slush on the inside. I was wearing a pair of this synthetic long johns, a Smartwool lightweight LS, merino sock and a cheapo skull cap.

I have heard that my bag doesn't live up to its 30 degree rating, but with a setup like the one you listed and a decent sleeping pad, I would feel confident taking it down to the low 20s. Maybe even the teens.

I don't know how much lower you can go adding layers but I think a pad should be part of the system. And a high R value pad when you are going below freezing. I have done a bit of research here about this and decided to get a better pad for my setup for times I expect colder weather. I also include adding layers of wool or a down jacket to my 30 degree Montbell bag.

+1 for a good pad. For cold weather sleeping, your pad makes a HUGE difference. You can have all the layers you want on top, but if your pad has inadequate insulation, the cold from below can sap your warmth. YMMV.

+2 for a pad ... Richard Nisely suggests a pad providing R5 insulation value for temps below freezing.

Forgot to say that I am using a full length prolite 3 on top of a 1/4 inch closed cell foam pad.

Thanks.

"+2 for a pad ... Richard Nisely suggests a pad providing R5 insulation value for temps below freezing."

Yes, to maximize the warmth rating of your sleeping bag / garments. However, you can get away with a lower R-value for a pad if you increase the clo of your sleeping bag / garments.

As we slip from summer into fall in my area of the country, I've been giving a lot of thought to a very similar question. For me the question has been stated as follows: Does it make more sense to carry some additional clothing or switch from a 35 degree bag to a 20 degree bag?

In addition the the sleeping pad, I will add two other factors (a) the type of shelter you are using and (b) the presence of lack of a sleeping partner. If you have a (mostly) enclosed shelter and another person to help warm it, I would suspect that you could use your current sleep system to a somewhat lower temperature than you could alone under an open tarp (in the same location).

I don't know if you have a warmer bag or if you always carry the exact same clothing you listed in your post, but if you're adding some layers and own a warmer bag, it may be worth doing the math to see which option is lighter.

Shelter I am using: 9x9 oware pyramid

Sleeping Partner: Yes but the pyramid is so large that I do not notice much difference in temp from one extra person.

I have a -7/20 degree W.M. Ultralight and a MEC -12 bag. I have the options but am just interested how cold people think my system would be comfortable to.

Thanks.

negative single digits ... lol

only way to find out is to try it ... shouldnt be too hard to do so soon in the rockies

if you're looking for a theoretical approach ala richard: it's been a while since i've been reading Richard's stuff about the theoretical warmth value of clothing etc., but i can give it a try.

you say WM summerlite + merino top = comfortable at 0/32.

this chart gives us a CLO of about 6 for that.

now we have to add the other items:
- down sweater: i couldn't find the eddie bauer jacket. lets assume it was the Montbell Alpine Light Down Jacket. here Richard gives this jacket an IClo of 2.51. multiply by % of body surface covered (i believe 40% for a jacket) gives 2.51 x 0.4 = 1
- merino bottoms: in some notes of mine i found clo of 0.3.
according to richards chart that would be about the same as the Patagonia R1 hoody (0.32), which sounds about right to me.
- wool toque: listed with 0.16
- wool socks: no clue. lets neglect them

summing up: your clo in the above system should be 6+1+0.3+0.16= 7.46

consulting richards chart again yields you will be comfortable at about -8/20°

of course, this is theory. ymmv.

btw, feel free to correct me if i'm wrong at some point. or maybe richard can tune in to double check.

Thomas pondered, "Does it make more sense to carry some additional clothing or switch from a 35 degree bag to a 20 degree bag?"

I'm there too. One take is that you will be carrying extra warm layers anyway, so I guess the question is: are you comfortable sleeping in them? The down sweater (for example) that you hauled up the hill for comfort while in camp would add a lot of warmth to your sleep system.

I got into this when considering a half bag and belay jacket. If you are going to haul both, why not have them work in concert rather than hauling a heavier bag, plus the jacket that ends up being a pillow?

David: Cool response. Interesting to see the math. Maybe I will take the plunge and be the test subject.

Eric: You are right about getting to try it out soon. I have a trip planned this weekend in Kananaskis. Going to do the Northover Ridge route, weather (snow) permitting. Should be camping around 2200 meters one night and 2300 meters the next. Expecting temperatures of -2 to -6 celcius based on forecast and elevation.

Dale: This summer I have been using my E.B. Down sweater as a pillow. It is excellent in this mode. Part of me thinks I should just suck it up and carry the extra weight of the heavier sleeping bag just to have such a comfy setup.

When I first started backpacking I use to do the sleep near naked in the sleeping bag thing. Over the past number of years I have been wearing my base layers and often my hiking pants in the sleeping bag. I find this more comfortable off the start of the night when I am too warm to be fully zipped in (minimizes feeling of drafts) and in the middle of the night if nature calls. I have however never purposely relied on my insulating piece to make up for a sleeping bag that might not be warm enough. I realize there is really only one way to find out if this is the way to go for me...

Hopefully I won't be shivering through the nights this weekend. :)

Thanks all.

you should be fine in that range i think ...

if yr worried and dun want to suffer ... just take a few long lasting handwarmers with you and if you need to stuff them around yr body ... sure its not UL ... but consider it backup if were all wrong ....

> Sleeping Partner: Yes but the pyramid is so large that I do not notice much
> difference in temp from one extra person.

Wrong sort of sleeping partner. You need one who wants to be warmed by you. Wives and GFs are good.

Cheers

I assume you've thought about this, but if I were unsure of a sleep system for cold, I'd spend a night or two in the backyard before the backcountry.

Also, depending on your sleeping bag and how it fits, if it's a tight fit it may compress the sweater too much, thus rendering it all but useless.

^ good point- the summerlite I owned was too tight for me and definitely would have been too tight w/ additional layers

if you have the room in your bag, I think the additional clothing you mention should net you in the 20-ish range (given the info that the summerlite takes you to 30 comfortably w/o any)

I have a Marmot Hydrogen which also (in my experience) is comfortable at 30, w/ a light merino top, light down jacket, R1 bottoms, socks and a R1 balaclava- I've slept comfortable into the low 20's- personally I wouldn't push much past that

Based on this conversation, I'd love to see a spreadsheet with a side-by-side weight comparison between (a) carrying your 32-degree bag and extra clothing vs. (b) carrying your warmer bag.

For example, my 20-degree bag weighs 11oz more than my 35-degree summer bag. In my mind, if the weight of the "additional" or "upgraded" clothing is more than that amount of weight, than I'm better switching over to the 20-degree bag. For me, the upgraded clothing doesn't seem to be worth the weight, since I don't need those upgraded items while hiking or in camp.

That's the way I've calculated things for myself. I'm sure other people's ways of thinking here will vary.

my "extra" clothing gets used most days in camp- cool evenings/mornings my down jacket is used around camp, quite often the pants as well, same w/ the hat- so not really extra weight for me- just a nice bonus that they can do double duty and stretch my bag just a little

Thomas - this is the idea with extra clothes. Pushing the warmth of your bag without any increase in weight. Hence the concept of a system. I encourage you to read a couple of BPL articles on the subject. You must be a member to read them.