I have a Western Mountaineering 'Caribou' down bag. It is a sewn-thru design and is rated to 35 degF. What are some field-verified ways to make use of a bag in weather cooler than it's comfortable rating?

Extra clothes, bivy cover, etc etc but what have proven to be the more efficient strategies for the LW/UL hiker? For example Mike Clelland advises wearing all your clothing within the bag, but other have noted that this causes body vapor to hit the dew point withing the sleeping bag's insulation, causing interal condensation.

Vapor barrier liner. A search here might yield some good info.

Z-Pack has just come out with their cuben VBL at under 2oz.
Ron

http://www.zpacks.com/accessories/cloudliner.shtml

"For example Mike Clelland advises wearing all your clothing within the bag, but other have noted that this causes body vapor to hit the dew point withing the sleeping bag's insulation, causing interal
condensation"
maybe that is because they are wearing too much and or the bag is already warm.
I don't usually sweat when I am cold, however maybe it is just me...
(the point here is that it will depend on your metabolism too...)

I would avoid tight clothing, particularly socks, possibly the commonest reason (IMHO) for having cold feet when wearing them.
Franco

Edited by Franco on 10/26/2011 15:06:19 MDT.

Regarding the dew point issue, I'm confused. Unless you are using a vapor barrier, won't the dew point occur somewhere in the bag, regardless of whether you wearing clothes or not? Or at least wearing clothes might open the possibility that the dew point occurs within the clothes (which might be better). In other words, on the outside of the bag, it is the temperature of the outside. Inside the bag, it is either your body temperature, or something colder. I can see why it might make sense to wrap a synthetic bag around down (or vice-versa) but I don't see why wearing extra insulation (clothes) would ever make things worse (with the exception that Franco mentioned, which is if the clothes are restrictive or wet).

> A search here might yield some good info

Whoops, my bad. For a long time the search function wouldn't work for me but it seems to be functional now. Sorry, I'm usually pretty good at searching before asking the same old questions.

Large dinner
Block all wind
Warm hat or balaclava
Warm light fluffy socks
Good mat underneath

Cheers

legs or at your feet can go a long way to warming you and your bag saving calories for later in the night. i'll wear what i have to sleep if needed, but i dont like wearing my jacket into my sleeping bag (unless it's part of my planned sleep system). if i need some extra insulation i drape my jacket (unzipped) over my torso outside the bag. if it has a snap-off hood i detach it and wear it to sleep.

Edited by RICKO on 10/26/2011 16:02:06 MDT.

Be careful of anything that compresses or reduces the loft of insulation. Too much clothing or an inner bag in an already pretty tight mummy can reduce the loft which is kind of going backwards.
There are overbags out there too, but I can't say whether that is better than buying a bag rated for the conditions expected.
The human body "loses" about 4# of insensible sweat at night with a breathable bag, if the temp is at or below the freezing point of water some of it accumulates in a breathable bag as ice. Will Steger's 1985 Artic expedition found their bags gained 20-35# of ice over a few weeks.
We also "steal" heat to evaporate that same sweat that we would use to keep warm. 4# of sweat requires 4250 BTUs of heat to evaporate. This is the equivalent heat needed to melt 30# of ice so we need a mechanism to turn off the sweat switch and that is vapor barrier.
My own experience is vapor barrier works for me but I prefer VB clothing to a bag liner and on a short trip I wouldn't bother with it.

+1 On what Larry said regarding compressing the loft of your bag.

I have found that Gooseweb down sleeping socks helps me a lot in adding comfort and warmth on cold nights.

In my case, I suffer from cold feet, so if I can keep my feet warm at night, the rest of me is much warmer.

A really good hat, down or otherwise will also help out.

I have used plastic UPS bags as a cheap Vapor Barrier and it does work, but you have to decide for yourself if you are comfortable with the high humidty and clammy feeling.

-Tony

"Whoops, my bad. For a long time the search function wouldn't work for me but it seems to be functional now. Sorry, I'm usually pretty good at searching before asking the same old questions".

No worries at all.:-) I didn't mean to sound short or imply that you should be searching.

clothes inside bag induces certain risks
- wet or damp clothes ... moisture needs to go somewhere
- down/synth clothing inside bag can push the dew point to the outer layer, which would be the bag in this case ... you dont use a down overbag over a synth bag ... but if you wear yr synth clothes inside a down bag, thats what you are doing IMO
- compression ... is it wise weight wise to spend the extra weight on a wide sleeping bag so you dont compress yr down clothes or the bag when wearing them inside

IMO if you have a synthetic or even a down puffy that you wear on belays/stops, it is better to drape it over the bag as someone mentioned ... that way you have the driest and best insulating part of yr system (bag) next to you ... it also acts as a partial overbag, and also protects the bag against outside condensation as jackets usually have better DWR IMO

the key to remember is that you can survive very damp clothes ... a very damp bag in poor conditions means you get the hell outta dodge if you cant dry it fast ... i suggest reading mister ures (sorry david =P) thread on condensation in his down quilt

the best booster to warmth IMO is a hawt nalgene which youll use for water anyways, or an emergency vbl which can be a pack liner... this is assuming you ate correctly .. depending on clothing to boost yr bag performance does leave you vulnerable to below average snaps IMO