I've used VBLs occasionally on my hands and feet for many years, and occasionally (usually inadvertently) slept in things that were effectively VBLs. More recently, I've been reading here and elsewhere about better-planned VBLs and their advantages, especially in cold weather.

What I'm wondering about relates to the trapping of moisture, sensation of clamminess, and effects on skin. For those of you who are VBL advocates, when does your skin get a chance to dry out? Do you change your base layers regularly and rotate them out to dry? Or does moisture just continue to build up?

My own experience confirms that it's better to be damp than to be cold, so I'd never hesitate to fashion a VBL in a pinch, but I'm having a hard time understanding why I'd plan to do things this way, unless there's some technique for getting a chance to dry out periodically.

What am I missing?

Thanks!

Best,

Bill S.

I'll give you my personal usage. I put on VBL once I get into camp, and remove it before I start to hike in the morning. For me, I sweat too much while on the move, but it works wonderfully at night when I'm idle.

Also, I only use it when it's substantially below freezing. I suppose I might be able to make more use of it if it were *really* cold, but I don't tend to get exposed much to anything below 0F.

Used this way, the base layer doesn't get saturated, and the skin doesn't "prune up."

Edited by backslacker on 11/16/2012 19:40:17 MST.

What exactly constitutes a VBL? How are they used? I have never really understood.

A vapor barrier, usually in the form of clothing or a sleeping bag liner, does not breath at all. Any perspiration is stuck underneath that layer. It's like putting a trash bag on your body. (a trash bag with holes cut in it for your arms and head actually works as a cheap vapor barrier.) This is to prevent your body moisture from evaporating into your down sleeping bag and freezing. From what I have read, in extended trips in arctic conditions your perspiration can keep building up night after night until you are hauling around a sack of frozen feathers.

Aw I see, so you put a VBL over your synthetic/wool layers and under your down puffy so it doesn't soak in the moisture that your body puts off into your puffy. Makes sense. Now how does this help Merino wool? Wouldn't the moisture just absorb in the Merino if the VBL was over it? Synthetics are better at releasing moisture.

It would be best to put all of your clothing over the vapor barrier to prevent it from getting wet. But some people like to have a layer under their vapor barrier because it makes things less "clammy". It wouldn't matter if synthetics are better at releasing moisture since it would be impossible for them to release the moisture under a vapor barrier.

In addition to keeping the moisture OUT of the down plumes, it also holds any condensation close to you where it can do the most good.
1) Saturated air can reduce your bodies need for insensible perspiration. This is what keeps your skin soft and from cracking. If you get dry, your body will perspire to lubricate your skin...not only for temperature regulation. You will do less sweating, hence lose less heat if you can maintain humidity.
2) Heat of condesation happens when water vapor changes from a gas to a liquid. This is the opposite of boiling water and producing water vapor. Your body warmth will cause sweat to evaporate. Condensing the water vapor will give back the heat lost from your body.

Essentially you conserve energy slightly by not evaporating so much sweat and conserve heat slightly by recovering heat from condensation when it is produced. As it was explained to me, this only helps about 2-3F degrees. It is more important to maintain dry loft for two or more nights out.

I think the best vbl is a cuben quilt, easy to vent so you don't get wet, also super lightweight.

I am not sure anyone has mentioned the really key thing with VBL liners. It's this:
Sleep Cool and Don't Sweat

Once you get past the idea that you have to sleep so hot you are sweating, everything becomes much simpler.

Cheers

Edited by rcaffin on 11/17/2012 03:23:19 MST.

In answer to the original questions, I use VBL socks for just about every trip in winter conditions here in the Midwest. I use a VBL suit (cheap silnylon raincoat and pants) on trips anticipated to last longer than 3 nights. I wear the VBL socks during the day, with the purpose of keeping my foot insulation dry. This keeps my feet warmer during rest stops and in the evenings, and prevents my shoes from freezing overnight. (I also tuck them under my pad at night). For short trips, I may never take off the vbl socks. For longer trips I use hydropel and remove the vbl socks at night to let my feet dry out. I sleep in designated sleep socks on those trips.

When using a vbl suit, I never hike in it. Rather it is used at night to keep condensation out of my bag. In this way, I can limit sleeping bag weight gain to less than 6 oz for trips of 5-6 days. I don't use it on the move as I can regulate moisture best by paying attention to layering and pace, so I'm basically airing out my layers all day long. I might throw it on at rest stops before putting on my down jacket to keep sweat from condensing in it. Others may do it differently but this works for me. I do not bring extra layers or sleep clothes except socks. I don't typically feel clammy because I take care not to sleep to warm. Base layer under the vbl is damp but not wet.

In response to Michael's comment, I don't believe a vbl quilt is the better solution. A rainsuit allows you to safely layer all your insulation layers (down jacket) over the vbl when cold. A vbl quilt puts the vbl layer outside your insulation so you can have condensation in your insulation layers. A quilt doesn't give you the same daytime versatility either.

Edit to fix the fact that my spell checker had converted all the vbl to bbl. Hope I didn't offend anyone. And for the record, I do not sleep with big boned ladies on any of my trips.

Edited by Ike on 11/17/2012 05:26:32 MST.

I have done my last two overnighters using some components of VBL. I am currently a novice so I'm trying to get the base understanding of how I might use the technology much broader in the future. It started when I made a vbl suit/rain suit from .74 cuben. This included two sets of booties. Heres what I have or intend to do:
1) test full vbl for use below freezing to see the comfort level and hassle of use. My first two tests were temps slightly above freezing and I was very pleasantly surprised. I used a mid weight capilene base layer and I would describe the sensation as a warm humid hug. It was different but not yucky at all. The big surprise was how warm my feet were . So this was a huge success.
2) my intent is not as much to eliminate the moisture gains over multi day trip as it is to put my dead weight rain suit weight to productive use at night. I do believe you sleep warmer with a vbl, beyond the loft reduction, but more test runs will be needed to confirm.
3) I don't expect to be able to use the pants and jackets for a vbl while hiking or snowshoeing. I rarely get cold once I get moving even with temps down to about zero. I can't image not overheating with it on but I will trial it once it gets a bit colder here in PA.
4) I will also use it if I ever sit around camp like the Sierra snowshoe trip with Jack and crew a couple if years ago. I don't usually hang around camp, I either hike or sleep but this is a case where vbl could help bridge that gap.
5) the biggest benefit and unknown may come from the booties. I have an absolute aversion to wet feet since hiking weeks on the PCT with continuous wet feet. It is irrational but I'm attempting to design around it. So my proposed systems is an upgraded bred bag concept. I made two set of 1.0 cuben booties, the outer set being a bit larger. The intent is to wear liner/vbl/insulation/waterproof/liner?. This would be for colder temps and the insulation could vary for temps. (the intent of the outer liner is to protect the outer booties from abrasion, may not be needed) for warmer temps I could eliminate the insulation and outer bootie and the inner bootie's primary mission is keeping my feet dry. This is the intent and I look forward to seeing how this works. I used oven cooking bags very successfully until they shredded due to abrasion.

I think there are some advantages of this system for cold weather. I also intend on pushing the upper temperature limits when used with sleep system to see how it could positively impact the rest of my sleep system.

"I think the best vbl is a cuben quilt, easy to vent so you don't get wet, also super lightweight."

The only bad thing about a VBL sleeping bag is you can't really wear any insulation inside the sleeping bag. So you have to take off the stuff you wear before going to bed, and then the sleeping bag has to be a little warmer and heavier.

Also with a VBL quilt or bag you have no way to adjust the amount of insulation with venting the VBL, and if you start venting the VBL you defeat its purpose. So a VBL liner or suit is better