using vapor barriers

Been doing some reading on the use of vapor barriers. It seams to be quite a controversial concept. I was wondering if anyone has had any personal experiences with the concept, good or bad. Not just in the sleeping bag at night but as body attire during the day. Does anyone recommend it?

After decades of winter camping I tried a VB inside my down bag while wearing a polyprope top and l. underwear. It was one of the best moves I've ever made in my entire winter camping life.

A cold-footed friend has tried them on her feet--says they work and she continues to use them in her XC ski boots. She also occasionally wears her mouse boots (which, of course, are VB) in preference to double boots for hiking.

Another friend has tried one in a sleeping bag. For use only in real cold (below 0F). Don't know if he feels the VB is worth using.

Stephenson seems to advocate them as all-body attire.
http://www.warmlite.com/vb_shirt.htm
http://www.warmlite.com/vb.htm
(I think he overstates the case, but then he is selling it.)
Don't know anyone who has tried it. Doesn't seem to be very popular.

I'd expect all-body daytime use to require frequent adjustment to prevent overheating since you have short-circuited the sweating mechanism. Might also be another "only in real cold" technique for most people.

One disadvantage of VBs is that they need to be worn next to (or at least very close to) the skin to be effective. This makes insulation adjustments less convient and getting up to pee at night less comfortable. I suspect the most popular uses are as socks or sleeping bag liners.

Doug

Use them in my boots in the winter with a LW wool sock under and a EW sock over and they work wonderfully. While your foot does get sweaty, they stay very warm. Even better, the inside of your boot does not get soaked in sweat and if by any chance your boots leaks, you know that water will not get in.....

Jkrew81 said:

Use them in my boots in the winter with a LW wool sock under and a EW sock over and they work wonderfully. While your foot does get sweaty, they stay very warm. Even better, the inside of your boot does not get soaked in sweat and if by any chance your boots leaks, you know that water will not get in.....

Click to expand...

The issue about water from the ouside is getting your insulation wet--not whether the water reaches your foot.

To prevent this, place a second VL outside the EW sock. That way, the insulation layer is protected from both sides. In essence, a home-made mouse boot.

Doug

I have read the advocates of the system use the shirts or vests, even mention that you can just use a trash bag as a vest. I tried it by cutting head and arm holes in a bag and placing it right on my skin then a polypro long underware top and a uninsulated rain shell, went for a 2.5mile walk along the frozen lake shore where I live at night with the temp about 20deg. I was amazed that I was more than warm enough. The best thing was that when I got home my polypro top was completely dry as was the inside of my rain shell (usually the inside of my rain shell is soaked from the perpsperation condensing when it hits it and turning to water. Though I guess I would consider my first test a sucess, I have concerns of over heating if I try to hike using this vapor barrier concept.

Just returned from an 8 night trip in northern Ontario. The night time temps were -15 to -30F. I took along a VBL (garbage bags) for my down bags for a trial, but never had the guts to use it. It was hard enough to get out of the bag in the morning, the thought of doing this while soaking wet was beyond consideration.

My outer down bag did get very icy without one, but I had access to a hot tent for drying purposes. No doubt in my mind that for long winter trips like this, a VBL is a must if you do not have a way to dry your bag.

Tony

tonycc said:

Just returned from an 8 night trip in northern Ontario. The night time temps were -15 to -30F. I took along a VBL (garbage bags) for my down bags for a trial, but never had the guts to use it. It was hard enough to get out of the bag in the morning, the thought of doing this while soaking wet was beyond consideration.

My outer down bag did get very icy without one, but I had access to a hot tent for drying purposes. No doubt in my mind that for long winter trips like this, a VBL is a must if you do not have a way to dry your bag.

Tony

Click to expand...

My VBL is basically a big condom that goes inside my sleeping bag. I sweat a lot, but in the morning, to my surprise, I was bone dry! And of course so was my down bag.
This in sub zero F temps.

Tony, where in Northern Ontario where you camping?

tonycc said:

It was hard enough to get out of the bag in the morning, the thought of doing this while soaking wet was beyond consideration.

Click to expand...

The key is to have the VB as close to body temp as possible--that is right next to (or at most a single layer of light weight long underwear away from) your skin. If the VB is at the same (or higher temp) then water doesn't condense on it and you don't get wet (unless sweating). If the VB is at a lower temp, the water vapor (~100% humidity at body temp) emitted by your skin will condense on the lower temp VB and soak into everything in between.

adirobdack46r said:

usually the inside of my rain shell is soaked from the perpsperation condensing when it hits it and turning to water.

Click to expand...

The outer layer is the absolute worst place to have a moisture barrier. That sets you up to get all of your insulation wet.


This principle is used in a device called a "heat pipe"--an enclosed pipe with a fluid in it and a wick between the hot and cold end. The fluid evaporates at the hot end (absorbing heat), condenses at the cold end (releasing heat) and wicks back to the hot end. The exact opposite of what we want our insulation to do...

All just basic physics.

Doug

adirobdack46r said:

Been doing some reading on the use of vapor barriers. It seams to be quite a controversial concept. I was wondering if anyone has had any personal experiences with the concept, good or bad. Not just in the sleeping bag at night but as body attire during the day. Does anyone recommend it?

Click to expand...

I use VBL socks 5 days a week, in my commute to work. I swear by them.

I've used VBL pants, not while hiking, but in the evening, after the hike. Works great for me.

I use a VBL in my sleeping bag, and the sleeping bag goes in a non-breathable bivy sack. It works very well for me, and I do not wake up soaking wet. I call it my micky-mouse sleeping bag.

I do not like VBL clothing (except for socks) when hiking. I find temperature control much too difficult. Sweating is much more of an issue here.

Neil and Pete,

Thanks for the advice and affirmation on the effectiveness of VBL. I guess I shouldn't have chickened out. In my defense, when the temperature difference between C and F get close enough that conversions are a waste of time it changes the amount of risk I am willing to take.

Neil, we were about 80 miles NW of Sudbury. We take the Budd Carr out of Sudbury and they drop off us off along the tracks in the middle of nowhere. The flag train service in Canada is an excellent way to get away from civilization to start a trip. This is a winter gathering of wilderness canoers, 26 people total at one point this year. It is a blast!

Tony

I use vbl 's (plastic bags) in my winter boots and would not winter hike without them.
I use one in my down bag along with one top and bottom thermal layer, boy do I wake up wet, quite warm but wring out the thermals wet. I can usually change thermals or throw on additional layers before I cool significantly. Besides my metabolism is usally roaring in the morning. I perpire heavily, my bag still gets a bit damp. I should try seam sealing the vbl.

Couchybar said:

I use one in my down bag along with one top and bottom thermal layer, boy do I wake up wet, quite warm but wring out the thermals wet. I can usually change thermals or throw on additional layers before I cool significantly. Besides my metabolism is usally roaring in the morning. I perpire heavily, my bag still gets a bit damp. I should try seam sealing the vbl.

Click to expand...

Perhaps you are over-insulated for the conditions? Perspiring inside a VB suggests that you are hot. (The other alternative is that the VB is below body temp.)

Doug

I think Pete is on the right track.

Here is my own FAQ on VBs. The info is mostly culled from several years of discussions on rec.backcountry with the input of several folks (both pro and con) combined with my own trial and error. I'm not doing as much winter camping these past 2 years and would suggest listening to Pete on this a lot. He also said in a few lines what I say in like 5 pages...

http://home.comcast.net/~pinnah/DirtbagPinner/vb.txt

Trains and winter camping in Canada.

tonycc said:

Neil, we were about 80 miles NW of Sudbury. We take the Budd Carr out of Sudbury and they drop off us off along the tracks in the middle of nowhere. The flag train service in Canada is an excellent way to get away from civilization to start a trip. This is a winter gathering of wilderness canoers, 26 people total at one point this year. It is a blast!

Tony

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We used to do that all the time leaving from Winnipeg heading east to the Canadian Shield. Always suspensefull waiting for the train to take us home. Will it be on time? What if it dosn't stop? No worries in severe cold about getting the car to start! And beer on the Transcontinental! Once we rode a milk run between Wpg. and Sioux Lookout and rode in the diesel with the conductor. I had the map out and got him to stop exactly where we wanted.
Great times!