View Poll Results: Have You Used a Vapor Barrier Layer (VBL)?

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  • Yes, although my clothes/insulation got really wet!

    19 5.01%
  • Yes, I think they work great.

    74 19.53%
  • No, I am skeptical that VBL's work at all.

    30 7.92%
  • No, I've never really looked into VBL's.

    256 67.55%
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  1. #1
    dejoha's Avatar
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    Illustration - Vapor Barrier Liners (VBL)

    I was asked by ChrisH to make up a simple illustration about vapor barrier liners (VBL) in an effort to help explain how they work and when to use them. I've experimented with VBL's in the past with good results (and some real disasters!), but the real experts are those who've successfully used them in the field. I contacted sclittlefield, one resident expert on VBL's in the forums, who helped frame a lot of my thoughts. I also read and researched several articles, but the one article I found that did the best job is from the long-distance hiking guru, Andrew Skurka. Skurka's article "Vapor Barrier Liners: What they are, how they work, and when to use them" was perfect, and I think his real-world experience is a must-read if you are interested in VBL's.

    My illustration and notes hopefully explain some of the basics, and perhaps add a visual reference to other, more thorough articles like Skurka's.

    The main points I've gleaned from personal experience and from what I've read is this:

    • VBL's work best when it is cold (<= 40°F/5°C).
    • A VBL should be close to and completely surround your skin to effectively create the micro-climate your body needs to stop perspiring and maintain its temperature. For comfort (e.g., to eliminate a clammy feel), you can wear a base layer before the VBL.
    • VBL's are critical for long-term winter camping, but can be effective for overnight trips as well


    From my reading, VBL's receive criticism because of excessive moisture build-up. Proponents argue that the presence of moisture build-up is an indication that the VBL was used incorrectly.

    A VBL can effectively "trap" the insensible moisture around your body to create a micro-climate where body's hydration and temperature are then regulated and stabilized. Once the micro-climate is stabilized, the body stops transmitting insensible moisture.

    That's Great, But How Does That Apply To Hammocks?

    A VBL can be used in a hammock very easily, as either a bag or quilt liner, or as Skurka recommends, as part of a layered clothing system.

    VBL's should not be used on the outside of insulation (either under quilts or top quilts) because moisture will eventually build up inside the quilts and will collapse the insulation. Underquilts are less of an issue since water vapor tends to rise upward.

    Some pads (e.g., closed-cell foam) create VBL's since they don't breathe, however, they only provide a VBL on one side of your body, which can create irregularities with your body's thermoregulation.

    You can use any non-breathable material to create a VBL: plastic bags, sil-nylon, coated nylon or polyester, etc. The real "trick" to a VBL is to make sure your body temperature is properly regulated. Skurka used VBL's while hiking, backpacking, and snowshoeing, proving that VBL's can be used during moderate exertions.

    Anyway, I hope the illustration helps. Again, I would refer you to Skurka's article, which I think does a much better job in explaining VBL's.

    Attached Images Attached Images

  2. #2
    Senior Member whayneneal's Avatar
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    Vapor barrier

    I have recently purchased an under quilt protector from 2q2z and I'm in the process of trying to decide what to use as a vapor barrier. I must admit I'm somewhat skeptical having no experience with one. I don't like the thought of waking up soaking wet in the middle of winter. Thanks for the information. This was helpful.

    I think I'm going to try an Adventure Medical Kits S.O.L. Thermal Bivvy with mid/heavy weight base layer.
    Last edited by whayneneal; 12-24-2010 at 13:07. Reason: Want to add something to it.

  3. #3
    Senior Member ChrisH's Avatar
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    Awesome illustration dejoha! Thanks so much, it makes it much easier for us noobs to understand. Really appreciate all the time and effort that you have put into this!

  4. #4
    MedicineMan's Avatar
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    Back in my ground dweller years, when backpacking in serious cold I'd carry a vapor barrier...it doubled as my pack liner and was long enough for a complete me to get into it. It was a pain sometimes loading the single cavity frameless pack (a Mithril by Moonbowgear) because of the excessssssssss material this pack liner had. That said, it was sil-nyl and as a true vapor barrier was/is designed to go directly against the skin, e.g. a naked body. With this method another potential 20F could be had and NO moisture would get on clothes or inside the sleeping bag because 1. it was eliminated from formation by stopping the process of insensitive sweating and 2. because this vapor barrier being sil-nylon was impervious to moisture.
    The only B%^&@ about using it was in the morning....picture yourself waking up in a very very warm VBL that is also moist and having to climb out of it naked at anywhere from -8F to 10F !!!!
    Of course you would transition from this VBL as FAST as humanly possible.
    This pack liner therefore performed several functions-pack liner, entire body VBL (I would cinch it around the neck and have balaclava on the head, and emergency bivy...not bad for 4+ ounces.
    I've not used it since 'evolving' but now that the subject has come up I might dig it out of the reserve kit pile.

  5. #5
    Redoleary's Avatar
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    Great illustration, and information. Thanks for that.
    Good luck,
    RED

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  6. #6
    Senior Member Bradley's Avatar
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    I seems counterintuative to me . . .
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  7. #7
    Senior Member Just Jeff's Avatar
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    Science often seems counterintuitive, and as with any piece of gear, VBLs only work well within a defined set of conditions. Just as you wouldn't say a winter quilt doesn't work well b/c it doesn't give good results in summer, a VBL will only give good results when used correctly.

    Great illustration, dejoha!
    “Republics are created by the virtue, public spirit, and intelligence of the citizens. They fall when the wise are banished from the public councils because they dare to be honest, and the profligate are rewarded because they flatter the people, in order to betray them.” ~Judge Joseph Story

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  8. #8
    Senior Member keys?'s Avatar
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    Wow! This makes so much more sense to me now than it ever has! Thanks for your illustration and link to that article. Now we just need someone to make/market a VBL union suit with pit/crotch zips...Dutch?

  9. #9
    Senior Member Danalex's Avatar
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    Excellent information, thanks!

  10. #10
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    Quote Originally Posted by Danalex View Post
    Excellent information, thanks!
    I second this!

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