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Frost free?

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  • m2b1997
    Okay, I have to admit I never do things the way everyone else does. Numerous years back I saw Ed give his hammock talk at the ALDHA Gathering and when I
    Message 1 of 13 , Jan 6, 2009
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      Okay, I have to admit I never do things the way everyone else does.
      Numerous years back I saw Ed give his hammock talk at the ALDHA
      Gathering and when I sat/laid down in the hammock I knew I had to
      figure out a way to change from sleeping on the floor to sleeping in
      a hammock in my house. My house is way too small to have a bed
      taking up what would seem like half the floor space of the house. I
      had been using anything from a therma-rest to a full size inflatable
      bed and was sick of them leaking air on me as well.

      I finally figured out where/how I could hang the hammock, given the
      room in question was full of windows. I started sleeping in the
      hammock and loved it. I eventually started using one of the other
      room in the house as the bedroom and moved the hammock into that
      room. I have been sleeping 7 days a week in a hammock now for three
      years if not four.

      This past fall I knew my old sleeping bag, North Face Blue Kazoo was
      getting on the old side. I have been sleeping each night in it now
      ever since the late summer of 2000, plus when I thruhiked in '97. I
      knew it was time, since I had some money available to get a new
      sleeping bag. I knew since I would only be sleeping in my house that
      I wouldn't need to worry about too much so I went to Wal-Mart to see
      what I might be able to find. Lo and behold I found that I could get
      a supposed 0 degree mummy bag for practically the same price as a 20
      degree bag, less than $40. I knew it would only be suitable for
      indoor conditions and that was all I really had it planned for.

      I bought it and also kinda thought about testing it to see how low I
      could actually take the bag down and still be comfortable. You know
      how Wal-Mart loves to overrate things.

      A couple of weeks ago I started testing by moving the hammock back to
      its original location, now an unheated part of the house. I had seen
      a few weeks prior to that one morning where it was only ten degrees
      in the room, while it had dropped down to around zero overnight
      outside. I knew I could stay inside and still test the bag.

      I spent a couple of nights out there testing out the bag and was
      surprised at how well it worked and how much more comfortable it felt
      to sleep in the COLD rather than a cool room(I normally keep my house
      no warmer than 60 degrees and quite often by morning it may fall to
      the mid 40s inside). I was seeing some of the coldest conditions I
      have ever slept in and I was feeling quite comfortable.

      I saw the forecast was coming up for a nice night, cold but no snow
      forecasted. I decided the heck with it and headed outside for the
      night. I laid on the ground with the old Wal-Mart ridgerest
      underneath, I normally use it underneath me in the hammock. I didn't
      last any time at all. I was out about two hours. Admittedly some of
      that was road noise, I live by a highway, and some of that was some
      dogs off in the distance as well. Quite a bit of it though was the
      simple fact of getting cold. It was ten degrees when I finally went
      inside. I found I was having a hard time getting to sleep.

      I spent several more nights in the cold part of the house including
      the past five or so straight nights. I decide to push my luck even
      further and started stripping down to butt nakedness and sleeping
      that way in the hammock/sleeping bag here Saturday and the first part
      of Sunday night. I have a bit of an unknown roof problem in that
      same part of the house and when I heard the freezing rain/rain/sleet
      hitting the roof I bailed for where I knew I wouldn't get wet Sunday
      night. I was still feeling quite comfortable even down to 22
      degrees, when butt naked. I had seen 16 degrees with the usual sweat
      pants/shirt on the I typically wear even when sleeping in the heated
      part of the house.

      Last night...the forecast was for clearing skies and a low of 17
      degrees. I decided to hunt down some trees in my backyard and set
      the hammock up outside and see what would happen.

      I do admit I made the hammock myself, very simply. I took a piece of
      cotton cloth, no nylon, and tied the ends off and hooked up the rope
      to it. That's what I've always been using. I don't do much in the
      way of camping/hiking anymore to have to worry about getting wet so
      nylon wasn't a concern when I bought the material and made the
      hammock.

      I headed to bed about 10:30PM and finally got up this morning about
      7:15. The forecast held pretty well and it did get down to 14
      degrees overnight according to the thermometer I had hanging on one
      of the ropes. I did find the shoulders were getting a bit chilled,
      especially the shoulder that was on top. Otherwise I was very warm
      and comfortable. I did find myself having trouble getting to sleep
      again. I wasn't the most tired when I went to bed which could have
      been part of the problem. For some reason sleeping outside I do seem
      to be more restless than when I'm sleeping in warm environments. I
      do find myself tossing and turning more at night. Inside the only I
      move during the night is to get up to go the bathroom.

      The one problem I noticed that I'm wondering about was the frost. I
      have typically noticed, sleeping in the cold part of the house and
      last night, frost pop up on the sleeping bag where the mouth/nose
      comes out of the sleeping bag. That has been a surprise. This
      morning when I got up I noticed that a nice chunk of the hammock also
      had frost on it. A lot around the head/chest area but I saw frost
      even down by where the feet were at.

      How do you prevent the frosting up of a hammock, or is it even
      possible? I had the hammock and ridgerest outside two or three hours
      before I went to bed. I took the pillow and sleeping bag with me
      when I went to bed.

      Also, no...their is no velcro closure on the hammock like you would
      typically find on a regular hammock, it remains open to the outside
      world unless you can curl your body up small enough. Again, it
      wasn't ever meant to be used outside but for the winter months I'm
      looking at being a convert.
    • Ralph Oborn
      How do you prevent the frosting up of a hammock, or is it even possible? The moisture is from your breath. If the air temp is below freezing and the air is
      Message 2 of 13 , Jan 6, 2009
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        How do you prevent the frosting up of a hammock, or is it even
        possible?


        The moisture is from your breath.
        If the air temp is below freezing and the air is saturated with water there
        (as evidenced by seeing your breath) it will freeze on things.

        Ralph


        [Non-text portions of this message have been removed]
      • Ed Speer
        M2b1997, I ve had the same experience many times as well. Frost on the outside of a sleeping bag, hammock, underquilt or on the tarp is natural when the air
        Message 3 of 13 , Jan 6, 2009
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          M2b1997, I've had the same experience many times as well. Frost on the
          outside of a sleeping bag, hammock, underquilt or on the tarp is natural
          when the air temperature drops below freezing, there is no wind & the
          outside humidity is high enough for the dew point to be reached. Frost near
          your head & mouth is probably frozen condensation from your expelled
          breath-not much you can do about that. Some of the frost elsewhere on the
          sleeping bag, hammock or underquilt is probably frozen moisture from your
          body's insensible perspiration that has been driven thru your insulation
          layers by your own body heat, condensed on the outermost fabric & then
          frozen by the low outside temps. This is normal & beneficial-it means your
          insulation layers are not trapping excessive body moisture, which as you can
          imagine can be a serious problem. Escape of some of your body moisture thru
          your insulation layers happens every night, only at warmer outside temps the
          moisture does not freeze & it may even evaporate entirely (especially if
          there is some wind or the outside humidity is very low). Of course, a
          sleeping bag or hammock wet on the outermost fabric can be a bit of a
          problem if it has to be packed up that way the next a.m.-I'll often lay mine
          out during a rest stop on the trail the next day to dry it off. In your
          case indoors, you might leave a window open for added drying ventilation
          during the warmer temps of the day.



          High humidity fog & moisture escaping from the ground can also contribute to
          the dew & frost buildup on the outside of a sleeping bag or hammock-but
          since you're hanging indoors, this should not be part of your problem. If
          there is frost on other surfaces in your sleeping room, then high outside
          air humidity may be the problem.



          For those of us who winter camp in the hammock, we're concerned about any
          loss of warmth. The fact that body moisture is being lost thru the
          insulation (as evidenced by frost in the winter) means that some of our body
          heat associated with that moisture is also being lost. But stopping that
          kind of heat loss is a major serious undertaking that is difficult &
          controversial. Here we enter the world of vapor barriers & a whole new
          topic. I'd love to see vapor barriers discussed on this List for I know
          many of you have tried them with varying results. Of course, sleeping pads
          are partial vapor barriers & we all use them when it gets really cold. I
          also often use a plastic sheet for a partial vapor barrier for added warmth
          on cold winter nights in the hammock.



          M2b1997, you might have success stopping some of the frost (that which is
          your escaped, condensed & frozen body moisture) by using a suitable vapor
          barrier inside your sleeping bag-never close it over your head or you WILL
          suffocate! Frost due to your expelled breath will still be present. But
          please do some research & planning first as this will be a real shock when
          you wake up dripping wet in the morning! You & your sleeping clothes will
          be wet & warm, but your sleeping bag should be mostly free of frost! The
          problem comes when you get out of your vapor barrier/sleeping bag & meet the
          subfreezing air! For this reason, most folks prefer NOT to use vapor
          barriers. However, they are a proven winter camping technique---I only wish
          I were more experienced with them...Ed



          Moderator, Hammock Camping List

          Author, Hammock Camping book

          Editor, Hammock Camping Newsletters

          Owner, Speer Hammocks Inc



          _,___



          [Non-text portions of this message have been removed]
        • m2b1997
          I agree Ed, that the moisture freezing around the mouth is to be expected, hence why I wasn t concerned by it or even thinking anything about. I was surprised
          Message 4 of 13 , Jan 6, 2009
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            I agree Ed, that the moisture freezing around the mouth is to be
            expected, hence why I wasn't concerned by it or even thinking
            anything about. I was surprised by it for a second or so, night one
            or two, until I realized I should be seeing it.

            The sleeping bag seemed dry, just cold, as could be expected given 14
            degrees. It was the hammock though that had the frost on it, other
            than around the mouth. That's why I'm a bit perplexed. I hadn't
            thought about the body heat being lost but that does make perfectly
            good sense.

            Around the face the frost was the worst...but I still had it, ONLY on
            the hammock, all the way down at the feet. The weather was cloudy
            turned clear by morning, no precip overnight. In the several times I
            woke up overnight it was anywhere from partly cloudy to clear. I'm
            not sure what the dew point was. I'm going to have to pay a little
            more attention the next time and see if I notice that being the true
            culprit as it doesn't seem like the breath should be able to make it
            all the way down to the feet.

            Just one strange/stupid curiousity that has come up in my mind. In
            the case of winter camping would you be better off with a cotton
            versus a nylon hammock? Yes, this seems like a real dumb question,
            but think about it for a moment. During the summer months, nylon
            only, I wouldn't consider anything else otherwise, simple because of
            the rain. Winter months though, when you find yourself in a
            situation like I did last night the cotton hammock would have the
            tendency to absorb the moisture instead of the sleeping bag. This
            would keep the sleeping bag drier. There's nothing 'waterproof'
            around you to keep the moisture in so it collects on the sleeping
            bag. Am I wrong on this thinking? Is that why the hammock had the
            frost at the feet but the sleeping bag was dry? The thought just
            came to me as I was typing this.

            MEANT 2B
            GAME '97
          • Ed Speer
            Cotton vs. nylon hammock might make a minor difference on the amount of moisture collecting on the outer side of the fabric, but not much. But you re right
            Message 5 of 13 , Jan 6, 2009
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              Cotton vs. nylon hammock might make a minor difference on the amount of
              moisture collecting on the outer side of the fabric, but not much. But
              you're right that a cotton hammock around a nylon sleeping bag might tend to
              absorb more of the body moisture that condenses on the outside fabrics. I
              guess you might end up with a wet hammock & a drier sleeping bag. But since
              they're still in contact with each other, they're both be wet. I find that
              a small chamois cloth is ideal for wiping off the condensed moisture that
              tends to bead up on nylon fabrics-especially those with durable water
              resistance (DWR) treatments. I use it in the am before taking down the
              hammock.



              But remember that your body moisture will be driven to the outermost fabric,
              no matter if it is cotton or nylon. In most camping temperatures, as long
              as the fabrics are breathable, your body heat will drive the body moisture
              to the outermost fabric. I suspect both your sleeping bag & hammock had
              moisture (frost) on them where they were directly contacting the outside
              air-where the hammock fabric directly covered the sleeping bag fabric, only
              the hammock fabric should have had frost. It's usually the outermost fabric
              that collects the moisture-it's the fabric directly in contact with the cold
              air that collects the condensation. The warmth from your body is enough to
              drive your body moisture all the way thru multiple layers of breathable
              fabrics; except in extreme cold conditions. Only when your escaping body
              moisture meets a vapor barrier or a cold interface like the freezing outside
              air, will it stop & condense. In extreme cold situations, that cold
              interface could occur inside your insulation! Members of arctic expeditions
              sometimes find that their very, very thick sleeping bags keep getting
              heavier and heavier each night-it's because their escaping body moisture
              meets the cold interface & freezes before it reaches the outside of the
              insulation; they end up with ice accumulating inside the insulation & no way
              to get it out!



              Your reply suggests one of my favorite tricks for cold weather
              camping-wicking long johns. This fabric moves my body moisture to the outer
              side of the fabric leaving the inner side of the fabric (the side against my
              skin) dry. I'll even use wicking long johns inside a vapor barrier bag to
              keep wetness away from my skin..Ed



              Moderator, Hammock Camping List

              Author, Hammock Camping book

              Editor, Hammock Camping Newsletters

              Owner, Speer Hammocks Inc



              From: hammockcamping@yahoogroups.com [mailto:hammockcamping@yahoogroups.com]
              On Behalf Of m2b1997
              Sent: Tuesday, January 06, 2009 11:44 AM
              To: hammockcamping@yahoogroups.com
              Subject: Re: [Hammock Camping] Frost free?



              I agree Ed, that the moisture freezing around the mouth is to be
              expected, hence why I wasn't concerned by it or even thinking
              anything about. I was surprised by it for a second or so, night one
              or two, until I realized I should be seeing it.

              The sleeping bag seemed dry, just cold, as could be expected given 14
              degrees. It was the hammock though that had the frost on it, other
              than around the mouth. That's why I'm a bit perplexed. I hadn't
              thought about the body heat being lost but that does make perfectly
              good sense.

              Around the face the frost was the worst...but I still had it, ONLY on
              the hammock, all the way down at the feet. The weather was cloudy
              turned clear by morning, no precip overnight. In the several times I
              woke up overnight it was anywhere from partly cloudy to clear. I'm
              not sure what the dew point was. I'm going to have to pay a little
              more attention the next time and see if I notice that being the true
              culprit as it doesn't seem like the breath should be able to make it
              all the way down to the feet.

              Just one strange/stupid curiousity that has come up in my mind. In
              the case of winter camping would you be better off with a cotton
              versus a nylon hammock? Yes, this seems like a real dumb question,
              but think about it for a moment. During the summer months, nylon
              only, I wouldn't consider anything else otherwise, simple because of
              the rain. Winter months though, when you find yourself in a
              situation like I did last night the cotton hammock would have the
              tendency to absorb the moisture instead of the sleeping bag. This
              would keep the sleeping bag drier. There's nothing 'waterproof'
              around you to keep the moisture in so it collects on the sleeping
              bag. Am I wrong on this thinking? Is that why the hammock had the
              frost at the feet but the sleeping bag was dry? The thought just
              came to me as I was typing this.

              MEANT 2B
              GAME '97





              [Non-text portions of this message have been removed]
            • m2b1997
              Are sweat suits designed just like long johns. I never thought they was meant to wick the moisture just to keep the heat in? The idea for the vapor barrier as
              Message 6 of 13 , Jan 6, 2009
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                Are sweat suits designed just like long johns. I never thought they
                was meant to wick the moisture just to keep the heat in?

                The idea for the vapor barrier as I see it right now would be to wear
                nothing but keep your clothes between the vapor barrier and the
                sleeping bag, make sure to include a towel. Granted I haven't read
                up on the idea any but this is what makes the most sense right now.
                Your clothes would stay dry and you would stay warm. Just make sure
                you can change clothes in a flash. Sorry about the pun, couldn't
                resist.

                Definitely would have to have it set up as a vapor bag so when you
                went to get out the moisture would stay in the bag. Yeah, just
                thinking.

                Like I said I did 14 degrees last night and it wasn't that bad. Much
                better than 10 degrees on the ground a week or so ago. MUCH BETTER.
                Strangely it seems like it is warmer to stay off the ground than to
                stay on the ground. I've heard you and others talk about how you can
                get so much colder by sleeping in a hammock. I seem thus far to find
                the exact opposite scenario. I guess I need to push the limits to
                change things around.

                MEANT 2B
              • Dave Womble
                ... Ed... seems like this comes up every year about this time, and for good reason. I think you, I, and a lot of winter campers use some type of material to
                Message 7 of 13 , Jan 7, 2009
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                  --- In hammockcamping@yahoogroups.com, "Ed Speer" <ed@...> wrote:
                  >... I'd love to see vapor barriers discussed on this List for I know
                  > many of you have tried them with varying results. ...

                  Ed... seems like this comes up every year about this time, and for
                  good reason. I think you, I, and a lot of winter campers use some
                  type of material to breathe through in cold weather. I use a bandanna
                  or some type of fleece to breathe through in cold weather to keep from
                  getting a sore throat and to limit how much moisture I lose due to
                  exhaling. That cuts down on the frost or moisture also.

                  I know Ed had things to say about vapor barriers in his book on
                  hammock camping. Over the years I have tried to keep an updated
                  document on my thoughts about vapor barriers and it is probably a good
                  time to re-post that. Here it is:

                  My Thoughts on Vapor Barriers... again.

                  Vapor barriers aren't that easy to use if you don't understand what is
                  going on and they aren't that hard to use if you do. Does that make
                  any sense? If it does, you don't need to read any further. If it
                  doesn't, then read on and see if this helps.

                  I use plastic or silnylon as a vapor barrier between my hammock and my
                  SnugFit Underquilt. The suspension system on the SnugFit helps keep
                  the vapor barrier against the fabric of the hammock to minimize air
                  gaps that would encourage insensible perspiration to condense and
                  pool. With the vapor barrier held in place against the underside of
                  the hammock fabric, the hammock fabric wicks away any slight buildup
                  of insensible perspiration where it can more easily evaporate and I
                  usually don't even notice it. I pick when I do that and understand how
                  to use it. It is been very effective for me at extending the lower
                  temperature range that I can use my underquilt. I would not use a
                  vapor barrier when I was using the underquilt in warmer conditions
                  because then I would be dealing with sweat and there would be larger
                  amounts of sweat/moisture to deal with as the vapor barrier would
                  cause me to overheat even more and prevent moisture from sweat from
                  passing through the breathable underquilt.

                  In general, breathable insulation works best when your insulation is
                  getting too warm for you and less breathable insulation works best
                  when your insulation is not quite warm enough for you. That has
                  everything to do with how, when, and why your body produces sweat (or
                  sensible perspiration) and insensible perspiration.

                  Your body produces sweat to help cool off at the outer surface of your
                  skin with evaporative cooling when you overheat. Your body does not
                  produce sweat when you are not overheating... you don't just leak
                  water through your skin all the time. When you are not sweating, your
                  body can produce insensible perspiration to keep your skin from drying
                  out. If your skin is moist enough, or not too dry, your body doesn't
                  produce insensible perspiration because it senses that it doesn't need to.

                  It takes energy for your body to produce insensible perspiration. When
                  you are not overheating and your skin is not producing sweat, a vapor
                  barrier will cause your skin to quit producing insensible perspiration
                  after some period of time. Your skin quits producing insensible
                  perspiration because the vapor barrier creates a high humidity
                  environment by trapping the moisture from your previous insensible
                  perspiration. When this happens your body does not use energy to
                  produce that insensible perspiration anymore and can use that energy
                  to help keep you warmer. It a sense, your body becomes a more
                  efficient furnace.

                  A vapor barrier is not so good when used at the wrong time or when
                  used incorrectly. When you are overheating and using a vapor barrier,
                  your skin continually produces sweat as a means of cooling off via
                  evaporative cooling. The vapor barrier prevents the evaporative
                  cooling because the sweat is trapped by the vapor barrier. You just
                  keep sweating and moisture can build up. You need to do something to
                  keep from overheating because what your body is doing isn't working
                  because of the vapor barrier. You need to remove the vapor barrier,
                  vent, or remove insulation.

                  When you use a vapor barrier with breathable insulation between it and
                  your skin, that breathable insulation is subject to getting moist or
                  even wet from insensible perspiration. The insensible perspiration
                  will initially pass through the breathable insulation and stop when it
                  hits the vapor barrier. This continues until the humidity builds up
                  enough for skin to quit producing insensible perspiration. But until
                  that happens that breathable insulation is going to be getting moist
                  too. What you want is a thin wickable sheet of fabric between you and
                  the vapor barrier such that it can wick any slight moisture buildup
                  away where it can evaporate into the surrounding air. Of course it
                  helps for the surrounding air to be able to absorb that moisture
                  because if it can't, it won't and you will be clammy.

                  And of course, if you use breathable insulation between you and a
                  vapor barrier while you are overheating, you will soak that breathable
                  insulation with sweat (sensible perspiration). That is bad and that
                  happens when people don't understand how and when to use a vapor barrier.

                  When closed cell foam pads are used with breathable underquilts in
                  hammocks, we get a situation where the overall insulation is greater
                  than the sum of the various components making up the insulation. That
                  is because closed cell foam pads are also vapor barriers. The vapor
                  barrier stops your body from producing insensible perspiration and
                  causes the breathable underquilt to provide more apparent insulation
                  (although it isn't doing anything different) because your body is now
                  operating more efficiently at keeping you warm. If you use a ccf pad
                  that provides 20F worth of insulation with a breathable underquilt
                  that provides 40F worth of insulation by itself, you will end up with
                  more than 20 + 40 = 60F worth of insulation. You might end up with
                  70F worth of insulation or more.

                  You can also wear a vapor barrier to help stay warmer. You can do it
                  selectively for parts of your body or you can do it for your whole
                  body (but don't forget you need to breathe). You can use vapor
                  barrier liners for sleeping bags or plastic bags over your feet, head
                  (as a hat), torso, etc or rain suits. I haven't tried a vapor barrier
                  liner for a sleeping bag but have used a rain suit for a vapor barrier
                  (even breathable ones work) and used plastic bags over feet, head, and
                  torso with success. I always have used thin liner material under them
                  with the understanding they would likely get slightly moist from
                  insensible perspiration.

                  Vapor barriers work well for people that know when and how to use them
                  and are often problems or even disasters for people that don't.

                  [I am a little conflicted about this particular paragraph. On one
                  hand I feel it is important if this write up is going to be used as
                  somewhat of a reference for vapor barriers. On the other hand I don't
                  want to scare folks about a problem they aren't likely to encounterÂ…
                  but here goes.] Understanding vapor barriers, how to use them, when
                  to use them, and when not to use them becomes more important the
                  colder it gets. I don't have experience in extremely cold
                  temperatures but my understanding is that if you use breathable
                  insulation at extremely cold temperatures you risk insensible
                  perspiration condensing inside the insulation as the dew point
                  temperature moves inside the bag itself. Vapor condensing inside the
                  bag creates moisture inside the bag and is just as troubling as sweat
                  or any other moisture getting inside the bag. When this happens the
                  insulation may not dry out at the temperatures you find yourself in
                  and can accumulate over the days you are exposed to extremely cold
                  temperatures. This can be a troubling phenomenon if it occurs as your
                  bag can become increasingly heavier and less efficient. For most of
                  us this isn't an issue as I am referring to extremely cold conditions
                  and we shouldn't be concerned about the dew point moving inside the
                  bag itself at the more moderate cold conditions that most of us camp
                  or backpack in. I only mention it because it should be of interest to
                  the few individuals that are camping or backpacking in extremely cold
                  temperatures.

                  Dave Womble
                  aka Youngblood AT2000
                  designer of the Speer Segmented Pad Extender, SnugFit Underquilt, and
                  WinterTarp
                  May 13, 2008
                  Revised December 1, 2008
                • Hollis Easter
                  Dave, I ve been reading stuff about winter mountaineering for a few years now, and your explanation of the theory and practice behind vapor barriers is
                  Message 8 of 13 , Jan 7, 2009
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                    Dave,

                    I've been reading stuff about winter mountaineering for a few years now,
                    and your explanation of the theory and practice behind vapor barriers is
                    probably the most cogent I've read. It matches my own experience with
                    them, too.

                    Something I might add about vapor barriers is that they're somewhat
                    different from other forms of gear in that you need some acquired
                    learning before it'll work well for you. The first few times you use a
                    VB system, chances are good that you'll get something wrong, whether
                    large or small. Maybe you've got too much insulation, so you start
                    sweating. Maybe you forget about the VB liner on your sleeping bag, and
                    you bring your wet gloves and hat inside it with you, and they're
                    sponges in the morning. Maybe... you get the idea.

                    The point being that it's never a great idea to bring new forms of gear
                    out into the field without practicing at home, but it's an especially
                    poor choice if you're just learning to use VB. Sleep out in the backyard
                    for a few nights first, where it doesn't matter if you soak your
                    insulation or get cold or whatever.

                    There's a neat trick I stumbled onto accidentally while testing my
                    Hennessy SuperShelter--it'll prove the worth of VB to you. I was
                    sleeping out in 20 F weather, with wind. I had the space blanket in VB
                    position (pressed up against the hammock body, with insulation OUTSIDE
                    it). I didn't quite snug the space blanket up properly the first time,
                    though, and there was a spot on my shoulders that didn't have VB.

                    I slept really comfortably, and didn't notice any problems (including on
                    my shoulders). However, when it came time to pack up, it was easy to
                    tell where I'd missed the VB: the open-cell foam was wet enough that I
                    could wring some water out of it. It really illustrated the point.

                    You could try that on your own by wearing rain pants to bed and then
                    looking at the difference in condensation between your legs and torso on
                    the inside of the sleeping bag... or you could tape a trash bag to half
                    the underside of your hammock. There are lots of ways to mess with it.

                    VB is a really useful trick that, like ultralight gear, requires
                    knowledge to make it go. I loved your article; have you considered
                    sticking it in the files section of the Yahoo group?

                    Best,
                    Hollis
                    On Wed, Jan 07, 2009 at 12:40:36PM -0000, Dave Womble wrote:
                    > --- In hammockcamping@yahoogroups.com, "Ed Speer" <ed@...> wrote:
                    > >... I'd love to see vapor barriers discussed on this List for I know
                    > > many of you have tried them with varying results. ...
                    >
                    > Ed... seems like this comes up every year about this time, and for
                    > good reason. I think you, I, and a lot of winter campers use some
                    > type of material to breathe through in cold weather. I use a bandanna
                    > or some type of fleece to breathe through in cold weather to keep from
                    > getting a sore throat and to limit how much moisture I lose due to
                    > exhaling. That cuts down on the frost or moisture also.
                    >
                    > I know Ed had things to say about vapor barriers in his book on
                    > hammock camping. Over the years I have tried to keep an updated
                    > document on my thoughts about vapor barriers and it is probably a good
                    > time to re-post that. Here it is:
                    >
                    > My Thoughts on Vapor Barriers... again.
                    >
                    > Vapor barriers aren't that easy to use if you don't understand what is
                    > going on and they aren't that hard to use if you do. Does that make
                    > any sense? If it does, you don't need to read any further. If it
                    > doesn't, then read on and see if this helps.
                    >
                    > I use plastic or silnylon as a vapor barrier between my hammock and my
                    > SnugFit Underquilt. The suspension system on the SnugFit helps keep
                    > the vapor barrier against the fabric of the hammock to minimize air
                    > gaps that would encourage insensible perspiration to condense and
                    > pool. With the vapor barrier held in place against the underside of
                    > the hammock fabric, the hammock fabric wicks away any slight buildup
                    > of insensible perspiration where it can more easily evaporate and I
                    > usually don't even notice it. I pick when I do that and understand how
                    > to use it. It is been very effective for me at extending the lower
                    > temperature range that I can use my underquilt. I would not use a
                    > vapor barrier when I was using the underquilt in warmer conditions
                    > because then I would be dealing with sweat and there would be larger
                    > amounts of sweat/moisture to deal with as the vapor barrier would
                    > cause me to overheat even more and prevent moisture from sweat from
                    > passing through the breathable underquilt.
                    >
                    > In general, breathable insulation works best when your insulation is
                    > getting too warm for you and less breathable insulation works best
                    > when your insulation is not quite warm enough for you. That has
                    > everything to do with how, when, and why your body produces sweat (or
                    > sensible perspiration) and insensible perspiration.
                    >
                    > Your body produces sweat to help cool off at the outer surface of your
                    > skin with evaporative cooling when you overheat. Your body does not
                    > produce sweat when you are not overheating... you don't just leak
                    > water through your skin all the time. When you are not sweating, your
                    > body can produce insensible perspiration to keep your skin from drying
                    > out. If your skin is moist enough, or not too dry, your body doesn't
                    > produce insensible perspiration because it senses that it doesn't need to.
                    >
                    > It takes energy for your body to produce insensible perspiration. When
                    > you are not overheating and your skin is not producing sweat, a vapor
                    > barrier will cause your skin to quit producing insensible perspiration
                    > after some period of time. Your skin quits producing insensible
                    > perspiration because the vapor barrier creates a high humidity
                    > environment by trapping the moisture from your previous insensible
                    > perspiration. When this happens your body does not use energy to
                    > produce that insensible perspiration anymore and can use that energy
                    > to help keep you warmer. It a sense, your body becomes a more
                    > efficient furnace.
                    >
                    > A vapor barrier is not so good when used at the wrong time or when
                    > used incorrectly. When you are overheating and using a vapor barrier,
                    > your skin continually produces sweat as a means of cooling off via
                    > evaporative cooling. The vapor barrier prevents the evaporative
                    > cooling because the sweat is trapped by the vapor barrier. You just
                    > keep sweating and moisture can build up. You need to do something to
                    > keep from overheating because what your body is doing isn't working
                    > because of the vapor barrier. You need to remove the vapor barrier,
                    > vent, or remove insulation.
                    >
                    > When you use a vapor barrier with breathable insulation between it and
                    > your skin, that breathable insulation is subject to getting moist or
                    > even wet from insensible perspiration. The insensible perspiration
                    > will initially pass through the breathable insulation and stop when it
                    > hits the vapor barrier. This continues until the humidity builds up
                    > enough for skin to quit producing insensible perspiration. But until
                    > that happens that breathable insulation is going to be getting moist
                    > too. What you want is a thin wickable sheet of fabric between you and
                    > the vapor barrier such that it can wick any slight moisture buildup
                    > away where it can evaporate into the surrounding air. Of course it
                    > helps for the surrounding air to be able to absorb that moisture
                    > because if it can't, it won't and you will be clammy.
                    >
                    > And of course, if you use breathable insulation between you and a
                    > vapor barrier while you are overheating, you will soak that breathable
                    > insulation with sweat (sensible perspiration). That is bad and that
                    > happens when people don't understand how and when to use a vapor barrier.
                    >
                    > When closed cell foam pads are used with breathable underquilts in
                    > hammocks, we get a situation where the overall insulation is greater
                    > than the sum of the various components making up the insulation. That
                    > is because closed cell foam pads are also vapor barriers. The vapor
                    > barrier stops your body from producing insensible perspiration and
                    > causes the breathable underquilt to provide more apparent insulation
                    > (although it isn't doing anything different) because your body is now
                    > operating more efficiently at keeping you warm. If you use a ccf pad
                    > that provides 20F worth of insulation with a breathable underquilt
                    > that provides 40F worth of insulation by itself, you will end up with
                    > more than 20 + 40 = 60F worth of insulation. You might end up with
                    > 70F worth of insulation or more.
                    >
                    > You can also wear a vapor barrier to help stay warmer. You can do it
                    > selectively for parts of your body or you can do it for your whole
                    > body (but don't forget you need to breathe). You can use vapor
                    > barrier liners for sleeping bags or plastic bags over your feet, head
                    > (as a hat), torso, etc or rain suits. I haven't tried a vapor barrier
                    > liner for a sleeping bag but have used a rain suit for a vapor barrier
                    > (even breathable ones work) and used plastic bags over feet, head, and
                    > torso with success. I always have used thin liner material under them
                    > with the understanding they would likely get slightly moist from
                    > insensible perspiration.
                    >
                    > Vapor barriers work well for people that know when and how to use them
                    > and are often problems or even disasters for people that don't.
                    >
                    > [I am a little conflicted about this particular paragraph. On one
                    > hand I feel it is important if this write up is going to be used as
                    > somewhat of a reference for vapor barriers. On the other hand I don't
                    > want to scare folks about a problem they aren't likely to encounter*
                    > but here goes.] Understanding vapor barriers, how to use them, when
                    > to use them, and when not to use them becomes more important the
                    > colder it gets. I don't have experience in extremely cold
                    > temperatures but my understanding is that if you use breathable
                    > insulation at extremely cold temperatures you risk insensible
                    > perspiration condensing inside the insulation as the dew point
                    > temperature moves inside the bag itself. Vapor condensing inside the
                    > bag creates moisture inside the bag and is just as troubling as sweat
                    > or any other moisture getting inside the bag. When this happens the
                    > insulation may not dry out at the temperatures you find yourself in
                    > and can accumulate over the days you are exposed to extremely cold
                    > temperatures. This can be a troubling phenomenon if it occurs as your
                    > bag can become increasingly heavier and less efficient. For most of
                    > us this isn't an issue as I am referring to extremely cold conditions
                    > and we shouldn't be concerned about the dew point moving inside the
                    > bag itself at the more moderate cold conditions that most of us camp
                    > or backpack in. I only mention it because it should be of interest to
                    > the few individuals that are camping or backpacking in extremely cold
                    > temperatures.
                    >
                    > Dave Womble
                    > aka Youngblood AT2000
                    > designer of the Speer Segmented Pad Extender, SnugFit Underquilt, and
                    > WinterTarp
                    > May 13, 2008
                    > Revised December 1, 2008
                    >
                    >
                  • Ed Speer
                    Thanks Dave, your input is most valuable. You & I have discussed vapor barriers many times & I know your understanding comes from experience plus your
                    Message 9 of 13 , Jan 7, 2009
                    • 0 Attachment
                      Thanks Dave, your input is most valuable. You & I have discussed vapor
                      barriers many times & I know your understanding comes from experience plus
                      your analytical mind! Some descriptions of vapor barriers by other people &
                      posted on various sites are confusing or even outright wrong. Thanks for
                      taking the time to write down your thoughts & for sharing them with us.



                      I often say that all outdoor fabrics used for camping exhibit some form of
                      vapor barrier-some fabrics are just better than others. Even no-see-um bug
                      netting is a vapor barrier-just not a very good one. Bug netting does hold
                      in some of your body heat & blocks a bit of cold wind as seen on subfreezing
                      nights. I've even had snow inside my hammock when the bug net trapped some
                      of my expelled breath & allowed the moisture to condense, freeze & fall back
                      on my face as snow. In warmer temps, the bug net can trap enough body heat
                      & moisture to make me uncomfortably warm & clammy. So we all deal with
                      vapor barrier fabrics each time we camp. Dave's observation is correct that
                      we'll be more comfortable when we understand how vapor barriers work & how
                      to add, remove, or vent them when needed as conditions dictate. Sometimes
                      outside temperature & humidity changes during a single night might require
                      the camper to make appropriate changes to maintain comfort. While I wish it
                      was otherwise, no one fabric or vapor barrier is magically perfect for all
                      conditions-so its camper be ware..Ed



                      Moderator, Hammock Camping List

                      Author, Hammock Camping book

                      Editor, Hammock Camping Newsletters

                      Owner, Speer Hammocks Inc



                      From: hammockcamping@yahoogroups.com [mailto:hammockcamping@yahoogroups.com]
                      On Behalf Of Dave Womble
                      Sent: Wednesday, January 07, 2009 7:41 AM
                      To: hammockcamping@yahoogroups.com
                      Subject: Re: [Hammock Camping] Frost free?



                      --- In hammockcamping@yahoogroups.com
                      <mailto:hammockcamping%40yahoogroups.com> , "Ed Speer" <ed@...> wrote:
                      >... I'd love to see vapor barriers discussed on this List for I know
                      > many of you have tried them with varying results. ...

                      Ed... seems like this comes up every year about this time, and for
                      good reason. I think you, I, and a lot of winter campers use some
                      type of material to breathe through in cold weather. I use a bandanna
                      or some type of fleece to breathe through in cold weather to keep from
                      getting a sore throat and to limit how much moisture I lose due to
                      exhaling. That cuts down on the frost or moisture also.

                      I know Ed had things to say about vapor barriers in his book on
                      hammock camping. Over the years I have tried to keep an updated
                      document on my thoughts about vapor barriers and it is probably a good
                      time to re-post that. Here it is:

                      My Thoughts on Vapor Barriers... again.

                      Vapor barriers aren't that easy to use if you don't understand what is
                      going on and they aren't that hard to use if you do. Does that make
                      any sense? If it does, you don't need to read any further. If it
                      doesn't, then read on and see if this helps.

                      I use plastic or silnylon as a vapor barrier between my hammock and my
                      SnugFit Underquilt. The suspension system on the SnugFit helps keep
                      the vapor barrier against the fabric of the hammock to minimize air
                      gaps that would encourage insensible perspiration to condense and
                      pool. With the vapor barrier held in place against the underside of
                      the hammock fabric, the hammock fabric wicks away any slight buildup
                      of insensible perspiration where it can more easily evaporate and I
                      usually don't even notice it. I pick when I do that and understand how
                      to use it. It is been very effective for me at extending the lower
                      temperature range that I can use my underquilt. I would not use a
                      vapor barrier when I was using the underquilt in warmer conditions
                      because then I would be dealing with sweat and there would be larger
                      amounts of sweat/moisture to deal with as the vapor barrier would
                      cause me to overheat even more and prevent moisture from sweat from
                      passing through the breathable underquilt.

                      In general, breathable insulation works best when your insulation is
                      getting too warm for you and less breathable insulation works best
                      when your insulation is not quite warm enough for you. That has
                      everything to do with how, when, and why your body produces sweat (or
                      sensible perspiration) and insensible perspiration.

                      Your body produces sweat to help cool off at the outer surface of your
                      skin with evaporative cooling when you overheat. Your body does not
                      produce sweat when you are not overheating... you don't just leak
                      water through your skin all the time. When you are not sweating, your
                      body can produce insensible perspiration to keep your skin from drying
                      out. If your skin is moist enough, or not too dry, your body doesn't
                      produce insensible perspiration because it senses that it doesn't need to.

                      It takes energy for your body to produce insensible perspiration. When
                      you are not overheating and your skin is not producing sweat, a vapor
                      barrier will cause your skin to quit producing insensible perspiration
                      after some period of time. Your skin quits producing insensible
                      perspiration because the vapor barrier creates a high humidity
                      environment by trapping the moisture from your previous insensible
                      perspiration. When this happens your body does not use energy to
                      produce that insensible perspiration anymore and can use that energy
                      to help keep you warmer. It a sense, your body becomes a more
                      efficient furnace.

                      A vapor barrier is not so good when used at the wrong time or when
                      used incorrectly. When you are overheating and using a vapor barrier,
                      your skin continually produces sweat as a means of cooling off via
                      evaporative cooling. The vapor barrier prevents the evaporative
                      cooling because the sweat is trapped by the vapor barrier. You just
                      keep sweating and moisture can build up. You need to do something to
                      keep from overheating because what your body is doing isn't working
                      because of the vapor barrier. You need to remove the vapor barrier,
                      vent, or remove insulation.

                      When you use a vapor barrier with breathable insulation between it and
                      your skin, that breathable insulation is subject to getting moist or
                      even wet from insensible perspiration. The insensible perspiration
                      will initially pass through the breathable insulation and stop when it
                      hits the vapor barrier. This continues until the humidity builds up
                      enough for skin to quit producing insensible perspiration. But until
                      that happens that breathable insulation is going to be getting moist
                      too. What you want is a thin wickable sheet of fabric between you and
                      the vapor barrier such that it can wick any slight moisture buildup
                      away where it can evaporate into the surrounding air. Of course it
                      helps for the surrounding air to be able to absorb that moisture
                      because if it can't, it won't and you will be clammy.

                      And of course, if you use breathable insulation between you and a
                      vapor barrier while you are overheating, you will soak that breathable
                      insulation with sweat (sensible perspiration). That is bad and that
                      happens when people don't understand how and when to use a vapor barrier.

                      When closed cell foam pads are used with breathable underquilts in
                      hammocks, we get a situation where the overall insulation is greater
                      than the sum of the various components making up the insulation. That
                      is because closed cell foam pads are also vapor barriers. The vapor
                      barrier stops your body from producing insensible perspiration and
                      causes the breathable underquilt to provide more apparent insulation
                      (although it isn't doing anything different) because your body is now
                      operating more efficiently at keeping you warm. If you use a ccf pad
                      that provides 20F worth of insulation with a breathable underquilt
                      that provides 40F worth of insulation by itself, you will end up with
                      more than 20 + 40 = 60F worth of insulation. You might end up with
                      70F worth of insulation or more.

                      You can also wear a vapor barrier to help stay warmer. You can do it
                      selectively for parts of your body or you can do it for your whole
                      body (but don't forget you need to breathe). You can use vapor
                      barrier liners for sleeping bags or plastic bags over your feet, head
                      (as a hat), torso, etc or rain suits. I haven't tried a vapor barrier
                      liner for a sleeping bag but have used a rain suit for a vapor barrier
                      (even breathable ones work) and used plastic bags over feet, head, and
                      torso with success. I always have used thin liner material under them
                      with the understanding they would likely get slightly moist from
                      insensible perspiration.

                      Vapor barriers work well for people that know when and how to use them
                      and are often problems or even disasters for people that don't.

                      [I am a little conflicted about this particular paragraph. On one
                      hand I feel it is important if this write up is going to be used as
                      somewhat of a reference for vapor barriers. On the other hand I don't
                      want to scare folks about a problem they aren't likely to encounter.
                      but here goes.] Understanding vapor barriers, how to use them, when
                      to use them, and when not to use them becomes more important the
                      colder it gets. I don't have experience in extremely cold
                      temperatures but my understanding is that if you use breathable
                      insulation at extremely cold temperatures you risk insensible
                      perspiration condensing inside the insulation as the dew point
                      temperature moves inside the bag itself. Vapor condensing inside the
                      bag creates moisture inside the bag and is just as troubling as sweat
                      or any other moisture getting inside the bag. When this happens the
                      insulation may not dry out at the temperatures you find yourself in
                      and can accumulate over the days you are exposed to extremely cold
                      temperatures. This can be a troubling phenomenon if it occurs as your
                      bag can become increasingly heavier and less efficient. For most of
                      us this isn't an issue as I am referring to extremely cold conditions
                      and we shouldn't be concerned about the dew point moving inside the
                      bag itself at the more moderate cold conditions that most of us camp
                      or backpack in. I only mention it because it should be of interest to
                      the few individuals that are camping or backpacking in extremely cold
                      temperatures.

                      Dave Womble
                      aka Youngblood AT2000
                      designer of the Speer Segmented Pad Extender, SnugFit Underquilt, and
                      WinterTarp
                      May 13, 2008
                      Revised December 1, 2008





                      [Non-text portions of this message have been removed]
                    • Ed Speer
                      Hollis, great post! Your advice to try new gear at home before trusting to the outback is right on! Thanks for reminding us of this most critical safety
                      Message 10 of 13 , Jan 7, 2009
                      • 0 Attachment
                        Hollis, great post! Your advice to try new gear at home before trusting to
                        the outback is right on! Thanks for reminding us of this most critical
                        safety measure.



                        I too have a tale that illustrates just how effective a simple vapor barrier
                        can be. A few winters back, hammocking at home, I awoke in the am very snug
                        & warm, but with heavy frost covering the entire top & sides of my PeaPod
                        (which is a large down insulated sleeping bag that goes completely around my
                        hammock). I was using a thin plastic sheet as a vapor barrier between the
                        bottom of the hammock & inside the PeaPod-but no vapor barrier over the top
                        or sides of me. Apparently some of my body moisture rose during the night,
                        passed thru the insulation on top of me & condensed on the outer shell of
                        the PeaPod where it froze. As an experiment, I removed the plastic sheet
                        without opening the PeaPod more than a few inches. Within 3 minutes the
                        frost on my PeaPod had melted & I began to feel cold seeping into the
                        PeaPod! I think the plastic sheet worked fine, prevented loss of body
                        moisture & warmth on the bottom of the hammock & added noticeable warmth
                        overall. Upon removing the plastic sheet, more of the warm moist air inside
                        my PeaPod was allowed to rise & escape thru the top of the PeaPod quickly
                        melting the frost, even though the outside temp was still well below
                        freezing. At the same time, cold outside air below my hammock could now
                        enter the hammock thru the bottom insulation replacing the warm air inside &
                        making me cold. The plastic sheet apparently disrupted the normal
                        circulation of the warm air around my body inside the PeaPod & kept much of
                        it from rising, escaping thru the top insulation, & being replaced by the
                        inflow of cold outside air from beneath the hammock. So a simple vapor
                        barrier sheet beneath me not only worked on the bottom, but it also worked
                        on the top! I credit my simple 1mil painter's drop cloth plastic sheet (<2
                        oz) with adding 10-200F warmth! .Ed



                        Moderator, Hammock Camping List

                        Author, Hammock Camping book

                        Editor, Hammock Camping Newsletters

                        Owner, Speer Hammocks Inc



                        From: hammockcamping@yahoogroups.com [mailto:hammockcamping@yahoogroups.com]
                        On Behalf Of Hollis Easter
                        Sent: Wednesday, January 07, 2009 10:26 AM
                        To: hammockcamping@yahoogroups.com
                        Subject: Re: [Hammock Camping] Frost free?



                        Dave,

                        I've been reading stuff about winter mountaineering for a few years now,
                        and your explanation of the theory and practice behind vapor barriers is
                        probably the most cogent I've read. It matches my own experience with
                        them, too.

                        Something I might add about vapor barriers is that they're somewhat
                        different from other forms of gear in that you need some acquired
                        learning before it'll work well for you. The first few times you use a
                        VB system, chances are good that you'll get something wrong, whether
                        large or small. Maybe you've got too much insulation, so you start
                        sweating. Maybe you forget about the VB liner on your sleeping bag, and
                        you bring your wet gloves and hat inside it with you, and they're
                        sponges in the morning. Maybe... you get the idea.

                        The point being that it's never a great idea to bring new forms of gear
                        out into the field without practicing at home, but it's an especially
                        poor choice if you're just learning to use VB. Sleep out in the backyard
                        for a few nights first, where it doesn't matter if you soak your
                        insulation or get cold or whatever.

                        There's a neat trick I stumbled onto accidentally while testing my
                        Hennessy SuperShelter--it'll prove the worth of VB to you. I was
                        sleeping out in 20 F weather, with wind. I had the space blanket in VB
                        position (pressed up against the hammock body, with insulation OUTSIDE
                        it). I didn't quite snug the space blanket up properly the first time,
                        though, and there was a spot on my shoulders that didn't have VB.

                        I slept really comfortably, and didn't notice any problems (including on
                        my shoulders). However, when it came time to pack up, it was easy to
                        tell where I'd missed the VB: the open-cell foam was wet enough that I
                        could wring some water out of it. It really illustrated the point.

                        You could try that on your own by wearing rain pants to bed and then
                        looking at the difference in condensation between your legs and torso on
                        the inside of the sleeping bag... or you could tape a trash bag to half
                        the underside of your hammock. There are lots of ways to mess with it.

                        VB is a really useful trick that, like ultralight gear, requires
                        knowledge to make it go. I loved your article; have you considered
                        sticking it in the files section of the Yahoo group?

                        Best,
                        Hollis
                        On Wed, Jan 07, 2009 at 12:40:36PM -0000, Dave Womble wrote:
                        > --- In hammockcamping@yahoogroups.com
                        <mailto:hammockcamping%40yahoogroups.com> , "Ed Speer" <ed@...> wrote:
                        > >... I'd love to see vapor barriers discussed on this List for I know
                        > > many of you have tried them with varying results. ...
                        >
                        > Ed... seems like this comes up every year about this time, and for
                        > good reason. I think you, I, and a lot of winter campers use some
                        > type of material to breathe through in cold weather. I use a bandanna
                        > or some type of fleece to breathe through in cold weather to keep from
                        > getting a sore throat and to limit how much moisture I lose due to
                        > exhaling. That cuts down on the frost or moisture also.
                        >
                        > I know Ed had things to say about vapor barriers in his book on
                        > hammock camping. Over the years I have tried to keep an updated
                        > document on my thoughts about vapor barriers and it is probably a good
                        > time to re-post that. Here it is:
                        >
                        > My Thoughts on Vapor Barriers... again.
                        >
                        > Vapor barriers aren't that easy to use if you don't understand what is
                        > going on and they aren't that hard to use if you do. Does that make
                        > any sense? If it does, you don't need to read any further. If it
                        > doesn't, then read on and see if this helps.
                        >
                        > I use plastic or silnylon as a vapor barrier between my hammock and my
                        > SnugFit Underquilt. The suspension system on the SnugFit helps keep
                        > the vapor barrier against the fabric of the hammock to minimize air
                        > gaps that would encourage insensible perspiration to condense and
                        > pool. With the vapor barrier held in place against the underside of
                        > the hammock fabric, the hammock fabric wicks away any slight buildup
                        > of insensible perspiration where it can more easily evaporate and I
                        > usually don't even notice it. I pick when I do that and understand how
                        > to use it. It is been very effective for me at extending the lower
                        > temperature range that I can use my underquilt. I would not use a
                        > vapor barrier when I was using the underquilt in warmer conditions
                        > because then I would be dealing with sweat and there would be larger
                        > amounts of sweat/moisture to deal with as the vapor barrier would
                        > cause me to overheat even more and prevent moisture from sweat from
                        > passing through the breathable underquilt.
                        >
                        > In general, breathable insulation works best when your insulation is
                        > getting too warm for you and less breathable insulation works best
                        > when your insulation is not quite warm enough for you. That has
                        > everything to do with how, when, and why your body produces sweat (or
                        > sensible perspiration) and insensible perspiration.
                        >
                        > Your body produces sweat to help cool off at the outer surface of your
                        > skin with evaporative cooling when you overheat. Your body does not
                        > produce sweat when you are not overheating... you don't just leak
                        > water through your skin all the time. When you are not sweating, your
                        > body can produce insensible perspiration to keep your skin from drying
                        > out. If your skin is moist enough, or not too dry, your body doesn't
                        > produce insensible perspiration because it senses that it doesn't need to.
                        >
                        > It takes energy for your body to produce insensible perspiration. When
                        > you are not overheating and your skin is not producing sweat, a vapor
                        > barrier will cause your skin to quit producing insensible perspiration
                        > after some period of time. Your skin quits producing insensible
                        > perspiration because the vapor barrier creates a high humidity
                        > environment by trapping the moisture from your previous insensible
                        > perspiration. When this happens your body does not use energy to
                        > produce that insensible perspiration anymore and can use that energy
                        > to help keep you warmer. It a sense, your body becomes a more
                        > efficient furnace.
                        >
                        > A vapor barrier is not so good when used at the wrong time or when
                        > used incorrectly. When you are overheating and using a vapor barrier,
                        > your skin continually produces sweat as a means of cooling off via
                        > evaporative cooling. The vapor barrier prevents the evaporative
                        > cooling because the sweat is trapped by the vapor barrier. You just
                        > keep sweating and moisture can build up. You need to do something to
                        > keep from overheating because what your body is doing isn't working
                        > because of the vapor barrier. You need to remove the vapor barrier,
                        > vent, or remove insulation.
                        >
                        > When you use a vapor barrier with breathable insulation between it and
                        > your skin, that breathable insulation is subject to getting moist or
                        > even wet from insensible perspiration. The insensible perspiration
                        > will initially pass through the breathable insulation and stop when it
                        > hits the vapor barrier. This continues until the humidity builds up
                        > enough for skin to quit producing insensible perspiration. But until
                        > that happens that breathable insulation is going to be getting moist
                        > too. What you want is a thin wickable sheet of fabric between you and
                        > the vapor barrier such that it can wick any slight moisture buildup
                        > away where it can evaporate into the surrounding air. Of course it
                        > helps for the surrounding air to be able to absorb that moisture
                        > because if it can't, it won't and you will be clammy.
                        >
                        > And of course, if you use breathable insulation between you and a
                        > vapor barrier while you are overheating, you will soak that breathable
                        > insulation with sweat (sensible perspiration). That is bad and that
                        > happens when people don't understand how and when to use a vapor barrier.
                        >
                        > When closed cell foam pads are used with breathable underquilts in
                        > hammocks, we get a situation where the overall insulation is greater
                        > than the sum of the various components making up the insulation. That
                        > is because closed cell foam pads are also vapor barriers. The vapor
                        > barrier stops your body from producing insensible perspiration and
                        > causes the breathable underquilt to provide more apparent insulation
                        > (although it isn't doing anything different) because your body is now
                        > operating more efficiently at keeping you warm. If you use a ccf pad
                        > that provides 20F worth of insulation with a breathable underquilt
                        > that provides 40F worth of insulation by itself, you will end up with
                        > more than 20 + 40 = 60F worth of insulation. You might end up with
                        > 70F worth of insulation or more.
                        >
                        > You can also wear a vapor barrier to help stay warmer. You can do it
                        > selectively for parts of your body or you can do it for your whole
                        > body (but don't forget you need to breathe). You can use vapor
                        > barrier liners for sleeping bags or plastic bags over your feet, head
                        > (as a hat), torso, etc or rain suits. I haven't tried a vapor barrier
                        > liner for a sleeping bag but have used a rain suit for a vapor barrier
                        > (even breathable ones work) and used plastic bags over feet, head, and
                        > torso with success. I always have used thin liner material under them
                        > with the understanding they would likely get slightly moist from
                        > insensible perspiration.
                        >
                        > Vapor barriers work well for people that know when and how to use them
                        > and are often problems or even disasters for people that don't.
                        >
                        > [I am a little conflicted about this particular paragraph. On one
                        > hand I feel it is important if this write up is going to be used as
                        > somewhat of a reference for vapor barriers. On the other hand I don't
                        > want to scare folks about a problem they aren't likely to encounter*
                        > but here goes.] Understanding vapor barriers, how to use them, when
                        > to use them, and when not to use them becomes more important the
                        > colder it gets. I don't have experience in extremely cold
                        > temperatures but my understanding is that if you use breathable
                        > insulation at extremely cold temperatures you risk insensible
                        > perspiration condensing inside the insulation as the dew point
                        > temperature moves inside the bag itself. Vapor condensing inside the
                        > bag creates moisture inside the bag and is just as troubling as sweat
                        > or any other moisture getting inside the bag. When this happens the
                        > insulation may not dry out at the temperatures you find yourself in
                        > and can accumulate over the days you are exposed to extremely cold
                        > temperatures. This can be a troubling phenomenon if it occurs as your
                        > bag can become increasingly heavier and less efficient. For most of
                        > us this isn't an issue as I am referring to extremely cold conditions
                        > and we shouldn't be concerned about the dew point moving inside the
                        > bag itself at the more moderate cold conditions that most of us camp
                        > or backpack in. I only mention it because it should be of interest to
                        > the few individuals that are camping or backpacking in extremely cold
                        > temperatures.
                        >
                        > Dave Womble
                        > aka Youngblood AT2000
                        > designer of the Speer Segmented Pad Extender, SnugFit Underquilt, and
                        > WinterTarp
                        > May 13, 2008
                        > Revised December 1, 2008
                        >
                        >





                        [Non-text portions of this message have been removed]
                      • Jeff
                        Re: vapor barriers, I agree with the earlier posts. Here s my story. One night on the Foothills trail I slept in silkweight thermals, a fleece jacket, and my
                        Message 11 of 13 , Jan 7, 2009
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                          Re: vapor barriers, I agree with the earlier posts. Here's my
                          story. One night on the Foothills trail I slept in silkweight
                          thermals, a fleece jacket, and my waterproof breathable rain jacket.
                          My fleece was damp in the morning. The next night in similar
                          conditions, I moved the fleece to the outside...silkweights, rain
                          jacket, then fleece. I was much warmer that night and the fleece
                          didn't feel damp. So like Ed says, even though the jacket
                          is "breathable" it's still a pseudo-VB. Makes me want to experiment
                          with VBs more b/c it seems like a very convenient way to substitute
                          knowledge for gear.

                          Of note, Warbonnet Outdoors is making synthetic underquilts and half-
                          underquilts from sil, and underquilt covers to fit over down
                          underquilts. These can act as VBs under the hammock as well.

                          I'm thinking of my next system being a half-underquilt with the inner
                          shell made of sil, a torso-sized CCF pad for under my legs, and
                          possibly a hoodless poncho that can be used as a Garlington Taco to
                          add an extra pocket of dead air space for colder nights. Any
                          thoughts on this setup?

                          Re: the original question, I use a few things to cover my mouth
                          with. Usually it's a Serius brand neofleece facemask. It has little
                          breathe holes over the mouth, and a shaped nosepiece that leaves the
                          nostrils open. Even with the holes it stops a lot of moisture coming
                          out and warms the air a bit when I breathe it.

                          When it's colder, I'll use a balaclava. I've used the both together
                          when it's really cold...not the most comfortable but it's warm.

                          Jeff
                        • Dave Womble
                          ... Done and thanks for the kind words. Dave
                          Message 12 of 13 , Jan 8, 2009
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                            --- In hammockcamping@yahoogroups.com, Hollis Easter <easter@...> wrote:

                            >
                            > VB is a really useful trick that, like ultralight gear, requires
                            > knowledge to make it go. I loved your article; have you considered
                            > sticking it in the files section of the Yahoo group?
                            >
                            > Best,
                            > Hollis

                            Done and thanks for the kind words.

                            Dave
                          • Dave Womble
                            ... experience plus ... people & ... Thanks for ... us. ... form of ... no-see-um bug ... does hold ... subfreezing ... trapped some ... fall back ... body
                            Message 13 of 13 , Jan 8, 2009
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                              --- In hammockcamping@yahoogroups.com, "Ed Speer" <ed@...> wrote:
                              >
                              > Thanks Dave, your input is most valuable. You & I have discussed vapor
                              > barriers many times & I know your understanding comes from
                              experience plus
                              > your analytical mind! Some descriptions of vapor barriers by other
                              people &
                              > posted on various sites are confusing or even outright wrong.
                              Thanks for
                              > taking the time to write down your thoughts & for sharing them with
                              us.
                              >
                              >
                              >
                              > I often say that all outdoor fabrics used for camping exhibit some
                              form of
                              > vapor barrier-some fabrics are just better than others. Even
                              no-see-um bug
                              > netting is a vapor barrier-just not a very good one. Bug netting
                              does hold
                              > in some of your body heat & blocks a bit of cold wind as seen on
                              subfreezing
                              > nights. I've even had snow inside my hammock when the bug net
                              trapped some
                              > of my expelled breath & allowed the moisture to condense, freeze &
                              fall back
                              > on my face as snow. In warmer temps, the bug net can trap enough
                              body heat
                              > & moisture to make me uncomfortably warm & clammy. So we all deal with
                              > vapor barrier fabrics each time we camp. Dave's observation is
                              correct that
                              > we'll be more comfortable when we understand how vapor barriers work
                              & how
                              > to add, remove, or vent them when needed as conditions dictate.
                              Sometimes
                              > outside temperature & humidity changes during a single night might
                              require
                              > the camper to make appropriate changes to maintain comfort. While I
                              wish it
                              > was otherwise, no one fabric or vapor barrier is magically perfect
                              for all
                              > conditions-so its camper be ware..Ed
                              >
                              >


                              Ed, I can't agree more with you about various fabrics and descriptions
                              like vapor barrier, waterproof, and breathable. Our first inclination
                              is to treat those terms as absolute... if it is a vapor barrier then
                              it is a VAPOR BARRIER and no vapor can pass through it, if it is
                              waterproof then it is WATERPROOF and no water can pass through it, and
                              if it is BREATHABLE then it is breathable and vapor will always pass
                              through it. Turns out, it doesn't always work that way. In fact it
                              doesn't with many of the materials we use- especially fabrics. There
                              are conditions (or requirements, qualifiers, etc.) that we often
                              ignore or don't even hear that affect to what degree something is a
                              vapor barrier, or waterproof, or breathable. Sometimes those little
                              details are inconsequential, other times they make a difference in
                              whether something performs the way we expect.

                              Dave
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