I'm confused too. I think the next step is to try the VB liner again up to my neck. I did try some VB clothing (suit) but it wasn't cold enough to wear that - only around 30° outside. But that's a prime temp for the problem to happen, so I kinda give up.Originally Posted by BillyBob58
Yep, it's crazy. One trick I have found to using VBs is to use less insulation than normal. Sometimes way less, especially if exercising, hiking. So, normally you probably wouldn't us a 40F quilt if it was 25 or 30. But maybe worth an experiment with a VB? From neck to feet, or VB clothing. But still, I admit, I would think that if a VB was going to help, it would have helped if you had everything but arms and upper most chest covered. When I did my most extreme VB test at 6F, my hands were not covered, and on my legs I only had a faux VB in the form of waterproof but supposedly breathable rain pants(+ a frost bib hanging from the RL). Still, bone dry, except for the bib. Inside a sock even!
Then again, even without a VB or frost bib I have not experienced the consistent problems you have . Though my TQ does tend to get soaked near my face with out the bib. Yours is a tough case!
Hey, here is an experiment for you some time. You say it has not been cold enough for a VB? And maybe you don't have a 40F or 50F TQ? How about, at 30 or 40F, trying some VB clothing under the warmest, puffiest clothing you have, with no TQ? Or maybe also with that fleece blanket over you if needed? Just for fun?
Haha! Yes! I was sleeping in a low temperature sauna, that is, I had a huge amount of water vapor making it sticky for my bare hands. I had all of my long sleeves and socks on, so those parts of me didn't stick to each other. The emergency blanket lasted for five or six nights before it completely shredded, but with each progressive night, either my brain adjusted to the high humidity or my skin lost less moisture. Overall it was pleasing to sleep warm and not have to hope for a sunny day to burn off the moisture in my quilt.
This is very interesting. Even air at a low temperature may have some water in gaseous form. When you pull your quilt out of the stuff sack it will expand & draw air into the insulation. If body heat can cause air in the quilt insulation to move toward the surface of the quilt, it will condense (can heat move without the air moving, too? Well, if we heat a copper bar, do the molecules at the heated end move to the other end along with the heat?). If the vapor barrier is 100% efficient, then that limits the amount of condensation at the surface of the quilt from the air within the insulation of the quilt. That was long. Do I make any sense?
Will cold moist air condense when it comes into contact with warm air? I wouldn't expect cold moist air to condense on the outside of a very hot cup of coffee, but just because I haven't seen it doesn't mean it can't occur in this or another universe.
Minor clarification: when I wrote "...experience with a mylar emergency blanket in the Sierra Nevada at subzero temperatures. " I meant zero degrees Celsius, or subfreezing. Poor editing for a mostly non metric culture.
Yep, that is why many VB users tend to wear our thinnest and quickest drying layers, and not much else, between our skin and the VB. As a layer that feels more pleasant against our skin than the VB would, but also a layer they are willing to sacrifice, realizing it certainly will be in high humidity, and may well also get wet. But personally, I find those layers do dry quickly. Particularly the built in super thin layer of "Fuzzy stuff" on the inside of the Stephenson's Warmlite VB clothing. I have to actually get hot and sweat before I notice the moisture when I sleep in that clothing. But, pick your poison, I guess. You can have a humid or even be wet at skin level, or you can have a damp, cold quilt in some conditions. One that gets damper by the night. It appears that you now make the same choice as I do in that area.
It is an interesting thought, because it is looking at it from somewhat the reverse of normal. Rather than "Will cold moist air condense when it comes into contact with warm air?", what we normally see is - everywhere, all the time- is moister in warmer air condensing when it contacts the dew point. Whether the air in front of our face as we exhale on a cold day, or when our breath contacts our quilt shell hear our face or the inside if a tent wall or "sock" or over cover we are using around/over our hammock, or our car windshield. Or how about our sun or regular eye glasses, cold from the car AC, when we step outside on a hot, humid day down south? The glasses are the dry, cold surface that the warm, moist outside air condenses on and blinds me for a minute. Or, how about wearing masks these days hoping to not catch or transmit the Covid-19 virus? Any one else have to deal with condensation on glasses? I know a bunch of us do. Same situation yet again: warm exhaled vapor is directed upwards by the mask, where it contacts the cold, dry surface of our eye glasses, boom, suddenly hard to see.
Now picture the reverse: external, cold, moist air is brought into contact with a warm surface, like the windshield that is well heated with a defroster. Probably not the best example, because the defroster has limited ability to warm the windshield all the way through. But still, in general, the warmer we can get that windshield, the less condensed moisture we will see inside and out, right? Or, how about in your example: take your cup of hot coffee outside into high humidity freezing temps. I'm like you, I have never seen condensation under those conditions, but maybe it can happen? I think I will soon put that to the test!
OTOH, many have all seen moisture or frost accumulate all over our hammocks, tarps and outer surface of our quilts. I think I have seen this even worse, a lot worse, when I am not in the hammock and quilt, keeping them warm. When I have put them up before sunset, then go back out at bed time to do some cold testing. So, is that a case of dry warm air in the quilt being contacted by the cold, moist outside air? If so, where is the warm air coming from if no one is in the hammock/quilt? So I don't know, I suppose it is possible. But even if possible, it must be very self limiting, not taking long for whatever moisture is inside the quilt to be driven out by body heat. Hence your recent experience with the space blanket? You warmed the air up in your quilt I'm sure, which proceeded to contact the outside cold air, but you still ended up with a warm, dry quilt, right?
One thing: I think I have read about a phenomenon where nylon surface end up being super chilled even colder than air or ground temps. Like with a tarp or sleeping bag under the stars. This can result in shell temps colder than the air temp, leading to all of that condensation I have oft observed. I just found the article, it is subscription and I can not copy, but I will summarize in next post.
Good examples of how moisture from atmosphere will in fact cause water to condense on objects.
OK, I found( at Backpackinglight dot com) the ( or an ) article(not the same one I was thinking of) on the subject of condensation not related to moisture being put out by a person. They suspended sections of various outdoor materials maybe 3 feet above the ground, and condensation was observed over 12 nights. Despite high humidity and cool temps, they did not get condensation on many nights. They usually got more condensation ON THE TOP SURFACE than on the bottom surface that was closer to any moisture that might have been coming from the ground! (that was a surprise to me) This was believed to be because the top surface was usually colder(they measured) than the bottom, and often often several degrees COLDER THAN AIR TEMP! This was thought to be due to radiation, more radiant heat loss on the top surface. So, with these surfaces actually colder than air temp, condensation often occurred, without the contribution of any warm vapor from humans. Wind, cloud and tree cover reduced this effect. The fabric with the least condensation was: aluminized fabric, because they absorb and emit less IR radiation, and resist cooling below ambient air temp at night.
So, this helps explain why I have sometimes gone back outside to find the surface of hammocks, quilts and most often tarps covered with water or frost when I have not been out there pumping out vapor from my breath or body which can then condense on top of all nearby fabrics. But also leaving me to wonder, if I warm up a quilt with body heat, with or without VB use, will I reduce this tendency towards condensation of the moisture in the air on the surface of my quilts? Will my escaping body heat(hopefully not too much little escaping)warm the surface of my quilts enough to keep them from becoming even colder than ambient air and keep them above the dew point? I don't know, but I suspect though, except I am now adding lots of body vapor into the mix, barring VB use. Now, OneClick, is there any way to apply all of this to your problem? I'm not sure.
That sort of explains why I have noticed when I use my bug net in winter my exterior materials get damp and inside bug netting does not. Cold yes but not damp.
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