Vapor Barriers

[TZBrown]

Hang_Time I'm Curious was that -20f or +20f

For me +20 is still to warm for a VB, at -20 I have had good luck, but you still need to moderate the top quilts to vent the moisture reflected upwards.

The only exception is if I use a very light top quilt and moderate from there

[BillyBob58]

Although not a true article of VBL clothing, I do remember wearing my Houdini windshirt through the night on a cold evening - that seemed to keep me quite warm, and also provided some vapor barrier quality to protect my UQ that night. It worked to some extent, but I see your point of essentially wrapping yourself in the VBL, as opposed to lying on top of it. Good point indeed.

No more space blanket for me, though.

Hang Time, It can truly be one of life's great mysteries. At the moment you're communicating with a man who has used a space blanket, on and off, for six years in his HHSS, And has never had a single condensation problem worth mentioning. Worst case scenario is finding a very few small drops of moisture on the space blanket at the lowest point under the hammock the next morning. But with neither me or any of my insulation perceptively damp. Plus there's all the times I've used a space blanket under the Hammock inside my Peapod. There are at least a few other people here who can report essentially the same experience. So what the heck is going on? Because there's also other people the report situations just as you have. Very hard to figure out. Maybe some of us don't put out any body vapor? I sure do sweat like a horse in warm weather.

Of course there are a bunch of variables to get right with the vapor barrier. Like keeping it warm and having no real insulation between you and the VB. This is one reason I lean towards vapor barrier clothing. So far it just seems nearly impossible for the dampness that occurs to also cause me to be cold. That moisture – whether dampness or sweat – cannot enter into any other insulation other than what I have sacrificed. That is, the very thin layer that is right next to my skin for comfort. In fact my favorite vapor barrier right now has a built-in fuzzy lining, so that I don't even use a separate liner. But then again, even though I like the VB clothing, I do have that long experience with the space blankets and so far without problems. Instead of problems only a significant increase in warmth and dry insulation every time. It's a mystery! To me anyway.

I'm guessing wild here, but what was the temperature rating of your under quilt – and for that matter top quilt? You said the Temps were in the mid-20s. And what else were you wearing other than a top quilt on top and an under quilt on the bottom? IOW, Is it even remotely possible that, before you got cold, that you were sweating? If so, that moisture would normally be absorbed into the down of your under quilt, and you would never notice it. At least until it happened enough to become a problem in the down insulation. Recently, Dirtwheels Used his 45° under quilt at 23° by adding a space blanket. ( and I think he was dry? ) But you can see that, if it's possible to get that much boost from a vapor barrier/radiant barrier that there might be some risk of sweating if used with a – say 20° – under quilt with temps barely into the 20s. I don't know, just guessing wild here!

Still, my experience is that even if I get noticeably wet inside the VB clothing, I don't get cold, in fact I am usually warmer than without the VB. But that is VB clothing, I can see where an SB might be different. With VB clothing, any moisture is pretty much trapped inside the VB with your body. It can't Evaporate (evaporative cooling). And it can't get any other insulation wet, wicking outward and carrying body heat with it and decreasing the loft. Unless you vent on purpose. Not so much with a space blanket. Over heat and sweat, and move around during the night, and I can see where any moisture that got on the Space blanket would be free to evaporate, and maybe float upwards into your top quilt, or into any jacket or long Johns that you might be wearing.

I guess there are all kinds of possible explanations, even though I don't really know what they are. But the mystery I'm always left with is why I ( And a few other folks) have not run into these problems, at least not so far, when other people do. Or to put it another way: why did a SB give Dirtwheels a 20+F boost and cause you to be cold just above the rated temp of your UQ? I don't know!

[drifter]

Here’s my experience on VB usage. Back in my ground dwelling days, my set up was a Therma Rest LE pad, Highland Feather 0* down mummy bag and an OR bivi sack. I would only break out the VB bag if it was going to be below freezing. I wore a very thin poly suit because I didn’t like my bare skin against the bag. This set up did create a very,very clammy feeling but I didn’t sweat or get cold (which I do easily). The only bad part was when I had to get out, at which point the chill factor from the moist suit would take my breath away! Having your day clothes ready to grab was a must.

[BillyBob58]

Here’s my experience on VB usage. Back in my ground dwelling days, my set up was a Therma Rest LE pad, Highland Feather 0* down mummy bag and an OR bivi sack. I would only break out the VB bag if it was going to be below freezing. I wore a very thin poly suit because I didn’t like my bare skin against the bag. This set up did create a very,very clammy feeling but I didn’t sweat or get cold (which I do easily). The only bad part was when I had to get out, at which point the chill factor from the moist suit would take my breath away! Having your day clothes ready to grab was a must.

Is that not a back handed testimony to the VBs effectiveness? That is a big sudden jolt of evaporative cooling which otherwise would have been going on all night, slowly but surely. And think of all of that moisture that was prevented from wicking from your bod through your insulation, or vapor radiating out into your insulation and, if conditions are right, condensing in the outer cold layers of that insulation! Instead, it was all there right next to your skin dying to escape and cause mischief!

But you are right, it can be "invigorating" to put it mildly and nicely! But usually for me, it evaporates so fast ( might depend on what you are wearing ) that it is over with quickly.

[Detail Man]

Some additional reading from our own HF members may be of some help.

Thanks for the link. Some very good info there.

Billy Bob, thanks for your comments as well. I've been learning a lot in the past couple of days about VBs. It's just not been cold enought to experiment with them so far this winter.

[BillyBob58]

Andrew Skurka has a write up on them on his site in the Blog section. Might be worth the look.

+1 on Andrew's article. It's a great summary:
http://andrewskurka.com/how-to/vapor...y-application/

.......................

Thanks for the link. Some very good info there.

Billy Bob, thanks for your comments as well. I've been learning a lot in the past couple of days about VBs. It's just not been cold enought to experiment with them so far this winter.

You are welcome. I was planning on doing a lot of new testing/experimenting with VBs last winter, but here in the south winter never came. But re: some of the experiments that I suggest people try - sitting around outside in the cold with a VB and little else to see how much you sweat: I have done some of that testing in a slightly different manner. Sitting around inside at temps around 69 or 70, wearing my Stephenson's Fuzzy stuff VB shirt as my only torso garment. Surprisingly pretty comfortable, with no sweat evident after an hour or so. Humid yes, but no sweat and really not all that bad in the "clammy" department. I really thought I would sweat at those temps, especially my back which was leaning against the recliner. When I feel like I can take some more wifely ridicule and rolled eyes for wearing my duct tape shirt, I will try it again for a longer period.

But I should just shut up: every one read the Andrew Skurka article linked to above. It does an excellent job of explaining the VB approach and it's use both for long trips in the deep freeze ( where it proved essential ) to even more every day, shorter trips or milder condition use. There are also some good comments with folks both agreeing and disagreeing with him. But you kind of have to pay attention to a guy who did 1400 miles in winter on the North Country Trail and then repeated the trip 2 years later, but this time using VBs. It is fascinating to read about his results in both situations. I saved a copy for future ref. Highly recommended.

One of the things he talks about is the poor availabilityl of VB clothing and why it is so. And the problems with VB pants while hiking. And I checked out one of the VB sources he referred to:
http://www.rbhdesigns.com/product/15...-nts-shirt.htm

Holy cow! Seems much nicer than Stephensons, but cost maybe 10 times more. I guess that would be the price of not having to wear a duct tape shirt? Plus has venting options and a hood. I was thinking about giving this info out for possible Christmas gifts, which is how I got my Stephensons shirt and socks. Then I saw the price. I'm sure it is much higher quality, and I think some of it has some minimal built in insulation. But way more $!

[MacEntyre]

My use of a VB layer is unconventional... I like to use a Molly Mac Gear Baby Orca, which is not vapor permeable, only above 40*F. Below 40*F I prefer vapor permeable down insulation.

- MacEntyre

P.S. I am not a fan of non-vapor-permeable clothing at all.

[Fronkey]

I have been experimenting with the entire RBH Vapor Barrier clothing system (Jacket with hood, socks, pants, mittens) and have had great success. I can't hike in above 10f weather because I cook in it.

Fronkey

[drifter]

Billy Bob, I like the way you described it better than I did “invigorating”. And you’re right it does evaporate fast. You look like someone that just stepped out of a hot tub with the steam rolling off of you.

[BillyBob58]

I have been experimenting with the entire RBH Vapor Barrier clothing system (Jacket with hood, socks, pants, mittens) and have had great success. I can't hike in above 10f weather because I cook in it.

Fronkey

OK then, I guess you should know, way up in MN! That stuff is expensive, but it looks very well designed and of high quality!