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Vapor Barrier question
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David Olsen
(oware)

Locale: Steptoe Butte
Re: Vapor Barrier question on 01/26/2009 11:00:09 MST Print View

Patagonia chose not to use eVent due to durability issues.

I don't see how it would be MORE durable than cubenfiber, even
in a lighter weight. The lightest eVent I know of is still
over 2 ounces per square yard.

David Olsen
(oware)

Locale: Steptoe Butte
Re: Re: Vapor Barrier question: WB semi-barrier on 01/26/2009 11:09:47 MST Print View

I used a Goretex shelled Northface bag for 5 years of full
time guiding and never had a problem with condensation.
It did eventually de-laminate, but Northface replaced it.

It was called the Gold Kazoo.

In very cold conditions, (-10 F) when out for 4 weeks at a
time, I used a polarguard overbag, which worked very well.

I don't know how the Goretex shell would have worked at
-40 as the outer layer but-

I have used Goretex bivys as stand alone shelter on long trips
to -5. At times I used a VBL, which did help a lot in increasing warmth for the
long haul, but I can think of only 2 times I noticed
serious condensation issues with the Goretex bivy, while
under the stars and no VBL. Both times I was sleeping
within a few feet of water and the humidity was
very high.

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: Vapor Barrier on 01/26/2009 11:51:52 MST Print View

>Yes but Cuben is not at all breathable. Doesn't this bring us full circle to the condensation problem?

The cuben comment was in reference to the *theory* that in a perfect VBL system you wouldn't need a breathable fabric at all, but also to point out that not all cuben is fragile and leaky as you implied:

>no need to use eVent unless you want durability and a higher hydrostatic head, which is irrelevant in a tent.

Maybe the 0.36oz per yard stuff is, but it is unfair to compare a 2oz per yard fabric to a 0.36oz per yard fabric when it comes to durability and waterproofness.

As mentioned before David, you were lucky, or living the ideal conditions, if you never had condensation problems with a GoreTex covered bag. Neither Roger or myself have a vested interest in making up condensation issues with this system. His wife and I both noticed problems, and in different conditions. At minus 40, my situation could have been deadly if habitation wasn't close by. Then again, I've also had condensation in a momentum covered bivy when the conditions are right (as you experienced, high humidity etc...), so sometimes it's inevitable without a VBL. The trick is to know when you are going to experience those conditions and be prepared. If you've only seen it once in a long life in the hills, then you must live in a very dry but not too cold environment.

The more I think on this topic, the more motivated I am to make that cuben quilt!

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Vapor Barrier question on 01/26/2009 12:57:14 MST Print View

Hi -

New member here. As a personal note, I don't like VBL clothing. Other than sleeping, I find them as a single use item. Don't work as a windshell, because they don't breath.

I use a Integral Designs Sleeping Bag VB Liner in sub-freezing weather along with my WM UltraLite Sleeping Bag (20F) and a water proof bivy. As a single use item, it weighs 6.1 oz, and is lighter than most VBL clothing set-ups I have found. I also sleep better with the liner, rather than VBL clothes. The only purpose of the VBL is to control condensation on my bag. In warmer weather, when I need a bivy and condensation is not an issue, I use a MLD Soul Bivy Zip under a poncho. This set-up really works well for me.

- Nick

Dave U
(FamilyGuy) - F

Locale: Rockies
Vapor Barrier question on 01/26/2009 13:41:20 MST Print View

"Maybe the 0.36oz per yard stuff is, but it is unfair to compare a 2oz per yard fabric to a 0.36oz per yard fabric when it comes to durability and waterproofness."

No it isn't. If I want something with more durability and waterproofness then I will go for 2 oz eVent.

@David Olsen - please provide the tear strength and hydrostatic head for the cuben you are referring to. Thanks,

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: Vapor Barrier question on 01/26/2009 16:31:55 MST Print View

>No it isn't. If I want something with more durability and waterproofness then I will go for 2 oz eVent.

You're assuming the eVent is more durable and waterprrof than 2oz per yard cuben? I seriously doubt it...anyone have the stats on 2oz cuben???

David Olsen
(oware)

Locale: Steptoe Butte
Re: Re: Vapor Barrier on 01/26/2009 18:13:41 MST Print View

I don't think lucky. During the 5 or so years I had the Gold
Kazoo, I slept in it the whole time, even when I wasn't
working. I was in the Winds, the Sierra Nevada, the North
and Central Cascades, Eastern Oregon in Winter, Joshua Tree
in Winter, Arkansa, Colorado, and the Olympics of Washington.
While much of it was dryer places, not all and most of my
time was during shoulder or winter trips. The Gore product
may have been their first generation version without the
plastic protective film. I bought the bag in 1981.

The bivysacks I have used tho, were more recent Goretex2.
I have used bivys of Bion2, which was less breathable
and had little problems with that too.

Maybe I don't sweat like some.

David Olsen
(oware)

Locale: Steptoe Butte
Re: Vapor Barrier question on 01/26/2009 18:15:06 MST Print View

I don't have a hydrostatic head for Cuben fiber.
Maybe I will play with some of the scraps of eVent and
Cuben I have.

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: Re: Re: Vapor Barrier on 01/26/2009 18:59:08 MST Print View

>Maybe I don't sweat like some.

Maybe. Or maybe you run on the hot side, so your perspiration never reaches the dew point before it hits the outer layer. Certainly, for me to have significant condensation inside a Momentum bivy indicates that I am not generating enough heat to push the vapour through. Maybe it's a female thing...we DO have lower metabolic rates than the guys (on average), but also tend to sweat less (especially on cold nights). It's not like I'm going "Oh my gosh, it's minus 20 and Im roasting in here"! Maybe my bags had too much loft for me to heat completely??? Doesn't matter-bivy or not, I go for a VBL when temps get substantially sub-freezing.

David O, do you have a variety of cuben fabric weights to play with?

Stephen Klassen
(SteveYK)
VBL and not on 01/27/2009 00:34:01 MST Print View

I have experience with Gore Dryloft vs Gore-tex covered sleeping bags over 11 nights where the temps were -20 to -10 C.

We didn't have VBL's with us. I had the dryloft bag, and I would simply leave it zipped up in the double wall tent for 15-30 minutes before stuffing it. The loss of loft over the trip was not noticeable (we dried out in a hut on the 5th night).

My two tentmates had Gore-tex covered bags - they wetted out by the end of the first and sixth nights, and they slept cold the rest of the trip, other than at the hut.

Reading what Mike Clelland writes here at BPL (and Jo Anne Creore in her book), I think I could get my Dryloft bag to work at -30C for an extended period, without VBL. -40C? Probably not. Not with my current skill set.

But for the last 10 years I've used a VBL bag. I was using an FF VBL (sylnylon with a half zip) with polypro and it worked very well for me. This winter I tried a Hot Sac with thin merino wool, and I started to get wet. I don't know if it's the Hot Sac or the wool, so I will have to try the different combos. Sure would like to keep the wool.

I tried the Dancing Light raingear as VBL clothing, but it didn't work for me. I'm small, and I lose heat too quickly through my extremities. Like wearing gloves when you need a mitt.

Some friends suggested that I make a non-breathable shelled bag, since I use the VBL bag - but that doesn't work. When I get to a hut, I can't use the VBL without getting soaked.

If anyone using VBL found they got more wet when using wool rather than synthetic underwear, please let me know.

nanook ofthenorth
(nanookofthenorth) - MLife
VBL vests on 01/27/2009 01:05:29 MST Print View

I just got back from a day of ski touring in sustained -25C weather (sometimes a little warmer, sometimes a little colder)over the weekend and had mixed reviews on a Golite Vapor Vest that I was wearing (silnylon on the back, thin breathable nylon on the frount).
Wearing that vest overtop a Cap 2 t-shirt and under a Cap 4 and R1 pullover and a EPIC hoody, I REALLY liked the vest for stoping the wind and for keeping my back insulation dryish.
Still I found that the moistere trapped at my back stayed there and eventually became clammy, a little chilling and very uncomfortable. I was wearing a pack most of the time and would like to try again w/o the vest.
Still, not sure what to think of the whole exparmint.
The clothing was apropreat to the temprature/effort involved

Huzefa Siamwala
(huzefa) - M
A possible solution VB wetness on 01/27/2009 01:52:28 MST Print View

edit: Just a thought:

Wear your WPB jacket/pants under your VBL.

This will add warmth, while at the same time keep you dry under your VBL.

Edited by huzefa on 01/27/2009 20:16:28 MST.

Jon Rhoderick
(hotrhoddudeguy) - F - M

Locale: New England
Re: Re: Vapor Barrier question on 01/27/2009 07:29:58 MST Print View

Does anyone have tips with integrating insulating clothing into a sleep system while using a vapor barrier liner (not clothes)?

Huzefa Siamwala
(huzefa) - M
Re: Re: Re: Vapor Barrier question on 01/27/2009 08:14:07 MST Print View

..

Edited by huzefa on 01/27/2009 20:17:18 MST.

Daniel Strange
(strangdj) - F
WPB inside a vapor barrier on 01/27/2009 09:02:50 MST Print View

What Huzefa posts about wearing WPB clothing inside a VB liner is interesting but I think misguided. WPB clothing only transports moisture from high humidity to low. As soon as you have a very high humidity inside the VB liner then the WPB clothing will cease transporting moisture and the moisture will back up into your insulating clothing.

I think a better option if you are using a VB liner is to simply drape your insulating clothing on top of the liner, or even on top of your SB.

Huzefa Siamwala
(huzefa) - M
Re: WPB inside a vapor barrier on 01/27/2009 10:35:53 MST Print View

I know it sounds like I was giving some advice here but I was just sharing a thought.

Daniel brings up an interesting point. I suppose most WPB do work in high humidity but not very well.

>As soon as you have a very high humidity inside the VB liner

I had like to know how long would that take. 8 hours of insensible perspiration?

James Dubendorf
(dubendorf) - M

Locale: CO, UT, MA, ME, NH, VT
MYOG VB Liner Test Last Night on 01/27/2009 11:22:45 MST Print View

Stephen,

Interesting- if a trip incorporated stops in huts or cabins, this certainly would test the limits of a system where VB and insulation could not be separated.

Jon,

Some ideas that have been put forward so far about incorporating clothing as insulation with a VB liner in an SB include include arranging items like jackets and vests outside the liner, putting the foot end of a VB inside a jacket or vest, and wearing the liner up to just below the armpits, therefore allowing for the option of wearing a jacket or vest while sleeping. It would seem this option would compromise, to some extent, the main goal of the liner, which is to prevent internal moisture from getting into the SB. While I've not experimented at all with heavier layers inside the liner, from what I've read it seems less effective- more layers to get wet, less chance of establishing that elusive VB microclimate around the skin, etc. VB clothing would seem to be more flexible in this regard, and yet others have said they still prefer a liner. No experience with VB clothing here.

I'll share the results of last night's backyard VB test session in low temps around 2F, cold enough to render an msr windpro chilled to air temps intert even with an inverted canister. Yes I know most stay inside in this weather, but I prefer to see my behavior as motivated by a passion for scientific knowledge (thanks to Roger C.) rather than an indication of deeper psychological unrest.

While I know many use VB liners effectively, and in much more extreme temps, my experience may be of interest to VB novices interested in extending the range of their sleep system and experimenting before making larger investments in VB gear. My MYOG VB liner consists of 3 hefty ultra flex large trash bags (30 gal, 113 l) taped end to end, with a doubled-over section near the head through which a line was run with a toggle for tightening- the toggle was operable from the inside, and this helped tremendously.

I slept in an mld soul bivy, on top of plenty of ground paddage, using an rei sub kilo 20F down bag, later complemented by an mh phantom down bag. Inside the liner I wore merino midweight layers, including gloves and liner socks. On my head a neckwarmer and warm fleece hat, underneath which I wore a buff (those tubular things).

First, the experience of a VB in temps from 20-25F versus 0-5F was a very different experience. While the higher temps made the VB, for me, clammy and unpleasant, I never experienced much moisture in the VB liner last night. The ability to effectively cinch the top of the VB (from the inside) helped keep it in place and seal warm air in. I stuffed the mh phantom SB into my bivy in the middle of the night to help with cold feet, but in retrospect stuffing the end of the liner in an insulated vest probably would have sufficed, and I did eventually overheat with the phantom in place.

While the full VB liner arranged up to the head regulates almost all interior moisture, the main disadvantage is that one's arms are inside the bag, making it impossible to adjust anything outside the liner while inside it. Taking steps to make sure your pillow or additional pieces of insulation don't move much in the night will make things more comfortable. With the liner up to the armpits, arms are free, and one can wear a jacket or vest on their body with the VB in place. In practice, with the liner in this position, a small amount of frost did form on the inside bivy surface above my upper body, most likely moisture from arms, chest, etc. Farther down towards the legs, everything stayed perfectly dry.

Roger wondered about the durability of the trashbag VB liner. I've seen no indications of wear, though the liner does include dust tape at certain stress points. I'm sure, though, that the primary merits of the trashbag liner are its easy repair, and its minimal expense.

As I get better at using the liner, I may find it easier to use it in full length form. Wearing it 3/4 length allows use of arms, yet also compromises moisture management to some degree. There is always the option of starting the evening at 3/4 length, and drawing it full length as things chill down.

Anyhow, I enjoyed the experiment, and would be eager to hear from others who have developed useful tricks with their VB liners. I am still trying to figure out how best to deal with frost from respiration forming around the head of the bag- breathing through material does seem to help. I am also investigating ways to fix in place the lip of my bivy so that it stays close to the breathing hole of the SB so that most condensation occurs on the bivy itself.

nanook ofthenorth
(nanookofthenorth) - MLife
... on 01/27/2009 11:28:48 MST Print View

I would bet (if your moving fast, say as part of a rope team sking) - maybe an hour, hour and half, at most.

It would be less confusing if when your forming a thought, or had no personal experice, you indicated as such in your response.

Besides the point of the vbl vest was to keep my back insulation dry. Thats hard to do when the vbl is on the outside of everything.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: MYOG VB Liner Test Last Night on 01/27/2009 14:33:44 MST Print View

Hi James

I will admit I had not expected such a fast response! But very interesting stuff, for which much thanks. I have summarised, with some Qs.

> My MYOG VB liner consists of 3 hefty ultra flex large trash bags (30 gal, 113 l) taped end to end, [with drawcord]
This is cheap enough for anyone to try it out.
* Could you give the ruler dimensions of the bags maybe?

> I slept in an mld soul bivy, on top of plenty of ground padding,
The insulation underneath is a critical factor, always.

> the experience of a VB in temps from 20-25F versus 0-5F was a very different experience.
Yes indeed. The comment from others has been that you need to be below 20 F to justify a VBL. Also you need to sleep a bit cool for best comfort.

> the main disadvantage is that one's arms are inside the bag, making it impossible to
> adjust anything outside the liner while inside it.
This is rather like being inside a cinched mummy bag of course.
* Did you have your pillow inside the VBL?

> the durability of the trashbag VB liner. I've seen no indications of wear, though the liner does include dust
> tape at certain stress points. I'm sure, though, that the primary merits of the trashbag liner are its easy repair,
> and its minimal expense.
* A photo would be great if possible? Where did you reinforce?

> I am still trying to figure out how best to deal with frost from respiration forming around the head of
> the bag- breathing through material does seem to help.
* So did you have the VBL over your head as well, or was your head sticking out? Not clear.

I have woken up vaguely wondering why snow was falling on my face. It was the water vapour from my breath condensing and freezing in the air above my head, and falling back down on me! I found that sleeping with my mouth shut was better...

Cheers

Jim Colten
(jcolten) - M

Locale: MN
Re: MYOG VB Liner Test Last Night on 01/27/2009 14:51:55 MST Print View

James,

Thanks for the nice test report.

Yes I know most stay inside in this weather, but I prefer to see my behavior as motivated by a passion for scientific knowledge (thanks to Roger C.) rather than an indication of deeper psychological unrest.

ya know, I'll have to try that line on my wife and neighbors ... ya think they'd grown accustomed to me doing that sort of thing after all these decades.

Edited by jcolten on 01/27/2009 14:52:56 MST.