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Anne Walker
(JonnyWalker) - F
Bivy Condensation on 11/24/2010 22:42:46 MST Print View

Is a bivy more likely to condensate with a bag that is a bit too warm for the conditions?

R C
(beenay25) - F

Locale: Midwest
Re: Bivy Condensation on 11/24/2010 22:44:18 MST Print View

Yes.

Dave U
(FamilyGuy) - F

Locale: Rockies
Bivy Condensation on 11/24/2010 22:53:21 MST Print View

Depends on the breathability of the sleeping bag shell, the breathability of the bivy fabric, whether or not you sweat, what the dew point temperature is, and whether you use the bivy under a tarp or not.

There are several factors to consider.

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
eVent on 11/24/2010 23:07:27 MST Print View

Buy an eVent bivy sack and be done with it. If you have condensation it will be minimal.

R C
(beenay25) - F

Locale: Midwest
Re: eVent on 11/24/2010 23:10:15 MST Print View

Do you own an eVent bivy sack? Just curious what made you say that.

Edited by beenay25 on 11/24/2010 23:10:46 MST.

eric chan
(bearbreeder) - F - M
Sweat on 11/24/2010 23:49:04 MST Print View

The more you sweat the more moisture there is in a system ... If you feel too warm vent the bag and zip it up later if yr cold

Event bibies will still get some condensation occasionaly, but short of a dwr bivy anything else will have more

Travis Leanna
(T.L.) - MLife

Locale: Wisconsin
Re: Sweat on 11/25/2010 00:47:08 MST Print View

I have a hard time managing my sweat without a bivy.

There are a lot of factors that will come into play, but as a general rule, any layer you add will increase the possibility of condensation, no matter how breathable it is.

Although eVent fabric is very breathable, you're still inhibiting the transfer of moisture to a certain degree.

Alex H
(abhitt) - MLife

Locale: southern appalachians or desert SW
all bivy's will condense on 11/25/2010 05:13:52 MST Print View

Every bivy I have used and been around has had condensation at some time or another, Event too.

Actually the best I have used (as far as condensation) is an OR Basic bag cover with Gore Dryloft and the worst I have used (I hate to say) is a MLD Superlight with the Momentum top.

Edited by abhitt on 11/25/2010 07:34:07 MST.

Steven McAllister
(brooklynkayak) - MLife

Locale: Atlantic North East
Air flow on 11/25/2010 06:28:04 MST Print View

I found if I hang/suspend the top of an over-sized bivy so that there is some air flow down most of the length, you can reduce the condensation even more.
It could be more drafty, but having a dry bag/quilt may compensate.

When I have done this on frosty nights, I tend only see condensation near the top where my breath is the issue. The rest of my bag is bone dry.

Brad Groves
(4quietwoods) - MLife

Locale: Michigan
Re: Bivy Condensation on 11/26/2010 17:06:01 MST Print View

If a bag is too warm, you'll sweat more. If you're sweating more, there will be more moisture in your sleep system... a bivy would be likely to get more condensation in that situation.

David Olsen
(oware)

Locale: Steptoe Butte
Re: all bivy's will condense on 11/26/2010 18:09:49 MST Print View

"Every bivy I have used and been around has had condensation at some time or another, Event too.

Actually the best I have used (as far as condensation) is an OR Basic bag cover with Gore Dryloft and the worst I have used (I hate to say) is a MLD Superlight with the Momentum top."

---

This just goes to show, as I mentioned in another post, how
the materials that clothing and bags are made from has only
some to do with how dry things stay.

Gore Dryloft has the same exact moisture transfer as
eVent. It is the same stuff before the eVent is treated
to reduce contamination.

Momentum is basically the safe stuff the eVent and Dryloft
are laminated onto.

So your experiences are caused by other factors.

David Olsen
(oware)

Locale: Steptoe Butte
Re: Bivy Condensation on 11/26/2010 18:12:13 MST Print View

m

Edited by oware on 11/26/2010 18:13:40 MST.

Dave U
(FamilyGuy) - F

Locale: Rockies
Bivy Condensation on 11/26/2010 18:19:20 MST Print View

Thanks for the info on fabrics, David. I had no idea about Gore Dryloft. My experience with eVent has been superb with respect to waterproofness and breathability. Can I expect similar results with Dryloft? Thanks!

David Olsen
(oware)

Locale: Steptoe Butte
Dry Loft on 11/26/2010 19:50:19 MST Print View

In something like a bivy, results should be comparable. In
a jacket or shoes, where the laminate would be contaminated
with body oils, the fabric would lose it's water proofness
over time, but continue to be breathable and windproof.

Windstopper is also the same.

Dave U
(FamilyGuy) - F

Locale: Rockies
Bivy Condensation on 11/26/2010 20:03:37 MST Print View

That's very helpful info. Thanks Dave.

Alex H
(abhitt) - MLife

Locale: southern appalachians or desert SW
Re: Re: all bivy's will condense on 11/27/2010 06:14:55 MST Print View

"This just goes to show, as I mentioned in another post, how
the materials that clothing and bags are made from has only
some to do with how dry things stay.

Gore Dryloft has the same exact moisture transfer as
eVent. It is the same stuff before the eVent is treated
to reduce contamination.

Momentum is basically the same stuff the eVent and Dryloft
are laminated onto.

So your experiences are caused by other factors."

Thanks for the material info and I always know that other factors are in play. That being said, I have used different bivys for nearly 40 years, as bag covers not stand alone shelters, and generally in similar conditions. The old taffeta topped ones never condensed (that I can remember). The OR with Dryloft has a cottony feeling material and in over 40 nights only 3 times have I had condensation, all near freezing (7% of the time). With the Momentum top, in over 20 nights it has had condensation nearly 25% of the time in temps from 20's to 50's, not acceptable to me.

This is almost entirely out in the open and not under a tarp. On a recent, dry, trip in Southern Utah I used the Momentum top and it had condensation 5 out of 6 nights and my partner used my OR with Dryloft and had a little condensation on 1 night. Temps 24-33 degrees. I have not used Event but have been out with friends who have them and they had ice in there bivy near freezing.

I have a Montbell Dry-Tec bag cover on the way to test this winter, hoping it might be more like the OR but lighter. I am beginning to suspect it may have to do with the cottony type material the Dryloft is laminated to. May have to just sew a silnylon bottom onto the Old OR top and bring the weight down to 10-12 oz. and call it good.

David Miles
(davidmiles) - F

Locale: Eastern Sierra
Breath on 11/27/2010 11:02:37 MST Print View

Breathing inside the bivy causes a lot of condensation.

I have had lots of problems with bivy condensation, so I built my own. I found a fabric that is fully waterproof but far more breathable. I also wanted a bigger and lighter bivy. I can get dressed in it!

The best thing is the vapor transfer in sub freezing temps.
--------------
David
You are welcome, but ...
A posting with a URL to a sales site owned by the writer is commercial, and is not permitted in this channel. Your (other) posting on this subject is also commercial and is being moved to Gear Deals. It is welcome there.

You must give full disclosure that you are a vendor when posting anything like this, and restrict commercial postings (eg with a URL) to Gear Deals.

I have deleted the URL and let this one stand.

Cheers
Roger Caffin
Online Community Monitor
backpacking Light

Edited by rcaffin on 11/27/2010 13:34:32 MST.

John S.
(jshann) - F
Re: Uber Bivy on 11/27/2010 11:54:42 MST Print View

It looks good David.

Is the floor the same material? I gather it is nonbreathable.

How many stakes out loops?

Is it seam-taped?

Is the bottom right pic loose looking because it is not staked out?

What holds up the foot end? I see one pole at the head.

Is the mid section supported for snow loading?

Edited by jshann on 11/27/2010 12:00:36 MST.

David Miles
(davidmiles) - F

Locale: Eastern Sierra
Re: Re: Uber Bivy on 03/01/2011 00:38:26 MST Print View

I'm new to these forums and I not sure if there is an appropriate place to post a commercial URL.
If there is, could someone direct me to it?
I guess you could just Google it for more info.

John S.
(jshann) - F
Re: Re: Re: Uber Bivy on 03/01/2011 08:16:09 MST Print View

You did post it above, but never answered questions and your website had no details at the time : ).

Edited by jshann on 03/01/2011 08:16:41 MST.