40°F or 50°F Over-Quilt Fighting Bivy Condensation

[Scott F.]

My dilemma…tying to minimize condensation in my bivy and remain UL.  Current set-up is a DCF pyramid tarp over an OR Helium bivy with a 20°F EE down quilt and NeoAir Xlite on top of a DCF ground sheet.  From the Forums I’m hearing an over-quilt will help.  My first question is should it be synthetic or down?  Of course, I would like the lighter down, but assume synthetic is best?  Second question would a 40°F or 50°F rated over-quilt be best.  Again I want the lightest system, but still want to be comfortable during the cold nights with the least amount of condensation.  Additionally, I would like the system to work for 4-seasons (hot summers-maybe just the over quilt, through shoulders seasons, and in winter lowest lows 0°F- 10°F).  Suggests are much appreciated.

[R]

By ‘in my bivy’ I take this to mean on the inner surface of your bivy?

Given that the source of water is you, via insensible perspiration while you sleep, you’ve got a few directions to take:

1. Don’t go out in conditions where the ambient temperature and humidity cause your perspiration to condense
2. Use insulation thin enough to let the outer surface put off enough heat to drive your perspiration through the bivy wall
3. Use insulation thick enough so the dew point occurs inside the insulation so your perspiration condenses there rather than making it all the way out to the bivy wall
4. Use a VBL to limit your perspiration and prevent what gaseous water there is from making its way through your insulation to the bivy wall.

Option 1 is presumably not acceptable.  Option 2 is not advised; using a more breathable bivy may help, but that begins to negate the point of a bivy if not for bugs.  You might want to consider option 4.

And then there’s option 3.  Pending conditions, this is likely what will happen with your over quilt, so synthetic is the way to go.  The rub of it is, w/o a VBL, you are producing water that *will* condense somewhere, it’s just a matter of where.  If you’re otherwise comfortable in your current set up, I’d just do what you can to dry it out during the day and be glad the moisture isn’t actually inside your insulation, where it would be more difficult to dry, and may actually cause some problems.

A half step towards an over quilt is to use a silk liner outside your bag to soak up condensation.  This will keep your quilt and bivy drier, and be easier to dry out than either.  Adds a smidge of warmth, and about 5oz.

See last paragraph: https://backpackinglight.com/forums/topic/condensation-issues-enlightened-equipment-quilt/#post-3614358

Also, you’re going to need more than an xlite under you for your target winter temps.

[Scott F.]

Thank you Rene.  A silk liner sounds like a reasonable step towards keeping condensation out of my down quilt rather than an over-quilt.  Also, thanks for the reminder for a better R-value in winter. For winter I plan on using the NeoAir Xlite pad on top of the Therm-a-Rest Z Lite Sol Sleeping Foam Pad. Warm enough?  Or should I upgrade the inflatable to the NeoAir® XTherm along with the foam pad?  Thank you again!

 

[Roger Caffin]

Silk liners are nice and very light, but sadly we have found them a little fragile.

Cheers

[Iago Vazquez]

Xlite and 1/2″ foam have been comfortable for me down to 0F. I sleep warm.

[S Long]

If you already have a pyramid tarp, what do you use the bivy for? Short of pretty heavy duty precipitation with high winds the pyramid should be enough coverage to keep you dry. If drafts are a problem, switch to a more breathable bivy than the Helium or invest in a sleeping bag rather than a quilt or more insulation. If there is no precipitation, I always just cowboy camp with no bivy. You may have conditions or weather that I am not taking into account, but on the surface I’d say you should perhaps rethink your system a bit.

[Scott F.]

Thank you for your insight Renee, Roger and Iago.

S Long – I carry both the pyramid and bivy.  The bivy because I enjoy cowboy camping and like the mosquito protection the arch netting provides.  The pyramid tarp comes in handy in rain/light snow allowing me some room to move about, change clothes, and dry-out.  My quilt is perfect and drafts are not a problem.  Perhaps my Helium bivy is not breathable enough to manage condensation?  Are there other bivys with better breathability as well as bug protection that could be recommended?  Do I even need a over-quilt?

Thanks again all.

[S Long]

Switch to a non-waterproof bivy. Borah Gear, Enlightened Equipment, and Mountain Laurel Designs are a few companies that immediately spring to mind. They all offer popular water-resistant and breathable bivys. If your quilt is warm enough and draft-free enough, then perhaps consider just going with a mesh bug-bivy? Or a solo innernet for your pyramind. It probably wouldn’t weigh a whole lot more than a bivy (and may even weigh less than the Helium bivy) and could be used as a stand-alone bug shelter in good weather. Good luck getting your system dialed in!

[Jerry Adams]

make sure you’re not breathing into your bivy.  That creates a lot of water vapor and it’s hard to avoid condensation

[dirtbag]

I use a katabatic gear Bristlecone bivy.. Works well. Also why not just use a bug bivy? .. I use Borah gears bug bivy in warmer temps. I say use, but should say used since I have not slept in my bivies for a few years now, but I do still own them and would not hesitate to use them with my tarp. Though in cold winter conditions you mention.. There should be no bugs or mosquitoes to worry about.. This is where I used to bring my Borah Gear snowy side Event bivy.. i have not had any time that I recall condensation being an issue for me with any of these. bug bivy

bristlecone go by

snowy side Event bivy

[dirtbag]

Fyi.. Someone selling a katabatic gear bivy on gear swap … $105

[Author]

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