So....drop the bivy, use down clothing with a synthetic sleeping bag. Use a tent with floor if possible, preferably double walled.

Sometimes I just fire up the stove with an empty Titanium pot on it. The radiant heat drys things out pretty fast-at least for a while. (make sure you leave the lid off and don't turn it up much) Sometimes a candle helps-sometimes not. Sometimes I wish I had my little primus lantern. Need to remember to stuff any wet clothes in a plastic bag so they don't add to the problem. Usually just suffer through it like everybody else. Type 2 fun eh?

You gotta admit, this is pretty fascinating, from a technical point of view.

Joe - I agree. Things got so bad for me, I had to trek out early - less a planned day. I could not spend another night out.

jeff ... hot nalgene ... which is why i love having one despite the weight , and love the jetboil for the fuel efficiency should i need to boil more water than expected ... also cords can help keep yr clothing in place ... or at worse some medical tape (which should be in yr 1st aid kit or something similar)

joe ... says the guy who lives in new mexico ...

david ... im not saying synth bags are the only option ... but if you do use down id suggest learning every trick in the book to dry out yr bag and prevent moisture ... like anything else sometimes the weight savings require more skill and fuss .. also consider that 900 fill down is effectively 700 fill at 50% humididity, never mind 90%+ ... so youll likely need a heavier down bag to make up for the loft loss

heres a good link for the oh shiet scenario ... also there are the old excellent BPL articles on condensation

http://www.andy-kirkpatrick.com/articles/view/wet_down_how_to_cope

and the excellent pictures at pages 6,7 here for clothing ... same applies to bags

http://umanitoba.ca/faculties/physed/research/people/giesbrecht/Cold_Weather_Clothing.pdf

Edited by bearbreeder on 10/04/2011 21:28:41 MDT.

Very interesting, especially as these are the type of conditions I could face here in NZ. So far, since switching to single walled shelters and bivies, I seem to have been blessed by the weather gods.

A few thoughts:

1. Did you have the bivy zipped up and the hood lifted up using the attached cord. This would potentially create a small gap between the bag and the bivy in some areas. Of course zipping the bivy up would also reduce ventilation. Also did you have Duomid fully sealed, or did you have the zip undone to the mid point clasp?

2. You may have seen it, but a solid inner is available for the Duomid - http://oookworks.com/duomid_ripstop.html.

3. I have often wondered if a primarily momentum bivy made in the style of the MLD Bug bivy would help in these situations, as the fabric would not be lying on the bag. It would be pretty light for a solid inner. A bit of mesh in the right places would help prevent the feeling of being in a coffin :).

4. As Eric said just using a bathtub ground sheet and no bivy may in fact be better in these situations, as long as condensation being knocked of the tent walls by wind isn't a big issue. The Duomid fully done up provides good protection against wind and driven rain.

5. I remember reading an article by Collin Ibottson (UK ultra lighter) where he explained that he felt the large size of the US style bivys (generally rectangular shaped rather then shaped like a mummy bag) increased the risk of condensation because of the large area of non breathable silnylon on the base.

I've had this happen to me a few times. Prolonged rain, close to freezing temperatures, even a little bit of sleet and snow. And every time I used a bivy, same problem. One other problem I created myself was breathing into my bag when I was really, really cold. A couple years ago Roger Caffin encouraged me to get an insulated balaclava and keep my head out of the bag!! That really made a difference the past couple of years. But the biggest difference was to get rid of the bivy and go back to a double size tarp or a larger tent. The worst two nights I ever spent was in a Wild Oasis, an REI Mimimalist bivy, and WM ultralight bag. Problem was the bivy. But even with my MLD Side Zip bivy I have had similar problems with the Wild Oasis and WM bag. Nothing wrong with the last 3 items, just the wrong combination in the wrong conditions.

Last winter I did a lot of poor weather camping in a Scarp 1, an enlightened Cuben quilt (acts as a vapor barrier) inside of my Nunatak Arc Specialist. Along with my insulated balaclava (head outside of my sleeping system), condensation has pretty much been a non-issue.

I do not do as much foul weather hiking as many here, so I have made a lot of mistakes, but I am a good learner! :)

Different conditions I'm sure, but maybe you'll find something applicable in my wet trip story...

About a month ago in the Otter Creek Wilderness, WV on the last night of a 2-night trip we got hit with an outer band of hurricane Irene right around 11 pm. We were sheltered from most of the wind by being on the leeward side of the mountain, but the rain was like being in the shower, and was blowing in random directions. Having only a rain jacket but still wanting to hang out with the rest of the group in the rain around the drowned campfire remnants (yes, I am crazy), my pants got soaked. I put them in the vestibule of my single wall tent, along with the rest of my gear. Humidity was 100% when I went to bed (visible fog and mist). It rained off and on all night. Condensation quickly formed, and started dripping on my down bag (Montbell, very new, thus good factory DWR). It was only in the 50's (F), but I didn't see anyplace where my bag had lost loft or the down seemed wet in the morning. I shook the droplets of water off and packed it away. Everything else in the tent was at least as wet as when I had went to bed.

I agree with the others who guess it was mostly the bivy at fault. Your quilt might need a good DWR re-treatment, but I think you'll have to determine that separately.

How much of a gap was there between your shelter and the ground? Maybe a little more ventilation would've helped?

Edited by AndyF on 10/05/2011 00:15:03 MDT.

the striking part of this story is the fact that you lost so much loft. It is also the most serious fact, the rest is just inconvenience.

I've been in similar conditions and with similar gear before. It wasn't fun but I didn't lose that much loft. It takes a lot of water to soak a down sleeping bag. One thing we seem to take for granted (but I still wonder) is with so much humidity would a synthetic bag survived any significantly better? Down clamps down and becomes nothing but, again, it takes a lot of water to get to that point. I wonder how useable would a synth bag be after so much water exposure.

As already mentioned, double-walling is a good idea. It adds insulation around you which contributes to avoid condensation. In your situation, as Jason suggests, you could have tried to implement a double wall by suspending the bivy from above and staking it down too if at all possible. I've tried that before with relative success but it's difficult to say what would have happened if I don't (hence the "relative"). It'd be nice to have a bivy specifically designed for this so it's easy to have clearance over the length of the bag.

This is all very interesting. I tend to think down collapse is a very unlikely event unless there's some gross user error or really prolonged such conditions, neither of them the present case. I still get out there in this confidence.

Edited by inaki on 10/05/2011 04:45:49 MDT.

Indeed. It has caused me to re-evaluate my technique for my up coming nine day Bay of Fundy coastal hike (we are no strangers to cold, rain and fog here). This sort of thread is the reason I subscribe to Backpackinglight - very useful.

You don't need to use a synthetic bag David. I last used a synthetic sleeping bag about 20 years ago, and haven't soaked a down bag/quilt yet. Maybe it's simply because i've learned my 'craft' in a cold/wet climate, that ir's become second nature to me. Most of my friends use down without any problems too.
I think the most important rule in these conditions is maximum seperation between the surface of the bag and the tent/tarp wall.

I have had similar experiences in the PNW.

Bivies just don't do it in all conditions.

As mentioned Dave would probably have been better of with just not using the bivy and sleep on top of it.


I stay away from bivies in wet climates due to similar experiences.
A bug net / innernet that doesn't touch your bag should work way better.


near 100 % humidity and temperaturs around freezing don't leave you much room for error.

am enjoying this thread...


The problem for me is that my bivy also protects my bag when i'm camping with the dog. So not using a bivy would potentially other problems! And when he's wet that makes the inside of my shelter (MLD supermid) more humid and gives a greater chance of condensation.

Whats interesting is that wet near freezing conditions would seem on the surface to be exactly the conditions one would want to use a bivy for. Seems not to be the case. Looks like a sleeping bag with good DWR in a double walled shelter would be the best bet.
That leaves the question -when is a bivy helpful? Seems that below freezing and dry would be best. I know in the hot summers I only use the bivy because of the bugs more than anything else. But I m leaning away from that after this summer for bug inners because of the heat and I find that with adequate shelter I don't need splash or wind protection. Especially with a good DWR on my bag.

You know that old line when a couple breaks up - One says “It’s not you, It’s me.” But what they Really mean is it’s All You.
So here is the story of the Bivy and the Down Quilt breaking up...but wait!!! Was there an evil ex GF/BF in the background pulling the strings?
I think a few posts got pretty close to putting it all together- so I’m more or less just condensing that info.
The first question is where did all that water come from to soak the down quilt? Inside the sleep system of course! Two sources: The body and wet clothing.
In this case the wet clothing would be the major source. If you are wearing insulated clothing near freezing with 100% humidity for any time at all around camp - it will gain and hold water. Synthetic pants and jacket can hold a lot but you would still feel warm and OK- maybe even dry while you are moving around and even only slightly active - that’s what it’s good for. Just weigh a synth jacket after a full day of hiking in that type weather vs a dry one- quite a few ounces and that’s all water weight.
Some folks sweat a lot - I’m thinking that may be the smaller piece of the water source here but it’s something. Dave’s bivy has a full net hood so I’m discounting exhalation asa big deal but at the same time all the netting can let in 100% humidity too. In general more net is better in this situation and using a line to hold it off the upper torso is a good and established practice- not sure if Dave did this..
So, as noted in other posts- as the moisture gets pushed by body heat from the skin out- that moisture in the clothing is pushed into the down quilt and as it gets near the outer edge of the sleep system is cools and condenses thus wetting out the down bag. In this high internal moisture situation down wets out pretty easy. One more very thin layer of the bivy top’s DWR fabric would add a small amount of slowing of that wet air moving out, but it is not the primary factor here. Moving thorough two layers of the bags DWR shell and through all that down is more of a factor than the super thin bivy DWR top. I’m not saying the bivy’s role in this situation is nothing- just not the over whelming one point factor to point at.

Remember that a DWR bivy is part of the Entire Sleep System. When there is a problem with condensation, etc. it is usually a combination of interaction of the whole sleep system (includes worn clothes) + shelter system + campsite selection + weather conditions.

In this example it was the “perfect storm” . The one thing that would have changed it all to a non-event would have been a synthetic quilt. Most likely it would have gotten the same amount of moisture but you would stay warm. Wet + Warm = Ok for quite a while.
I think other posters had some good ideas and what to do if you are in this situation to possibly and maybe only very slightly mitigate the effect. Recapping them here:
1: Lie on top of the bivy- everything else the same.
2: Take off the wet clothes and only use the bag + bivy.
3: Dry clothes by fire before wearing them under the dry down quilt + dry bivy.
3: My Choice: Strip off all damp clothes and use the dry quilt and bivy with a hot water bottle inside - possibly using the damp synthetic pants and jacket over the outside of the bivy.

One more note: We offer eVent WPB strips on our quilts as an option but do not recommend it inside bivys most of the time or for 100% humidity. DWR has a far higher air permeability than any WBP material - like on your down quilt foot and head. Those strips are great at stopping outside water getting in but not so good at letting inside vapor get out- that aded some problem here.

so whats wrong about using a VBL inside a SB inside a bivy, even above freezing temps? given a condensation problem INSIDE the bivvy, AND the necessity to use one (people with wet dogs for example, or millions of snow crystals flying around in your
snow bivouac and melting on your SB), a VBL seems to ME the one logical answer to the problem.
Mary D. says it helps, Roger doesn`t recommend it without saying why, so any other opinions?
regards, Paul

I disagree that the bivy was the problem.

The bivy top is momentum, a fabric of similar weight and breathability to the sleeping bag shell. If you could see inside the sleeping bag shell, you would see condensation here too.
The problem was that the dew point was inside the sleeping bag and this is where the condensation collects. This would still happen (even worse) without the bivy.

Solution: use a fully enclosed tent - ideally double wall with vent.
The aim here is to raise the temperature of the air inside the tent, ideally to above the dew point. Then the condensation will collect on the outer wall of the tent and not inside the sleeping bag.
2nd best - enclosed single wall tent - but not as easy to warm up inside and drips can be a problem.

Would heating up water and putting it in your water bottle which you then keep with you in the bivy perhaps raise the temperature in your bivy enough to drive the dew point out further?

I think most folk are saying the same thing, but in different ways.
The bivvy itself wasn't the problem, but using the bivvy in an open shelter caused the dew point to occur inside the bivvy/sleeping bag in these circumstances. There is a very sharp temp differential over a small distance using the bivvy in an open shelter. ie, using the same bag/bivvy inside an enclosed shelter would have pushed the dew point out to the shelter wall, and the bag would have been fine. Of course you wouldn't need the bivvy. :)
My experience tells me not to use a bivvy/open shelter in those conditions. I have (and love) a MLD Duomid, but chose an enclosed shelter this past weekend expecting similar conditions.

Eric - thanks for the links.

Jason:

-The bivy has netting at the top - it was hung from inside the Mid but not zipped over my head. The upper fabric of the bivy was zipped to my shoulders.
-The Mid was pitched fairly low to the ground given the blowing rain. I didn't think the condensation on the inside of the Mid was too bad, to be frank. It was manageable and I could not feel any droplets falling down.

Thanks for the link for the fabric inner for the DuoMid.