> my silnylon floor can be condensation prone (I still don't understand that one).

Very simple. You have this very cold floor and this warmer humid air. Exactly the same as dew.

Yeah, happens sometimes in the snow, which is why we usually try to keep the groundsheet pretty much fully covered with gear, food, clothing and so on. keep the humid air away from the floor. All the same, it is not uncommon to find a slightly wet underside on the mat in the morning.

Cheers

"down can be dried off just as fast as synthetic"...
...that`s maybe a little too optimistic, but surprisingly fast, i agree!
i had 2 nights with severe condensation in lapland this spring(temps around 0°C), frost being shaken from the cuben roof by the wind and melting on the SB, and the tyvek cover which should have taken care of this only made things worse by adding condensation from within.as a consequence the SB was absolutely soaked, the down reduced to wet clusters, and me close to panic.
next day it took only seven hours in a strong wind to get the bag back to shape, i never would have thought that beforehand.
and as so far there are no contradictions to the theory, i guess a VB would have avoided the problem in the first place, as then the tyvek cover could have done its job properly - even with temperatures slightly higher than freezing.

David,

Thanks for posting this and starting this thread. Excellent information -- and important information -- for those of us who like cold weather backpacking!

I agree - this is definitely one of the better BPL threads I've read in awhile. Perhaps similar in content to the super-informative Richard N. CLO threads from a few years back.

I hike in the high Sierra during non-winter months, but near/above 10k. The bottom line for me is that I take a (slightly oversized) tarp for 3 reasons:
-wet (rain)
-wind
-wings (bugs)

Since it's a MYOG tarp that essentially follows Henry's original tarp tent design, I've got netting sewn on both the front & back, but not full enclosure flaps. This means the tarp provides minimal warmth, if any, so I need to rely on MYOG (over sized & stuffed) APEX quilt.

If any of the three conditions above are met, I break out the tarp. For example, if the typical afternoon showers look like they will continue past evening, out comes the tarp. If it's particularly windy, out comes the tarp. And of course, if the mozzies are really bad, and don't look they are leaving @ dusk, out comes the tarp.

For my quilt, I used one layer of 5oz, one layer of 2.5oz & M90 as the shell/liner. The insulation & M90, which has a good DWR, is a sufficient combo to allow me to cowboy camp. In effect, this approach is similar to a bivy, except I'm missing the add'l top layer of M90/Event/etc.

(I use a Tyvek GC, so whether it is sewn to a bivy or just laid out, the net effect is similar. My quilt is oversized by around 2" on each side as to comfortably tuck under without allowing cold air to enter.)

Where I'm SOL is if it's wet (humid), windy & cold. This is the formula for condensation, which only a double walled tent can really combat. (It's the reason why the tarp is slightly oversized - to keep from brushing the wall.) While my tarp provides protection against direct rain, it doesn't provide warmth, so the dew point ends up inside. In this case, I wear my down vest in an attempt to move the dew point to the outside of the quilt.

That's the reason for the syn quilt. It may not be perfect, but there is a certain fail safe aspect. There are just too many stories of down malfunction - like they say, it only takes one time.

Edited by Hobbesatronic on 10/09/2011 10:02:10 MDT.

Thanks guys - glad to suffer for you all.

; )

"my silnylon floor can be condensation prone (I still don't understand that one)."

I have a silnylon floor

Water from my breath sometimes condenses on the silnylon, within a foot or so of my mouth

Worse if there's no wind and it's cold

It would be better if I slept on my back, but I usually sleep on my side

Great thread. I used to be in a Special Ops unit in the military and we had a light-weight Gortex covered synthetic bag that I frequency slept in out in the rain, laying in a puddle, in a ditch etc... etc... in temps down right above freezing. I always marveled how warm it was (relative term) and how I could climb in there, warm-up and dry clothing. This was with no tent...fully cowboy camping.

Don't mistake me... it was never comfortable but I survived and kept my core body temp up. I hated getting out of that thing. At the time I didn't have any background in the physics but I think the fact that it wasn't thick helped it to push moisture out. The WPB layer was relatively close to the skin rather than 2"-3" out like we use with bivys.

My experimentation on a recreational level with bivys (breathable) has always been negative outise of the wind break they provide. Of course even though I may be damp I'm warmer in a tent with a damp sleeping bag than I ever was sleeping exposed in that thin Gortex bag. I think in general when you have to live for extended periods of time in 100% humitiy environments like this you better adapt to being wet and stay focused on retaining heat under those conditions. It doesn't end up being a "fun" experience for recreational campers but I don't mind the challenge of dealing with it for a couple days. A couple weeks.... that would be another matter.

Hi I live in the SW of the UK, where it tends to be warm wet and windy.

My current system is a Tarptent Squall, and a Down quilt.

I have struggled along with this combination for a number of years. The last trip I did made up my mind to change this system. It was cool, nighttime temperatures about 40 degrees 100% humidity.

My quilt lost loft every night, fortunately in the day it was dry and windy with some sunshine so I was able to dry out my quilt. If it had been damp in the day I think I would have been very uncomfortable. The main source of the dampness seemed to be from condesnsation forming both on the quilt itself, but also on my ground sheet. The ground sheet had pools of condensation on it, which obviously made my quilt wet.

I have decided to go with:
A Bivi made from silnylon and ripstop nylon. Having read the rest of this thread I am now wondering about the widom of this, but as I am half way through making it I am going to see it through! The main reason for going with the bivi is that I need a waterproof bathtub groundsheet anyway and I sometimes find draughts creeping under the quilt when I move about (I seem to be an active sleeper!).
A shaped tarp, I have drawn something in sketchup somewhere between a hexamid, a lair and a cricket tent. This should cut down on draughts over the squall which I have found to be a cold place to be when it is windy.
A climashield Quilt. If it does get damp it shouln't be such an issue.
A long wide ridgerest, which should keep me and my bag off the ground sheet.

I'll let you know how it goes.

James

I've only experienced a huge amount of moisture in my sleep system once, last February. I went out with a friend in the Columbia River Gorge in NW Oregon for a two night trip. I didn't anticipate rain because Portland's forecast was dry, but was very wrong. We hiked all day in steady rain up to a frozen lake surrounded by frozen, iced over ground. I hadn't brought a change of shirt—just my R1 hoody which I had worn all day under my rain jacket and was drenched. Foolishly, I threw on my down jacket and climbed into my down bag inside an MLD SL bivy under my Trailstar still wearing my extremely wet R1.

The down in the jacket flattened and the bag lost a lot of loft and stayed thin for a couple hours. Eventually, I figured out I could build up steam inside the bag and bivy while tightly closed, and then quickly unzip and let a cloud of moisture pour out. I vented like this maybe five times before eventually falling asleep.

It was a cold night, but I woke up to a predominately dry sleep system. It was still raining outside and ~32º. We still hiked out a day early because I couldn't stand the thought of another night like that.

* * *

I've since slept out in similar conditions on numerous occasions and never had an issue. Even the most humid, cold, still nights in the swampy woods of the PNW won't deflate a down bag that's been protected from wet clothes or excessive sweat. I exclusively use a bivy and down quilt for all four seasons and have never had an issue with condensation that wasn't my fault.

It's good to find your limits and know what you can withstand, even when making bad choices in bad weather. Grows a hair somewhere.

Edited by kylemeyer on 05/21/2012 00:20:35 MDT.

Man after reading this I am sticking to a tent. I'll carry a couple extra pounds. I cant even imagine the hell I would take if this happened to my wife and our 3 kids.

This has been a good thread. Several important points were repeated. One observation which I think I only saw once, but would be useful to pull out. If you have synthetic insulated clothing, a down quilt, and a DWR bivy in those conditions, draping the synthetic clothing over the quilt and under the bivy might have been quite a help. Doing this might very well have keeps the interface nearest to your down quilt (the inside of the synthetic clothing) above dew point. Your body heat would have pushed the moistures through and into the synthetic clothing which would tolerate the moisture build up more than the down. There have been a couple of trips where I did this, and the people I was with didn't. My quilt more mostly ok, and theirs collapsed.

Of course you now have excess moisture in the clothing… but the good news is that it's easier to be active (generate heat) wearing the clothing, so if in the morning you move enough to generate a heat, but not enough to sweat, you can help the synthetic clothing recover.

--Mark

"Man after reading this I am sticking to a tent"

I have a couple tents. You set them up, then put the fly over them. If it's raining, it all gets wet while you're setting it up and taking it down.

If you get a floorless, single wall tent/tarp, you can quickly remove it from your pack and make your pack waterproof again, then set up the tent, then put your stuff under it. Like a MLD Trailstar or MLD or Oware or whoever has pyramid tents.

Roger has a good article that talks about this, describes a few tents that are better,...

> Man after reading this I am sticking to a tent

a good double walled tents (especially one that lets the fly go up first and then you deploy the inner tent) does make many things easier, especially in the conditions described. But there are lots of good reasons to go with a floorless shelter beyond weight. For example, in the case of rain which hasn't saturated the ground, it can actually be easier to manage with a tarp or shaped tarp because the ground can absorb the moisture drying from you wet things where a double walled shelter has a floor which keeps everything in.

--Mark

We had two tents and two tarp shelters on this trip. The two with the double walled tents (one was a Hubba Hubba and one was a Big Anges Fly Creek) were just as wet as I was. It didn't matter on this trip given the weather.

As far as growing a hair, this all took place at over 9000 feet. I suspect most would grow a beard.

Glad this thread was revived--good stuff.

Do you typically use a bivy under your 'mid, David? I ask because I moved to a shaped tarp setup last year, but haven't experienced severe weather in it (yet). Not using a bivy, but I had thought an advantage of a shaped tarp is not needing the additional splash protection. Is this your experience?

Edit: Changed post title.

Edited by DavidDrake on 05/21/2012 12:45:03 MDT.

It seems a lightly insulated bivy, would work for pushing the dew point out of the down. It also seems a nest would be a better solution, as it provides more air space / flow. Yes both will weigh a few ounces more, but less then a double wall, and probably less than replacing an 800 + fill quilt with synthetic.

I had the same issue as David on a trip to Ireland last month, I found placing a synthetic jacket over my chest area really helped.

Edited by stephenm on 05/21/2012 18:47:06 MDT.

Hi David - yes I normally do use a bivy but for additional warmth / bug protection with my quilt(s) and not additional rain protection so your assumption is correct that in using a shaped tarp, a bivy is not necessary for weather protection, at least not for me. The conclusion of my experience based on input from others would be that I would have been better off not using the bivy in these conditions and if possible, layer with a synthetic bag or clothing on top of the down quilt. Or...use a synthetic quilt.

FWIW, the DuoMid was excellent at weather protection!

I must not have read this thread the first time as carefully as I thought. I didn't catch the tidbit of draping a syn garment over the down quilt- sounds very plausible

I'm guessing that this technique would also work draping a down garment over down and would also work if the quilt was syn????

Great thread, don't know how I missed it - Guess I'm more of a stealth reader. I don't claim to be an expert, but I did survive a 9 day Canadian expedition with temps ranging from 30F to -20F. We did experience the same problem as you on the 30 degree day. It's kind of a "given" that our sleep systems gain weight (ice balls) as we progress in the trip. Every effort is made to move the dew point out of the sleeping bag when possible, but we do use our body heat to dry items while sleeping. If we are lucky the dew point will be outside the bag and we just shake out the ice in the morning. One the above day - everyone was wet and the "down people" had it worse.

I've read quite a bit about moving the dew point and I am going to try a synthetic overquilt next year - a light over-sized climasheild quilt made by Tim Marshall. This is used to purposely trap the moisture and can be dried out by wearing it around camp or hanging in the sun - if it is out. it will be easier than trying to dry your bag. Many long term arctic expeditions use this method and swap out the sacrificial over bags on re-supply. Of course this will also extend the use of my sleep system to lower temps - a desirable side-effect, but the weight vs. function must also be justified.

Has anyone else tried the double quilt or double bag method?

Very good discussion,

Dave