Sleeping Quilt Condensation

are you sleeping out in the open or under a tarp

if you’re sleeping out in the open it probably comes from the air

I sleep under a Zpacks hexamid solo with the door always at least half open.  I’m certain it is from body-heat condensation as no other gear has any similar moisture on it (except the tent roof).  Also, the only relief I have found is when I sleep a little cold by opening the quilt up a bit, but that’s a rough trade-off to take for too long.  Is it something about the nature of DownTek?  Something about Enlightened Equipment’s shell material (Revelation 20d)?  I just can’t figure out why now.

weird

You mentioned your sleeping clothes being a constant between your old mummy and your new quilt. Have the following factors also remained constant: shelter, sleeping pad, types of meals before bed, campsite selection and hiking trip locations? Do the quilt and mummy have similar loft and similar liner and shell fabrics? Lots of factors at play.

I’ve experienced similar condensation after moving to a quilt, but then again it was about the same time I started using a shaped tarp instead of a TarpTent and got a lighter sleeping pad. There are many variables at play, but shelter type and especially campsite selection seem to be two of the biggest ones IMHO. In WA state, if you want to sleep high out of the trees, drying out gear during the day is par for the course, unless the weather is just right (warm and breezy). Some partial solutions include a full bivy, a “hybrid” bivy like the EE Recon, and/or a Zpacks poncho/groundsheet (more for splash than condensation).

Is there condensation inside the tent, under the top?  You stated there’s condensation on the roof, but’s it not clear if you meant under or over.  Are the droplets consistent along the entire top of the quilt?

When you sleep, is your head under the quilt or outside the quilt?

Great questions.  Here are a few answers/clues to consider:

1.  As weird as it is, I eat the exact same, and I mean, the exact same food every trip (I’m feeling very “Rain Man” right now);
2. Same exact sleeping pad and same exact sleeping clothes;
3. The problem occurred consistently on a February-thru of the Florida Trail (cool and humid) and a July-thru of the Colorado Trail (cool and dryer) regardless of tent-site location (though I do avoid camping near water or under open sky if at all possible);
4. I sleep with my head always outside of the quilt;
5. Their is usually condensation on the underside (interior) of the hexamid roof most mornings, but I am convinced the droplets are not from interior-splashing (see next answer);
6. Droplets are always concentrated between my rib cage and top of my shins (never near my head or toes);
7. All former bags have seemed to be made of similar materials and certainly similar temp ratings (20-deg).  The only variable has been the introduction of the moisture-resistant DownTek, ergo my suspicion of it as the culprit.  Could it be so moisture-resistant that the moisture that traditional down would otherwise capture gets released and then condenses?

Hi Matthew

A couple thoughts:

1. If you have condensation on the underside of your Heximid, than it’s clear to me that there is enough ambient moisture in the air around you to create the opportunity for condensation, depending on the temperature differential.
2. What was material was your previous bag made with? I have a couple EE DT quilts, and they are noticeably “more permeable” than my older bags. I have a suspicion that your body’s vapor is passing more freely though your new quilt, but condensing once it encounters the colder temperature outside the quilt. The reason why you notice this around your torso, is because that’s where the greatest temperature differential is between you and the air around you. If you were using your old bag, it’s likely your vapor never successfully passed through the outer layer to hit the cold air, so it never actually condensed. (But you might have experienced a little extra “clamminess” inside the bag, as a result.)
3. A suggestion that works for me very well: I use a lightweight silk liner that I drape over top of my quilt. The thin/lightweight layer acts as a ‘buffer” between the quilt and the air around it. I find that while it, adds a tiny bit of warmth to my system, Its main purpose is to , quickly wick any condensing moisture up from either my quilt, or whatever may drop from the underside of my tarp (I often use a Gatewood Cape.) In the winter, I use a two bag/quilt system, and it also works very well.

My 2 cents,

Matt

I believe that condensation occurs when there is enough of a differential between temp/humidity to cause it. So, a somewhat less insulated bag/quilt, like a 30F, will show less condensation on the outside of the bag than a 20F bag/quilt, given the same conditions. Downtek resists moisture, but doesn’t really stop condensation. Regular untreated down, under the same conditions, will collapse a bit, loosing a bit of warmth as it absorbs moisture. This will cause you to sweat less (not counting insensible perspiration) and be somewhat cooler (along with the loss of loft.) So, yes…in part the Downtek treatment is responsible. But, it is also somewhat warmer under those conditions. I, personally don’t care for treated down. It looses some of the temperature comfort range due to this.

I have found it simply requires more fussing with to reduce the loft around my “warm” spots (meaning those areas that will be overly warm after 5 minutes under the quilt.) I have an EE Revelation that is supposed to be good to around 20-25F (rated at 20F.) Try folding it in half, lengthwise, then shaking the down to the shoulder and foot areas.If your feet are too warm you can open them up a bit. If your shoulders are too warm you can slip your arms out from under it. You could actually open it up and stick your feet out, I guess. But, under a tarp, I worry about bugs. You might have to DEET your sleeping socks. Anyway, on a warm night (~50F) you could also fold it lengthwise and shake it down to the edges as much as possible.

In any case, I believe all the moisture (or most of it) is coming from your body. As it passes through the insulation(down) it will eventually reach the point of condensing. Warming the bag slightly (perhaps a shirt over the quilt would work?) should extend the range it will travel before condensing. Reducing the insulation will also extend the condensation range out of the quilt and into the surrounding air. Depending on conditions, both will work, I think. One methode will be warmer than the other, obviously.

You might also consider bringing a cooler bag. It really sounds like you have more quilt than you need for summer.

Maybe it is coming from your body.  The downtek makes the water pass through the down more easily (cause water wont stick), so more moves through the quilt to condense on top where its cooler.  The head and feet arent as warm so the moisture doesnt get passed through as much.

If this is right I agree with Marco… Less insulation

All of your great info caused me to dig a little deeper.  My former bag was a Feathered Friends Hummingbird UL 20 degree.  The shell is Pertex Endurance UL.  I never noticed a problem with condensation.  My new quilt is the Enlightened Equipment Revelation 20 degree.  Its shell is constructed of Phantom 10d nylon.  EE characterizes it as “maximum breathability”.   I think I’ll try a “huff and puff” test on the two materials tonight to see if I can detect a permeability difference, but the shell material must be the primary answer with the DownTek being a contributing factor.  Unfortunately it seems that  the final solution will not be moisture elimination as I had hoped, but moisture mitigation in the ways you all have suggested.

“I believe that condensation occurs when there is enough of a differential between temp/humidity to cause it. So, a somewhat less insulated bag/quilt, like a 30F, will show less condensation on the outside of the bag than a 20F bag/quilt, given the same conditions. ”

Hmm,,, on the contrary…

While I agree that greater the temperature differential increases the probability of condensation, this would actually mean that if I were sleeping with less insulation, I would actually increase the risk of condensation, since the vapor leaving the outside surface of my bag would be at a higher temperature gradient than vapor leaving a thicker bag.

Imagine viewing a person sleeping under a 40d bag with an IR camera, compared with a person sleeping under a 0d bag. You would see a lot more heat emanating from the person in the 40d bag. That heat transports the vapor, and when it hits the outside surface of the bag, the temperature differential (plus the relative humidity of the surrounding air) will create condensation.

So… If I’m sleeping in a very dry climate, I would’t experience condensation either on my bag, or on the inside surface of the tarp over my head. But if there’s condensation already on the inside surface of my tarp, than the air around me is already pretty much at it’s saturation point, so I WILL get condensation from anything with a great enough temperature differential. A more insulated bag will prevent more heat loss than a thinner one, thus less condensation potential.

But I certainly wouldn’t recommend adding additional insulation if you are comfortable. Overheating would be just as dreadful. That’s why a thin “sacrificial” layer might be warranted.

I do agree that the Downtek might be a contributing factor, by helping the vapor along better than normal down plumes (due to their water-resistive makeup.) But I still think the EE’s highly permeable 10d fabric is a lot more “breathable” compared to his old bag, so it simply does it’s job better. Has anyone done any research on the permeability of water resistant down vs. normal down?

I disagree. Water vapour will travel in BOTH directions as it escapes from your bag/quilt…towards the bag and away from the bag. Water vapour is NOT condensation. IFF the bag and material are warmer than the outside air, it will get some condensation(real H2O, not vapour,) but hopefully, your body will warm it enough to cause it to enter the water vapour state again. A tent that is condensing does so because it gets it’s moisture from somewhere, given that the tent is about 5F above ambient, anyway. Usually it is a bit more than that. I see around 3-5F on my tarp. Anyway, I would expect the condensation on the quilt to be reduced by at least 50% under a lighter quilt, therefore. This is not counting the reduced perspiration under the lighter quilt or rewarming of any condensation.

I would guess that the fabric in use has a higher specific heat, possibly polyester based(?), hence is “cooler” to the air than the air itself. Soo, warming it with body heat will tend to dry off the material as quickly as it is formed under most conditions. Only under long, continuous rain showers(>1hr) has this trick not worked for me. Yup, the down will get a bit damp feeling. Roughly speaking, the actual condensation is displaced to the air as water vapour, then to the tent surface to condense…likely the coldest part of the system.

There is a reason I don’t use a 0F bag in 20F conditions. The condensation will actually occur INSIDE the down and freeze there. This won’t bother me till night two. Now the day has had a chance to warm up and soak the entire bag with the condensation. Downtec doesn’t matter, since it will only protect down for an hour or so. The outside layers will freeze quicker and the inside will remain wet, added to by my perspiration. By the third night, I am getting cold at 30F, even though I brought a 0F bag. It gets worse in colder weather. Over-bagging is not a good thing and is a well known phenomenon.

The air may not be at it’s saturation point. At the surface of the tent, it will be cooler, soo, this is where a large portion of the more permanent condensation will happen. The tent/outside air is cooler than inside your tent…perfect for condensation. Now, this is all statistical, so that does NOT mean it cannot happen on your face, as well, or, back on your quilt. It just evaporates as quickly as it forms, so you never really feel it as wet. However, I have a longish beard. Often enough I still get some on my beard when it is around freezing.

Hi James,

While I completely agree that haiving too warm a quilt/bag can result in pulling the dew point inside the insulation, I see this primarily an potential issue when I’m sleeping in temperatures at or below freezing.

I’m still not quite seeing how a thinner quilt will result in less condensation, based on your description. I understand that the OP experienced condensation only in his mid section, not at the foot box or the top edge. Our mid section is measurably warmer than our feet, so I’d presume that the outside quilt surface would be warmest in the mid section. But that’s where he had the most condensation.

So if I understand what you wrote correctly, you are implying that the higher outside surface temperature of a thinner quilt will aid in “re-vaporizing” condensation. Is this right?

I’m also having a difficult time understing this statement:

“Water vapour will travel in BOTH directions as it escapes from your bag/quilt…towards the bag and away from the bag”

Can you offer some clarification for me please?

Thanks much,

Matt

Well, the same idea applies to water (condensation) or frost. It doesn’t really matter if the temps are above freezing, as long as we are hitting the dew point.

A thinner quilt will be, by nature, warmer at the outside. So, it will aid in re-vaporization of any H2O (condensation.) For instance, iff the dew point is 35 and your quilt surface temp is around 35, then you will get surface condensation. If, however, you raise the outside surface temp of the quilt to 37, then little or no condensation. Not quite true, that was just to get the point across. Condensation will still occur, actually. The overall thermodynamics will be driving more moisture off than what it is collecting. Of course other things will effect this and it is just a simplistic example.
The amount of perspiration (water) added to the system
The materials used
The actual temp/dew points
etc…

The overall gas laws will guarantee the roughly 50% movement of the water vapour away from the sleeper. Water vapour is a gas. It is NOT individual particles of water suspended in air. As such, when it moves into the outside air at the dew point, it will move according to gas laws, not gravity or only slightly influenced by gravity. It will be somewhat warmer than the outside air so by convection it will tend to move up. As it cools it will cause a bit of “fog.” This is the condensation forming. By nature the upward flow of air will cause about 50%, statistically, to rise up and away from your quilt. Likely to drop on the nearest item. If it is warm, it will re-vaporize as it gets there or slightly before it gets there, if not it will settle and leave a droplet. Water also will attract other water…

I assume that the feet and shoulders were at a colder temp than the midsection. So, I would move down to those areas and away from the sleepers torso. If you cannot shake the down enough, then the sleeper is pretty clearly over-bagged.

I believe the problem is over bagging, I would simply shake the down away from the condensation areas, thus allowing them to warm slightly.