Impact of High Humidity and Condensation on Properly Overstuffed Quilt?

Question

It's well established that condensation can compromise down loft and therefore sleeping bag/quilt warmth. However, I'm curious what the effect of high humidity would be on an appropriately overstuffed quilt.

Background info: I slept in an appropriately rated 20 degree quilt (2.75" loft) with significant overstuff paired with an XLite NXT (r=4.5). I slept in dry base layers, had a full dinner of rice & beans, and was well hydrated. Because we were planning to summit early in the morning, our group opted to sleep in extremely humid conditions, practically in a cloud at ~10,000 feet elevation. From my Govee thermometer, it got down to 35 F with 95% humidity.

Given the forecast, I was expecting to be extremely toasty but was surprised to wake up slightly cold throughout the night. There was some condensation on my quilt but it appeared to still be fully lofted.

I'm making this post because I felt like I took all of the necessary steps to sleep warm except taking into account humidity. I'm wondering if I'm missing something that I can do to sleep warmer?

tldr; Even if a quilt is at full loft, does high humidity compromise the thermal efficiency of down to reduce a quilt's comfort rating by ~15 F?

in Ultralightby shim12

81%

13d

liveslight

🍰

https://lighterpack.com/r/2lrund

13d

I just spent 4 days and 3 nights in Great Smoky Mountains National Park. It rained a lot (Video: https://imgur.com/a/rb5Corq ) It was foggy. I had a Govee which showed that the relative humidity was never below 92% the entire time. (graphs: https://i.imgur.com/zV78mlL.png ). I didn't have any problems with my 40F down quilt. That's even with setting up my tent in the rain. Nor with the one time I slept in a shelter with only 3 walls.

Here's what I do that others may not have told you about: My body heat is important to keep my quilt dry. Therefore, 1. NEVER remove my quilt from my pack liner/dry bag unless I am going to put my body in it. That means pitch tent, cook and eat dinner, hang out in camp with the quilt stuffed and compressed INSIDE the dry bag.

When I am ready to sleep remove quilt from dry bag and GET IN IT IMMEDIATELY.
After waking up in the morning, DO NOT GET out of the qulit and let it absorb moisture. Instead, while I am still in the quilt, I put the dry bag over the footbox then put the dry bag with quilt and feet into my pack. Then I peel / push the quilt down into my pack squeezing out all the air and any moisture that the air contains. I don't even care if the footbox is damp because I know it is only damp on the outside.
I DO NOT let the quilt sit out and cool down allowing the temperature inside the quilt to go below the DEW POINT.

When possible I always dry my quilt in a clothes dryer. I weigh my quilt to see that it has lost all possible moisture. I clean my quilt in a special way after EVERY TRIP: I take a cotton beach/bath towel (or two) and wash in hot water. Then I put the wet beach towel in my clothes dryer alone on moderate heat to heat it up to create an oshibori for my quilt. Then I toss /stuff in my quilt and run the dryer on low/gentle heat until the towel is dry. Thus the wet towel wipes the fabric shell of the quilt, creates some "steam" that goes into the down, but does not make the down wet. Also the weight of the wet towels act like the proverbial tennis balls that folks often are told to toss in the dryer. The down never clumps. Of course, I know the quilt is completely dry by weighing it.

oeroeoeroe

13d

I suspect that it's less about your quilt loosing loft (since you say it seems fully lofted) and more that humidity making the cold temperature effectively colder. High humidity amplifies perceived temperatures: high rH makes heat worse, and high rH makes cold chill you more.

I did some quick googling but I didn't find anything too specific for colder temperatures. Some discussion on the phenomenon here which might be interesting: https://physics.stackexchange.com/questions/97893/does-humidity-make-cold-air-feel-colder

ovgcguy

13d

I have no science to quote, but my experience says Yes.

35* and high humidity/rain/dew/mist/fog/clouds are the worst conditions for staying warm.

Id take 25* any day.

This exact scenario is how I decided I prefer ~160% overstuff. Only very high overstuff ratios keep full loft in adverse conditions like sleeping in a cloud. Even then, some insulation capacity seems compromised.

oeroeoeroe

12d

If you need 1,6 times the down amount, wouldn't it just make sense to go synthetic? Sounds like the weight is getting very close.

dantimmerman

12d

Overstuff does not indicate weight at all. It is purely a density measurement, defined as a percentage added above the base volume fill. You can change density by changing the fill or changing the volume. The weight and temp rating targets are set for the finished system, not set and then added onto for density.

oeroeoeroe

12d

I try to explain my question better.

Let's say synthetic insulation is half the insulation/weight of 950fp down. So you'd need half the insulation amount and save a lot of weight by using down vs synthetic.

..But if you need to use 1,6 times the down amount to stabilise it, the weight difference gets smaller, doesn't it?

ovgcguy

12d

Most makers overstuff to 130% as standard, so really I'm only saying add ~20-30% extra, or ~2-3oz on a 20 or 30* quilt.

Down will still be lighter even with excessive 180% overstuff on Gryffon gear quilts.

Down also compresses much better. A 20* comfort rated synthetic quilt is HUGE.

and high compression of synthetics is shown by BPL testing to reduce loft by 20-30% pretty fast, then it levels off. So to have a 20* comfort synthetic quilt would mean buying a 10* accounting for expected delofting. look up the weight and packed size of a 10*. Then you will see why Down is superior

oeroeoeroe

11d

Thanks for the comment. I had a back and forth with dantimmerman on a separate branch, I had a different understanding of what overstuff amounts mean.

dantimmerman

11d

It's semantics, but I think it is important to get this right. When you say "130%", I think you mean 30%. I could be wrong about what you mean.........but "overstuff" is an amount over the base fill amount. The base fill is 100%. The overstuff is 30%. Yes, to the builder, it is 130% in total, but if we are talking about the overstuff amount, it is 30%. A builder looking for 30% overstuff would multiply by 1.3. A builder looking for 130% overstuff would multiply by 2.3.

dantimmerman

12d

Nah. That really isn't how it works. You don't run all your calculations, based on targeted temp rating, and then just add in 160% overstuff. That 160% overstuff is factored in from the start, as part of the formulas that eventually arrive at your target temp rating.

This is a bit moot anyway. The per-unit warmth to weight ratio for synthetic never looks good compared to down. It's way off the mark. Synthetics have other strengths that often justify its weak warmth to weight to bulk ratio.

oeroeoeroe

12d

Ok, thanks for that. I still think I don't quite get it, what is the "base value", where does that come from? I thought that it is the measure of minimum amount of down which lofts the baffle to desired height in a lab, but seems I was wrong?

Thanks for the clarification.

dantimmerman

12d

Yeah, base fill amount would be the amount needed to just fill the chamber and no more. Maybe I'll try explaining by example. Say you want 2.5" average measured loft for a 20 degree rating with 160% overstuff density. You wouldn't sew in a 2.5" tall baffle because you'd overshoot your temp rating by miles once you multiplied by 1.6 to add 160% overstuff density. You'd probably end up with something like a 0 degree system with 5" mid chamber loft. So how do you hit your temp rating AND density requirements? You first determine how much fill you need for the rating and then reduce the baffle height to increase the density. That looks like this....

Chamber - 50" long (arbitrary) x 7" wide x 1.5" tall baffle = 525ci base volume

Fill volume - 50 x 7 x 3.74 (calculated loft) = 1309ci fill volume

This gives us a system with an average measured loft across the system of about 2.75" since the baffle height is 1.5 and the mid chamber "puff" should reach around 3.75" - 4".

The fill density is approximately 160% overstuff - 525ci x 2.6 = 1365ci.

Remember overstuff is an amount added above the base, so the base is 100%, we add 160%, so it is 260% in total.

The more we explain it, the more complicated it sounds, but really all we are doing is setting a target average measured loft for a temp rating and then reducing the baffle height to get the density needed for control.

oeroeoeroe

12d

Oh ok, so 160% overstuff actually means there's 2,6 times the theoretical minimum of down, much more than I thought. So in that case the difference between 130% overstuff or 160% is much smaller. That's the first way I was off.

And secondly, it sounds like the overstuff is more integral part of the design. I thought of it as "extra down", which is there to compensate if some down clamps collapse etc. How you calculate those makes it seem like it's also part of what determines the average loft. I thought that the base value already maximises chamber volume, so overstuffing wouldn't affect the puffiness of the chamber. But as there are also neighbouring chambers with that overstuff, the chamber gets more distorted and puffs out more, and thus it affects the average height, and loft anf warmth. And also all other measurements of the bag/quilt/garment, if I'm picturing this right.

I think I've seen you explain these in your blog, but I didn't quite get it then. Thanks for explaining further!

Editing in one more question: would you be able say that the way you define and think about overstuff is the industry standard ?

dantimmerman

11d

Right, multiplied by 1.6 would be 60% overstuff.

The "industry" is a big umbrella with lots of variety and there is usually not much standardization. However, I think overstuff has a pretty basic definition that really can't have too many different interpretations. It is literally just density. A space has a volume. Down has a known volume (fill power) to fill that space so that you can calculate how much of it you need to just fill that space. Anything you add above that is overstuff density.

The way that you're thinking of it doesn't change this fundamental definition. You're kind of over-complicating it though. You described adding a density to get the chamber puff and then adding another density as "extra down". The reality is that density is density. It is always going to be an integral part of design because any changes to it will effect all other aspects, regardless of the reason you add it. It isn't like you can add a density to puff the chamber out and then add another density that is just "extra down" that won't puff the chamber out. Both of those added densities are going to do the exact same thing and effect everything around it in the same way.

In summary, density is a single metric that influences all the other critical metrics like chamber volume, chamber width, baffle height, etc. These all interplay together. You can say that you want X density for chamber puff and X density for "extra down", but you'd just factor both of those into the single overstuff density value added. I mean, you could do it twice, but it isn't like those two added densities are doing different things.

dogpownd

13d

I live in San Francisco where it is often cool and very humid. No science involved, but yes, it can make things feel a lot colder.

Bagel_Mode

Skurka's Dungeon Master

13d

It sounds like you had no cover above you and likely had some wind. Both of which won't cause the mercury to drop, but can make you feel cold thanks to radiative heat loss and convective heat loss. The temp may be "high," but you can still be very cold as all the heat you make is lost.

NaturalOk2156

13d

I have had some pretty rough experiences cowboy camping in the wrong spot on the wrong night. Condensation makes a huge difference, even if it doesn't seem like much.

IMO it's all about location, location, location. Especially once you get up to high altitudes like that, and especially if you're using some kind of super-duper ultralight shelter. Camping in the clouds is usually not going to be fun unless you can really nail down some kind of extremely sheltered spot.

dantimmerman

12d

First we should define and understand what "overstuff" is. Overstuff is only density. A percentage added above the amount of fill needed to exactly fill a volume. In response to some comments, it does not indicate a finish weight because you can adjust density be increasing fill or decreasing volume. It does not indicate temp rating because it is not like you are calculating a fill based on a temp rating and then adding overstuff. You are targeting a temp rating at the end, after overstuff density is added.

Whether it has anything to do with you being cold or not, an overstuffed system is also subject to insulation loss from moisture build up. You may not see it as much since there is enough density to fill in and it might not happen at the same rate as a system with lower density, but if there is moisture being absorbed inside the fill, then those plumes will clump just the same, reducing the insulating air pockets. A low density system that gets wet will show gaps and cold spot because the starting density is only enough to fill out the space. Moisture clumps the down and reduces its fill power, hence the gaps. Those gaps result in much more heat loss than a dense system that has density to fill in for the fill power loss in the moist areas. However, again, that loss still would have an effect on the insulation, even in a densely stuffed system. Just, typically, not as much.

I would suspect that, as others mentioned, your sleeping cold has more to do with the moist air feeling colder, than it has to do with loft loss in your fill....but then again, I wasn't there. Here is why I think that.....Moisture absorbed from external condensation would soak in to the outer shell and top layer of down. Internal condensation from your body is the one that tends to be more hidden because it moves from the inside and condenses wherever the dew point is inside of the loft. You would probably notice loft loss from external moisture because the outside would be noticeably wet. The loft loss would be visible as soaked down on the top, under the outer shell.

Ill-System7787

13d

Has the quilt otherwise been comfortable at lower temperatures?