Tarp Condensation

[Tim Czarkowski]

So this weekend my wife and I were camping with my 10×10 flat tarp here in Florida. It was about 70 during the day and then dropped to around 45 at night. It had rained all day the day before so it was fairly humid as usual.

I set it up as an A-frame with my trekking poles fully extended and the guy-lines 3 feet out on the sides. My wife's quilt had a ton of beaded up condensation on it in the morning. Mine seemed dry but I was using a cheap army navy job and I just assumed it absorbed it where the higher quality quilt resisted it.

What can I do to avoid that in the future? It was warm and sunny that morning so I laid it out to dry while we at breakfast and broke camp. However if that wasn't the case and that happened a few nights in a row I think we'd have a problem. I figured having the tarp setup nice and open like that would avoid condensation problems but it was a pretty still night. Would a different setup have avoided it? Are there certain conditions where I should expect heavy condensation?

Thanks.

[Jerry Adams]

How big was the gap between ground and edges of tarp? Bigger gap helps.

[Tim Czarkowski]

The sides were probably around a foot and half or two off the ground. I had the trekking poles fully extended, so around five feet high and the guy-lines were also fully extended, so around 3 feet long. This was setup as an A-frame. I was thinking maybe a lean-to or modified lean to might have been better but haven't tried either before other than screwing around in the yard.

[Jerry Adams]

Condensation on under side of tarp?

[Dale Wambaugh]

Welcome to life at the dew point in a single wall shelter! Ventilate, use a bivy, or get a double wall tent.

A sponge or pack towel can help manage the moisture.

[Steven Paris]

Some thoughts: What kind of surface did you set up on? What kind of groundsheet, if any, did you use and how much ground surface area was covered under the tarp? Were there any breezes? Where you in a low point (dare I say "valley" in Florida?) or camped adjacent to water?

There are just some places where condensation can't be avoided. Not just you and your wife, but vegetation, especially tall grasses, can give off a lot of condensation into the air, straight up onto the tarp. It sounds like you had decent ventilation around the edges, but maybe there wasn't enough air circulating to move that moisture anywhere.

While Dale is right about a double-wall shelter, there would still be some condensation on the inside of the fly; it just wouldn't have a chance to come into contact with your bags.

[Tim Czarkowski]

There was condensation on the underside of the tarp but that's not usually a problem. It was the condensation on the quilt that was the problem.

Ventilation is what I'm after and I thought I had the tarp setup pretty well for that. I'm not really interested in carrying a double wall tent(or a tent at all) and certainly not bivys. I could see wiping it down helping. Does the condensation usually come from condensing on the tarp and then dropping, or actually condensing on the quilt, or some combination of the two?

We were setup on a grassy area next to what is apparently a prairie although it looked more like a marsh like to me. Being the dry season the prairie was actually mostly dry. I used a 5×8 poncho/tarp as the ground sheet. Does a ground sheet generally make it better or worse? The was very little if any wind and I assume that was a big part of the problem. We weren't in a low point, the area is pretty flat and I certainly wouldn't call anything I've seen here a valley, lol.

I was hoping that setting it up differently might help, but thinking about it now, if there really is no wind I don't think it would make much different. What do you think?

[Dale Wambaugh]

Location, humidity, and dew point are all contributors. A full ground sheet can help on grass or wet ground.

When the conditions are bad, there isn't a lot to be done. You could have moisture on the sleeping bag from the tarp, or just dew in general. I have cowboy camped and was covered in dew in the morning. A light breathable bivy gives another layer of protection.

[James Marco]

Yeah, like Dale says, sometimes there is nothing you can do. Around the dew point, you will get condensation. Grass, leaves, and other plant growth (even fungi) will all transpire or breath, putting moisture into the air. Wet ground can contribute to it, even if it appears dry for the first inch or two. Breathing under a tarp adds moisture to the air. Generally, when the entire area has condensation, your tarp will, too. No amount of ventilation will protect you under all conditions.

Even a double walled tent will have condensation. But, body warmth will drive a good majority of it to the outside layer. Second nights can be a problem, though. But I have had frost over everything in my tent, too. One of those things you just deal with the best you can. Usually this means a delayed start, opening up as much as possible to dry stuff off. Or, if it is real early, just packing up shaking it off, and drying what you can with a bandana. A fire in the morning helds quite a bit, adding warmth to the surrounding air and raising the dew point, hence evaporation rather than condensation. This is where a lean-to pitch can really help, since it is set up near a fire.

Would a lean-to help over an A-frame? Sometimes slightly, sometimes not at all, sometimes a lot. Depends on the exact conditions. Would a ground cloth help? Again, maybe. Plastic or cuben would have helped. Silnylon, not so much. Tyvec, less than silnylon. Even plastic sheets will bleed moisture vapour. Silnylon will hold water, but will not stop water vapour from penetrating(set a water filled bag on top of some raw wood.) Tyvec is designed to allow a house to breath moisture out (since you never trap insulation between two moisture barriers in a wall.) A PU coated ground sheet or tent foot-print will stop a lot of it. It depends.

Basically, sometimes, you end up getting a lot of condesation with a tarp. Is it better than a tent? Depends on how you look at it. Usually the total amount is less. Some will say you get less with a double walled tent, but, you usually get at least as much; you just don't notice it on the inner body so much. Some will say it is easier to deal with using a single walled tent, just wipe it down. With a tarp, you can just shake most of it off. But, I hate to carry dead weight.

[Jerry Adams]

That's weird there was condensation directly on sleeping bag. Normally, the problem is condensation on under side of tarp, then getting on sleeping bag.

Even if there's no wind, there's a little, so maybe raising tarp would help.

Sometimes a treed area will be a bit warmer, and thus less condensation.

[Link .]

Night Time Condensation on Tarp and Tent Fabrics
Condensation in Single-walled Shelters: Contributing Factors and Tips for Reduction

[Larry De La Briandais]

If the temperature of an object drops below the "dew point" then condensation will form. I other words, if the temperature of something (such as the outer layer of a quilt/SB) drops low enough that it cannot support the water vapor in the surrounding air it will form condensation. The only thing you can do is keep the object warmer than that, or keep the percent of water vapor in the air low enough. A quilt that was rated for a higher max temperature could work, if it will keeps the user warm enough. Trying to keep the percent of water vapor low enough can be difficult. You already had a fairly open environment and the water vapor percent probably wasn't much higher than the surrounding air. That's the benefit of a tarp and there isn't much more you can do, unless you plan to carry a dehumidifier. ;^)

[Ben C]

Tim, I think there are some conditions in the southeast US when everything gets wet at night. I fairly recently spent a night in an AT shelter. It had rained most of the day and everything felt wet outside. I slept in a dry shelter but woke up with some condensation on my quilt. There was no tarp to collect condensation and the shelter was a 3 walled shelter with plenty of ventilation. It seems that when the air is that wet, water condenses on everything.

[Dale Wambaugh]

"The dew point is the temperature at which the water vapor in air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At temperatures below the dew point, water will leave the air. The condensed water is called dew when it forms on a solid surface."

The real clue is to look at the vegetation around your camp the next morning. With heavy dew conditions, it can be soaking. I have walked out brushy trails in the early morning that were so wet that I needed rain pants. One memorable time was in a river canyon, so there was no lack of water and it was the middle of summer with no recent rain. Like walking through a leafy car wash!

It is a regular thing in the PNW, where there the temperatures are usually cool with high humidity. Take the dew and then freeze it later in the night and you have frost everywhere to add to the fun.

I wonder if a fabric coating could be made to impede the formation of dew?

[Franco Darioli]

"The real clue is to look at the vegetation around your camp the next morning"
I have stated many times that having had well over 300 tents set up over the years on the same lawn, one thing they all had in common was :
if the grass was wet in the morning after a non rainy night, the tent was wet too.
That was the same for silnylon. PU coated nylon, Gore Tex, Cuben, polyester and Epic. (I seam seal tents and play with them too…)
Often I had 2-4 tents up and no , no real difference from one to the other.
When I read of "zero condensation in my tent" I automatically translate that to : I was not in a situation where condensation occurs.

[Larry De La Briandais]

"I wonder if a fabric coating could be made to impede the formation of dew?"

I have wondered that also. I tried Never Wet as an experiment and if anything it allowed more condensation, not less. I guess something that would absorb the water then "liberate" it back into the air when possible…

[Lance M]

I can't speak for conditions in Florida, but the times I've had condensation problems seemed to be strongly related to site selection. Here's a few pictures. July, NoCal, clear sky, slight breeze, near a ridge-top, but with green vegetation.

Tarp or cowboy camping, I've had better luck under tree cover on pine needle covered ground while avoiding low spots/valleys.

[William F]

Good point Dale. I feel like I get more wet on those dewey mornings than if it was pouring rain. The amount of water that some underbrush plants can hold when undisturbed is ridiculous.

I agree with Franco. Under certain conditions it is inevitable and the best we can do to mitigate the dew is through appropriate ventilation, site selection, and a sponge/rag to mop up what we can't control. Sounds like Tim just had ideal conditions for dew formation. Do you have any weather condition info Tim? Temps and temp swings? Relative humidity estimation? Hard to say without accurate readings to work with.

[Michael Gillenwater]

It maybe coming. New nanotech hydrophobic coatings may one day have tents and sleeping bags that are not just waterproof but actively repel water like two same pole magnets.

as or the condensation, i wonder if the conditions were just right such that it was not moisture from the air condensing on your wife's bag, but moisture given off by her body as the temperature dropped dramatically.

[Jerry Adams]

I have noticed that for the fabric near where I exhale, the shiny nylon fabrics tend to get wet with condensation. Supplex is better. Something about the micro texture.

Supplex is too heavy though. I put a couple square feet on the flaps next to my face.

[Larry De La Briandais]

"It maybe coming. New nanotech hydrophobic coatings may one day have tents and sleeping bags that are not just waterproof but actively repel water like two same pole magnets."

It doesn't appear that repelling water and inhibiting the formation of condensation are the same. I tried Never Wet, which is a commercially available nanotech hydrophobic coating and it did not repel condensation. If anything it made it worse.

[Ryan Smith]

I will second what Ben said. Seems like about 1/2 the nights I'm on the trail, I wake up with moisture all over everything. Conditions in the SE are perfect for creating a lot of dew I guess. Green leaves, green grass, lots of water and a lot of humidity.

Ryan

[Desert Dweller]

Given the scientific evidence, moisture on one bag and not the other I would say that the aforementioned reason is the most plausible.
"air condensing on your wife's bag, but moisture given off by her body"

Certainly atmospheric and duff vegetation and moisture content contributed.

[Glenn S]

Guess I'd say it was the sharp temp drop combined with all the previous rain. You got covered in dew, might have even been sleeping in a cloud if there was some overnight fog that didn't burn off until the sun came out. Might have actually been drier inside a tent. Sleeping higher might help a little, but only if there was fog I suppose. It's a pretty common occurrence up here, with the wide temp swings and 10k lakes and all that.

[Tim Czarkowski]

Thanks for the link to the article, I feel like I just got out of condensation school, lol. It seems to confirm what many of you have said, given the conditions(Lots of rain the previous days, damp ground and plants, high humidity, 35 degree temperature change, no wind, sleeping near large prairie, two people) condensation was coming no matter what.

I think there were two factors leading to the condensation on my wife's quilt vs my bag, difference in ratings and humidity given off by her vs me. The quilt is rated 20 degrees where mine was rated 45 and really not comfortable much below 60(yes I was cold). She also gets cold easily and tends to want to duck her head under the quilt even though I have told her that is counter productive(I think I'm going to get her a down hood.) There is of course the possibility that the DWR on my $30 bag was not as effective as hers and simply absorbed the water.

It seems there were two things I could have done to help, wipe the tarp down every now and then and try to pitch the tarp with steeper walls, both of which would minimize any dripping. The only way for me to get steeper walls would be to lower the sides closer to the ground or raise the ridge-line. Since I already had the trekking poles fully extended I would have to setup a ridge-line between two trees to get it any higher. I really don't care to do that. It seems like dropping the sides lower down would be counter productive in that it reduces airflow. However if it was truly a calm night it might be an option and if some wind did come up I could always raise them.

Are there any pitches that have steeper walls but still have excellent air flow while setup with trekking poles? Do you think setting it up so one end of the ridge-line is a bit lower help?

I still love my tarp by the way ;)

Tarp on a different morning.

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