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Condensation . . . a foolish obsession?
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Home › Forums › Gear Forums › Gear (General) › Condensation . . . a foolish obsession?
- This topic has 29 replies, 19 voices, and was last updated 5 years, 9 months ago by Dale Wambaugh.
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May 19, 2018 at 11:54 am #3536613
For those of us who occasionally obsess or at least worry about tent ventilation and condensation, a timely reminder. It’s just simple physics and sometimes there is nothing we can do about it. Last night I rigged my cuben flat tarp over my bug bivy . . . a test pitch, nothing more; I didn’t even spend the night in the bivy. It was a cold, clear, still night with temperatures falling to near frost levels in the morning. The grass was soaked, and both the outer and inner surfaces of the tarp were covered in dew . . . condensation, in other words. The tarp set-up of course, was the ultimate in perfect ventilation, and there was nothing that could be done to prevent this. It’s just the way it is sometimes :)
May 19, 2018 at 12:06 pm #3536614In other words, if the leaves, grass, bushes, ground, etc. are wet in the morning…your gear will be wet :) Adopt nature’s strategy and deal with it.
May 19, 2018 at 12:15 pm #3536616Yeah, at times there is nothing you can do. You simply have to generate less Relative Humidity inside the tent/tarp than outside it.
Inside heat is the usual method to reduce the RH. A candle, your body, etc are all heat producers. Dry, heat will let more moisture dissolve into the air. But, most heat producers also produce water vapor adding to the interior humidity.
Ventilation is the other method. This will exchange interior air (heat and moisture) with outside air. Under most conditions this works OK, but under your conditions, it won’t do much.
Unfortunately, cuben conducts heat a bit better than nylon. So, it is hard to hold a heat “bubble” inside. Typically, you need a 1-3 degree difference between inside and outside air, assuming you hold the humidity constant. If you sleep under the tarp, you also add humidity soo, this often fails as a good method.
As you say, it is often impossible under some conditions to avoid condensation. But, I have noticed my bag remains dry, even during a rainstorm, despite condensation on the tarp. The trick is managing the condensation and getting it to run off.
May 19, 2018 at 1:05 pm #3536620Would putting your sleeping bag inside a large trash bag be a lightweight means to keep the bag dry while sleeping in such conditions?
May 19, 2018 at 1:25 pm #3536624You’ll soak it from within if the bag can’t breathe
May 19, 2018 at 1:45 pm #3536629If it’s clear, your tent fabric will cool maybe 10 degrees from radiative heat loss
Because of radiative heat loss, it cools everywhere until the RH reaches 100%, but your tent fabric will be 10 degrees cooler.
There’s no way to prevent condensation in this case. If you just hang a piece of fabric out with perfect ventilation it will still get condensation
If you set up under a tree so you see no clear sky, it’s much better, although if it’s 100% RH you’ll still get some condensation
May 19, 2018 at 7:29 pm #3536685Tarptent’s more recent offerings seem to deal with the ventilation problem as well as anyone and better than most.
Both my Scarp 2 and Moment DW have “eyelid” vents at the peak area and have low vents at the ends which gives a nice natural upward convection air flow. This gets moist air out about as well as possible but there are always cold/damp conditions that overwhelm it.
Any tent with two opposing doors can vent well if there is not a windstorm during rain or snowstorms. My TT tents’ doors have mesh in the top 1/3 which, again, helps with the natural convection of rising body heat.
BTW, I’ve found that most tent floor tub “walls” tend to collect condensation at times, especially in winter in the form of frost. To keep the foot of my bag dry I zip up my WPB parkas and slide them up over the foot of my bag.A bit more warmth and good moisture protection.
May 19, 2018 at 8:30 pm #3536691Those small vents don’t do a lot in my experience
Two opposing doors is good. Opening one door completely is pretty good.
May 20, 2018 at 12:37 am #3536739Basically, if the temperature at the surface of the fly is below the dewpoint, there will be condensation. Lots of things affect those two variables, including ventilation, but in my experience the two most important things one can do to minimize condensation are (1) set up under a forest canopy on clear nights, and (2) don’t set up where outside sources add moisture to your tent. W.r.t. the latter, it means stay a good distance from water and don’t set up on vegetation or wet ground. A third thing would be to have a tent configured for cross-ventilation, but that doesn’t help much on still nights.
May 20, 2018 at 12:59 am #3536749Often when people comment that they don’t get condensation on their tent , what they really mean is : I haven’t camped in the same situation as you have.
(ever noticed that after reporting heavy condensations inside a tent the next comment sometime is : all the other tents nearby also…)
May 20, 2018 at 1:51 am #3536761Yeah, I agree with Jerry. Small vents at 100% RH and still conditions don’t help enough to bother with. Though, in cold weather (ie <40F) you can place a small candle lantern under the peak vent to drive the ventilation.
May 20, 2018 at 2:05 am #3536767Tent condensation in the coastal mountains of central / northern California happens most of the time, no matter where or when you camp.
IME, silnylon is both a condensation and dirt magnet, resulting in a much wetter, heavier, and dirtier tent in the morning, even if I wipe it down repeatedly while constantly wringing out the towel.
Is DCF / Cuben much better? Are any other lightweight fabrics much better?
— Rex
May 20, 2018 at 3:01 am #3536782Would doors that expose some of the bathtub floor offer much more ventilation? I’m thinking about hot nights more than moisture management. I know they let in rain, by it’s not usually raining.
May 20, 2018 at 3:27 pm #3536852I have abandoned the fight and wave a pack towel in surrender each morning.
May 20, 2018 at 4:30 pm #3536869Yup, there are times when a good pack towel in the final solution :)
May 20, 2018 at 4:59 pm #3536883” I know they let in rain, by it’s not usually raining.”
Yeah, I leave door open and close it only as much as required to keep rain out. Wind is also a factor, if it’s raining and not windy I can leave door open.
May 20, 2018 at 7:56 pm #3536920I have a cuben tent and rain jacket. Because they do not absorb water unlike sil nylon, I can just wipe it dry in the AM and pack it dry. The tent condenses a little; the jacket none. I am amazed and happy. Sil nylon is fine in low rain..
May 20, 2018 at 9:55 pm #3536944Being a “belt & suspenders” type I’ve re-coated both my Moment DW and Scarp 2 with a 5:1 mix of, respectively, “odorless” mineral spirits and GE clear Silicon II. Shaken VERY well in a 1 pint jar and applied with a small (6″), short knapped roller. I applied the mix in 2 ft. square sections and immediately wiped each section down with a sturdy blue paper shop towel for even coating.
That treatment has added maybe an ounce or so to each tent but they will never “mist thru”.
HOWEVER, I later discovered that Henry Shires’ more recent Tarptents (say since about 2010) have a heavier silicone coating and do not need this treatment for even monsoon rains. Nobody has ever reported “mist thru” since Henry changed to the heavier coating. And I suspect most “mist thru” reports actually came from condensation being knocked from the inside of the flys by the heavy rain. Jus’ sayin’…
Wish I’d known that before I treated my own Tarptents.
May 20, 2018 at 10:10 pm #3536949I’ve spent most of my life living at the dew point! Ventilation will help keep your breath and body moisture from adding to the fray. When you are camping in cool high humidity conditions, dew happens. A bivy with a breathable DWR top and waterproof bottom can help. A sponge, bandana or microfiber cloth can be used to bail things out. Having a shelter big enough to avoid touching the fabric really helps. In the old days with wax treated cotton tents, you didn’t dare touch the fabric as that it is where it would drip and of course that was right over your face.
Camping away from lakes will help avoid the higher humidity. I’ve never been wetter than when sleeping under the stars on grass next to a beach. It was such a lovely summer night when I dropped off to sleep and like waking up in a car wash at 5AM.
I’ve woken up to dew frozen to the inside and outside of the tent when the temperature continued to drop past the dew point and freezing. Like a big ripstop popsicle to pack up in the morning and all the brush and grass in the camp was the same way. Hiking brushy salal trails early in the morning dew might require rain pants.
May 23, 2018 at 4:34 pm #3537807Don’t worry if you get a little wet. You wont melt…unless you are made of sugar.
Of course, If it’s winter tenting you will get a little frost. It shakes off easily when breaking down.
Happy trails to all!
May 23, 2018 at 4:53 pm #3537810frost on inside of tent isn’t too bad, it won’t soak into you if you brush against it
shake tent off before packing. it helps if it warms so that the ice starts melting
May 29, 2018 at 7:45 pm #3539101How do hot tents handle fog, excessive dew, and other extreme condensation scenarios?
May 29, 2018 at 7:58 pm #3539103Wood heat is super dry. They make iron kettles to keep on a wood stove to keep it from getting too dry. Having lived in a couple places with wood-only heating, you can feel it coming in the door.
Of course the challenge is getting it light for backpacking use.
Jun 2, 2018 at 4:32 am #3539760Dale,
“…you can feel it coming in the door.” (cold air)
The key to efficient wood burning stoves is to bring ALL the combustion air into the fire box via a pipe from the fire box through the house or under tent wall from the outside.
This keeps the stove from sucking up warmed air and reduces fuel consumption quite a bit.
Jun 2, 2018 at 4:49 am #3539768No, I meant you can feel the dryness when coming inside. Half the year here is 45f, 90% humidity and overcast. Can I send you some moss salad with mold and algae dressing?
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