How to Prevent Internal Condensation

I get a lot of questions about tent condensation and how prevent it from forming on the inside of a tent or tarp shelter. Condensation is  a nuisance because it can drip onto your sleeping bag and gear and it makes your tent wet and heavier to carry when you pack it up. It doesn’t matter if you sleep in a “traditional” double walled tent, a single walled ultralight tent, or under a tarp, the causes and cures for condensation are all the same.

Why does internal condensation occur?

The main source of tent condensation is your breath. When you sleep at night, you exhale about 1 liter of water when you exhale. That water vapor is trapped by the outermost wall of your tent or shelter because it has no place to go. If there are 2 people in the tent, then you have to deal with 2 liters of tent condensation, and so on as you add more people.

Storing wet clothes, wet gear, or cooking in a tent can also contribute to internal condensation. So can sleeping near a stream, lake or other wet area when it’s humid and there’s no wind at night.

How can you prevent condensation from occurring?

The best way to prevent the build up of condensation in a tent is to leave your rain fly open at night to promote as much ventilation as possible.  If water vapor can escape out a vent, window or door, you can significantly reduce or eliminate the amount of tent condensation that occurs.

What if it’s raining?

If it’s raining and you are sleeping in a double-walled tent, make sure that the rain fly is stretched as far away from the inner tent as possible, particularly along the sides and corners of the tent. If your fly clips onto the base of your inner tent, consider staking it out separately to promote more airflow between the layers.

Well Ventilated Vestibule of a Tarptent Squall 2

Well Ventilated Vestibule of a Tarptent Squall 2

Another thing you can try is to unzip or clip the rain fly half way up so that you get more ventilation. The same holds for a tent vestibule. Here’s an example of what I’m getting at (above). Shown here is the front vestibule of a single walled Tarptent called the Squall2, but you could rig something like it up with the rain fly of a double-walled tent. I’ve slept through incredible rain storms in this tent and never had rain blow inside, but depending on the shape of your tent and its fly, you’ll need to find the perfect balance between rain cover and ventilation.

How can you reduce the weight of a wet tent or tarp?

If you’re not in a rush, you can let it dry in the morning sun, but that might take a while. If you have to get going, another option is to wipe down the rain fly using a clean camping towel, which will remove a significant amount of that water. After that pack the fly away in an outer pack pocket or in a separate plastic bag to keep it from making your other gear wet.

Can you set up a wet rain fly at night?

Absolutely, although you might want to pitch camp a little early that evening so that your tent has a chance to dry out before you want to get into it. I’ve set up damp tents in summer and had them dry within an hour, but your mileage may vary.

Do you have any other internal condensation tips?

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29 Responses to How to Prevent Internal Condensation

  1. marco October 19, 2011 at 2:40 am #

    Yeah, condensation is a pain. There are a couple things you didn't mention, but, given the brevity of the article, that's OK. Evaporative cooling can intensify condensation. This is where the water from condensation begins to evaporate, further cooling the surface of a tent and causing *more* condensation. "Like begets like" as the saying goes… Also, the material of the tent itself. A highly breathable material, like Epic or even Gortex, will allow moisture vapoure to escape, but will not allow water to penetrate. But, this is expensive. This is a huge drawback to cuben. Silnylon (a common tarp material) breaths slightly, not enough to do any good, though.

    The main problem in three season tents is lack of temperture regulation along with the moisture. It is the difference between the two areas separated by a fairly impermiable film (the tent skin) that causes condensation. The ventilation scheme for most UL tents and tarps is ignored. You need a low inlet and a high outlet, given still conditions. The vents should be about the same size and large enough to ventilate your breath and any escaped body heat. One thing that can help is to have a high vent (about 8-10" diameter or ~39.5 to ~50.0 sqin) and hang a candle (say a UCO candle lantern) about 6-8" below the vent. This will "drive" the ventilation using the fact that "Heat rises" and moist air is lighter than dry air. Of course, you will *still* get some condensation…in some conditions it will happen. No tent manufacturors I know of bother with large top vents, unfortunatly. It is fairly easy to modify your tarp or tent, though. Even the Stephensons designed tents have too small a top vent.

    Larger volume works well to mitigate much of the temp/moisture difference. A two man tent with a single ocupant will not produce as much moisture, as you say. Not as warm in winter, also not as condensation prone. In winter it is easier to shake off most ice dropplets or condensation, anyway. And the air is usually much dryer, to start with. But for those bad temps (between 25F and 40F) a larger tent/tarp can help. But, you pay the weight penalty.

  2. Chris (i-cjw.com) October 19, 2011 at 4:07 am #

    "Clean camping towel"? That must be American for "your mate's sock"…

    Pitching your tent so the vents align with the prevailing wind also makes a heck of a difference.

  3. Earlylite October 19, 2011 at 4:08 am #

    yes it does – good point.

  4. Earlylite October 19, 2011 at 4:12 am #

    Marco – I have an fancy tent with Epic walls and it gets as much condensation as any other tent as far as I can tell, and I have to keep the door and rear window open at night It's only saving grace is that it weighs under 3 pounds.

    Maybe the event tent from Rab is better, but I'm skeptical. I think we generate (exhale) too much water vapor at night for a breathable fabric to keep pace.

  5. Guthook October 19, 2011 at 6:31 am #

    I don't have enough experience with mostly enclosed single-wall tents like Tarptent to make a good call on condensation, but I've never had condensation in my tarp pitched a-frame style. My Six Moon Designs Wild Oasis, despite a vent at the top, always collected condensation in wet weather or in humid environments (anywhere on the east coast, for example). That vent probably just wasn't enough. The condensation sure was annoying, though.

  6. marco October 19, 2011 at 6:38 am #

    Yeah, probably not enough of a help to notice. You are right. I am thinking of dumping a 1 liter bottle of water all over the inside of the tent and sleeping bag…ouch. Probably it will take more than breathable materials to make a difference. Bibler had the older single dome tent that built up condensation, too.

  7. Earlylite October 19, 2011 at 6:49 am #

    I've had very good luck with Tarptents on the east coast. My squall 2 and lunar solo rarely had any condensation because they had that hiked up vestibule (even when deployed). If you have a double-walled tent today and want to move to something lighter anyway, I recommend people get a tarptent like a contrail or a squall2 instead of a tarp, which is a harder transition to make since it's so open all around and doesn't have a floor. Using a tarp is the ultimate way to stop most condensation, but even then you need to crack open shaped tarps, like a pyramid, to avoid getting wet.

    • Oscar September 18, 2013 at 12:26 pm #

      I love my Tarptent Double Rainbow with the dual vestibules for exactly this reason – I always leave both vestibules fully opened and that makes for great ventilation even in rain (unless it is really windy and rain coming in at a severe angle).

      • Grandpa September 18, 2013 at 1:19 pm #

        I’d give a double thumbs up on the Tarptent Double Rainbow I have, however, my thumbs are immobilized in braces right now for arthritis, carpal tunnel, tendinitis, and nerve damage. I have to settle for a virtual thumbs up. The Double Rainbow is an awesome tent.

  8. Grandpa October 19, 2011 at 10:33 am #

    I have a Tarptent Sublite (made of Tyvek) and a Tarptent Double Rainbow. I haven't had much problem with condensation in either one. Both have netting all the way around and ventilate well (sometimes too well if it's really windy outside). The Sublite also has a top vent. My brother in law and I will give the Double Rainbow a workout next week for forty miles on the Buffalo River Trail. The Double Rainbow has vestibules and doors on each side and the Sublite has a single vestibule and door.

    My brother packs a synthetic chamois in a Ziploc bag to wipe down the condensation on the inside of his tent. Of course, the last time we hiked together, the chamois and Ziploc were a frozen brick in the morning.

  9. Earlylite October 19, 2011 at 1:50 pm #

    I never realized that the Sublite was made out of Tyvek – how interesting. How's the waterproofing? Did you have to seam seal the stitching? Curious, I'm starting to mess around with Tyvek myself.

  10. Grannyhiker October 19, 2011 at 4:27 pm #

    I've found that the closer the tent ceiling is to my face, the more condensation. That's why I've given up on side-entrance tents.

    Trying to crowd myself and my 75-lb. dog into a solo tent (such as the SMD Lunar Solo) completely overwhelmed the ventilation system. Add the ceiling right over my face, where I could hardly sit up without brushing my sleeping bag against the wet tent–horrors!

    A larger tent really helps, despite the increased weight. I've had little to no condensation inside a Tarptent Squall 2, even with 2 people plus dog inside, with drizzling rain and fog, close to the coast. The same is true for Tarptent's Rainshadow 2 with three inside.

    With a double-wall tent: I used to have horrendous condensation inside the fly of a Sierra Designs Clip Flashlight, to the point that the moisture would drip through the inner tent, leaving puddles on the floor and my sleeping bag. The outward-slanting screen door meant that even in the mildest drizzle I had to close the fly over the door. I urge anyone getting a double-wall tent to make sure that the screen doors are vertical so they can be left open unless the wind is blowing in!

    If the wind is blowing, even if it's raining, you won't have a ventilation problem. The problem comes if you don't wake up and open things up when the wind stops!

  11. Grandpa October 19, 2011 at 5:31 pm #

    The Sublite is made of Tyvek, the Sublite Sil is Silnylon. I don't remember if I seam sealed it. I'll have to check. I did seam seal my Double Rainbow.

    The Sublite I have stays relatively cool in warm weather. Henry Shires says it will handle moderate rain but recommended the Sil for a planned Alaska hike. I don't think I've ever had to test it in the rain.

  12. Grant November 1, 2011 at 2:26 pm #

    Packed a few tents in all types of good and bad weather. Never noticed condensation in a tent until last weekend. My Squall 2 was a bit misty eyed in the a.m. Temperature dropped into the 30's from the evening 60's. Ground was a bit moist. We were uphill from a large acre lake. Maybe one quarter mile as a drunk crawls. Never noticed or cared too much until I started to read about tent condensation. Of course my first experience as a child I woke up in a stream in a WWII floorless tent. Since then everything seems kind of dry. Peace out

  13. Susan "Backpack45" Alcorn June 28, 2012 at 2:50 pm #

    Where you pitch your tent is important, too. Setting up your tent of an appealing little patch of green grass will cause more condensation to occur than setting up on a dry patch of ground will. And as Grant pointed out, staying out of stream beds is important, too!

  14. Keith "Popeye" Rayeski June 28, 2012 at 2:56 pm #

    and even better solution, use a tarp, not a tent…..less weight, no condensation. Problem solved…thank you very much! ;>)

  15. Hikin' Jim June 28, 2012 at 4:17 pm #

    My biggest problem is in weather from about 25F to about 35F. I have a SMD Gatewood cape that is open all the way around on the bottom and has a top opening, but in cold weather, I get condensation like nobody’s business. As Grannyhiker observed above I think the issue is that my face is so close to the tent wall.

    HJ

  16. Oscar Lazarp June 28, 2012 at 9:36 pm #

    One of the things I like about my Tarptent Double Rainbow is the double vestibules/porches that are designed to be held open with hiking poles. They allow for great ventilation even if it is raining. With no wind – leave both open. With wind – depending on the wind direction – you can leave one side closed and the other open. You can also adjust the height of the bathtub floor walls for more or less ventilation

  17. Barney schoonover January 3, 2013 at 10:13 pm #

    I wrote in about living in a car cover and having a condensation problem, i want to know what you think if i put heavy plastic over the poles just like the cover is, just about a 2 inch space between the plastic and the outside cover. I have a heater, tv refrigerator and freezer in the space along with my bed and a chair. so the I need to stop the condensation. Any help or suggestions will be appreciated. Thank you.

    • Earlylite January 3, 2013 at 11:46 pm #

      I think people who live under a car cover is beyond my area of expertise.

      • Keith Rayeski January 4, 2013 at 9:08 pm #

        AGREED Philip! If I may add to that…those who live under a car cover, have all the modern conveniences to INCLUDE, the INTERNET, are beyond ANY of our singular or combined area of expertise!!

  18. Harold King August 11, 2013 at 6:20 am #

    It’s not a perfect solution but try snuggling into a good quality sleeping bag. Maneuver your head until just outside the tent and then close the door zip down as far as it will go. Result tent condensation minimal.

  19. Derek Hansen September 17, 2013 at 4:57 pm #

    Is there anything that can be done for mist, fog, or low hanging clouds? I tarp camp a lot, particularly with hammocks, and condensation has rarely been a problem except in these conditions. The moisture is palpable, thick, and you can feel it collecting on your as you walk. Breath condensation seems fairly easy to mitigate, but I have yet to really solve condensation when Mother Nature brings it.

    • Philip Werner September 17, 2013 at 6:57 pm #

      I think the only thing you can do is pick sites where mist or fog won’t be an issue. I’d stay away from the bottom of valleys and water. People don’t realize how much moisture is generated from camping beside a stream or pond.

  20. Andy Kowalczyk September 17, 2013 at 5:08 pm #

    For winter camping, condensation is not a problem in a quinzee :-)

  21. Stanley Mckinney September 17, 2013 at 8:30 pm #

    Backpack in the rain, problem solved, :) Guys, no way to stop condensation in in climatic weather conditions, live w it and take a pack towel along for the ride. most of all, have fun and remember, this is very important. The minute you stop letting condensation ruin your trip the sooner it will stop i promise!

    • Grandpa September 17, 2013 at 11:46 pm #

      Love your thinking. As they say, life is 10% what happens and 90% how you react to it.

      Every day I’ve backpacked in the rain was better than being in the office on a sunny day.

      • Stanley Mckinney September 18, 2013 at 7:35 pm #

        see everybody, listen to your grandpa, he’s got it figured out.

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