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How to Prevent Tent Condensation

How to Prevent Tent Condensation

Tent condensation happens to everyone. It’s one of the unavoidable consequences of camping or backpacking with a tent, but it’s usually just a nuisance and not the end of the world.

Still, there are a lot of misconceptions about tent condensation and whether you can buy a tent that completely prevents condensation. Unfortunately, the laws of physics are hard to avoid. Condensation is a natural process that occurs with all tents, both single-wall and double-wall tents, no matter what fabric or materials they’re made of.

What causes tent condensation?

Condensation forms when humid air encounters a colder surface like the interior walls or roof of your tent. It’s the same process that occurs when you take a hot shower and the steam makes your bathroom mirror wet. Steam, which is simply water vapor in a gaseous form, is cooled when it hits the mirror, converting it to liquid water droplets that cover the mirror with moisture.

How to reduce tent condensation

The amount of condensation you experience is a tent is a function the humidity in the air around you and the moist air you expel from your lungs when you exhale. In order to reduce the amount of condensation that forms in your tent at night, you should:

  1. Ventilate your tent by rolling back the rain fly or leaving the vestibule door open so humid air and moist exhalations from your breath can escape.
  2. Remove wet clothes or shoes from your tent at night. Dry them outside or put them inside a stuff sack to reduce nighttime humidity.
  3. Cook and boil water outside your tent to avoid increasing the interior humidity level.
  4. Avoid camping near streams, lakes, ponds, or in wet or marshy areas where the humidity is higher. Yes, it’s nice to camp next to a water source, but you’re asking for tent condensation when you do it.
  5.  Avoid setting up your tent at a low point in the landscape where cold air pools at night. If your tent’s walls and fly are warmer, you’ll have less condensation.

What is the best tent for avoiding condensation?

There really is no best tent for all climates, seasons, and locations. Good campsite selection is always going to be the most important factor in preventing tent condensation. But different styles of tents have different pros and cons that are worth considering.

Single-wall Tents: Ultralight-style tents, tarp tents, and tarps are usually quite easy to ventilate, although they can also be quite drafty in cooler weather. You might even have to bulk up on your sleep insulation to stay warm at night. However, if you only camp in warmer weather, they can be a good choice.

Double-wall Tents: Double-wall tents tend to have less air-flow, but can be used across a wider range of temperatures because they retain more body heat at night. While they don’t eliminate internal condensation, they keep it away from you and your gear. Any water vapor inside your tent, from your breath for instance, will pass through the mesh inner tent and collect on the inside of the rain fly instead.

What if it’s raining?

If it’s raining, your chance of experiencing tent condensation will increase because there’s more humidity in the air. It’s a lot like camping next to a stream or a pond, but many times worse. If you have a single-wall tent or shelter, your best bet is to carry a small camp towel or bandana that you can use to wipe away any tent condensation before it drips onto your gear. If you’re in a double-wall 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.

How significant is moisture in your breath?

When you sleep at night, you exhale about 1 liter of moisture. You’re not aware of it, but its one of the reasons why you wake up thirsty at night or in the morning. 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. If you’ve ever camped in a tent in winter, the inside of the rain fly will usually be covered in frost in the morning, mainly from occupants’ breath.

What if your sleeping bag gets wet from tent condensation?

Most sleeping bags and quilts have a water-resistant exterior shell fabric or one that has a DWR coating to repel water. If however, the shell gets wet or damp, your best bet is to dry it in the sun the next morning while you’re having breakfast or during a rest break during the day. Stopping to dry wet gear, tent flies, and clothing is a normal everyday activity when backpacking and it’s good to get in a habit of doing it when necessary.

What if your tent or tent fly is soaking wet in the morning?

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 and dry it later in the day during a rest break.

Can you set up a wet tent 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.

Written 2018.

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16 comments

  1. Another benefit of hammock camping is that I do not have anywhere near as many problems with condensation buildup during the night. Sometimes toe-box of my Warbonnet Blackbird collects some moisture, but that’s about it. I also like that I can easily pack the hammock separately from my wet tarp in the morning so that it stays dry

  2. Good outline, Philip!
    I would add:
    1) Avoid wet ground, if possible. Sleeping on saturated ground is worse than camping on a mound. You touched on this with not camping near water sources. Step on the ground, if it is “squishy”, look elsewhere.
    2) Grass is worse than forest duff. Forest duff is worse than well drained mineral soil. Avoid rock and sand.
    3) Check for deadfalls, but sleeping under a tree is a good choice.
    4) Add a 6″ length of line to tents before staking them out. This lets the poles lift the floor slightly off the ground. Note that dome/freestanding tents don’t work.
    5) Use a 6″ to 18″ extension on a tarps/fly. This will provide ventilation room along the bottom edge.

    Of course, these are only a few. The key to understanding condensation is the sources (for example plants transpire water vapor,) breathing (evaporation), rain(air humidity,) wet or soaked ground (capillary action), run-off(on rocks, logs, etc,) and how it builds up on cold surfaces. You can develop your on scheme on the fly with a good basic understanding.

  3. My brother keeps a section of synthetic chamois to wipe the walls of his tent in the morning. He stores it in a Ziploc between uses.

    When I first typed this, Swype changed “brother” to “butthurt”. I know he’d appreciate it…

  4. Well there is one way to keep out condensation, it’s expensive and not a back packer tent; Arctic oven tents.
    0 condensation , rain,snow,heat,you name it.
    Inner wall passes all moisture out.
    Ck them out.

  5. Good tips! I’ve read where some people have tried small, battery-powered fans to help move air in the tent when there’s no natural breeze, but it’s not clear those do much good.

    I’m curious to know the source for the one liter figure given for volume of condensed, exhaled water per night. Most figures/estimates i’ve seen are somewhat lower, on the order of a pint or so. It would depend on a number of factors, including ambient air temperature and humidity level, how hydrated the person was, etc. And also, maybe, on how the calculation was done. We inhale some moisture with each breath, and we add to that, so is it the net added moisture that is estimated?

  6. In a single wall tent does using a groundsheet do anything to diminish condensation?

    • It’s probably marginal. If the ground all around you is wet, the water vapor is already in the air.

    • Robert, a short answer is no. I think of a tarp as anything without an attachment to a ground sheet (of course there are some exceptions to this, An example: I used a tunnel tent in winter and dropped the inner net tent in summer, but the tent fly was still anchored to the ground.)

      A tent will usually consist of two pieces, a tarp or fly over a net tent/ground cloth. If set up normally (ie tight to the ground) in most cases, there is no difference in how much condensation gets on the fly. It only places the condensation away from you and your gear and on the tarp. Using a ground cloth under a tarp that is anchored to the ground does the same thing, really.

      The ground sheet is “usually” sewn to the net tent body, not the fly or tarp over it. IFF (if and ONLY if) you can raise the tarp/fly above the ground about 4″ or so, then you can reduce the condensation by increasing ventilation and reducing the temperature differential between inside and outside air. But, you will sleep a bit colder. In a rainstorm in summer it doesn’t really matter. With the 100% humidity, the slightest temperature drop will cause condensation. But for other times, spacing the tarp above the ground will help a lot. For two reasons: 1) you get extra ventilation that will help remove any exhaled, high humidity air, and, 2) it will reduce the temperature between the sides of the tarp, ie inside and outside, hence removing one culprit to causing condensation.

      Again, understanding the causes for condensation will help keep condensation down, not eliminate it. Once it starts forming, it will form faster. Evaporation from the water droplets will cause the fly to cool off a bit more. Hence more condensation… Condesation and evaporation happen together. Condensation takes water vapor out of the air and slightly warms up the surface. Evaporation will pot water vapor into the air slightly cooling the surface. One way to eliminate condensation is hold the surface temperature above the dew point. Cooking under a tarp at 40F will usually keep it fairly dry, however cooking also adds moisture to the air depending on how you are cooking.

  7. This topic reminds me of camping in an old orange Gerry (the baby backpack company) brand tent that my father purchased in the 60’s. It was a “four season” tent with some interesting features. For winter camping, it came with extra fabric & instructions to sew it around the outside of the fly. It made a fabric trough that snow could be packed into in order to stake out the tent without using ground stakes. We never got around to using that feature, since the extra fabric would need to be unsewn when you didn’t want to use it. Haha. Another feature was a thin white fabric (mostly cotton if not 100% cotton) frost liner that could be attached to points on the ceiling/corners. It hung down to just above the tent floor. That frost liner sure did an excellent job of soaking up all the condensation! In the morning, the liner was very wet/frosty, but the moisture wasn’t on us! It was however extra heavy/wet when packing up. That fabric sure collected moisture. I love that tent! I haven’t slept in it in a few years. I should get it out again next winter. I feel like it ought to end up in a tent museum if there is such a thing!

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