When you compare single wall tent to double wall tent usually you will hear short summary "double wall tent prevents condensation from building up".

So in most fair comparison it should work like this -- I have imaginary single wall tent (i.e. tent with only one layer, the rainfly) and using it will cause condensation to build up. OK.

So now let's add to this tent inner tent (mesh layer) and this prevents condensation.

Hmm... I don't see it. I mean, condensation occurs when the warm air is cooled down to the point it no longer can hold steam. I guess the mesh barrier can slow down the process (i.e. you would have warm space inside, middle space between layers, and the cold air outside), the warm air from inside not so soon reaches the outer layer. But eventually it will reach it.

Second guess would be that inner mesh gets a little wet, and by this it helps the air to hold the rest of the amount of steam. But this effect I would say is a condensation anyway, just not visible because of the nature of the mesh.

So is there any other effect that contributes to the notion "inner tent prevents condensation"?


1 Answer 1


They don't prevent condensation. They just reduce the chances of condensation getting onto your kit down to practically nothing, if you do it right.

The condensation stays on the inside of the outer layer. Your kit is on the inside of the inner layer. The condensation doesn't cross the gap between the inner and outer layer. It runs down the inside of the outer layer. And then it can't pond inside the inner layer.

  • $\begingroup$ Thank you very much +1, I was "afraid" that this is explanation. The reason for my feeling is -- (1) inner tent is still my gear, if it gets wets, my gear gets wet (2) as in the my question, double tent does not get bigger, you have exactly the same distance from your foot/head, so if you touch outer layer with your foot in the first example you will touch it in the second example as well. In other words, there is no physics-magic there, it is more of a hiding problem or pretending the inner tent is not your "core" gear. $\endgroup$ Feb 19, 2020 at 18:21
  • $\begingroup$ The second issue is that the condensation can escape via crossflow. The gap between the fly and the breathable layer has a lot of air circulation. On better tents, this can be adjusted to suit conditions. $\endgroup$
    – Phil Sweet
    Feb 19, 2020 at 23:40
  • $\begingroup$ It's true that inners do little to prevent condensation on the fly in terms of the basic physics. But solid inners do shelter the user from draught. This means that in a well-vented tent design it will often be possible to allow a stronger through-draught through the gap between the inner and the outer which should help control condensation somewhat. That's about as far as it goes. $\endgroup$ Nov 13, 2020 at 21:35

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