Tent Condensation

do you have a picture or what tent do you have?

I think both strategies have their advantages. Your way with a sealed up tent is to let the condensation happen, but control it and hopefully limit to the outer fly and stop it affecting you inside the tent. A lot of that will come down to the shape of the tent, the angle of the walls etc, and how much that encourages the condensation to run down the walls and drip onto the ground, rather than form points where it will drip onto the inner.

Ventilation tries to work by letting air flow through the tent and not let the moisture vapour in the air build up too much in the first place. But yeah any that does should hopefully be controlled in the same way and run off the outer fly and not affect people inside.

K

I’m skeptical, but can’t really say.  What I can say is that, from my experience, nothing affects condensation more than visibility to a clear night sky.

As I understand it, condensation is formed on an inner surface when warmer inside air strikes a thin wall that is made cold by cold air outside.  And the greater the humidity or amount of water vapor in the inside air, the more potential for condensation; hence the need for both ventilation that vents damp inner air, plus double walls that lower the difference of inside vs outside temperatures, aka ‘temperature differential.”  But none of this may apply in some conditions, like desert areas where everything including the air is dry as a bone.

An old Sierra Designs tent had little or no venting higher up, and a fly that did not cover the lower foot or so of the solid inner wall.  This exposed the lower part of the inner wall to the cold outside, and the warmer air inside condensed on the colder surfaces on the single wall part of the tent.  So the foot of the sleeping bag got soaked  from contact with the exposed lower fabric.  Got rid of that tent in a hurry.

Hope that makes sense, as am not schooled in expressing scientific concepts.  But from experience I know that a double wall + ample air circulation is needed to prevent inner condensation and breathe fresh air.

I’m also told that fabrics that don’t give off, or transmit as much heat, will suffer less internal condensation; but am not so sure of that one.  If mylar film is laminated to the woven tent fabric, just the greater thickness of the tent wall alone would create a lower temperature differential between the inner and outer fabric surfaces, so less condensation.  But when the focus changes to material that is less or more “emissive,” the subject is over my head.  There are a number of posts and articles on BPL about “emissivity” to consult.  And I’ve read on BPL about severe condensation in single wall tents of DCF mylar laminates, while others report less condensation.  Those differences may result in part from lower vs higher temperature differentials.

And there are other supposed factors that are said to effect condensation, like whether the tent is under a tree, or too close to a body of water, or high humidity, and so on.

So double walls, coupled with vents to allow air to circulate, have worked very well for me, and the rest is left for the experts to debate and discuss.  Daryl’s OP indicates a double wall with a solid, not just a net inner, and that alone would account for a low temperature differential that might permit generation of more warmth inside without creating condensation.  Maybe his tent is so good at controlling condensation he can warm up a bit.  And maybe Todd’s clear night sky is an indication of low humidity that is less conducive to condensation.

I recall an example of what I’m referring to from 50 years ago.

Four of us were on a multi day snowshoe trip in the Olympic mountains of Washington.  Wet, heavy snow was falling most of the time.  Temps just below freezing.

We all spent a crowded night in a 5 foot tall 3 person tent with a shape and  construction similar to the one shown above.  No problem.  We were warm and the inner tent had little or no condensation on the fabric.

Condensation always happens on the fly – wheter it is single wall or double wall tent. Its just that you are protected from it in a double wall – that is you don’t touch the fly because you are inside the solid inner tent or some innner mesh that supposedly protects you from touching the wall. In a single wall, your chances of touching the wall and getting condensation on your sleeping bag etc are higher. But, condensation always happens on the inner of the outermost layer. So I guess you are not really eliminating condensation. You are just managing it inside your solid inner tent.

Murali,

What you said makes sense.

Also, drips from the condensation formed on the inside of the fly can more easily splash through a mosquito net interior than a solid nylon interior.

As I understand it, condensation is formed on an inner surface when warmer inside air strikes a thin wall that is made cold by cold air outside.

That’s only partly true.  That thin wall can be made colder than the outside air when it can “see” a clear night sky.  Radiative heat transfer to the black coldness of outer space is significant.  On cloudy nights, the outdoor air temperature is the dominant factor and condensation tends to be less.

As I understand it, condensation is formed on an inner surface when warmer inside air strikes a thin wall that is made cold by cold air outside.

And its worth noting that this isn’t always the fly of the tent.

At cold-ish, but not excessively so, temperatures, as people have said the barrier between hot and cold is usually the flysheet. Inside the tent your body heat keeps the temperature up just enough that moisture evaporates away from you and floats up into the tent, and then it touches the much colder flysheet and condenses back to water.

However at very cold temperatures, even the inside of your tent can get very cold and so that barrier moves. The warm pocket is simply your sleeping bag/quilt, and its the outer surface of this that becomes the barrier between hot and cold. The outer layer of pertex or whatever is very cold because that is the first thing that is exposed to cold air and so that becomes the layer of material that condensation starts to form on the inside of. As discussed on the latest podcast, if you’re using a down bag it’s very important at that point to consider layering to prevent the down from getting wet.

K

“That thin wall can be made colder than the outside air when it can “see” a clear night sky.  Radiative heat transfer to the black coldness of outer space is significant.  On cloudy nights, the outdoor air temperature is the dominant factor and condensation tends to be less.”

exactly – the worst condensation is when it’s clear and your tent has clear view of sky

Camp under trees would help

But if you’re in the open, at least you won’t be radiating heat to sky, the tent will protect you.  If the condensation freezes it won’t drip on you.

Ventilation helps in some conditions.  But, I’ve just suspended fabric horizontal to ground, so it has ventilation, but it still has condensation.  As does the dew or frost all over.