Condensation in Single-walled Shelters: Contributing Factors and Tips for Reduction

[Benjamin Smith]

Companion forum thread to:

Condensation in Single-walled Shelters: Contributing Factors and Tips for Reduction

[Scott Smith]

Bummer :(

[Franco Darioli]

For various reasons I have had a pyramid style tent up in my back yard on and off for a few weeks.
What I have noticed is
1) on occasions the walls will be coated with condensation even without me spending the night in it
(this one does not have a floor, so it is evaporation from the ground)
2) the condensation is minimized or eliminated by keeping the apex vents open, as expected, more so when the tent is a few centimeters off the ground.

Nothing new here, just confirming the same results in a different environment.
Franco

[Roger Caffin]

Hi Chris

> While everyone seems to agree that perimeter venting is essential, there doesn't seem to be unanimity about peak vents.

I assume that 'perimeter' => ground level and 'peak' => top level.
In that case, I would argue from snow experience that you need both. Well, at least you need somewhere for the fresh air to come in and somewhere for it to go out, carrying water vapour with it. In still conditions this usually means the airflow will be driven by heating from your bodies, so a low inlet and a high outlet are what's needed.
However, in windy conditions the inlet can be high as well. The problem then may be to limit the incoming gale and spindrift of course :-)

Two nights in the snow a couple of years ago illustrate this very well. On each night we had the vents at each end of our double-skin snow tent open, and the tent fly was an inch or two off the snow as well.
The first night was still and we were in a valley. In the mrning the inside of the tent fly was caked with ice. The inside of the (breathable) inner tent had ice on it as well. Sigh: a heavy tent to carry.
The second night had a gentle breeze blowing all night and I pitched the tent end-on to the wind direction. In addition I was on a slight shoulder well above the valley. (Not as sheltered in case of a storm, but I gambled …) In the morning the inner and outer layers of the tent were DRY.
I attribute most of the difference to air flow.

Under more severe conditions I have shut the top windward vent right up and relied on the ground-level ventilation. I had to: the spindrift coming in the top vent was building up on the inner tent and starting to melt – and drip onto my head. As I remember the inner tent dried right out and the outer tent was reasonably dry on the inside in the morning. Mind you, the outside of the fly was another matter!

[P. P.]

I've never considering using a single-walled shelter in the winter due to condensation considerations. I prefer down bags and quilts so I am extra conscientious about keeping them dry. It would be nice to take a 2.5 lb. shelter instead of a 4.5 lb. shelter but I'm chicken.

[Frank Ramos]

I fail to see what all the hullabaloo is about condensation on the shelter, at least for 3-season backpacking. I get condensation on my tarp about half the nights I camp. I don't like it, any more than I like heavy dew on the grass in the morning. But I fail to see how either condensation on the shelter or dew on the grass is a major problem. If the temperature is near or above freezing, then there is plenty of body heat to burn off any moisture that drips onto your sleep gear or gets onto your clothes. If the temperature is well below freezing, then the condensation will freeze and hence drippage isn't a problem.

The real danger is condensation that occurs INSIDE your sleeping gear, which is mostly a problem at temperatures below freezing (there is usually enough body heat to avoid this problem at tempatures above freezing). There are basically two ways to deal with this. First, a vapor barrier will solve the problem completely. But this is a nuisance for many people. Second, by using a good double-walled tent, you can often raise the ambient temperature inside the tent sufficiently that the dewpoint is moved outside the sleeping bag. But this isn't guaranteed to work, so you need to be prepared for condensation inside the sleeping gear (either use polarguard, which is minimally impacted by condensation, or else be prepared to get back to civilization in a hurry if using down).

[Michael Davis]

Frank,

I agree with you 100%. Personally, double-walled tents don't make much sense to me: they are just extra weight. Most of what is referred to as "double-walled" tents in the marketplace are in fact mostly mosquito netting inside a single-walled tent. IME this does nothing (except keep bugs out). A true double-walled tent, for the topic in this thread, must be two SOLID walls, inside breathable, outside waterproof, set up to actually trap some dead air between. This is hard to do, for me. And, on a still night there is going to be condensation, no matter what.

Either way, frozen condensation inside one's sleeping bag is a very real problem. If it's 10F inside the tent and your body is 98.6F (assuming your not dead yet), then it is 32F somewhere between you and the air in the tent: that puts it inside the sleeping bag! There is no other outcome given the situation.

So, Frank, you are right! We would be better off preparing for that inevitable situation than worrying about condenation on the tent walls. I can see various solutions for this problem, given different circumstances.

Since my winter trips are confined to one night out (although I prepare for two), my solution is to carry a better down bag than what the temperature is expected to be. For overnighters, an extra few ounces of down is the most efficient solution that I have found.

However, a longer, multi-night trek in winter where expected temperature below freezing night and day is an entirely different matter. For that situation, heavier and bulkier synthetic insulation is probably necessary as well as perhaps, vapor barriers.

[Connie Yang]

John,

I know this was a while ago, but nice mods on the Gogo! You get some nice tension from the pole replacement, as well as a bit of weight savings. All of us here at NEMO are impressed with your handiwork.

FYI, we are furiously working on an alternative airbeam construction that will cut down on the bulk of the current construction. Look for a great ultralight tent to come out in the spring using this technology.

Connie

[Ritchey Ruff]

I just modified my gogo and it rocks! I've been paranoid about the airbeam (being in QA I focus on point-of-failure problems sometimes to excess ;-). Now no more pump or air beam or spare or patches. It is a bit of a trick getting the new support in the tent: I settled on putting it in crest-first then slipping each foot in one-at-a-time. If the beam is in the grove it fits snug and tight and is not going anywhere. THANKS again!!!

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