moisture condensation igloo vs tent

General discussion on winter camping.
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Matti Verkasalo
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moisture condensation igloo vs tent

Post by Matti Verkasalo » Mon Oct 20, 2014 11:38 am

Just wondering - I haven't ever slept in a tent in winter, in igloos a few nights nearly every winter over some 12 years or so. Now i have been again reading the campers' forums and problems with sleeping bags condensing moisture which evaporates from skin, and freezes within the sleeping bag filling.

This coming winter our trek might require some tent living, but mainly igloo living. Does anybody have experience or frank knowledge of this: If conditions turn out to be very cold, I assume that sleeping bags will stay more dry in igloo than in a tent, because the temperature in the igloo is only around freezing whereas the tent may be 10-20 degrees below. Right?

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Igloo Ed
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Re: moisture condensation igloo vs tent

Post by Igloo Ed » Fri Nov 14, 2014 6:37 pm

Matti Verkasalo wrote:Just wondering - I haven't ever slept in a tent in winter, in igloos a few nights nearly every winter over some 12 years or so. Now i have been again reading the campers' forums and problems with sleeping bags condensing moisture which evaporates from skin, and freezes within the sleeping bag filling.

This coming winter our trek might require some tent living, but mainly igloo living. Does anybody have experience or frank knowledge of this: If conditions turn out to be very cold, I assume that sleeping bags will stay more dry in igloo than in a tent, because the temperature in the igloo is only around freezing whereas the tent may be 10-20 degrees below. Right?
I've winter camped in a tent a little in years past and you are indeed right about moisture building up in one's sleeping bag.
If you manage your moisture through the day or wear dry clothes to bed, the moisture your body gives off accumulates reasonably slow. The first night is fine and the second night takes a little longer to warm up the bag. Depending on how warm your bag is rated, it might feel a little chilly on the second night. The third night is when I notice it most, the bag is noticeably colder and I wear some extra layers to bed. Those extra layers are generally clothes that I have worn through the day and they contain moisture. Because of the moisture in the clothes, the bag will get wet a bit faster. Without an igloo or fair weather to dry the gear, the night wearing extra damp layers is generally the last night for me.
If you are going to be using igloos from time to time, it may take more than one night to dry the bags out again.
Another way the bag gets wet in a tent is from the frost on the tent walls caused by one's breathing. If the sun melts it, your gear will get wet. That frost needs to be cleaned out of the tent.

Happy to see you here again, Matti.

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Re: moisture condensation igloo vs tent

Post by Matti Verkasalo » Thu Nov 20, 2014 1:53 pm

Thaniks Ed. I began to wonder this as some experienced winter campers staying in tents in -5 to -25 degrees Centigrade for 5 nights had just by weighing their sleeping bag immediately after the trip and then after the sleeping bag was thoroughly dry, come into conclusion that the bag accumulated about 100 grams of water each night - about a pound in the 5 nights. The amout really surprised me. Btu I've been sleeping max 3 consecutive nights in an igloo with a 3-season bag which probably retains much less moisture as the condensation point is most likely outside the outer surface of the bag...Maybe I'll have to take a fishing scale with me this winter. :-)

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Igloo Ed
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Re: moisture condensation igloo vs tent

Post by Igloo Ed » Sat Nov 29, 2014 7:55 pm

Matti Verkasalo wrote:Thaniks Ed. I began to wonder this as some experienced winter campers staying in tents in -5 to -25 degrees Centigrade for 5 nights had just by weighing their sleeping bag immediately after the trip and then after the sleeping bag was thoroughly dry, come into conclusion that the bag accumulated about 100 grams of water each night - about a pound in the 5 nights. The amout really surprised me. Btu I've been sleeping max 3 consecutive nights in an igloo with a 3-season bag which probably retains much less moisture as the condensation point is most likely outside the outer surface of the bag...Maybe I'll have to take a fishing scale with me this winter. :-)
Heh, knowing you, you probably will take a fishing scale. :) Never know, might be some nice lakes to icefish from an igloo...
Yes, the moisture thing is real. I've read of bags weighing ten pounds more after failed attempts on Denali. Hanging them out for three days or more to dry in the Talkeetna airplane hangers.
Back in the day when we used snowcaves, I used a synthetic bag that was rated to 0F. I used one rated to -20F. if it was more of an expedition. We normally went back to out snowcave every weekend so we left out sleeping bags in the snowcave. They had no chance to dry out through the winter. The bags did gain a bit of weight the first few trips but then it seemed to level out and stop gaining weight.
I once had an inexperienced friend come along that wore all his warm clothes through the day in spite of being told to layer down and not overheat. At night, he got a chill in the cave due to his wet clothes and went to bed in my -20F. bag (I loaned it to him) with all his clothes on. I'd told him to strip down so he'd be warmer sleeping but he insisted on wearing everything to bed. He had so much on that he blew the zip once in the night which he was luckily able to repair. By morning all his moisture had migrated into the bag and it must have weighed 4 or 5 lbs more.
Well, like you, I had to experiment. I left the wet -20F. bag at the cave to see if I could dry it out with use through the winter, this was an early winter trip.
The bag felt very clammy for most of the season but it did get a bit lighter by spring. With our mild temps here in Colorado and the igloo very seldom freezing my down bag rated at +15F. gains just a bit of weight the first couple nights and then stops gaining. In the cold temps of Yellowstone, the bag seemed to hold a little bit more moisture but again leveled off after two nights. I even had some wet clothes to dry on that trip due to a stream crossing.
I'd think you'll be just one step colder in Finland.

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Re: moisture condensation igloo vs tent

Post by Matti Verkasalo » Mon Jan 25, 2016 1:46 pm

I have to get back to this topic; about a year ago I had an opportunity to build two igloos with 6 people; four slept the night in the igloos, one was in a 4-season tent and one under a tree in a bivouac sack. The night was quite cold, -20C. We weighed the sleeping bags in the evening and in the morning. I calculated the sleeping bag weight change in relation to the sleeper's weight.

Bivouac: 3 grams/kg

tent: 1,2 grams/kg

igloo; 0,7 grams/ kg ( Iomitted one outlyer because the bag was much lighter in the morning than in the evenimg. incuding this the result would have beem 0,4 grams/kg!!!).

So it seems that physics do work, and for at least one night winter camping, igloo will keep your sleeping bag 30-50% drier than tent, and 400% drier than sleeping in bivy in snow.

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Igloo Ed
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Re: moisture condensation igloo vs tent

Post by Igloo Ed » Thu Feb 11, 2016 4:37 pm

Nice!
It's good to see some science behind it. It takes quiet a bit of effort to do experiments like this. I've always been lazy and went skiing. ;)
You results are what I've suspected and I wondered exactkt how much difference in type of sleeping methods had.
It'll be interesting to see what you come up with over an extended period of time.
My bag seems to gain the most weight the first night out. The second night it gains a little more but then after that it seems to even out and stop gaining.
With you airing/drying them out daily, I would think you could keep them at a lighter weight gain than I do. I don't dry my bag, I tend to go skiing (again). ;)

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