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Single-wall tents are made from waterproof breathable material, which is heavier and more expensive than a simple impermeable layer.

But if a single-wall tent were made of impermeable material, wouldn't excess moisture generated inside the tent simply condense on the inside surface of the tent since that will be colder than other surfaces in the tent (such as the outside of a sleeping bag)?

Then, with a good system of gutters to drain the condensed water away, couldn't the tent stay comfortable?

Would there be more condensation on the roof of the tent or the floor?

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No, you don't want to trap water in your tent. –  hillsons Mar 12 at 18:47
    
I think I get what you're asking, but it takes some deciphering, and I'm not sure if I'm right about it. So it I think it would be good to work on your question. It's just somewhat confusing. And look up sil-nylon (or cuben fiber) tarp tents. –  manoftheson Mar 14 at 3:44

2 Answers 2

If condensation formed on the inside of a tent it wouldn't simply flow down the sides of the tent into gutters. It'd drip, it'd drip all over you and everything in the tent making you wet. Every time you touched the sides or the wind blew, you'd get rained on.

When you're wet your body loses a lot of heat.

Your body would heat the liquid forcing it to evaporate (again, taking the heat with it). This evaporated water would then condense on the tent (again) releasing the heat into the fabric, which in turn would release the heat into the atmosphere. You would quickly become cold and wet and miserable.

This applies to all non permeable fabrics (not just tents), which is why products such as GoreTex are popular. Because permeable fabrics allow the water to leave the garment i.e. the initial heat is lost, but that's it. It does not condense and then evaporate again and again, releasing lot's of heat into the atmosphere and away from your body.

Also, tents are small confined spaces. While your sleeping you will be breathing in all the Oxygen of said tent and breathing out lots of CO2. Now I doubt this is going to be enough to cause you any damage but I would imagine you will become very uncomfortable quickly. This is why, even breathable tents have vents to allow a good flow of air.

Would there be more condensation on the roof of the tent or the floor?

Does it matter? Any water on the floor means your sleeping in water.

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Sure, in practice it might be hard to get the water to flow down the sides of the tent into gutters, especially in high wind conditions. I am not convinced that the reevaporation phenomenon you describe would be significant, however. And the heat of condensation would not all be lost. –  mark Mar 12 at 20:38
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Next time your nice and sweaty, put on a cheap waterproof jacket that does not breath. You'll soon see how significant an impact this has. This used to be the norm in the mountains and it wasn't pleasant. –  Liam Mar 12 at 21:05
    
@Liam overall I like your answer. But I am unsure if the water would really be "raining" on you if you aren't touching the tent itself. Lots of water can stick to the surface of the tent due to adhesion (and cohesion of the water). The tent isn't sealed. Nonetheless I didn't try this and would be interested in real live experiences :) –  EverythingRightPlace Mar 12 at 21:25
    
It could depend on the shape of specific tents. I've had moisture condense in my tent after a warm night/cold morning. Take my word for it, it 'rains' on you. –  hillsons Mar 13 at 3:53
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@Liam I didn't mean the real rain. Sorry for the confusion. I just wanted to say that I am not convinced that the condensed water on the inner tent surface will drop on you. –  EverythingRightPlace Mar 13 at 10:35

Scottish mountaineer Hamish Brown used such a tent back in 1974 while completing the first round of Munros (Scottish mountains over 3,000 feet) in a continuous walk.

Hamish’s tent, made by Tulloch Mountaincraft, was a single skin nylon tapered ridge that weighed “a bit over 3lb” (1.3kg), which is lighter than many solo tents today. This tent had a tray-shaped groundsheet that attached with elastic tabs and floated inside the tent so that condensation ran down the walls and into the ground rather than onto the floor. Now why has no-one revived that idea?

From Chris Townsend's WebSite

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