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I have problems with condensation, dew when I camp above tree line in European mountains. The problem is that my down sleeping bag gets wet from the outside. Even when I use single wall tent the fabric is wet and some of it goes to my sleeping bag.

I think the issue is when camping, bivouacking in the open. If I do that below tree line under cover of trees I don't have that issue. The problem are always exposed spots with no tree cover. Ventilation is good. I don't know is that issue solvable, because dew is present almost every morning even if the days are hot, grass is wet. I don't have time to dry down sleeping bag every day and sleeping on the top of the mountain is just so great.

How would you solve the problem? Double wall tent is just too heavy.

Thank you!

3 Answers 3

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It's not exactly the tree line that's the issue - it's how much the temperature drops overnight, and without tree cover it will drop more. I've camped under a tarp under trees, and had plenty of dew, not just the time the clouds came down overnight to below my altitude.

Hot days can even make things worse - the warm air can carry a lot of water vapour if there's water to pick up, but when it cools at night, that water condenses on every available surface.

A cover over your sleeping bag (for example a bivvy bag) would have to be really quite breathable as otherwise it will trap condensed sweat on the inside and you'll still end up damp. This could either be breathable fabric or suspended over you as a tarp. Even a fairly well-ventilated tarp will reduce the rate of cooling a little, as well as reducing the amount of air your sleeping bag comes into contact with.

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Gore-tex top. Rubber bottom. 1kg. Only problem is the import tax from the USA brings the price to over 100EUR.

The outside will get wet but is very fast to pack and will rapidly dry out during lunch - simply remove it from the backpack and drop it on the grass for half an hour.

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  • 1
    My recommendation: snugpak - used in all weather conditions for 14 years
    – root-11
    Jul 27 at 6:24
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    The British army also use a similar bivvy bag, they can often be picked up very cheaply from army surplus stores
    – aucuparia
    Aug 14 at 14:20
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Thank you for the effort and answers. I did not have any problems when under tree cover at least not the one I would notice. Perhaps is the climate, I do not know.

I already tried to use survival blanket only on top of sleeping bag as you would use normal blanket. In that case it made it even worse, because the temperatures were high enough and the heat was reflected so the foil and the sleeping bag and foil were even more wet.

I could try something that does not reflect heat so much as thin plastic foil.

To use survival blanket only on top or as an outer shell of sleeping bag is a nice trick otherwise at least it works nicely in some more cold situations if you need few degrees extra.

Perhaps bivy bag yes, but much lighter one that 1 kg. It has to be light and breathable enough so the inner part wont get wet.

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  • from this it sounds like guttation (water put out by the plants) is your problem rather than dew (condensation) - try a groundsheet or bivvybag.
    – bob1
    Jul 26 at 20:51
  • If I use single wall tent, the (upper) fabric is wet from the outside and also inside. I think that guttation doesn't cause that. I will try plastic foil or seperately mosqito net in combo with single wall tent to test if it will protect the sleeping bag.
    – Alex J.
    Jul 28 at 15:30

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