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  1. #1
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    condensation with zrest and emergency blanket

    Using a zrest on top of an emergency blanket produces condensation trapped in the holes of the zrest. In a tent, insufficient air flow produces condensation, but a hammock is all open, unless the bug net makes a difference. What gives?

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    Senior Member lattie11581's Avatar
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    I was reading a thread here I think... couldn't find it ... but if I remember correctly, it has something to do with the greater temp differential / constant "change of air" under your hammock. When on the ground you don't see it as much because your body heat actually warms the ground too to a degree and closes that "differential. ... I think
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  3. #3
    Prefers life at 12 MPH. FLRider's Avatar
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    From what I've seen, the prevailing wisdom is to use the vapor barrier (the emergency blanket) next to your skin, with any other sort of insulation outside of that rather than the other way 'round.

    This means that any condensation is trapped before it can get to the insulation and ruin its insulating value.

    Note, though, that I do not have any personal experience with using vapor barriers; it just doesn't get cold enough here in FL for it to be worth it most of the year.

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    Senior Member Hector's Avatar
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    CCF is itself a vapor barrier. Best solution I've seen is something breathable between you and the CCF pad.

    I use a Big Agnes Mystic in really cold weather with CCF pad in the breathable sleeve, vent the bag as needed given outside temperature, and no condensation.

    However, condensation issues are also a personal thing; if you sweat like a pig regardless, you're probably going to get some condensation. Uh, I mean no offense to anyone (or any pigs) there.

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    Senior Member BillyBob58's Avatar
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    Quote Originally Posted by Hector View Post
    CCF is itself a vapor barrier. Best solution I've seen is something breathable between you and the CCF pad.

    I use a Big Agnes Mystic in really cold weather with CCF pad in the breathable sleeve, vent the bag as needed given outside temperature, and no condensation.

    However, condensation issues are also a personal thing; if you sweat like a pig regardless, you're probably going to get some condensation. Uh, I mean no offense to anyone (or any pigs) there.
    Plus keep in mind that sweat and condensation are 2 dif things. Once some part of you gets too hot, top or bottom you sweat(liquid). That sweat can then either be trapped against your skin or closest thin base layers if using a VB or waterproof pad as the next layer, or it can go on into your insulation. Hopefully, your body heat can turn it back to vapor and it can escape a breathable shell, but certainly not guaranteed.

    Vapor is produced whether you are hot or cold. If it contacts a cold surface or air, it then becomes liquid. Hopefully, it can travel on out of your insulation and breathable shell material to the outside air before ever condensing to liquid. But again, not guaranteed if the outer layers of insulation are cold enough.
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    so...should I have the zrest on the bottom and then the emergency blanket on top?

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    Senior Member Hector's Avatar
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    Try not laying *directly* on either the pad or the reflective surface, and vent if you get too warm.

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    Senior Member BillyBob58's Avatar
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    Quote Originally Posted by Girotogo View Post
    so...should I have the zrest on the bottom and then the emergency blanket on top?
    You mentioned condensation in the "holes" in your pad? Do those holes go all the way through? So that the pad is partly breathable? If so, then I can see some body vapor getting past the holes and warm(next to your body/clothing) pad to the "cold" space blanket and condensing. So, yes I would have the completely non-breathable space blanket on top.

    But I have no experience with a space blanket right next to me. I use them all the time under but fairly snug up against my hammock and then with all under insulation under that SB. Also, I use the SB under my hammock inside the PeaPod. I have never had any condensation with this technique, but YMMV. Normally, vapor does not condense against a warn surface. Just like with your windshield when it is cold vs warmed up with the defroster, or on a warm day.

    If these holes in do not go all the way thru, then the pad should be a vapor barrier. Is it possible you got to warm, at least on your back, and started sweating?
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  9. #9
    New Member hikerb's Avatar
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    Quote Originally Posted by Girotogo View Post
    Using a zrest on top of an emergency blanket produces condensation trapped in the holes of the zrest. In a tent, insufficient air flow produces condensation, but a hammock is all open, unless the bug net makes a difference. What gives?
    My wife and I experienced this last night. We were testing out my seam sealing job on our double rainbow (she still is leary of hammocks ) last night in the rain. No rain got through, but when we woke up our zrests had water in a bunch of the little holes. It was warm out last night, probably didn't get below 65 here, but that was the first time we had experienced that much condensation on our pads.

  10. #10
    Senior Member HappyHiker's Avatar
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    Quote Originally Posted by Girotogo View Post
    so...should I have the zrest on the bottom and then the emergency blanket on top?
    *Both* are essentially VB's. With both configurations, you can experience condensation. I'd keep the pad on top so at least the condensation collects in the grooves. With the emergency blanket on top it could potentially wet whatever is in contact with the blanket (ie your back, sleeping bag etc).

    That, and I find reflective surfaces tend to work better with a small amount of space between them and you, so you don't lose any heat to the conductive surface. As has been mentioned, a layer between you and a pad made of fleece can absorb and distribute the moisture and provide a higher level of comfort if you're laying directly on the pad with nothing in between.

    HTH
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