???Non-breathable top layer for a UQ???

[HomeMadeHiker]

I'm looking into a buying or building 20* UQ. I'm considering a non-breathable upper layer (towards hammock), either Cuben or the reflective stuff from DIYGS. I'm curious about moisture issues. It seems that since the moisture has no where to go it would collect and become bothersome, but I've seen a lot of folks lately using non-breathable stuff like Cuben or IX on top. So, I hoping some experienced folk can shed some light on this for me.

[HomeMadeHiker]

Really...Nothing?

[raiffnuke]

So far, my cuben top layered Phoenix has worked very well for me with no condensation issues at all. That being said, I have not had it in the summer heat yet. YMMV.

[FLRider]

It seems like that would be useful for long trips in deep winter, when the temperatures never get above freezing. It would prevent degradation of your insulation due to moisture buildup, but would require all of the usual tricks associated with vapor barriers.

I don't know enough about winter camping to be able to intelligently comment on this, though. Living in Florida means that even when it gets down below freezing, it doesn't stay that way for more than four or five hours.

If you've got the funds and the time, give it a try and let us know how it works!

[BillyBob58]

It seems like that would be useful for long trips in deep winter, when the temperatures never get above freezing. It would prevent degradation of your insulation due to moisture buildup, but would require all of the usual tricks associated with vapor barriers..................

That sounds about right to me. For me, if the vapor barrier ( like a space blanket right under the hammock in my HHSS or PeaPod) is kept close to your body it should be warm. Vapor condenses into liquid when it contacts a surface or air below the dew point. As with your breath on a real cold day or on your windshield or on your glasses when you step out of an air conditioned car into 100F. ( sorry, I'm sure you already know all that)

Point is, if you keep it WARM ( snug against your body) there SHOULD not be any condensation. Though some parts might be warmer than other parts. Like your the part against your back compared to the leg area on the non-diagonal side with a full length quilt.

In practice, the above theory has always worked perfectly for me, but others have had less positive experiences.

And sweat is a different issue. If your back is warm enough ( what ever temp that is for you) you are going to sweat. But condensation or sweat, I guess you can decide if you would rather have that moisture against your skin and maybe in your fleece clothing, or (especially on long cold trips) inside your down quilt?

[MedicineMan]

same as raiffnuke with no problems with a cuben top layered Phoenix...have used it 5 or 6 times now in temps ranging from 26-38F...dont plan on using it in summer.