Foot condensation w/bivy

Interesting that you say that, because I just tried a bivy for the first time in the Pecos this past Labor Day weekend. I used it with my trailstar…and holy cow was I wet. It rained one night, but interestingly enough that was the night I was the driest! There was so much dew outside every single night, and so much condensation inside – I literally didn't know what to do. I was way wetter inside that tarp and inside the bivy than I have ever been in all my years of backpacking. YIKES! Anyway, I was trying the MLD Superlight bivy (thanks to a VERY generous fellow BPLer!) for the first time and found that I was quite soaked inside that bivy every night, worse at the footbox. The one night things were dry under the tarp – yet the footbox of my quilt was quite wet with condensation. I did NOT zip it up all the way (it wasn't cold enough…), but instead was inside the bivy with it mostly zipped, but my head outside. It was me and the pup under the trailstar – one night camped next to a river (yes, I know…) but the next night I was up high on a ridge with a wide open view and nice ventilation. That didn't seem to matter – i was still wet. So as someone experimenting with using a bivy, i'm also very interested in what others might say about this.

If it's raining, the humidity is not necessarily that high. Humidity from the air will condense onto the cold rain drops so humidity at ground level won't be that high. If it's really cold, and if you're under a clear sky so there's radiative heat loss, the outside of bivy will be colder so you'll get more condensation. It seems like cold temperature is what causes condensation more than the humidity. If you have too much insulation and are too warm, you'll sweat more so have more condensation.

Yes, I've experienced this. It is the primary reason I've given up on bivies.

Interestingly, I had lent my cuben duomid (the one starring in the previous discussion about water retention…) to try out while I used the silnylon trailstar…. She had NO condensation in the duomid…while it literally RAINED on me inside my trailstar. We were set up right next to each other each night. Hmmm……. Granted, I had a dirty dog under my tarp, so maybe that had something to do with it…………

Not much condensation in my BD bivy. Yes there is some, but not always, and it's not that bad. Love my bivy for sleeping under the stars. billy

"It is the primary reason I've given up on bivies." me too.

Love love love using all of my bivies. Yes, in certain situations I get minor condensation but nothing crazy to worry about. I also use the Enlightened Equipment Enigma pro with the dri down and the 20d strip at head and foot. If I had any condensation it would dry quickly..<img src="/backpackinglight/user_uploads/1442072737_131817.jpg" alt="Katabatic gear bristlecone bivy" width="550" height="978">

"It is the primary reason I've given up on bivies." "me too." Me three. I've used a number of bivies over the years and have experienced condensation, regardless of fabric. I really like the concept behind the bivy so it seems every couple years I decide to give the bivy another shot but the results are always the same. Sometimes condensation, sometimes not. It's impossible to predict if conditions are going to promote condensation so it's pretty much a gamble. I finally learned my lesson last November when I woke up in the middle of the night extremely wet. Not just a little damp, but pretty darn wet. And it was freakin' cold out. My down bag was useless and I had to get up and do jumping jacks and make some tea. Luckily I had a light down jacket with me otherwise I would have had to break camp and start hiking to warm up. Very unpleasant. Now bug bivies are a different story. I still use a bug bivy intermittently during the warmer months. edit: here are a couple photos of a cozy little cowboy camp with an MLD bug bivy

Love it chad…nice looking bug bivy. Thats the way to go!!

… I overnighted where the temps went 5-8* past the rating on my 20* sleeping bag–I had cold feet all night and a layer of frost on the sleeping bag. The next night under about the same conditions, I used my mylar space blanket inside my sleeping bag–it blocked moisture movement through the sleeping bag and it was steamy, but I slept warm and had no frost on the bag. The Stephenson/Warmlite people may be right on the vapor barrier liner, even in above freezing temps. Interesting, maybe.

Jen, one way to minimze condesation under a tarp and therefore on your bivy is to use a large groundsheet. If the ground was wet, you would have had more condensation than expected and it may have gotten through the fabric on your breathable bivy. Add in possibly breathing into your bivy while you slept and as well, the natural emission of water from your body over a 7-8 hour period, the conditions were ripe to have condensation inside your bivy. After years of experimentation, at least where I trek, I could not manage these things sufficiently.

My experiences have been like Chad's – Bug bivies are enjoyable for me.

I did the Haute Route Pyrenees this summer. One night I camped in thick French mist near the border, and woke up in the early hours to find everything soaked inside the tent, top of sleeping bag, gear, packets of food, everything. I was under a Trailstar with a bug net inner tent (Hexanet), with the temperatue at 12C/55F. I've never experienced anything like it before. On other nights I had condensation on the Trailstar (silnylon), but nothing that bad. Fortunately I had followed a tip from guys on the forum and brought along a sponge. You'll be interested to know that some mornings I sponged off a total from inside and out of 600 ml = 1lb 5ozs ! I know because I squeezed the sponge into my 600ml pan.