Bivvy Sack Blues -- The Case of the Condensation

[Hikin_Jim]

So, I slept out last Thursday night in the SGW overnight in sleeping bag and bivvy sack. The overnight low was in the 20's. In the morning when I woke up, there was a lot of condensation on the inside of my OR Aurora Gore-Tex bivvy sack. I had slept with the mouth of the bivvy fully unzipped. Are bivvy sacks just a bad idea in cold weather? I've not had this problem before in warmer weather.

I'd love to hear the experiences of others particularly if there's a good work around.

HJ

[jfr]

Are bivvy sacks just a bad idea in cold weather?

I'd love to hear the experiences of others particularly if there's a good work around.

I'm not sure if VBL's (Vapor Barrier Liners) qualify as a "good" work around:
http://www.andrewskurka.com/advice/technique/vaporbarrierliners.php

Basically, he wears a rubber suit and adjusts his insulation layers to minimize sweating. But his gear stays dry on longer trips. Anyway, it's interesting reading, and written by National Geographic's "Adventurer of the Year" so he knows what he's talking about.

Personally, I'd rather carry a tent and keep the condensation on the inner wall rather than on my sleeping bag...

[Hikin_Jim]

Andy Skurka is one crazy dude. As much as I like to hike, I can't imagine doing what he does. Still, the guy absolutely does know what he's talking about. I've heard about vapor barrier use before. It sort of sounds like sleeping in a sauna. Not too attractive on the face of it, but when I get a chance, I'll read what Skurka says and see if it sounds good.

My challenge is weight. I've got really bad knees, so I'm trying to lighten my pack. Double wall tents are pretty much out because of their weight. My bivvy only weighs 1.5 lbs and is a nice option in that regard, but in cold weather, condensation seems to trump the weight advantage. Rats.

It kind of sucks that Goretex isn't even breathable enough to pass the vapor I emit while I'm sleeping! I mean I get it that heavy exercise with its incumbent sweating is going to overwhelm Goretex, but I mean come on, Goretex can't even pass what vapor I emit when I'm completely inert. FAIL.

Maybe I need to look at tarp camping or a tarp tent although I'd love to hear some more experiences from bivvy sack users.

HJ

[Andy]

Jim,

I also have an OR Gortex bivy that I used to use quite often. The last time I slept in it in cold weather was in the snow near Round Valley and I don't remember any issues with condensation. I slept on top of the snow, with only a Ridgerest below the bivy and a Thermarest inside. I'm not sure what the temperature was, but it did snow overnight.

I do agree that Gortex is vastly overrated in it's "breathability" especially during heavy exertion like skiing or snowshoeing.

Usually I'm a tarp or nothing sleeper but last year I picked up one of these guys http://www.amazon.com/Eureka-Spitfire-T ... B002OJBRS4
on sale for $75. I've used it once and it works better for me than the OR bivy (not so constricting) but because of its full length rain fly, it too becomes very stuffy when you're forced to batten down the hatches.

[Hikin_Jim]

Thanks, Andy.

I've got a nice one man Big Agnes Seedhouse 1 SL tent. It's worked great on every trip I've taken it on although it's not a four season tent by any means. The bad part is that it weighs 3.75 pounds whereas my bivvy weighs less than half that.

Weird. Maybe I'm the only one having bivvy condensation probs in cold weather.

Thanks for the input,

HJ

[phydeux]

VBLs were a trend back in the 1980s to extend the range of a sleeping bag. As I remember, they worked quite well in below freezing temps, but sucked bigtime about 32F.

How about a Shire Tarptent? Single walled silnylon with great ventilation. I've had a Cloudburst model (with the sewn-in floor) for the last four years and its worked great. Its about 2.5 lbs, keeps the bugs off me, resists a good wind load, resists mild rainshowers with a little wind (haven't had it in an 'epic' downpour), it easily fits two persons (or one with gear), and you can sit up in it near the entrance. Even took it out on a mild winter trip and it worked OK for sleeping and gear storage. You can't completely seal it up, so it wouldn't work in a snowstorm or sideways rainstorm. It ain't cheap (mine was about $220), but it works. Look it up at Tarptent.com.

[hvydrt]

For about a half pound more than your bivy, tarp tent seems like the way to go. I have been looking at the rainbow. You could sit up, read a book, cook, etc. I cant imagine riding out any kind of weather in a bivy. http://www.tarptent.com/rainbow.html

[Hikin_Jim]

I've heard nothing but good about Henry Shire's tarp tents. I was kind of hoping not to buy yet another expensive piece of gear. I've been kind of wanting one but unable to justify spending the money since I have a ton of freakin' gear. Maybe I now have a little bit of an increase in justification for the purchase.

Kinda disappointed in the bivvy although it's been fine in temperate weather for BP'ing in Southern California. I wasn't planning on taking the bivvy anywhere that would be buggy or where I might get some real weather.

I do appreciate people chiming in about the tarp tents. It only corroborates what I had already pretty much concluded: that tarp tents are a good product and a good way to go.

HJ

[SoCalJim]

I have the Sierra Designs Vapor Light 1 and I'm pretty happy with it. 2 lbs 14 oz, plenty of head room, and it's double-wall. Unfortunately, list price is $250. (I got mine on sale.) Sierra Designs also makes the Light Year 1, which is $170. 2 lbs 11 oz, but a little less headroom.

[EMan]

FWIW, I've had good experiences -- particularly in the snow -- with the floorless Megamid. Doesn't add any warmth, but it keeps the precip off of you and water doesn't pool beneath you...If it's windy, though, you need to build a snow wall around it. Old school technology, but it has worked for me in the past. However, I use an OR bivy as SOP, but always keep it as vented as possible under the circumstances.

Edit: BTW, I got to check out a tarptent that was being used by a very experienced, "state of the art" Canadian JMT through hiker along the HST a few weeks ago. Pretty impressive, IMO.