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bivy sack = not fun
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Steven Hanlon
(asciibaron) - F

Locale: Mid Atlantic
bivy sack = not fun on 01/02/2010 11:08:27 MST Print View

went out yesterday and had to call someone to get me a few hours after sunset. i was staying in an AT shelter that had only 3 walls and a large front opening. the wind was blowing right in the face of the shelter and i could not stay warm. it was around 20F and the wind chill took it down at least 5 more degrees.

i have camped in much colder weather but the difference is the use of a tent that provided much better wind protection vs. the bivy sack. the wind would hit and push the warm air inside the bivy out past my head. i could tell it was happening and tried several things to stop it but nothing seemed to work.

so sit here today bummed out about having to call for a ride after being told by my wife i was nuts for going out in the 20F weather.

Juston Taul

Locale: Atlanta, GA
Details on 01/02/2010 11:11:01 MST Print View

What bivy were you using? If the wind was blowing in on you, why didn't you move you setup to the back side of the wall outside of the "shelter"?

Jim Sweeney
(swimjay) - MLife

Locale: Northern California
Re:Details on 01/02/2010 11:16:02 MST Print View

Justin, sometimes, depending on the geometry of everything, the turbulence can be higher downstream of a wall, and there can be a pool of "quiet" air just at the base of the wall on the upwind side. Of course, one can only know by checking, and it's hard sometimes to leave a warm, or at least not freezing, sleeping bag to go and check.

Steven Hanlon
(asciibaron) - F

Locale: Mid Atlantic
why not move? on 01/02/2010 11:16:58 MST Print View

the way the wind was blowing, there was no place out of the wind. it was coming at a 45 degree angle to the face, hitting the one wall and whipping around inside. outside there was a rock wall cut into the hillside where the area was leveled to build the shelter. between the chunks of ice coming off the roof, and the wind funneled along the wall, i didn't think was any better.

there was several inches of snow and ice on the ground and that was blowing around too. nothing like getting hit will a cold, wet, gust.

the bivy i used was the REI Minimalist.

this is what the shelter looks like:

i tried up top to the far right thinking that would be more protected, but the wind was coming into the shelter along the roof on the right side. there is a gap for ventilation, sadly, it was working in the opposite direction. i moved back to the floor and finally gave up.

Edited by asciibaron on 01/02/2010 11:20:26 MST.

Steven Hanlon
(asciibaron) - F

Locale: Mid Atlantic
more thoughts on 01/02/2010 11:28:58 MST Print View

i would have been fine if it was warmer and still windy or cold and not wind. i think the bivy would work fine in March thru October in the Mid Atlantic.

the wind gusts last night were around 25mph - so that took the wind chill down to around 3F - wow - no wonder i was cold.

Edited by asciibaron on 01/02/2010 11:29:59 MST.

Diplomatic Mike

Locale: Under a bush in Scotland
Re :"bivy sack = not fun" on 01/02/2010 12:20:48 MST Print View

I think wind chill is only an effect if applied to unprotected skin?

Juston Taul

Locale: Atlanta, GA
Options on 01/02/2010 12:54:14 MST Print View

I guess one would have to be there to really know if there was a solution to the problem.

I see a large picnic table that if placed on its side, would have blocked a huge amount of wind. :D

ETA - I guess i'm just not getting it. Is the bivy you were using not windproof as described on the REI website? What sleeping bag or quilt were you using? What ground pad were you using?

Edited by Junction on 01/02/2010 12:57:37 MST.

Sean Nordeen
(Miner) - F

Locale: SoCAL
Campsite choice = not fun on 01/02/2010 13:50:59 MST Print View

Being out west where shelters are a rare sight, I'm having some trouble with your attachment to the shelter. When I camp out in just my bivy sack and no tarp/tent (which is 95% of the time), I hunt around for a natural wind break outside of most of the wind such as in a dense group of trees, behind a rock, somesort of depression in the ground, opposite side of the ridge, etc. Be more flexible and don't insist of staying in the wind tunnel just because it has a roof that you aren't even using for the weather. Just think of how cold you would have been in that shelter without the bivy sack. If you are talking about bringing a tent to stay warmer, just bring a tarp which is simple to arrange to block some of the wind.

The fabric of bivy's top can make a difference. I use to use a TiG bivy made with DWP that broke the wind pretty good. I replaced it with a MLD bivy made from Momentum fabric that has less condensation issues due to being more breathable, but it doesn't cut the wind as well.

Tad Englund
(bestbuilder) - F - MLife

Locale: Pacific Northwest
Re: more thoughts on 01/02/2010 14:35:02 MST Print View

Steven- how about some more information like what was asked above-
The REI minimalist is made of the same material as there WPB shell jackets- from their website "REI Element® laminate blocks rain and winds to 60 mph;..."
There must have been other problem areas that should have been addressed-
The minimalist does have a mesh face area but your bag/quilt (you didn't say) should be able to handle that-

You can go out when it's 20*, yes with the minimalist (I've done it in the wind.
BTW, my wife also thinks I'm crazy for sleeping in the cold but I would have walked home before calling her to pick me up, making her think she was right. I'm making no judgments here.

Steven Hanlon
(asciibaron) - F

Locale: Mid Atlantic
more info on 01/02/2010 14:55:45 MST Print View

the problem wasn't that the wind was getting thru the bivy material, it was pushing the warm air out the top of the bivy. my sleeping bag is a Marmot Sawtooth which is rated to 15 degrees - i've never had a problem in weather that was in the teens while in a tent with the bag.

the table isn't getting moved anytime soon - it is stuck in several inches of snow and ice. i tried moving it earlier to no avail.

i tried a new sleeping pad, and i think that created some of the problem. it is a Big Agnes Insulated Air Core. i think it was sucking some of my body heat to warm up the air. i had it inside the bivy and might have done better with it outside. i didn't think of that until after i had someone on the way.

it sucks calling for a ride, this is the second time in 5 years that i have bailed on a trip. i'm sure i could have toughed it out but i was more worried about making bad choices because i was so cold. given i was out by myself and was the only one to have used that section of trail since the last snow fall a week ago, i think i made the right choice.

Eugene Smith
(Eugeneius) - MLife

Locale: Nuevo Mexico
"bivy sack = not fun" on 01/02/2010 15:23:13 MST Print View

Sounds to me like you may have been much better off ditching the AT shelter and pitching a tarp low to the ground somewhere with some natural windblock. Sorry about your unfortunate evening but I think it is safe to say that your cold night woes drive home the importance of proper camp selection. That shelter looks from the photo to be totally exposed and all the foliage cleared around it, not ideal. That shelter became an object for the wind to funnel in and around possibly even picking up speed as it did so. You possibly mentioned one of the sources related to the problem which was relying on that Big Agnes Air Core pad, those pads are really better suited for warmer conditions and are rated to 35F at best with an R-Value of 1.0! Which is barely even worth mentioning. Seriously, that is a summer pad, you were sleeping on cold air with compressed down underneath you providing little to no insulation. The combination of a cold uninsulated shelter floor, wind passing underneath you and no wind protection is too blame, not the bivy sac.

I wouldn't give up on the bivy and definitely supplement or save the Big Agnes Aircore pad for later in the season. Just my thoughts. Sorry though you had to bail out, definitely doesn't help in the wife department for future trips, as she'll always remember and bring up that one time when you had to get picked up.

Mark Stalbird
(Off-road) - F
Hitch hike the next time on 01/02/2010 16:41:06 MST Print View

then sneak in the basement door.

I had to bail in early spring,the wife picked me up at midnight at the same location she dropped me off earlier.
It was a humbling experience as she kept challenging my manhood all the way home.

Oh...i was invaded by deer ticks before waving the white flag,they were crawling all over the inside of my tent.

Steven Hanlon
(asciibaron) - F

Locale: Mid Atlantic
the sleeping pad on 01/02/2010 17:19:23 MST Print View

the sleeping pad is the insulated version with a 4.0 R value. i chose the spot because i figured it would be a good test for my sleep system - i was right, it needs some improvements.

the ride i got was from the park service. home was 1.5 hours away and there was no way i was going to call home and have my wife pack up the kids to drive me 10 miles to my car.

the worst part - i work for the park service and now i'm expecting to get a bunch of comments on my "skills" come monday.

Rod Lawlor
(Rod_Lawlor) - MLife

Locale: Australia
The Book of the Bivvy on 01/02/2010 17:58:17 MST Print View


I have to agree that it was probably your basic tenet to stay with/in the shelter that brought you undone here. Instead of using your bag as a bivvy, you used it as a sleeping bag cover.

A really good book to cover the whole idea of using a bivvy is Ronald Turnball's Book of the Bivvy. $14.33 including postage from

He also would have suggested dropping into a more sheltered spot in the woods nearby the shelter.

It's a great book and I highly recommend it if you're interested in getting into bivvying

As far as the situation you were in, and the wind blowing the warm air out of your bag, could you have shoved a jacket (shell?) in as a collar to reduce this. I also find it worth manufacturing a microclimate beside my head to minimise airflow directly across my face. I use my pack for this, but anything bulky enough will work. You can also turn the bivvy upside down with a small breathing hole facing away from the wind.

Just remember, in a cheap (ie non-eVent) bivvy, you can be warm and wet or cold and dry. Warm and wet is fine if you're only out for one or two nights.

Just remind your wife that the fact that you called her up for a lift shows how responsible you are. You could have toughed it out, and tried to walk out alone the next day in a dangerously depleted condition, but instead you chose the safe and sensible option. Pick a really crappy night sometime soon, and try the bivvy again in the back yard or with a tent along as back-up. She'll soon start to trust your judgement.

The comments at work are easy. Just invite any of them along next time. It's fantastic that you are getting out there in less than ideal conditions, since it gives you an insight into how others may be doing it, and what the possible consequences of not making smart choices can be.

Edited by Rod_Lawlor on 01/02/2010 18:03:34 MST.

Tom Clark
(TomClark) - MLife

Locale: East Coast
Re: bivy sack = not fun on 01/02/2010 20:43:04 MST Print View

During the trip I just posted a few days ago, the temps got down to 8F with high winds. I had a nice flat spot for my tarp and bivy...except that the wind was blowing straight through my A-frame. I really found that I needed to keep the extra foam pad between me and my "insulated" Insul-Mat(I agree with the other poster...they don't keep you warm), and to keep my sleeping pad pulled shut to a small hole above my face. The bivy's no-see-um netting helped for a microclimate for my to breathe some warmer air.

Ryan Jordan
(ryan) - BPL Staff - MLife

Locale: Greater Yellowstone
Re: Re: bivy sack = not fun on 01/02/2010 21:22:10 MST Print View


That's an uncomfortable scenario.

The biggest thing I've learned about bivy-sackin' is that I've learned never to remain constrained by the types of campsites available to tent- and shelter-campers.

When the weather is nice, you have your pick of campsites, and can sleep on perches tent and tarp campers can only dream about.

And when the weather is nasty - your options likewise expand, for increased comfort.

So, in calm conditions, go for high places and good views. One of my favorite bivy sites was this one, on a knoll below the western faces of the Grand and Middle Tetons, August of 2001. Photo by Alan Dixon.

Ryan Jordan - Teton Bivy - Photo by Alan Dixon, Aug 2001

But when you're expecting inclement weather, or you're otherwise "underdressed" with respect to your sleep clothes / sleeping bag / pad, consider tucking away into the bushes to stay a little warmer. This was my strategy most nights of a stormy trip in the Bob Marshall Wilderness this summer. On one particularly foul night, I tucked deep into the bushes on a small bench, just off the banks of the South Fork Flathead River. I had bushes all around me, touching my bivy - it was almost coffin like. But I stayed warmer, and drier, than if I'd picked the perch that was more aesthetically pleasing - which was on the sandbar overlooking the river.

Dennis Park
(dpark) - MLife

Locale: San Francisco Bay Area
bivy sack = not fun on 01/02/2010 23:01:51 MST Print View

I've read that the Minimalist can be quite snug. Could you have lost insulation because of the having too much bulk inside the sack?

Jim Colten
(jcolten) - M

Locale: MN
Re: bivy sack = not fun on 01/03/2010 04:04:29 MST Print View

Folks who've already pointed out that the three main considerations in camping with challenging weather are 1) location 2) location and 3) location are dead on.

But there may be more to it that that in your case:

the sleeping pad is the insulated version with a 4.0 R value.

Richard N. (who measures stuff, hence is well worth listening to) has frequently suggested that you want pads totaling R5 when sleeping on frozen ground.

Richard has also posted a graph showing that ground temps are closely correlated with air temps until the ground freezes and then they tend to be independent of air temps and steady in the neighborhood of 30F (hundreds of data points). So his R5 recommendation is for a pad resting on a 30F surface ... not the 20F you have when on a platform in 20F air temps. Going to the ground may have helped.

Lastly, although I've never seen one in the flesh ... many folks have reported that the BA Insulated Air Core seems colder than other alleged R4 pads they used so maybe the BAIAC R-value is not quite 4???

Steven Hanlon
(asciibaron) - F

Locale: Mid Atlantic
awesome info on 01/03/2010 07:52:29 MST Print View

thanks for all the great followup info here. i'm not ready to give up on a bivy, i just need to refine my system.

Tad Englund
(bestbuilder) - F - MLife

Locale: Pacific Northwest
Re: awesome info on 01/04/2010 20:54:26 MST Print View

Steven- I is/was the BA insulated aircore!!!! That was totally your problem- the air being pushed out by the wind was just an illusion. There are a number of threads about this- One that I started a year ago last fall- Question of the day
Read the entire thread. BTW, I returned the pad and went back to my old Thermarest for the next winter and had no problems.
Change the pad- keep the bivy

Edited by bestbuilder on 01/04/2010 20:56:11 MST.