Warmth of Bivy?

[stickman]

I've never used a bivy or seen numbers on how much it would extend the range of a down sleeping bag, but I would think it adds some warmth, owing to the extra layer of trapped air between the bag and the bivy, as well as protection against the wind. Anyone with experience care to comment? Any advice on what to look for / avoid if I buy a bivy, or brand preferences? Thanks in advance.

Stickman

[SGT Rock]

Creates moisture problems in wet weather likethe AT.

[SalParadise]

Creates moisture problems in wet weather likethe AT.


condensation problems inside the bag? are different materials better or worse--I don't have a tyvek one but am planning on hiking with one.

[hikerjohnd]

What kind of moisture problems? Wouldn't the bivy act like a waterproof overbag? Or do you mean condensation?

[SGT Rock]

Well, most any breathable material waterproof enough to be a bivy will typically end up with condensation on the inside next to the bag. The problem is the outside of the bivy will be cooler than the air inside and the amount of vapor your body releases can and usually will be at higher rate than the moisture transpirates (I think that is the correct term) because the moihumidity on the outside of the bivy may fairly high. When the warm wet air hits the cool barrier of material it will condense, and that condensation from your body could wet your bag. If you go with something even more waterproof, then you get even worse problems. I have seen folks use bivies in cold weather at Ft Polk and end up with a wet bag while the person next to them didn't use a bivy and had a dry bag in the morning. I would recommend maybe a sil-nylon tarp and a tyvek ground cloth instead of a bivy for this weather.

Now out west and in Iraq where the air is dryer, bivies worked great for me.

[hungryhowie]

I often use a bivy in the winter time to extend the range of my bag. I own several bivies but typically use a goretex one throughout the winter and haven't really had any terrible moisture problems, even in the humid south. Most of your moisture will come from your mouth, and a goretex bivy will trap that. If it's cold enough, you wake up to millions of tiny ice crystals, just like in a tent. For strict winter use, I'd consider a winter bivy (where the top is made of something ultra-breathable like dryloft or pertex, etc, to decrease the amount of moisture that is trapped by the bivy.

As far as temperatures go, I'd say it extends a bag's range about as much as a small one-man tent, maybe 10 degrees. I don't know, if it's cold enough for me to take the bivy, I figure I"m gonna be cold anyway.

I also usually take a small 5'x7' sil nylon tarp, just in case it rains, so I'll have a little area for my gear and my head.

-howie

[SalParadise]

If anybody's used a bivy for a thru-hike, I'd like to hear your experiences. I'm planning on using a waterproof one this year as my primary shelter. Mine is thinly insulated, so I guess I won't get quite the degree of condensation than a tyvek one would, but I'm getting the impression a bivy is almost unusable when it turns spring and especially summer.
Thanks.

[hungryhowie]

If anybody's used a bivy for a thru-hike, I'd like to hear your experiences. I'm planning on using a waterproof one this year as my primary shelter. Mine is thinly insulated, so I guess I won't get quite the degree of condensation than a tyvek one would, but I'm getting the impression a bivy is almost unusable when it turns spring and especially summer.
Thanks.

Well, I suppose if you plan to stay mainly in shelter, the bivy would be alright. There have been people that hiked the entire trail carrying a bivy, probably some who've even slept in it a majority of the nights. But you are correct in your assumption that the warmer it gets, the less you'd actually want to be in one. I'd consider getting (or making) a silicone impregnated nylon tarp for warmer weather. Buying one will run you about ~$75, making one could cost as little as $10. But like I said, if you plan to stay primarily in shelters (which many thruhikers do each year), a bivy's probably not a bad option. You still may want to consider a small tarp, however, to use over the head of your bivy to protect you as you get in and out, and to have somewhere to keep your gear.

-howie

[SalParadise]

Thanks for the tip. I've got the head protection for the rain, and my head sticks out of the bivy, so I won't get mositure from my breath. I guess I'm just crossing my fingers that the bivy will be manageable camping outside of a shelter a third of the time.
Does the quality of the sleeping bag matter for condensation? I've got a 900-fill. Would that hold in all of the body heat to help prevent condensation?

[stickman]

What prompted my question in the first place was some earlier threads about hypothermia and winter hiking. I haven't carried a tent for some years, using shelters or an 8x10 sil tarp. I'm thinking my tarp set up by itself might not suffice for real winter nasties, but combined with a bivy it should be great, all at a pretty reasonable weight. I wouldn't expect to need it for three season use.

Thanks to all for the tips.

[goneSW]

Ive used my bibler bivy for 2 seasons now and would recomend it for section hiking. Ive slept in the freezing rain outside my houe to test it out?. other than the condensation around my mummy hood, every thing went good. I have a marmut 800 fill down, 35 degree bag by the way. I diddent however unzip the window infront of my face at night. Ill have to try it out this winter, Ill let you know how it turns out. I do most of my hiking in PA in the fall. I have yet to run into any condensation problems in this tent. I need to try sleeping out in the rain on a hot night. or just a hot night. I hate sleeping out when its hot!.
all in all, the bibler tri tod is a bit expensive, but im happy with it and plan on using it for some time.

[highway]

I have used a Salathe by Integral Designs

http://www.integraldesigns.com/product_detail.cfm?id=683

that opens to the waist and has its own mosquito netting. Some small tarp or poncho/head&gear cover is real important, though

[Pencil Pusher]

I have a REI Cyclops bivy. It's worked well enough. I think you just need to be more creative because you're dealing with such tight confines. Much like it can be a hassle sharing a tent with someone on a winter climb, so to is it when you up/downgrade to a single person tent and then on down to a bivy. If I had it to do all over again, I'd go with this Mountain Hardwear bivy I've had my eye on. It's water resistant only and not meant for full-on conditions and costs around $80 which is about what I paid for the REI bivy. Then like the other poster on this thread mentioned, bring some sort of rain protection tarp.

The Cyclops has the non-breathable waterproof fabric up several inches from the bottom on each side and condensation collects there. I've used it for all four seasons with the most posh being in a snow cave for the New Year. One combo that has worked reasonably well is to only take an emergency blanket and bivy bag. Get in the bivy and wrap yourself up like a burrito. Probably wouldn't recommend this for winter hiking though...;) You don't escape the condensation but then it really doesn't matter anyway since you sleep warm (albeit damp). Those bags with the single pole for space for the head seem like a good idea. Bibler even makes a bag with an integral tie in, for those more exposed bivies.

[SalParadise]

This thread's making me a bit nervous about taking by bivy bag to thru-hike.

Though the bag says waterproof, do you all still use a footprint/ground cover or can you go without? The rain's going to hit my bivy bag directly at the base, so would a ground cover matter?
And where is this condensation coming from? From the heat the sleeping bag releases or from your breath? My bivy bag won't cover my head and it's double-layered, so should I still worry about condensation?

[The Solemates]

This thread's making me a bit nervous about taking by bivy bag to thru-hike.

Though the bag says waterproof, do you all still use a footprint/ground cover or can you go without? The rain's going to hit my bivy bag directly at the base, so would a ground cover matter?
And where is this condensation coming from? From the heat the sleeping bag releases or from your breath? My bivy bag won't cover my head and it's double-layered, so should I still worry about condensation?

I would not hike with a bivy and never have, but from witnessing from others and by my common engineering sense, here are my thoughts.

Even if a bivy was completely waterproof, you still need some sort of ground cloth or else the bivy will get so filthy from lying it in the dirt and mud every night that it will change colors and be uncomfortable. The ground cloth will also provide another small layer of insulation. I would never sleep out in the rain with just a bivy. Where would you put your pack? Even if you had a rain cover, eventually everything will get soaked.

And yes, you will have condensation. Many nights you will have much condensation. This comes from your body putting off heat and this heat being trapped between the bag and the bivy, and thus turning into moisture, especially if the dew point temperature outside is low. On the AT, this moisture factor increases even more since it is often quite damp. Your sleeping bag will get wet no matter what. Some nights it will only be mildly damp, others it will be soaked.

The more waterproof your bivy is, the more condensation you can expect because your body heat will not be able to escape and will continue to be trapped, "suffocating" if you will, your sleeping bag. Some may argue that adding a Vapor Barrier Liner (VBL) would help cut down on the condensation, but I have my doubts. Additionally, adding a VBL would just add more heat to an already hot, sticky condition.

If your head is not covered by your bivy, then wont you get wet if rained on?

Bivies were first used, and since still have been, as an emergency shelter for mountaineers that are forced to spend the night while climbing because for unforeseen reasons they could not make it back to base camp. It started as a back-up plan, and while it may help save your life, you wont be comfortable.

I would at minimum go with a tarp on the AT. Personally, I like tents better because it gives me better weather protection in a storm, and you will have plenty of those on a long distance hike like the AT. There are many solo tents out there that are well under 3 pounds, making them almost as lightweight as a bivy. My choice is the Mtn Hardwear Waypoint.

Hope this helps.

[goneSW]

Id have to disagree with what most people suggest about bivies. Maybe the ones that they bought were inferior?. The premis behind a gortex fabric is the diferent temperatures between whats inside and the outside temperatures. as long as the inside of the faberick is relatively warm, the water proofness should hold. And really, I dont hope that you plan on doing a thru hike and not get totally soaked or even moderatly wet alot is crazy to think. unless you carry a 8 lb expidition tent with you. Sooner or later you will get wet. ALL TENTS LEAK SOONER OR LATER. Im not saying that a bivy is right for everyone. The construction of my todd tex bivy is second to none. It is extreamely robust construction and every thing is tap sealed with an application of seam sealer over it. The only help I caint provide you with is the performance in the summer months.check out www.bibler.com (http://www.bibler.com) Tripod bivy.

[Panama Red]

I had a slumber jack bivy i had used for many years and i had moisture problems like sgt rock was saying but one night on the uhwarrie trail changed that. it was the worst rainstorm i had ever seen and i set my tent up in a hurry and realized that the entire time i had owned it i was ssetting it up a little wrong once i had every thing taunt it was absolutley the driest tent i had ever slept in.

[SalParadise]

Thanks for the help everybody, it's hugely appreciated. Here's a link to what I'd like to use:

http://www.backcountryoutlet.com/outlet/AMK0035/Adventure-Medical-Thermo-Lite-Outdoor-Bivy-Sack-1-person.html?mv_pc=r156&CP=AdwordsAutomatorOutlet&CMP=KAC-GoogleAdAutomator&ATT=emergencyshelters

Hope the link works. It's double-walled, too, if that makes a difference, and waterproof (so it says). I'll have a tarp over my head, it's just that my legs will still stick out. The pack being outside isn't a problem. When I used a tent last year it still stayed out there--hanging it against a tree with the cover worked beautifully. I'm also confused as to the amount of condensation these get. Like dew? Enough to deflate a down bag?

[SGT Rock]

I am afraid something like that will most likely produce a lot of condensation. Howmuch does one weigh?

[The Old Fhart]

SalParadise: "Here's a link to what I'd like to use" I believe the "double walled" they refer to means aluminumized mylar. This means it is totally waterproof. Any one inside it will be sweating to some degree. This moisture can't pass through so you and everything inside the sack will be getting damp. If you've ever done dishes and worn rubber gloves you know your hands get clammy in the short time that takes. Now just imagine wearing these gloves for 8 hours and you'll get the idea how this sack will work.

Also if you are in something made of Goretex and the outside is totally wet, the Gortex membrane will prevent the water from going in but the water on the outside will basically seal the surface and prevent the sweat from passing through so you still get wet.

I used a bivy-tent in 1987 which was lightweight and worked well until one morning it was raining hard when I woke up. I tried to put my rain pants on inside that confined space. It took me a long time and I pulled a leg muscle doing it. It was then I decided I needed something with more room.

[hungryhowie]

Id have to disagree with what most people suggest about bivies. Maybe the ones that they bought were inferior?. The premis behind a gortex fabric is the diferent temperatures between whats inside and the outside temperatures. as long as the inside of the faberick is relatively warm, the water proofness should hold. And really, I dont hope that you plan on doing a thru hike and not get totally soaked or even moderatly wet alot is crazy to think. unless you carry a 8 lb expidition tent with you. Sooner or later you will get wet. ALL TENTS LEAK SOONER OR LATER. Im not saying that a bivy is right for everyone. The construction of my todd tex bivy is second to none. It is extreamely robust construction and every thing is tap sealed with an application of seam sealer over it. The only help I caint provide you with is the performance in the summer months.check out www.bibler.com (http://www.bibler.com) Tripod bivy.

Ah, but you assume incorrectly that temperature is the only variable that affects how well goretex works. One must not forget humidity, something that is very prevelant in eastern states, and along the Appalachian Trail. You also assume incorrectly that expedition tents are somehow inherently more waterproof than a bivy. W.L. gore and associates has a more rigorous waterproof standard than any other manufacturer with published standards.

Personally, however, I've stayed drier under a 1-person homemade tarp than in either a fully seam-taped tent or goretex bivy. And the best part was that the tarp weighed 8oz vs the tent's 5 pounds, and the bivy's 2 pounds.

-howie

[Youngblood]

That is only for emergency use to keep you from freezing if you get trapped outdoors overnight unexpectedly. It is a reflective vapor barrier with a foot vent(?) and probably not as durable as you think. I wouldn't think it should be compared to a regular bivy sack or expected to perform as such.

Youngblood

[The Solemates]

Thanks for the help everybody, it's hugely appreciated. Here's a link to what I'd like to use:

http://www.backcountryoutlet.com/outlet/AMK0035/Adventure-Medical-Thermo-Lite-Outdoor-Bivy-Sack-1-person.html?mv_pc=r156&CP=AdwordsAutomatorOutlet&CMP=KAC-GoogleAdAutomator&ATT=emergencyshelters

Hope the link works. It's double-walled, too, if that makes a difference, and waterproof (so it says). I'll have a tarp over my head, it's just that my legs will still stick out. The pack being outside isn't a problem. When I used a tent last year it still stayed out there--hanging it against a tree with the cover worked beautifully. I'm also confused as to the amount of condensation these get. Like dew? Enough to deflate a down bag?

Major condensation problems with this thing. It seems more like a heat blanket than a bivy. I thought you were talking about a real bivy. In my opinion, I would be willing to bet that you ended up in the shelters at least 75% of the time if you carried something like this.

[tlbj6142]

Even if a bivy was completely waterproof, you still need some sort of ground cloth or else the bivy will get so filthy from lying it in the dirt and mud every night that it will change colors and be uncomfortable. Won't your ground cloth get dirty? A pad takes care of the lumps.
Where would you put your pack? Even if you had a rain cover, eventually everything will get soaked.Who cares if your pack gets wet and dirty? Unless your pack is an old cotton canvas pack, it is made from materials that do not retain water. You put your dry gear inside your pack liner inside your pack and place the pack under your feet, or head.
And yes, you will have condensation. Many nights you will have much condensation. There are two types of shelters that are commonly called "bivies". Those that are designed to be a standalone shelter (like the Bibler Bivy) (http://www.biblertents.com/2002/lightsabre.html) and those that are really sleeping bag protectors or shells (like those from Mountain Laurel Designs (http://www.mountainlaureldesigns.com/bivys.html), Oware (http://www.owareusa.com/), Bozeman Mountain Works (http://www.bozemanmountainworks.com/quantum-vapr-bivy.php) and Equinotx (http://www.equinoxltd.com/Cart/description.php?II=8101)).

The former do have condensation issues in certain scenarios, the later are made from higly breathable (not waterproof) fabrics have very little, if any. Assuming you keep your breath out of the system (where most the "so called" body moisture is released every night).

The shell versions are indended to be used under a tarp (or in an open shelter) to keep your bag clean, fend off dew, rain splatter, snow spindrift, wind, bugs, etc. They also make your sleep system a bit warmer by reducing convectional heat loss by reducing air currents around your bag. They can weigh less than 7oz and replace your ground cloth, thereby only adding a net gain of 4-5oz to your sleep system.

They are the perfect addition to your sleep system if you are a tarp and quilt user. I hope to make one this winter, as they appear to be fairly easy to make.

[goneSW]

I agree with having more room in doing a thru hike. or maybe even an extended

trip out. having a bivy, no matter how big, just is'nt big enough to do much in. I know that people have done the trail in one, but that dosent mean having one makes life any better. Even though I use a bive and am having alot of sucess with it. Im not sure that using one on a thru hike would be in your best interst.
Mainely due to rain, and being stuffed in side one for long periods of time. I know that you might plan on using a tarp over on, but than you are closing in on the weight that you are trying to loose. And besides, there is nothing like having a dry place to sleep and move around in.

Long live bibler.

[Pencil Pusher]

Don't forget how creative you need to be if it's raining before you set up your bivy. I guess that's about the same for any go-light consideration... being more creative with what little you have to work with. Solemate, you'll love this answer: Your head is covered by the fabric, you have one zipper with four sliders to allow for air 'vents' on either side of your head. The Cyclops has a hood in the middle which also means it has a hole which I have fretted over to no end when it rained. But most bivies don't have this hood and you just get your air from the sides. Definitely not for the clausterphobic.

[highway]

I would not hike with a bivy and never have, but.....
Should one really opine about what they have not experienced? What if they are wrong? And another believes it? Hmmmmmmm.....????

[Lilred]

Should one really opine about what they have not experienced? What if they are wrong? And another believes it? Hmmmmmmm.....????

You don't always have to directly experience something to form an intelligent opinion. Observation of other's experiences are sometimes, and hopefully in some cases, all you need to know. When I first started looking at shelters, I asked at an outfitter about a bivy. The thru-hiker/salesman let me know I didn't want one. I trusted his observations as good enough.

...Although, that bibler with a tarp looks pretty good.......maybe when I have more experience......

[SalParadise]

hey I found a dude who's done the same thing I was thinking: http://www.monmouth.com/~mconnick/bivynote.htm
He said he didn't get any condensation in his bivy when he put his sleeping pad inside. Just thought some of you might enjoy reading it.

though to be honest I'm thinking that since I'd basically have to set up a tarp to cover my face, anyway, I might as well buy a full-size one and not bother with the bivy alltogether. Looks like Shires' tarps are $50 off right now, so may as well.