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Bivy Sack Buyer’s Guide

Mountaineering Bivy Sack

Bivy sacks are an alternative lightweight shelter for mountaineering in winter and under a tarp in 3-season conditions as protection against rainsplatter. I pulled together this list of the bivy sacks so I could compare them by weight, fabric, and price.

Please also note the Fabric Guide below, where I have attempted to explain, in English, the differences between the different bivy top fabrics.

Outdoor ResearchAlpine Bivy32 ozGore-Tex219
Outdoor ResearchAdvanced Bivy Sack39 ozGore-Tex299
Big AgnesThree Wire Bivy28.5 ozeVent300
REIMinimalist Bivy15 ozREI Elements90
Outdoor ResearchAurora Bivy24 ozGore-Tex199
MSRE-Bivy10 ozSilnylon80
Black DiamondHooped Bivy26 ozToddTex200
Black DiamondBig Wall Bivy30 ozToddTex240
Black DiamondBipod Bivy19 ozToddTex270
RabStorm Bivy17 ozWatergate90
Mtn Laurel DesignsSuperlight Bivy6.9 ozMomentum175
Titanium GoatPtarmigan Bivy5.8 ozIntrepid90
Mtn EquipmentBorealis Bivi19.5 ozGore-Tex267
Mtn EquipmentPtarmigan BivyIon Bivi10 ozDrilite134
RabRidge Raider33.2 ozeVent280
EquinoxSprawler Ultralite6.6Silnylon60
Terra NovaUltra Bivi2Cuben Fiber399
RabNestor Bivy35eVent360
RabSouth Col II Bivy15eVent280
The North FaceAsylum Bivy23DryWall Ripstop229
Mtn Laurel DesignsEvent Soul Bivy13eVent/Cuben355
BorahSnowyside eVent Bivy20eVent185
KatabaticBristlecone Bivy7Pertex149
Brooks RangeAlpini Bivy15BR UL180

Bivy Fabric Guide

One of the most important elements of a bivy is the breathability of the fabric used on it’s top half. If you’ve ever had your sleeping bag drenched by touching the condensation that accumulates on the inside of a silnylon tent, then you know exactly what I’m talking about.

Here’s a quick definition of the fabric types listed in the table above:

Gore-Tex is a waterproof breathable membrane that has pores in it. Each pore is about 1/20,000 the size of a water droplet, making it impenetrable to liquid water, but still large enough for water molecules to pass through. The breathability of Gore-Tex and other proprietary laminates like it (Conduit SL, HyVent DT, REI Elements, MemBrane Strata, Watergate, and DriZone), depends a lot on the fabrics that it is sandwiched between. A lot of the proprietary laminates have 2 or 2.5 layers of fabric making them potentially more breathable than 3 layer Gore-Tex.

ToddTex is a proprietary membrane like Gore-Tex that was originally developed by Todd Bibler of Bibler tents. ToddTex is also treated with a fire retardent. Black Diamond acquired Bibler and uses ToddTex for its tents and shelters.

Sympatex is a waterproof, windproof, and breathable membrane, but it does not have pores in it like Gore-Tex that let water molecules pass from one side to another. Instead, water molecules are absorbed by the membrane and evaporate on the outside. Reflexion is a variant of Sympatex that is coated on one side with a reflective coating that traps body heat and reflects it back, like an emergency blanket.

Silnylon is silicone impregrated nylon. It is waterproof but it does not breathe. Epic is silicone impregnated polyester which  is waterproof and breathable.

Momentum is a breathable, wind and water resistant fabric, but not waterproof. Pertex is also wind resistant and has better breathability than many waterproof laminates. Pertex is made with two fibers of different filament  thicknesses. Moisture is absorbed by the larger filaments on the inside of the fabric and is transferred to smaller ones on the outside, moving moisture by capillary action.

eVent is the current top dog in breathable waterproof membranes. Like Gore-Tex, it vents moisture through millions of tiny pores. It is different from Gore-Tex in that it does not require an inner coating, providing a more direct  path for moisture to evaporate.

Written: 2009. Revised 2013.

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  1. I'm not sure if the guys at Alpkit ship to the US (you could always ask I'm sure) but they do a bivibag called the Hunka – simple and effective, and cheap 25GBP.

  2. You've forgot the great RAB Ultra Bivy with 7.75 oz in your list

  3. I'll add these – we have limited visibility to them in the US, but I would like this list to be as complete as possible. There's great gear in the UK and Europe and Japan that no one in the US really knows about.

  4. Oware's bivy's are not listed, they made some of the BPL bivy's. bivysack.com or http://www.owareusa.com gets you there. They always seem the best bang for the buck. Titanium Goat are also well regarded: http://www.titaniumgoat.com

  5. Karl – thanks for directing me to the new oware site. I had left the oware bivies out because the old site was so confusing. The new site is much better, but still pretty esoteric. I also got the TG onto the list.

  6. I hope you write about your decision.

    This is a great template for most gear decisions:

    price, weight, gear specific differences

  7. Equinox Ultralite Bivy Cover — Just 6.6 oz.

    Here's an unbelievably light bivy if you don't have to worry about heavy rains or bugs. The super tenacious 1.1 oz. ripstop nylon is silicone impregnated on bottom and water repellent and breathable on top. A 27" zipper gives you easy access. Simple design doesn't include netting. Generous 82" x 34" "Foot to chin" portion is 68". Only 6.6 oz. No-see-um mesh storage bag adds just .2 oz. Color: Purple and black Mummy shape

    $64.95 No. 2414 Equinox Ultralite Bivy Cover

  8. Carl – that doesn't match what equinox is manufacturing. I assume the one you found is slightly older model, so I've put an entry in for the current one on their site which is fairly similar.

  9. Maybe off your radar for this test, but I came across a pattern a few weeks ago: http://www.therainshed.com/patternpages/RSpattern… I thought it an interesting idea, especially as you can pick and choose the materials you want (subject to availability, of course) … it is also available as a (GTX upper) kit here: http://www.rockywoods.com/Fabrics-Hardware-Patter

  10. I have 4 different bivvy bags (I know, I know!)

    The Rab Ultra

    The Alpkit Hunka

    The Equinox and

    The MLD Soul

    The Soul is my favourite although the Equinox is insanely light and cheap too


  11. That's good feedback. Do you have the soul with the Momentum Top? Do you use it in winter too, under a tarp, or standalone?

  12. I've had decent luck with the outdoors research micronight bivy. My best results have been when conditions have been extreme (3-4 inches of rain floating me out of the tent (only a slight exaggeration) or being near the edge on a platform in the Okefenokee swamp in a heavy rainstorm). It's not been as good at repelling heavy dews which seem to soak through the breathable fabric. It certainly has worked for me as a backup or additional layer (it has saved me from hypothermia more than once), but I'm not convinced I'd use is as my sole shelter.

  13. Proud owner of an Integral Designs Salathe and an Integral Designs Penguin Reflection here!

    The Salathe is bomber, although weighty. Having said that, the underside is tough enough not to need a footprint under it, and it's large enough to bring your mat inside. The eVent breathes well. A new trick I learned this fall was to stick a hot-pocket in the foot of my sleeping bag, which not only keeps feet warm, but raises the temperature gradient down there and blasts any moisture up and through the foot of the bivy. No moisture build-up as a result.

    The Reflection is new for me this winter, but I like it already. It does feel warmer, although in fairness I've got a new sleeping bag as well which might be contributing. I very much like the fact that it is cut so that I can lie on my side but still have the vent in front of my face. We'll see how it holds up as the winter gets underway.

    For 3-season use, I take (but rarely use) a 5' x 8' tarp. In winter, I dig snow holes/trenches and quite often use my tarp as a partial roof.

    I love my bivys :-)

  14. Chris – I was thinking of you when I listed the Penguin Reflection since I knew you were going to try it this year. Like you, I am heading in the direction of snow trenches. Gotta try this a couple of times. Are there any best practices that are worth knowing about how to dig them?

  15. Good to hear!

    I usually start with a 2 foot wide by 4 foot long trench, and dig down around 3 feet (or more if I can). Then I dig down and outwards to the required size, so I end up with a bell-shaped cross section, if that makes sense. Keeping the opening as small as possible is the key to staying warm. The tarp goes over the top as a roof. The entrance depends a lot on the location – sometimes I build an igloo-style side entrance if I'm on a steep bank, or just leave the end of the end of tarp free enough to wiggle out.

    As with a snow cave, I also dig a channel around the walls of the trench to funnel away any water that runs down from the walls, and also (I suspect) to act as a sink for some cold air.

    You might get a bit of an idea from this: http://www.flickr.com/photos/phaedrusredux/346839… (although this was not one of my better efforts..)

  16. Good advice there – I would not have thought of the bell shape or the channels (like a little platform). I like that photo. Did you sleep with your crampons on!

  17. Heh, when you sleep in your crampons that's when you know you're hardcore..

    Actually I'd been wandering around for a bit, photographing the dawn, before retiring back to the trench for a pre-climb coffee. Doesn't get better than that.

  18. The TiGoat Ptarmigan bivy is great except that the foot box is too small if used with a inflatable pad such as a NeoAir regular or BA Clearview. You might want to add the Mont-Bell Breeze Tec products to your list.

  19. That's good feedback about the TiGoat bivy. I thought about adding the Mont-Bell UL Breeze Tec sleeping bag cover to this list…I actually own one…but didn't since it's not technically a bivy, imho. It really is a sleeping bag cover which I mainly use as with a tarp to prevent rain splatter.

  20. The TiGoat news came a little late so I'll just confirm it is pretty tight at the foot with my Exped-9 inside. Being a side sleeper and on the short side I can probably make do though. Also have to be extra careful of zipper suck both ways.

  21. I ended up buying a MLD Superlight long with full face bug netting. It's sized to fit a neoair. That Exped 9 must be huge!

  22. Interesting, I also ordered the MLD Superlight long, but with the standard hood/noseeum window configuration. I agree that the round foot panel should be more roomy for the feet. I ordered it on Dec. 6 with a MLD Grace solo tarp. I'll let my daughter use the Ptarmigan on future trips.

  23. The Exped-9's a good deal thicker than the BA insulated air core it's replacing.

  24. Follow up on MLD Superlight Bivy. I used the MLD Superlight in my backyard under a MLD Grace Solo tarp. It rained all night with little wind. Humidity 100%. Bivy was set up on saturated grass. Air temp 38 degrees. Absolutely no condensation inside the bivy. Plenty of room with a GoLite Ultra 20 quilt, NeoAir regular pad, and a mostly empty GG Gorilla pack kept above my head inside the bivy. Also used an inflatable Cocoon pillow. A very dry, warm, comfortable night!. I'm very impressed with this piece of equipment. Immaculate craftsmanship & design. Side zip makes entry & exit no problem.

  25. That's fantastic feedback – can't wait to get mine from MLD.

  26. I'm new to bivy's but already a fan of side-zip; squirming in and out through the top is a royal pain.

  27. Hey not to sound like a complete novice for asking but…as I'm just getting into the use of a bivy sack instead of a tent… How do the goretex army bivies stack up against the name brands?. Looking for a cheaper alternative if only for summer trips. I usually use my I-tent for the snow but wandered if anyone had tried a cheaper winter solution like the army bags before I experiment an freeze my….

  28. I great inexpensive Bivy are the US Military Surplus Gore-tex covers on Ebay. I picked up a used one it was virtually new for $30 bucks. I also picked up one that had been repaired for my son for $20, at the time the others were not available. The repair on the Bivy were fresh from the factory taped. Turns out the repairs are sent back to the maker, then back to inventory and then surplus'd.

    They are a little heavy at 35 oz. but they have quality construction.

  29. Titanium Goat now makes three bivys. I have a Ptarmigan with an optional short side zip. That isn’t listed on the site, but was added at my request. The bigger Raven Omni would be slightly better for me and comes with a side zip, so I’m not sure if they still do custom side zips for the other ones. The Kestrel is the lightest.

    I mostly use my bivy under a tarp or pyramid to handle spray and block breezes. The Ptarmigan is a good choice for that and the side zip opens up the temp range a bit. I can keep the hood over my head and still let a bit of heat out.

    I put my pad outside of the bivy because I like to curl up a bit. An inflated pad forces the bivy to a very straight shape.

  30. I was searching for a the perfect bivy and stumbled on your list which is one of the most complete lists on the net so much thanks! After trying lots of different brands I ended up with one not on your list but well deserving. Little to no condensation, waterproof and lots of ventilation. The Über bivy by Miles Gear, there’s one hanging in the Whitney Portal store. Best I found and I tried them all!

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