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Reviews > Shelters > Tarps and Bivys > Big Agnes Three Wire Bivy > Test Report by Peter Spiller

Big Agnes Three Wire Bivy Sack

A Test Series by: Peter Spiller

Initial Report: March 8, 2008Tester Information
Field Report (May 20, 2008)Product Information
Long Term Report (July 21 2008)

Tester Information:

Name:Peter SpillerBackpacking Background: I have been camping and hiking avidly since childhood.  In the last several years my passion for backpacking and kayaking has grown.  I am a Chapter Outing Leader for the Sierra-Club, I have trained in Wilderness First Aid, and am a staff member for a Wilderness-Basics course.  I enjoy solo backpacking and group trips.  I have an adaptable style that is fueled by my interest in backpacking gear.  I pack as light as possible when the situation dictates, but I am not against hauling creature comforts. I average 1 hike a week, and 1 backpack a month year-round.
Age: 38
Height: 6 ft 0 in (1.83m)
Weight:190 lb (86 kg)
City, State, Country:La Mesa, California United States

Product Information:

Manufacturer:Big AgnesBA Three Wire Bivy
Photo from Big Agnes' Website
Manufacturers Website:
Model:Three Wire Bivy Sack
Floor Length:90 in (229 cm)
Width:Head: 23 in (58 cm)
Shoulder: 31 in (79 cm)
Foot: 25 in (64 cm)
Height:Head: 20.5 in (52 cm)
Foot: 12 in (30.5 cm)
Packed Size:5 in (13 cm) by 17 in (43 cm)
Weight (manufacturers):Trail Weight: 28 oz (794 g)
Packed Weight: 32 oz (907 g)
Weight (as delivered):Trail Weight: 27 oz (764 g)
Packed Weight: 34 oz (964 g)
Fabric:Top: eVent waterproof fabric
Bottom: Cordura
Model Year:2008
Trail Weight Includes: Tent Body, Poles, and fly with out guy-lines
Packed Weight Includes:Tent Body, Poles, Fly, Guy Lines, Stuff Sacks, Stakes, Instructions and Packaging
Manufacturers Description:From Website: The Three Wire Bivy provides shelter from the storm and piece of mind for the solo camper or alpinist.  Top shell features eVent waterproof fabric while the bottom in durable, lightweight Cordura.  The easily-pitched pole system provides good headroom and ventilation.  The Three Wire also uses a DAC Featherlite NSL poleset, which feature an Eco-Friendly anodizing process that significantly reduces the use of hazardous chemicals,  as well as Reverse Combi pole optimization for increased strength and weight savings.
100% GuaranteeFrom Website: Our number one priority is to make functional and dependable outdoor products.  If you are not satisfied with any Big Agnes product at the time you receive it, or if one of our products does not perform to your satisfaction, return it to Big Agnes for a replacement or refund.

Initial Report:

March 8, 2008

Product Description:

The Big Agnes Three Wire Bivy (here after referred to as the bivy, or the bivy sack) is a unique bivy shelter constructed with eVent fabric.  It is designed to have a raised structure over the head area supported by a pole assembly with three poles reaching the ground, similar to a tripod, and a fourth shorter pole that supports a peaked visor that covers the top of the zipper area.  This visor provides protection from the elements while allowing the zipper to be opened up and used as a vent.  The tripod like structure provides a significant amount of room, keeping the fabric from touching my face, and allowing more room to maneuver inside the bivy sack.

bivy side viewEntry to the inside of the bivy is accomplished by a right-hand side zipper that extends over the top of the peak area, and down about half the length of the bivy sack.  Behind this flap, there is a panel of no-see-um mesh that zips closed following the same zipper track with the intent of providing more ventilation while maintaining bug protection. 

The body section of the bivy is voluminous down the length to the foot-box which has an oval panel sewn on the end providing a boxed end that will not compress the insulation of a sleeping bag.

The upper portion of the bivy is made of a bright orange square grid textured nylon material called "eVent" fabric which Big Agnes describes on their website as "a breathable, waterproof fabric that vents moisture directly to the outside, keeping you and your bag dry inside". The interior of the "eVent" fabric is unique, as it appears that is has a very fine mesh laminated to it. The bottom of the bivy is comprised of a black diamond shaped grid textured nylon that Big Agnes identifies as "Cordura". The website describes it as "durable" and "light weight". The storm flap for the zipper and the peaked section of the hood area are a dark maroon color, made of the same material as the stuff sack, and similar in texture as the Cordura bottom of bivy. There is a black Big Agnes logo silk screened on the chest area, and a much smaller eVent logo silk screened on the lower right side of the hood area.

The zippers all have black nylon ribbons attached to them with the Big Agnes name embroidered onto them. The eVent storm flap, and the mesh panel both can be secured by hook and loop tabs positioned at the center of these panels.  There is a tag located on the inside right of the hood area with instructions on caring for the fabric of the bivy.

Initial Impressions:

bivy in retail packagingThe bivy arrived in a maroon colored stuff sack made out of a rip-stop type nylon material, with four hangtags attached.  One tag was a list of features of the bivy, another providing information on event fabric, another providing information on the Cordura nylon, and the final providing information about the DAC Featherlite poles. 

Upon opening the stuff sack and removing the contents, I assessed that all the pieces were present ( 1-bivy, 1-pole set, 6- aluminum stakes, 3- stuff sacks, 1-set of directions). The contents appeared to be without defects, and very well made.

I inspected the bivy sack first, and was struck by the bright orange of the fabric.  The orange color is very similar to the color in safety vests, and I could see using it as a signal device in emergency situations, as it would stand out from the more muted colors found in nature.

After the initial set-up of the bivy, I climbed in it to give it a quick test drive, and found it somewhat awkward to get in.  The combination of the 1/2 zipper and the peaked head area made it difficult to sit and then lay down without some minor acrobatic contortions.  I believe this is not a problem unique to the Big Agnes Three Wire Bivy, and I am confident as I gain some experience I will work out a system, which will allow quicker less awkward entry and exits.  I will report on this after field-testing.

Over all, the bivy and its components appear to be extremely well made, and the quality of craftsmanship and attention to detail are apparent throughout, from flawless seam taping, to such details as the reinforced stake loops.  I am very pleased with the bivy, and anticipate that is will hold up well during testing and beyond. 

seam taping
An example of the taped seams


My initial research into this bivy included downloading and reading the directions from Big Agnes' web site.  I was unclear as to how the structure of the head area of the bivy was constructed, and the directions cleared up my confusion.  The instructions downloaded from the Internet were the same as those included with the bivy, and they were clear enough that I had a pretty good idea of how to set it up previous to receiving the bivy itself. 

During the initial set up, I briefly reviewed the instructions included in the package, and began. I had to push on the poles pretty significantly to tension them far enough to fit into the pockets in the front and back of the hood area, and in each grommet on the sides of the hood area.  The tension was never great enough that I was worried about breaking the poles or tearing the fabric and it provided a taught pitch.

detail of stakeDuring the second set-up, I did find that after seating the long pole in the small pocket at the head of the bivy, and moving back to seat the other end of the bivy in the pole pocket at the peak of the hood, the first end slipped out, and was pushing into the fabric.  It did not do any damage, but I had to start again to set up the pole correctly.  This problem was most likely user error, but I will keep an eye on this during future set ups to see if this continues to happen.  During this set up I also was able to stake it down. I used the six provided stakes to secure the bivy to the ground.  The stakes are high quality and light, but I foresee a challenge in keeping the stake loops secured on the stakes.  The stakes have small notches near the top meant to catch the loops, but the reinforced stake loops on the head area are bigger and stiffer than the regular loops near the foot end, and slipped off easily when I first staked it down.  I remedied this by angling the stakes away from the bivy to trap the loops.  I will reassess this during field-testing on rockier more challenging terrain.

The first two times I set up the bivy, it was fairly quick. I was slowed slightly by the problem with the pole mentioned previously.  I anticipate with practice, I will become much quicker at setting up this bivy, and will report the ease of set-up during the field report. 
Pole Pocket
Internal Pole Pocket

After setting up the bivy, I placed my sleeping pads and my three-season down bag into it to assess the amount of room.  I was happy to see that the bivy accommodated a closed cell pad, an inflatable pad, and my sleeping bag with room to spare.  There bivy with sleeping bag and padswas no compression apparent.  In my opinion, the bivy could handle a larger sleeping bag without a problem.  I will assess this during a cold weather trip during field-testing when I use a larger warmer synthetic bag.  The floor dimensions of the bivy easily accommodated my 20 in (51 cm) by 70 in (178 cm) mummy shaped inflatable pad.

Quality Assessment:

I was happy to see the quality and care apparent in the sewing and construction.  I did not see any broken threads or loose seams.  The quality of the seam taping was impressive.

The pole assembly appears to be very high quality, and the hub of the assembly is a unique molded plastic piece, that looks very durable.  I will keep an eye on this hub to conform my impressions. The poles themselves also appear to be very well made and durable.  The x-shaped aluminum stakes appear very sturdy, and light at .5 oz (14 g) each.

A note about Big Agnes and conservation:

recycleWhile a manufacturer's commitment to conservation is just a very small factor in my buying decisions; second to quality and performance. It is worth noting when companies make a positive effort in making their products environmentally friendly.  Big Agnes has made this effort in the construction of the Three Wire Bivy by using DAC Featherlite NSL poles.  These poles are manufactured using an anodizing process that almost eliminates the toxic chemicals using in the traditional process.

Test Plan:

I am planning to test the Three Wire Bivy under a multitude of different conditions. If Mother Nature works with me, I hope to use the bivy during snow and rain, as well as milder dry weather, where I can test it using the bug screen.  During all tests, I will evaluate the bivy using the following criteria:

 Set Up/Packing:

  • Does the bivy set up easily and quickly? 
  • Can I set it up during inclement weather? 
  • Is it easy to set up with gloves on in cold weather? 
  • How long will it take to be proficient at setting up the bivy?
  • Does it pack easily and quickly


The Event fabric comprising top of the bivy is one of the signature features of the Big Agnes Three Wire Bivy: 
  • Does the use of this fabric allow it to breathe?
  • Does it eliminate condensation in the bivy during a wide variety of conditions? 
  • Are their conditions in which the Event fabric is not effective?


  • Is the Big Agnes Three Wire Bivy durable? 
  • Will it hold up under the field conditions I put it through? 
  • Will the reinforced stake loops at the head and shoulder be durable enough during long-term use? 
  • Will the regular stake out loops at the feet hold up as well as the reinforced ones? 
  • Will the Cordura rip-stop fabric that composes the bottom hold up to when used in rough terrain? Will it protect my sleeping pad from stray cholla cactus?
  • Are the DAC aluminum poles durable enough to maintain their shape with repeated use and packing?
  • Will the head structure shed wind and rain effectively?


  • Is the Big Agnes Three Wire bivy comfortable to sleep in? Is it comfortable enough to wait out severe weather?
  • Is the bivy easy to get in and out?  Is it possible to get in and out during inclement weather while keeping the interior dry?
  • Does the design of the head area hinder entry and exit?
  • Does the design of the head area eliminate the claustrophobic feeling of most bivy sacks?
  • Can I vent the head area with the mesh and cloth flaps?  If so, can I control the amount of ventilation with the zippers?
  • Does the mesh flap allow a good view of the stars while maintaining a bug free environment?

Field Report:

May 20, 2008

I have used the Big Agnes Three Wire Bivy on three overnight trips thus far during the testing period.  To date the bivy has performed admirably under a variety of different conditions.  Testing this bivy has opened my eyes to the possibilities that a lightweight minimalist shelter can bring to backpacking.

Trip #1 March 20-21, 2008: Dos Cabezas- Anza Borrego State Park, California

The first trip using the Three Wire Bivy was an overnight in the desert east of San Diego, California.  It was springtime with mild weather, and a fantastic display of wildflowers responding to the rains in the previous weeks.

The night before the trip, I was happy to note that the bivy packs up much smaller than the one-man tent I have previously used, and I had spare room in my pack.   The stuff sack is long and narrow, which is good for stashing vertically in a corner of the pack.

As I mentioned before, the weather was fair during this trek, a perfect opportunity to try out a new piece of gear.   The daytime temperatures were well above 80 F (27 C), and the nighttime temperatures only fell into the high 50’s F (14  C). There was not a cloud in the sky, and a weak breeze coming from the west. The humidity hovered at around 39%  After a refreshing hike, I found a perfect campsite situated in a natural amphitheater formed by huge boulders at about 900 ft (274 m) elevation.  I began setting up camp with the bivy.  It set-up relatively easy, although I did need to redo the poles as the top pole slid out of its pole pocket when seating the other three ends. I staked the bivy down with the supplied stakes noting that they held better than I initially expected.  I slid in my 15F (-9C) down bag, and my 20 in (51 cm) wide by 2 in (5cm) thick inflatable mummy shaped pad, and noted that the volume of the bivy swallowed up this sleeping combination with room to spare.  I zipped up the screen and went about enjoying the evening.

BA Bivy in desertWhen I went to bed, the temperature was still warm, and there was no real measurable wind.   I decided that I would sleep with just the bug screen zipped up to take advantage of the warm weather, and the very bright full moon making it almost seem like day light in the quiet desert.   I crawled a bit awkwardly into the bivy and slid into my sleeping bag, and struggled to get the bug screen closed as I could not really tell which zipper went to the bug screen, and which was for the storm flap, as the zippers are close together, and are in such a position that it is hard to see. It seemed that I would inevitably grab the wrong zipper and start zipping up the storm flap.  Changing the zipper pulls to differentiate the zippers would help solve this problem.  The second thing I noticed is the peak of the storm visor extends out farther, and is lower than I expected, partially obscuring my view.  This was not a problem as much as an observation.

I slept very well during my first night in the bivy, and loved the fact that those moments I woke up; I was able to see out into the desert while being protected from the elements and critters.  I did not experience any claustrophobia, and it was very roomy and very comfortable. I basically forgot that I was in a bivy as I slept the night away.  In the morning I noted no condensation as expected with the dry conditions. The bivy packed up easily and quickly and I was soon off hiking with a greater appreciation of this new tool in my camping arsenal.

Trip#2: Inyo Craters March 29-30, 2008: Mammoth Lakes, California

The second trip in which I slept in the bivy was to the Inyo Craters area of Mammoth Lakes California.  This trip was the culmination of a 10-week outdoors skills course in which I was helping lead a group of fresh new backpackers on their first snow camping experience.   While I was not a student in the class I learned a great deal as well, as it was my first experience bivy camping in the snow. The Big Agnes Three Wire Bivy opened me up to the possibilities that bivy camping has to offer.

Initially conditions for this trip looked rather ominous.  Precipitation was forecast, but the temperature was warm, bringing the possibility of rain and sleet.  These are messy conditions when combined with the approximately 8 ft (2 m) deep snow pack already in place.  Fortunately the temperature dropped enough that the precipitation turned into more snow.

BA Bivy in snowAfter a short snowshoe hike to our proposed campsite at an elevation of 7900 ft (2256 m), I set up the bivy in a stand of Douglas Firs, enjoying the vanilla scent that these magnificent trees exude. I wore a pair of light liner gloves while setting up, and had no problems manipulating the bivy. The snow was deep in this area, making it impossible to effectively use the supplied stakes, so I rigged up four “deadman” anchors to secure the bivy.  Due to the expected temperatures and possibility of rain and snow, I had a much more robust sleeping system.  I slipped in my 77 in (196 cm) by 25 in (64 cm) by 1.5 in (3.8 cm) self-inflating pad, along with my 72 in (183 cm) by 20 in (51 cm) by .75 in (1.9 cm) closed cell foam pad as well as a 0F (-18C) synthetic fill sleeping bag.  All this fit well with no signs of compression, and plenty of room to move around.

When I went to bed in the evening, I stashed my boots, and most of my warm clothes in the head area .  In my opinion, one of the great advantages to the bivy’s configuration is this spacious area in which one can stash gear.  While not big enough for a pack, it is large enough for boots and miscellaneous items.  As I have gained experience with the bivy, I found sitting on top of it, getting ready to turn in, and sliding myself inside has made it a lot less awkward.

I woke during the middle of the night to a tapping sound from above my head, and it took me a few moments to realize that it was snowing pretty heavily.  I checked the temperature inside the bivy and it measured about 29 F (-2C) with a humidity hovering around 67%.  I went back to sleep and slept very well until morning.  As it grew lighter I looked around, and noticed that there was condensation built up on the interior walls of the head area in the form of frost.  I also noticed I was virtually buried in snow.  I felt around in the sleeping bag area, and found no detectable condensation on my sleeping bag.  It appears that the design of the bivy isolates the sleeping bag area from the head area, helping protect it from condensation caused by breath.

It was still snowing when I decided I had to come out of my warm cocoon.  I prepared my gear to allow me to quickly get dressed, and then thrashed about a bit to knock off the accumulation of snow and unzipped the storm flap to greet the day.   In the process of getting out, I did manage to get a measurable amount of spindrift inside the bivy, and the falling snow dropped in more during the process.  While I was able to simply brush it away, the experience caused me to speculate that using this bivy in rain without a supplemental tarp would have potential of being wet and uncomfortable. 

The Big Agnes Three Wire Bivy performed very well in these snow conditions, and made me confident that it is a viable winter shelter.

Trip#3 April 5-6, 2008: San Mateo Canyon Wilderness- Riverside County, California

The third trip I used the bivy was on an overnight in the San Mateo Canyon Wilderness. We camped in a lush riparian area, dominated by large trees, and a fantastic spring wildflower bloom. The hike in was dominated by the damp misty weather, which made the weather cool, and threatened rain that never did develop.   The high temprature during the trip was 66 F (19 C) while the low was 55 F (13 C)  with a humidity around 83%.

BA Bivy in grassI set the bivy up in our designated camping area near a small stream, and under a grove of large oak trees.  I took a little extra care during set-up to make sure the poles stayed in place, and found that the process has began to become very routine.   My initial concern about the ability of the stakes to stay in place on the stake loops is proving to be unfounded, as they have performed flawlessly the times I have been able to use them.  Getting in and out has also become more routine, and less awkward as I have gained experience using the bivy. 

I slept with the storm flap open and the bug screen closed during this trip, as the temperatures were mild, and the threatening rain never materialized. As with the other two trips, I slept well, only waking when a trio of great horned owls decided to surround our campsite and hold a lively conversation with each other.

A morning check of the bivy, revealed no significant condensation, and the night was a comfortable success.  I broke down the bivy ready to head out, and found (as I had previously) that the bivy rolls up easily, and fits into its stuff sack with only minimal coaxing.


The Big Agnes Three Wire Bivy performs very well as a light alternative to a full-blown solo tent, or even a convenient easy to set-up alternative to a minimalist bivy and tarp combo.  The bivy has performed admirably in mild conditions, and even in more severe winter weather.   While unfounded at this point, I do have some concerns about its functionality without a supplemental tarp in rainy weather, and will comment on this if I am able to use it in the rain. 

The eVent fabric has functioned for the most part as advertised.  The only conditions in which I have encountered measurable condensation were during a snowstorm in which the exterior was subject to cold and snow, freezing the vapor from my breath onto the interior of the bivy.  Even with these conditions, the parts of the bivy isolated from my breath appeared to effectively dissipate vapor produced by my body.

The bivy had proven to be durable.  I have found no damage or flaws as of yet.   The only sign of use comes from the light coating of dust on the black Cordura bottom that does not readily brush off.  As of this point, I am very impressed with this bivy, and look foreword to continuing the test in the upcoming months.  Please check back towards the end of July for additional data on the testing.   Thank you Big Agnes and for the opportunity to test this fine shelter.

Long Term Report:

Test Locations:

I slept in the Three Wire Bivy for three nights during a 14-day base camping trip in early July to the Sierra Nevada Mountains in Central California.  The three nights were spent near Mammoth Lakes at an elevation of approximately 8600 ft (2621 M).  The temperatures ranged from the low 60 f (16 C) in the evening to the mid 90 f (35 C) during the day.  Two of the evenings were dry and warm, the third I had the opportunity to experience the shelter in light precipitation as an early evening thunderstorm passed overhead.

Long Term Performance:

Setup of the bivy has become routine, and generally takes less than five minutes from pulling it out of the stuff sack to pushing in the final stake.  Despite my initial concern with the stakes ability to hold down the bivy, I am very impressed with them.  They have worked flawlessly, and have proved to be extremely durable.  I like them so much I am considering replacing some of the stakes from my other tents with the same style.   

During the two nights without precipitation, I used the bivy primarily as a barrier from the bloodthirsty hoard of bugs zeroing in on me. I slept on a 25in (64 Cm) wide by 77 in (196cm) long 1.5 in (4 cm) thick self-inflating pad along with my 3-season down bag unzipped and used as a quilt. The bivy would have been too warm with the storm flap zipped up, and the bug netting has proven ideal for using the shelter in warmer weather when mosquito protection is a must. 

It rained early one evening, and I decided to crawl in and test the bivy as the summer thunderstorms in the area usually short in duration. I was able to get into the bivy and my bag with only a small amount of the light rain entering with me.  It helped that I have developed enough experience entering the bivy that I am able to do it quickly.  I sat on top of the bivy, removed my boots, unzipped the storm flap and threw my boots into the head area, and crawled in.  This was a summer thunderstorm, and the weather was still warm, so I did not zip the storm flap completely and left a small gap under the sheltered peak of the head area for ventilation.  I noticed after a few minutes that a small amount of water was bouncing off the fabric of the bivy and into the gap in the storm flap.

While listening to the surprisingly loud patter of the rain on the fabric, I decided to inspect the interior to see if there was any apparent wear.  The interior was in fantastic condition other than a very small spot near the pole pocket that was slightly frayed.  I later looked on the exterior of the bivy and the fraying did not extend to the outside.  I can only speculate that my initial problems with the pole not seating in the pocket during set-up and pushing on the fabric were the cause of the fraying.

minor wear

After this trip with the rain bouncing the sticky sierra soil all over the exterior of the bivy, I deemed it necessary to clean it.  I let the bivy air dry for a couple of days, and then used a brush to remove the majority of the dirt, and then wiped a few spots off with a damp rag.  Other than the slight haze on the black bottom, and a couple of dots of tree sap, the exterior of the bivy appears as new.


The Three Wire Bivy continues to impress me as a solo shelter.  While initially I was a little skeptical about sleeping in what I perceived as a very confined space it has proved to be unfounded.  After 6 nights in the 3-wire bivy, in a multitude of different conditions, I found that I sleep as comfortably in the 3-wire bivy as any of my other shelters.  The shelter and its components have proved to be durable, and aside from the one area of minor wear on Cordura floor panel the shelter appears new.  The poles and the stakes have performed flawlessly, and show no wear from packing, setup or use. The zippers have functioned flawlessly, and show no wear. The bivy sets up and breaks down very easily, and packs into the included stuff sack with little effort. The compact elongated shape of the bivy in its stuff sack fits well into the corner of my 3051 cubic inch pack (50 l) and the 32 oz (907 g) weight of the entire package has been a joy to carry.

  • light and compact
  • Easy to set up and break down
  • Very roomy throughout the bivy
  • The zipper and flap configurations allow for a myriad of venting options
  • Small amounts of precipitation bounced into the bivy when I vented the storm flap under the visor
  • I have a hard time distinguishing the zipper pulls for bug screen and storm flap.
  • The pole-set came easily dislodged from the internal pole pocket several times as I set it up.

Continued Use:

I plan to continue using the Big Agnes Three-Wire Bivy in the future.  In fact, I foresee it replacing my one-person tent during shorter solo excursions.  The Three-Wire bivy had held up admirably during the four-month testing period, and I see it being a valuable piece of equipment long into the future.   

This concludes my report of the Big Agnes Three Wire Bivy.  Thanks you Big Agnes and for the opportunity to test this great shelter.

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