Guest - Not logged in 

Reviews > Shelters > Tarps and Bivys > Big Agnes Three Wire Bivy > Test Report by arnold peterson

July 13, 2008



NAME: Arnold Peterson
EMAIL: alp4982(AT)yahoo(DOT)com
AGE: 70
LOCATION: Wilmington Massachusetts USA
HEIGHT: 5' 8" (1.73 m)
WEIGHT: 165 lb (74.80 kg)
TORSO: 19 in (48 cm)

Backpacking Background: Presently almost all my experience has been hiking in New Hampshire, Florida, Colorado USA, New Brunswick, and Nova Scotia Canada using an 11 lb (5 kg) day pack. I have backpacked on Mt. Washington and at the Imp shelter located between North Carter and Mount Moriah mountains in New Hampshire. The gear I will be writing about has been used a lot hiking mostly all year around in New Hampshire. I have completed the forty-eight 4000 footers (1219 m) of New Hampshire. My day hikes have been as long as 12 hours covering almost 20 miles (32 km).



Manufacturer: Big Agnes
Model: 3 Wire Bivy Sack
Year of Manufacture: could not verify
Manufacturer's Website:
Phone: 877.554.8975
MSRP: US$ 299.95
Listed Weight: 32 oz (907 g)
Measured Weight: 33 oz (935 g)
Body Color: Orange
Peak Color: Maroon
Bottom Color: Black
Listed Length: 90 in ( 229 cm)
Measured Lenght: 89 in ( 226 cm)
Listed Foot Width: 25 in ( 64 cm)
Measured Foot Width: 25 in ( 64 cm)
Listed Shoulder Width: 31 in ( 79 cm)
Measured Shoulder Width 31 in ( 79 cm)
Listed Head Width: 23 in ( 58 cm)
Measured Head Width: 23 in ( 58 cm)
Listed Head to Shoulder Distance: 20 in ( 51 cm)
Measured Head to Shoulder Distance 20 in ( 51 cm)
Listed Foot Height: 12 in ( 30.5 cm)
measured Foot Height 12 in ( 30.5 cm)
Listed Floor Area: 17.5 sq ft ( 1.6 sq m)
Listed Head Height: 20.5 in ( 52 cm)
Measured Head Height 20.5 in ( 52 cm)
Poles: Featherlite NSL DAC
Body Material: E-event Waterproof breathable fabric
Floor Material: Cordura
Entry: Right Side Zippers
Capacity: one person

Product description: The 3 Wire Bivy sack, is a cross between a Bivy bag and tent. The bottom two thirds of the sack is a shell that the sleeping bag slides into. The top one third is more like a tent in that it provides overhead protection from wind, snow, rain and insects. The height is less than 21 in (79 cm). From inside the sack one can leave the front fully open providing minimum protection and maximum ventilation. The screen can be closed to protect against insects, snakes or other things that crawl. To get more protection with the screen closed, I can open the screen and close the outer shell to the desired amount. Then the screen can be adjusted as desired. A visor provides protection from rain or snow when the outer layer is partially open.

This being a standalone sack staking is optional. The six stake loops are located as follows: One at each foot corner, one at each end of the poles where they meet the ground, and the last two being the ones at each corner of the head.

The two poles are joined by a swivel and this facilitates the sack setup. They are light, semi rigid and are shock corded for easy assembly. The stakes are made of aluminum in the shape of an x and thus are called x stakes. This is a way to provide strength without more weight. The stakes are notched at the top to provide a place to catch the tie down loops and I use the notches to remove the stakes from the ground with either the tie down loops or a short piece of small diameter rope.


The Big Agnes 3 Wire Bivy sack came packed in a Maroon stuff sack. The poles are light and strong. The body material has a tough feel to it. The mesh screen is also feels durable. The zippers operated very well. Although there are 2 poles, they are united by a swivel and this means one item does it all as far as poles go. I think the 3 Wire Bivy sack will be a good replacement for my backpacking tent, except for times when there is need to add a second person. It is slower to get in and it will be harder to be dry when setting up and entering in the rain.

complete set

ready for storm

screens up

swivel connecting poles

pole tie down

head end tie down

pole going in to out

flap tie back

front pole end

securing pole


The instructions are clear and concise. Always store Bivy in a dry and clean condition. To clean sack sponge with warm water or use Mirazyme cleaner, made by McNett Corporation. Seam sealing is not required unless added protection is desired. Keeping the zippers clean will improve operation and the longevity of the product. The product is guaranteed against defects but not misuse.
The instructions for setting up the tent were written in 8 steps.


I read the instructions quickly and quickly set up the 3 Wire Bivy Sack, to find that the setup was incorrect. It was incorrect because I forgot to put the pole through the transitions hole. It worked except the zippers did not have full range as they were stopped by the pole. On the second attempt, I followed the instructions better, except for the insertion of last end of a pole into a stake tie down. I removed the end section out of its sleeve and slid it into the sleeve leading to the stake down loop and then reinserted the pole back in place. Now it was easier to slip the end of the pole into the stake tie down.

I took my Big Agnes Battle Mountain sleeping system and inserted it into the sack. It fit but there was not much spare room. This was the regular size sleeping bag. It is fortunate I had a right zipper sleeping bag to match the right zipper on the sack. However, it still was a bit difficult for me to enter the sleeping bag. Maybe with more practice I can find a better way. If it is rainy and windy this will be even more of a problem. Once inside the bag, I could easily operate the zippers. There was a small space between my head and the end of the bag. This is probably a good place to put my boots. I will be trying to read a book while in the sack.


My test plan would be built around function, ease of use, and durability. I will be testing in New Hampshire, Massachusetts and Vermont USA. The overnight temperatures could be as low as -20 F (-29 C) and sometimes lower. Rain or snow is a certainty on many trips. The initial testing will be a 1-2 night backpacking at a local forest. This is something I have done with all my backpacking equipment.

Function and ease of use
I will investigate compatibility issues with my backpack. Will it fit easily into my backpack? I am testing the Big Agnes Battle Mountain sleeping bag and I will be looking at how well it integrates with the BA 3 Wire Bivy. One of my goals is to explore products that will extend the amount of time I spend living outdoors. The following issues will be addressed using the 3 Wire Bivy: Ease of setting up the 3 Wire Bivy even in low light conditions. Getting up in the morning and ready for the trail. Will I be able to easily stake the Bivy in snow ice and frozen ground? Will the stakes be durable enough for this kind of treatment? How good is the ventilation? I will find any problems associated with putting the sleeping bag into and out of the 3 Wire Bivy. How well will this gear ventilate? Will any layers trap moisture and result in cold spots? Will the zipper get caught easily in the material? If it does get caught, is it easy to fix? How well will I be protected from wind driven rain or snow? How easy will it be for me to get in and out of this Bivy? For my height I have a large frame and this could pose problems.

How well will the Big Agnes 3 Wire Bivy stand up to trail use? I will be using the zipper a lot especially for nature calls. I will be looking for smooth operating zippers over the long haul. Will the seams stay water resistant over time? Will any of the stress areas show signs of weakening?


I am impressed with the overall quality of the material. The idea that the canopy provides some space between me and the outside is very appealing to me. Being smaller and lighter is also an advantage. Getting in and out is more difficult than I anticipated.

This concludes my Initial Report. The Field Report will be amended to this report in approximately two months from the date of this report. Please check back then for further information. I wish to thank and Big Agnes for the opportunity to test the 3 Wire Bivy sack.



Originally I had planned 3 one night overnight backpacks in the Lincoln New Hampshire area. The good news this year was that New Hampshire set records for snowfall. The bad news was that on 3 weekends when I traveled to prospective trailheads, I was unable to negotiate the ice and snow in the parking lots with my Scion XA. I then made phone calls about the trailhead in southern New Hampshire and found that there was ice where I would be parking. I have recently returned from a one night backpack in a forest east of Manchester New Hampshire.

I spent 3 one night backpacks in a forest in Middlesex County, Massachusetts. This forest is flanked on the east side by the railroad. The west side is bordered by the Middlesex Canal (operational from 1793 to 1853). There is a small section of the canal that had been restored but now has gone back to nature. Beyond the canal is a cranberry bog that has not been harvested in over 45 years. Between this and the canal there is a swamp once used as an aquifer for the town water wells. The wells were closed due to contamination. The brush, thorny bushes and trees keep most people out of this area. Under certain conditions it is near ideal for radiational cooling, which means that the temperature drops lower just before dawn. The temperatures for these backpacks ranged from just above freezing to a low of 13 F (-10.6 C). There was little or no wind on these backpacks. The ground was covered with snow or ice on the first two backpacks with the exception of small areas under the evergreen trees and a few bare spots where it was rocky. On the third backpack most of the snow was gone but the ground was frozen and icy in places. The ground under the shelter was frozen and ice glazed. The forest east of Manchester is fairly flat with some rocky outcrops, several small ponds and a mostly hardwood forest. At the time I backpacked there all the snow and ice had gone.


My first backpack was started knowing that a rain storm was coming and could last all night and for most of the next day. It was after sunset when I started and the temperature was just above freezing and the humidity was high. There was little or no wind. Due to the rain arriving, I decided to pick a closer location to camp. I found a place where evergreens gave some protection. The needles provide a smoother surface to setup the Big Agnes 3 Wire Bivy. I had no trouble setting up, and as I was finishing, the rain was starting. In my hurry to setup I had forgotten to stake out the Bivy. I did not notice any serious effects. I put my boots in a plastic bag and put them inside the head of the Bivy. I got into the sleeping bag slowly and with some difficulty. Once inside, I left the sleeping bag unzipped and only zipped the sack to about eye level. This way I could see out and have as much ventilation as I could without expecting rain to enter. This also made it easier to remove my outer clothing layer. I read for a short period before going to sleep. I slept comfortably for about 6 hours. When I woke up, I was warm and it was raining moderately. I started to feel around and found that almost everything I touched was wet. I turned on my headlamp and inspected my surroundings. There were big water droplets all over the ceiling and the pole. Also the visor was really wet underneath. I had to use my fingers to check other areas and found that there was a lot of water on the outside of the sack, but only a small amount of dampness between the sack and sleeping bag. The part of the sleeping bag behind my head was wet. There were large drops of water falling from the trees. When these drops hit the visor, sometimes it was as though I was hit by a small mist. Even though there was dampness on the exposed surface of the sleeping bag, I went to sleep again quickly. When I woke the next time, the rain had reduced to a drizzle. I decided to pack and leave before it really started to rain. When I got home I found the Bivy was wet in places. I spread it out along with the other items that had gotten damp. Everything was dry within 4 hours.

It was almost 2 hours after sunset when I started the second backpack with a temperature of 15 F (-9.4 C) and a slight wind coming from the north. This time I staked out the Bivy and found there was more stability and slightly more space on the inside of the Bivy. I used the heel of my boot to push the stakes of the Bivy into the frozen ground. The Battle Mountain sleeping bag does fill most of the space in the Bivy and there is little room for shifting. To get in this time, I knelt on the Bivy, took my boots off put them in a plastic bag and put them inside the head end of the Bivy. I took off my hiking jacket and put it inside the Bivy head also. I then crawled into the front end of the Bivy and inserted my feet into the sleeping bag and slid backwards facing down to get in. It is still not a quick operation. Once inside the sleeping bag I took off my outer layer and realized that I had left the zipper on the sleeping bag open. I found I had to get out and crawl down head first to get the zipper attached. It seemed easier than removing the sleeping bag. It was accomplished with the aid of my headlamp. I found with the aid of the outer zipper in the Bivy sack I had full control of the air flow into the canopy area. I soon became warm and toasty. I did a little reading and soon I was asleep. When I woke several hours later, I checked for condensation and found none. I checked everywhere I could reach and did not find any moisture. I was also comfortably warm. Soon I was back to sleep and when I awoke again, I was still very comfortable and I could not find any condensation anywhere. It was time to pack and return. The temp had dropped to 13 F (-10.6 C) during the night. This was a really good experience.

The third backpack was started about 2 hours after sunset with a temperature of 20 F (-6.6 C) and there was a light breeze all through the night. The frozen surface was quite rough and quite slippery in places so I made full use of my Kahtoola traction devices. This being the third time setting up using the 3 Wire Bivy and Battle Mountain Sleep System, I was setup and ready for some reading in a very short time. With little chance of rain, I stopped zipping the Bivy where the zipper makes a turn upward. This allowed a little more area for ventilation. I also had the Battle Mountain sleeping bag zipped half way. I kept the foot of the sleeping bag open a small amount to allow for ventilation. I woke up only once during the night and in the morning I found all surfaces were dry. I had spent a very comfortable night. The temperature had dropped to 16 F (-8.9 C) by morning. I was packed and heading out before dawn and was able to see the sun rise before arriving home. I checked all the gear for dampness and found everything dry. I still spread the gear around for a few hours before storing to make sure things were are dry.

For my fourth backpack, east of Manchester, New Hampshire, I arrived at the place I was going to camp at about 5:30 pm. It was warm, so I put my temperature/humidity meter out and recorded 82 F (27.8 C) and 56% humidity. While I was setting up, a pair of wild ducks flew in and settled on the pond. I could also see tracks of wild turkey near the shore. After setting up, I became aware of the No-See-Ums and I was ready to do some hiking. I hiked for over 3 hours and when I returned it was 49 F (9.4 C) and 76% humidity. The frogs in the pond were also quite noisy. I read for only a short time before going to sleep. At midnight I woke and found my legs were sweaty, so I opened the Bivy and sleeping bag as much as I could. I lifted the sleeping several times with my legs to ventilate the bags and then went quickly back to sleep. When I woke at 3 AM on my back, my right side (the open side of the bag) was cold and my left side was warm. The temperature had dropped to 38 F (3.3 C) and 86% humidity. I was cold but not uncomfortable. I closed up the sleeping bag and quickly went back to sleep. It was almost 6 am when I awoke, the temperature had dropped again to 32 F (0 C) and humidity was 86%. There was some condensation on the unexposed surface of the sleeping bag. I packed and headed for the trailhead. When I got home, even though the gear felt dry, I spread it out in the sun.
east of Manchester New Hampshire


Over the test period I have gone on 4 one night backpacks and was comfortable and warm. I have been in rain and was able to stay dry and comfortable. The exception was that when large water drops landed on the visor, a small amount of mist penetrated the fabric as described in this report. The stakes were easy to use, even in frozen surfaces. The stakes provided good stability. The ventilation in the canopy area was excellent. The viability through the screen was good. Other features include ease of assemble, quality of material. The zipper action was excellent, but I would like to have the zipper extend further down the side of the Bivy to facilitate entry and exit. I am comfortable with the amount of space in the Bivy.


I will continue to use the 3 Wire Bivy as my one person shelter for the remainder of the test. I would like to thank and Big Agnes for the opportunity to test the 3 Wire Bivy Sack.



I backpacked in Douglas State Forest Massachusetts with a temperature of about 80 F (26.7 C) and no wind. When I backpacked for three nights on the Monadnock Sunapee Greenway Trail and the surrounding areas of Washington New Hampshire, day temperatures were at least 80 F (26.7 C) with little or no breezes and the nights were about 60 F (15.6 C) with lots of insects.


I backpacked with 5 other hikers to a shelter in Douglas State Forest Massachusetts. The 5 (8 km) miles to the shelter took about 4 hrs, it was hot and I required a lot of stopping for rest. Setting up on the pine needles was quick and easy. The temperature dropped to about 60 F (15.6) and the humidity was about 85%. Despite the high temperature and humidity, I slept very well. I tend to turn more in warmer weather. I had plenty of space to turn and did not feel closed in. The insects were kept away with the screen. One of the backpackers had tics enter her tent, I had no unwanted visitors. When I woke in the morning I was surprised not to find any condensation. This is a good spot to have a repeat backpack.

During the three night backpack on the Monadnock Sunapee Greenway Trail I hiked with 3 other backpackers. We did about 6 hour hikes on 2 days of about 6.3 mi (10.1 km) and 5.5 mi (8.9 km). We spent our first night at General Washington Shelter. See picture below. We used the shelter to store out supplies and a place to hang out if it rained. The second day we drove north and spotted a car at Pillsbury State Park and hiked to the Max Israel Campsite. See picture below. The temperature that day was about 80 F (26.7 C) and the humidity was high along with the insect count. After we reached to campsite we heard thunder north of us and sensed that rain was coming soon. We set up a tarp over part of the camping platform to have a place to cook and eat out of the rain. We pitched our bivys and tents around the platform. It did rain very hard during the night. It rained heavily and even though my Bivy was heavily rained on, very little water did enter. I suspect that most of that was because I did not close the outside layer enough. On the third day we hiked back to General Washington Shelter where we spent our last night on the trail. My hiking partners had a surprise 70th birthday party for me. A great way to start another decade of outdoor adventure. It rained again that night and this time I was completely dry in the morning. During this backpack I was comfortable in my 3 Wire Bivy at all times and I had plenty of room to turn. This was a memorable backpack and I will be back with this group or others to do more of this trail. My last backpack of this test was in a forest east of Manchester New Hampshire. See picture below. The temperature was close to 90 F (32.2 C) when I set up camp. At sundown it was about 80 F (26.7 C) and no wind. It takes getting used to hearing mosquitoes and realizing that they can't bite you. During the night the temperature dropped slightly and I slept very well.
Douglas State Forest Shelter

General Washington Shelter

Max Israel Campsite

east of Manchester New Hampshire in July


The Big Agnes 3 Wire Bivy has proven to be a shelter I can use most of the year. It is quick and easy to set up and light to carry. The stakes have been reliable and easy to insert into the ground. I have used the zippers a lot and they have performed very well during the test period. After careful checking I could find no defects or evidence of wear after 10 nights of backpacking. I have used it in the rain and it did a great job of keeping me dry. With practice I am getting better at getting in and out of the 3 Wire Bivy. I still find a slight problem getting in and out, if it is raining.


I will be using the 3 Wire Bivy for all my backpacking trips, unless I will be needing to share a shelter with someone. I will be looking to have a light weight tarp to have when rain is possible, especially on a multiday backpack.

I would like to thank and Big Agnes for the opportunity to test the 3 Wire Bivy Sack.

This report was created with the Report Writer Version 1. Copyright 2008. All rights reserved.

Read more reviews of Big Agnes gear
Read more gear reviews by arnold peterson

Reviews > Shelters > Tarps and Bivys > Big Agnes Three Wire Bivy > Test Report by arnold peterson

Product tested and reviewed in each Formal Test Report has been provided free of charge by the manufacturer to Upon completion of the Test Series the writer is permitted to keep the product. Owner Reviews are based on product owned by the reviewer personally unless otherwise noted.

All material on this site is the exclusive property of
BackpackGearTest software copyright David Anderson