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Reviews > Shelters > Tarps and Bivys > Integral Designs Penguin Bivy > Test Report by Ernie Elkins

About the Tester
Name: Ernie Elkins
Age: 35
Gender: Male
Height: 5'9" (1.75 m)
Weight: 130 lb (59 kg)
E-Mail Address:
Location: Denver, North Carolina, USA
I've been an avid hiker and backpacker since the late 80s. In a typical month, I spend two to three days in the field, and I usually travel 10-20 miles (16-32 km) per day. I prefer to travel light: my base pack weight (excluding consumables) averages about 8 lb (3.6 kg) in summer and 12 lb (5.4 kg) in winter.

Initial Report
March 3, 2008

Product Specifications

Manufacturer: Integral Designs
Year of Manufacture: 2008
Manufacturer's Website:
MSRP: $265 US
Length: 7’ (2.13 m)*
Girth: 76” (1.93 m) chest, 64” (1.63 m) hip, 42” (1.07 m) foot*
Packed Size: 14” (35.6 cm) long x 3.5” (8.9 cm) square*
Listed Weight: 23 oz (650 g)*
Color: Yellow

*My own measurements have confirmed the accuracy of the listed weight and dimensions.

Product Description

Stiffened Panels Keep Fabric Away from FaceIn designing their new Penguin Reflexion Bivy, Integral Designs looked to Antarctica’s Emperor Penguins, whose “aerodynamic shape and built in insulation”* allow them to withstand “brutally cold winter weather.” The result is a streamlined bivy made from Sympatex Reflexion, “a 3-layer fabric with a specially engineered ‘waterproof breathable’ silver reflective inner membrane.” In their 2008-2009 Gear Guide, Integral Designs explains that the Penguin bivy owes its reflective properties to “aluminum vapor” which “is deposited on the Sympatex membrane.” They also cite tests of Reflexion that “have shown that 75% of infrared rays – heat that the body gives off – are reflected back to the body.” Hence, Integral Designs claims that that the Penguin bivy will “add dramatically to the warmth of the sleep system.”

The Penguin bivy’s sleek shape differs noticeably from Integral Designs’ other bivys. At 76” (193 cm) in girth at the shoulders, it offers slightly more upper body room than most, but it tapers sharply to a tight, 42” (107 cm) girth footbox (by comparison, other Integral Designs bivys offer 52” [132 cm] to 58” [147 cm] foot girths). It also offers a very different method of entry and exit: rather than a horizontal zipper, the Penguin features a waterproof, vertical zipper with three sliders that runs for 44” (112 cm) along the center of the bivy, beginning at the head and terminating at the hips.

Rear-Facing Tunnel VentFor additional ventilation, the bivy includes a rear-facing tunnel vent behind the user’s head. The vent has a no-see-um mesh cover, and it can be closed via an integrated drawcord with cordlock. Integral Designs has included a small tie-out loop at the top of the tunnel vent, but there’s no tie-out loop or wire stiffener to keep the bivy off the user’s face. Instead, they explain that the bivy’s “stiffened shape keeps fabric away” from the user’s face and “allows for maximum heat retention within the bivy.”

On the product information card that they packed with the bivy, Integral Designs provides two warnings: “Always leave a gap between zippers to ensure proper ventilation,” and “use on top of pad to protect fabric.” They’ve provided additional usage and care instructions on two small fabric tags that are stitched into the tunnel vent seam. One specifies that the bivy should be hand washed with mild soap and allowed to drip dry. The other warns that the bivy poses a “suffocation hazard” and that the user should always leave at least a 6” (15 cm) zipper opening for proper airflow.

*Unless noted otherwise, all quotations are from the Penguin Reflexion Bivy product page on Integral Designs’ website.

Initial Impressions

I won’t be able to provide any concrete conclusions about the Penguin bivy’s performance until I’ve had a chance to try it in the field, but I have taken the time to inspect it and briefly try it on for size. For starters, it appears to be very well constructed: the seams are neatly sewn, the fabric panels fit together precisely, and all seams are taped on the interior face of the fabric. The fabric itself feels and looks like a typical waterproof-breathable nylon fabric: it’s slightly stiff, has a smooth outer face, and a slightly textured inner face that looks like fine mesh. There’s no obvious evidence of the aluminum vapor that coats the inner membrane.

As I expected, the bivy was easy to set up in my backyard trial run: I tossed it on the ground, inserted stakes in the two loops at the top corners, and climbed in. I also set up a small tarp that I’ll use for additional overhead protection in inclement weather. I experimented with tying out the tunnel vent, but I’m not sure if that will really be necessary. I did discover that you have to be careful not to pull it too tight, because this distorts the shape of the head area.

I tried the bivy in combination with a three-season synthetic sleeping bag rated at 15 F (-9.5 C), and there appeared to be plenty of room inside for the bag to loft fully. Entry and exit were relatively easy thanks to the deep, vertical zipper. There was also ample elbowroom in the torso area, and I didn’t find the footbox to be constrictive. The stiffened fabric forms a sort of elongated dome that floats a few inches (7.5 cm) above my face. I found that I had to be careful to position my head properly (too high or too low and the fabric does touch my face), but, when it was in the correct position, the design appeared to work reasonably well.

Test Plan

Over the next four months, I’ll use the Penguin bivy as my primary source of shelter while backpacking in the southeastern US. As I mentioned above, I’ll add a small tarp for overhead protection when conditions warrant. Since Integral Designs markets the Penguin bivy for winter and high altitude excursions, I expected to begin this test last November. Unfortunately, production delays on their end delayed the bivy’s shipment until late February. Now, with spring fast approaching and daily temperatures on the rise, I’m likely to be testing the bivy in less than ideal conditions. Nonetheless, spring weather here often takes unpredictable turns, so I’ll keep my fingers crossed for my trips to line up with cold snaps. Here are some of the questions that I’ll seek to answer in the coming months:

  • Fit

    Given my body size, the shoulder and hip girths will likely be fine, as should be the overall length. The foot girth, however, is a lot tighter than I would have expected. Other Integral Designs bivys boast noticeably more room in the foot area. I assume the tighter dimensions tie in to the penguin-inspired aerodynamic shape of the bivy, but will it be too tight for comfort? Will it restrict the loft of my sleeping bag?

  • Functionality

    Integral Designs appears to be trying something new with the stiffened hood area. How well will it work? Will the stiffness of the fabric and cut of the bivy work together to keep the fabric off my face? Will it sag in the middle of the night? Will it be affected by my sleeping position? Will it be affected by outside elements, such as wind or rain?

    Another point of interest will be the waterproof zipper. The fact that it has three sliders suggests that it offers the user a lot of versatility in determining the size and precise location of any openings. Will this prove to be the case? Waterproof zippers can sometimes be stiff and hard to operate, so I’ll also consider its smoothness and overall ease of use, especially when I’m operating it from the inside in the middle of the night.

    Finally, although stake out loops are relatively straightforward, I’ll also consider their placement at the head of the bivy and their absence at the foot. Will two be enough to keep the bivy securely in place?

  • Warmth and Temperature Regulation

    All bivys provide added warmth to a sleeping system, but Integral Designs is obviously aiming high with the Penguin. They claim that the Sympatex Reflexion fabric will add “dramatically” to the warmth of the occupant, but that really doesn’t tell me much. Will it allow me to carry a lighter sleeping bag than the conditions would otherwise require? What about temperature regulation if I get too warm? Will the zipper and tunnel vent allow enough air circulation to cool me down, or will I have to resort to sleeping on top of the bivy?

  • Weather Protection

    Does the waterproof zipper do a satisfactory job of keeping rain out? How about the tunnel vent? Will it be able to keep the elements at bay, as well? Is the fabric reliably waterproof, especially in sustained precipitation?

  • Breathability/Condensation Management

    Breathability will be of particular interest to me. Will condensation be a problem, or will the bivy's fabric and design promote good vapor transfer? Will the bivy feel clammy? What about the foot area? Especially given the tight dimensions and lack of foot vent, will this area be prone to condensation?

  • Durability & Maintenance

    Finally, how durable is Sympatex Reflexion? Is the bottom reasonably puncture and abrasion proof? Will the fabric membranes separate or wear through? Does it resist dirt and stains reasonably well? Does it require periodic cleaning? If so, what does this involve?


My test of the Penguin bivy is off to a good start: I’m impressed by its meticulous construction and pleasantly surprised by the accuracy of its listed weight and measurements. Nonetheless, I won’t be able to reach any conclusions about its performance until I’ve tested it in the field, so please check back for my field report in early May.

Field Report
May 13, 2008

Test Locations and Conditions

Over the last two months, I’ve spent a total of three nights in the Penguin bivy. The first was in early March, Camp on Commissary Hillduring a two-day backpacking trip to the Black Mountains in North Carolina’s Pisgah National Forest. After climbing the eastern flank of Mt. Mitchell, I set up camp at a spot called Commissary Hill at about 5800 ft (1768 m) of elevation. The night was dry, mostly clear, there was a light breeze, and the low temperature hovered around the freezing mark. I set up a small tarp for additional protection, but I slept with my head and shoulders exposed so that I could enjoy the night sky. I slept in a lofty, synthetic sleeping bag rated to 15 F (-9.5 C).

I spent my second and third nights in the bivy in early May during a three-day trip the Linville Gorge Wilderness Area, also in Pisgah National Forest. For this trip, the sky was mostly clear, the wind was calm, the nighttime lows were in the low to mid 50’s F, and I camped at an elevation of about 1600 ft (488 m). Since there was no hint of rain in the forecast, I didn’t set up my tarp on either night. For this trip, I switched to a lighter, synthetic bag rated to 30 F (-1 C).

On both occasions, I placed the bivy on top of my sleeping pad (as recommended by Integral Designs) and protected both pieces with a plastic ground sheet.


Although it’s designed for winter and high-altitude use, the Penguin bivy has performed surprisingly well in the mild conditions that I’ve encountered. Here’s a breakdown of my experiences so far:

  • Fit

    For starters, I’ve found the fit to be ideal. It’s roomy enough that I don’t feel claustrophobic yet, at the same time, there’s not an excessive amount of dead air space to heat. Because I’m of modest height, there is some empty space at the foot of the bivy. While I haven’t bothered to do so, it would be a good place to store extra clothes, etc. in inclement weather. Although I had expressed concern about the seemingly tight footbox in my initial report, it proved to be a non-issue – my feet had plenty of space and my winter bag had plenty of room to fully loft.

  • Functionality

    My initial impression of the stiffened hood area proved to be entirely accurate – as long as it’s positioned properly (which is relatively easy to accomplish), it works as advertised. When the zippered opening is mostly closed (6-8 in, 15-20 cm), I occasionally have to the readjust hood. When it’s open wider (12+ in, 31+ cm), as it was on my recent trip, readjustment is rarely necessary.

    As for the zipper, it’s a little stiff (as waterproof zippers tend to be) but not enough that I had trouble operating it. The only annoyance that I discovered was that, occasionally, the ribbon on the exterior pulls would dangle through the opening and brush against my face. When that happened, it was relatively easy to flip them back outside. Although it makes them a little trickier to grasp, the interior pulls don’t have ribbons for, I assume, just this reason.

    I’ve also been happy with the presence and placement of the stake loops. Since I use an inflatable pillow and need a bit more room in the head area, I’ve discovered that the fit is best if I place the stakes less than an inch to either side of my sleeping pad (as opposed to staking them bivy tightly, as you would a tent). If I do stake the bivy out tightly, the head area becomes much too constricting. The lack of stake loops at the foot hasn’t proven to be a problem -- the two loops at the head do a good job of keeping the bivy in place. I really appreciated their presence on my most recent trip, when I had to sleep on slightly uneven ground.

    One obvious but nonetheless noteworthy result of staking the bivy is that, when I roll on to my side, the bivy can’t roll with me. That means that my breath isn’t vented directed through the opening on the hood, a fact that I’ll comment on below.

  • Warmth and Temperature Regulation

    In order to be as objective as possible about the Penguin’s claim “to add dramatically to the warmth of the sleep system,” I’ve slept with a thermometer close at hand. Evaluating this claim has proven to be a bit more complicated than I anticipated, though. My approach has been to monitor the air temperature outside the bivy, inside the bivy, and inside my sleeping bag. The problem is that, short of carrying two or three thermometers, I have to wait for my thermometer to adjust between locations. Since this can take a while, I’ve had the unfortunate habit of falling asleep while waiting. I’ve also discovered that the interior temperature of the bivy varies (not surprisingly) based on the location of the thermometer. Nonetheless, my analysis of the less than perfect data that I’ve compiled is that the interior of the bivy (outside of my sleeping bag) averages anywhere from five to 15 F (2.8 to 8.3 C) warmer than the outside air temperature.

    This estimate is in line with my experience on my recent trip, when the temperature in the early evening would hover in the mid 70’s (23-25 C). I slept in a pair of nylon pants, a synthetic short-sleeve t-shirt, and a long-sleeve nylon shirt, and I started out each evening on top of the bivy. Once the mercury dipped to around 70 F (21 C), though, I would get a little cool. At that point, I’d climb into the bivy and leave only my shoulders and head exposed. As the air cooled a little more, I’d tuck my whole body in the bivy but remain on top of my sleeping bag. Finally, when the temperature hit the low 60’s F (16-17 C) in the early morning hours, I’d climb in my sleeping bag. Therefore, the bivy provided me with a full 10 F (5.6 C) buffer before my sleeping bag became necessary.

    As for temperature regulation, the zipper’s three sliders and rear-facing tunnel vent allowed me to regulate airflow reasonably well. As the nights grew colder, I could progressively close the zipper to boost the bivy’s warmth, yet when I grew a little too warm it was easy to widen the opening or add a second opening (with the third slider) for added ventilation.

  • Weather Protection

    Since I haven’t yet had an opportunity to test the Penguin bivy in wet weather, I can’t yet comment on how it handles rain or snow. It provides good wind protection, though, as I discovered on my trip in early March. I enjoyed being able to look at the night sky through the open zipper while the bivy kept the light wind at bay.

  • Breathability/Condensation Management

    The bivy has proven to be very breathable in the conditions that I’ve faced so far. On my most recent trip, I noticed no condensation on either night. On my first night out, when the weather was cooler, breezier, and I zipped up more tightly, I did notice condensation around my head and chest. I noticed especially heavy condensation around my face after sleeping for an hour or so on my side, when my breath wasn’t vented out the opening.. Otherwise, the condensation was relatively light and never became a concern.

  • Durability & Maintenance

    So far, the bivy has remained relatively clean and I’ve had no concerns whatsoever regarding the strength of its materials or construction.


Despite the fact that it was designed for more severe weather conditions than what I’ve experienced, the Penguin bivy is handling spring here in the southeast US quite well. I’ll be curious to see if that changes as the mercury rises in the coming months. Please check back in early July when I’ll post my long term report.

Long-Term Report
July 15, 2008

Test Locations and Conditions

Camp on the Eastern Slope of Mt. MitchellDuring the long-term test phase, I spent an additional three nights in the Penguin Bivy. The first two were in mid-June in North Carolina’s Black Mountains. On night one, I set up camp in a sheltered spot on the eastern slope of Mt. Mitchell at about 5,800 ft (1,768 m) of elevation. Since the forecast included a chance of thunderstorms, I pitched a tarp over the bivy in a low, a-frame configuration. Despite threatening skies and the occasional distant rumble of thunder, though, the night was dry and calm. The temperature dropped from the upper 60’s F (19.5 to 20.5 C) just after sunset to the lower 50’s F (10.5 to 11.5 C) by morning, and I slept in a lightweight bag rated to 30 F (-1 C). I spent the second night in the Toe River valley at the foot of Mt. Mitchell, near the confluence of the Toe and a large creek. The elevation was about 3,500 ft (1,067 m) and the weather conditions were virtually identical to those of the preceding night.

My final night out in the bivy was in early July in the Linville Gorge Wilderness Area, also in North Carolina. My campsite was a short distance from the Linville River at about 1800 ft (549 m) of elevation, and the weather was dry. The temperature dropped from about 71 F (28 C) at dusk to 61 F (16 C) just before daylight. For this outing, I substituted a lightweight fleece blanket and an insulated vest for my sleeping bag.


The Penguin bivy has functioned exceptionally well in North Carolina’s warm, late-spring and early-summer weather. I slept comfortably on all three nights, and my observations are in line with those that I recorded in my field report:

  • I’m still very happy with the fit – I have plenty of elbowroom, and the foot area has offered ample space despite its seemingly tight dimensions.
  • In order to keep the fabric off of my face, I do still have to readjust the hood on occasion. This seems to happen more frequently when the zipper is open and one side or the other sags. Nonetheless, it does work surprisingly well given its simple design.
  • My temperature measurements continued to indicate that the bivy offers, on average, a 10 F (5.6 C) boost to my sleeping system.
  • The deep, vertical zipper works well for regulating the bivy’s interior temperature and makes entry and exit relatively easy.
  • The Sympatex Reflexion fabric breathes quite well. In fact, the only condensation that I’ve observed has been along the taped zipper seam. Since the rest of the interior has remained dry, I took this as compelling evidence that the fabric itself moves moisture very effectively.
  • I still haven’t encountered any wet weather while sleeping in the Penguin bivy, but a few trial runs in the yard (tarp, empty bivy, and a thunderstorm) have yielded good results (no water penetration).
  • Overall, the bivy shows no noteworthy signs of wear – in fact, it still looks virtually brand new.

One different circumstance with which I’ve had to cope has been the presence of flying insects. Since the bivy is designed for winter and high altitudes, it has no built-in insect protection, so I’ve tried two different approaches to keep flying insects at bay. The first is a simple headnet, which works reasonably well as long as I’m mostly zipped up in the bivy. On my final trip, though, I expected that gnats and mosquitoes would be more prevalent, so I packed a larger net that I suspended from my tarp. Not surprisingly, this was a more effective solution.


While I would have preferred to test Integral Designs’ Penguin Bivy in the winter conditions for which it was designed, it has performed exceptionally well in nighttime temperatures ranging from the freezing mark to the upper 60’s F (19.5 to 20.5 C). It offers a significant and noticeable temperature boost, a comfortable fit, good ventilation and breathability, and a novel hood design that, although slightly temperamental, is surprisingly effective.

This concludes my test of the Penguin Bivy, and I’d like to thank both and Integral Designs for the opportunity to test this innovative product.

Read more reviews of Integral Designs gear
Read more gear reviews by Ernie Elkins

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