Manufacturer’s Website: www.integraldesigns.com
Size: Small, Regular, Large
The Integral Designs Endurance Bag Cover is what most of us call a bivy sack. It is made of very water-resistant Pertex Endurance fabric and has taped seams. The fabric is almost waterproof. Pertex Endurance is a reasonably breathable fabric, breathing nearly as well as popular waterproof-breathable fabrics with laminates, membranes, or microporous coatings. However, do not expect the Endurance Bag Cover to remain condensation-free in wet, humid conditions.
The Endurance Bag Cover is one of two mass-market bivy sacks using Pertex Endurance. (The other is the Rab Carrington Survival Zone, available only in the UK.) The Endurance Bag Cover is also one of the very lightest of the bivys in the waterproof or nearly waterproof class of fabrics. It is also one of the simplest designs on the market with no zippers, bug netting, pad straps, or such.
At $130, the Endurance Bag Cover is in the price range of many bivy sacks and costs less than many heavier and more complex ones. It is a feasible purchase for many mainstream backpackers.
Integral Designs intends the Endurance Bag Cover to be used with both a groundsheet for protection from wet ground and a tarp for protection from overhead moisture. Because Pertex Endurance is not completely waterproof (based on our own objective testing), we think that this is an appropriate recommendation. We put the bag cover through its paces as per Integral Designs’ recommendations, but as well we extended its use range to more extreme conditions. We used the Endurance Bag Cover in snow caves, under tarps, and as a stand-alone shelter. Our reviewers agreed that it is ideally suited for use as a solo shelter for summer or otherwise fair-weather mountain hiking when the following criteria are met:
- only intermittent rain is expected, and
- the user is not sleeping directly on snow.
In addition, the Endurance Bag Cover is ideal for use with a tarp. With it our reviewers could “size down” their tarps and worry less about getting their sleeping bags wet with rain spray under the tarp. In addition, most of our reviewers did not need a ground cloth when they used the bag cover. We found that with minimal care in campsite selection, Pertex Endurance is durable enough for extended use.
Fit, Styling, and Aesthetics
The average weight of the samples we reviewed was 13.2 oz, although we found that products being delivered more recently are less than 11 oz in the regular size. The Endurance Bag Cover was roomy enough to accommodate a 1″ thick, full-length, sleeping pad as well as a typical three-season down sleeping bag (with 5-6″ of loft). Winter sleeping bags with a larger girth and more loft (7-8″) were a tight fit. With an average-sized user (e.g. 5’10”, 175 lbs) the bivy somewhat compressed the loft of a winter bag. There is enough room in the Endurance Bag Cover’s hood to stow plenty of extra clothing for a pillow, along with our water bottles and water filter (for protection from freezing on cold nights).
We tested the Endurance Bag cover during more than sixty nights in the backcountry, ranging from warm and dry conditions in the Desert Southwest, warm and humid conditions in the southern Appalachians, the cold and wet conditions of the Washington Cascades, and the cold and dry conditions of the northern Rockies. We made observations on condensation, wind and water resistance, and general ease of use.
In our field tests, the Endurance Bag Cover was more resistant to condensation than similar bivy sacks made from Ultrex, two-layer Gore-Tex, and Conduit SL (Mountain Hardwear). However, it lacks a face-fabric layer (as in three-layer Gore-Tex and clone laminates). This made the bivy prone to condensation in humid conditions. In similar conditions, bivy sacks made with three-layer Gore-Tex and TegralTex (Integral Designs) had less condensation. Their inner layer (often a tricot knit) disperses droplets from water condensation across the fabric’s inner surface area, preventing them from clogging pores through which vapor “breathes.”
The greatest amount of condensation occurred in warm, humid conditions. However, we had significant condensation in cold (subzero), dry conditions when we slept in clothing that was damp from a full day of snowshoeing, skiing, or winter climbing. Neither of these results is very surprising. Under these conditions even the most breathable of bivy sacks would probably collect condensation as well.
Based on our experience inside the bivy sack in windy conditions, we believe the Pertex Endurance to be completely windproof. Air cannot be “sucked” through Pertex Endurance fabric; and we could not move measurable amounts of air through the Endurance fabric under a 20 psi vacuum.
The bivy is made of highly water-resistant Pertex Endurance (1.9 oz/yd2) and has taped seams. In the field, the bag cover was impervious to melting snow and rain spray. However, when the user is sleeping on wet ground or snow, the high pressure caused by body weight seemed to allow some moisture to seep through the material. This effect was only an issue in a snow cave or on extremely wet, hard ground. We found that the Pertex Endurance has enough water resistance for almost all three-season backpacking in the mountainous areas of the West.
The Endurance Bag Cover is simple in design: it consists of two pieces of mummy-bag shaped fabric sandwiched together with a head opening secured by a drawstring. A contoured foot box prevents compression of a sleeping bag’s loft in that area. It has no weight-adding items like zippers, bug netting, pad straps, or other gizmos. The bivy lacks a storm-proof head opening. This is a problem if you use the bivy alone (e.g. without a tarp) in serious rain. Our reviewers solved this problem by sleeping with the bivy “upside down” (i.e., with the head opening towards the ground rather than the sky). Unfortunately, this caused a variety of problems, not the least of which was difficult entry and exit, and increased condensation (due to poor ventilation of the warm and humid air inside the bivy sack). However, if it is to be used only occasionally in this mode, it may be only a minor inconvenience.
The design of the drawstring and hood, with its pattern cut, is unique, and it allows the chest of the bivy to be cinched tight while the hood remains wide open. This is a smart design that traps heat in the body of the bag cover while allowing free circulation of fresh air where it is needed the most — around the head so one can breathe easily. For the most part, we found the design to be both effective and comfortable. One reviewer who tested the bag on only four nights, found the design quirky and annoying.
Recommendations for Improvement
Integral Designs has designed one of the lightest waterproof bivy sacks on the market. During the early stages of testing, we were somewhat dismayed at the lack of “storm- proof-ness” (fabric leakage under high pressure and drawstring hood closure). However, over time and with experience in different conditions, we agreed that the weight loss justified sacrifice of these features. This was truer for reviewers who used a tarp with the shelter. Our reviewers agreed, however, that a more water-resistant floor (such as 1.4-oz silicone-coated nylon or 1.9-oz urethane-coated nylon) could be used in the floor to make the bivy more suitable for snow caves and very wet ground.
The Endurance Bag Cover is ideally suited for tarp camping in wet and stormy conditions. Paired with a lightweight poncho such as the SilPoncho (also from Integral Designs), the bivy-poncho/tarp combination can provide an incredibly light and versatile raingear-shelter combination for the backpacker skilled in tarp camping.
Final Grade B+
We found the bag cover to be a very good design, but we would have appreciated a floor that was waterproof under high pressure and the option (perhaps in another version) of a more storm-proof hood design.