The Emergency Bivy Sack is a simple rectangular bag sewn along the bottom and one side. It is touted as a survival bag for safety on the unexpected night out. The Thermo-Lite material is waterproof but not breathable. For access it has 3"-long Velcro patches at 9" intervals along the top and half of one side.
It has a 3" by 6" mesh window at the bottom to allow ventilation and control condensation buildup.
It comes with a heavy-duty nylon stuff sack that weighs 0.7 oz and so adds 10% to its weight. The stuff sack has a mesh base to drain water and make it easy to confirm that the bivy sack is inside.
The Thermo-Lite material is a soft, waterproof, windproof fabric. It is made from four-ply non-woven polyolefin and vaporized aluminum. The fabric has a papery feel and can be ripped with a firm pull but is considerably more durable than thin Mylar. The outside has a dull silver coating. There is no seam sealing.
The packaging hints that the non-conductive material is better in a thunderstorm than other reflective materials (presumably they are referring to Mylar). The material is quite flammable, which may be an issue when the user is huddled next to a fire.
This bivy sack is roomy for one person and in an emergency two can squeeze inside. This could be life-saving when hypothermia threatens. Compared to a Mylar space blanket the material is quiet and the soft fabric feels warm against the skin.
The Velcro-opening side should be helpful in getting an injured person into the bivy sack. The bivy sack is long enough to cover a tall person completely and the Velcro tabs on the top allow it to be closed over the head or fastened around the neck.
The material is waterproof but not breathable, so there is potential for condensation and dampness inside the bag. This makes it more suitable as an emergency bag than for normal use. Along with the mesh patch at the foot, the 6" gaps between Velcro patches allow for some ventilation. Ironically, the ventilation features prevent the bag from being thoroughly sealed for use as a vapor barrier.
The Emergency Bivy Sack is more than twice the weight and nearly three times the cost of the Mylar Adventure Medical Kits Emergency Sleeping Bag, but it offers improved comfort, easier access, and better durability.
It is a cheap, light alternative to carrying a fully featured waterproof-breathable bivy sack. This bag is half the weight of most of the lightest of these, and it is 25% lighter than an Epic breathable-but-not-fully-waterproof bivy sack.
This is a functional, waterproof, non-breathable bivy sack for emergencies. The Velcro and soft fabric make it more comfortable and easier to use than a space blanket. Light and affordable, this bag and a warm jacket may get you through an unplanned night out in fine fettle.