Thermo-Lite Emergency Bivy Sack

Whether day hiking or on summit day, this is always in my pack. For the light weight, compactness, and piece of mind, it get's 4 stars. I haven't had to use it yet, so when I do, I will re-evaluate my review.

I carry it with me anytime I'm in the mountains and even for quick summit attempts or day hikes. I have never had to use it (fortunately), but doubt it would work better than a bivy bag. However, these things are WAY cheaper so I dutifully carry one with me.



For the money it's great, but doubt its effectiveness as a heat reflector.

Unless it's winter or early spring, I don't bother carrying a tent or tarp in the Sierra; I use a synthetic sleeping bag, and this bivy sack (really a glorified space blanket) is my main protection against an unexpected storm at night. Fortunately, I haven't had to use it as such yet--I'll update this review if I do!



I've tried using it once or twice in combination with a 50-degree bag, in an effort to gauge how well it's likely to work for fastpacking trips in the Sierra during the summer. It certainly seems to help for a while, but I'm a bit skeptical about how much body heat it actually reflects back. Nonetheless, for the size and weight (it really weighs next to nothing), and the peace of mind it affords, I can't complain.



Incidentally, it makes a great groundsheet, too--compared to a normal tarp or tent footprint, there's something about the space age material that makes dirt and other stuff brush off very easily!

For lightweight summer alpine trips, where the weather will be warm, this thing is great. I have a 40 degree synthetic bag that I use with it. I've stayed warm just fine. The sack keeps the dew off your bag and reflects heat nicely. If the weather is too cold or windy for this thing to work, I'd rather be in a tent than one of the other expensive and bulky bivy sacks.

This bivy combined with a TNF Nuptse + MH Chugach pants + Ridgerest has been the ideal sleeping setup in numerous ice/snow caves. For the minimal weight you can't beat the added piece of mind for whatever your outing.

I'm not sure if I have the 2 person or 1 person version, but regardless, I've used it a few times. My sleeping bag is an old beat up rectangle bag I got when I was 13. Slipping my sleeping bag inside this "emergency" bivy kept me warm at 13,800 on Shasta, inside a tent. I also used it without the tent in the N Cascades, for a nap, in a sleeping bag keeping my boots on. The bivy is held together by velcro, which obviously tears open without much force, so I found I kept accidentally opening the the shoulder area of the bivy, which I found extremely annoying. I'd rather not have the velcro openings, because in the emergency you're using this in, you're probably not too interested in opening the bag, which is the equivelent of unzipping your sleeing bag half way. The ventilation opening around the feet is nice, I guess, but I just kept it closed in order to keep as much heat inside as I could. I was toasty warm, and without it I probably would have been miserable. If you're sleeping with just this emergency bivy in the open elements, without a sleeping bag or tent, in alpine or wintery conditions, morning couldn't arrive fast enough, but I think this will be in every alpine trip I take. Get one.

I haven't had to use this either but I take it with me on any outings that have the potential to be extended outings. It is very lightweight, I hardly notice it's even there. I'm sure any emergency bivy is bound to not be comfortable, so I don't think this would keep you very comfortable, but keeping you alive is ultimately what is important. If I ever have to use it, I will update this review.