Exactly! And that's why they're worth their weight in gold in cold climates.

As a side note - one of the things I'm curious about is how well my various daypacks could work as improvised insulation. Only one test sample so far. My biggest day pack (55 liters) worked quite well - but that pack has a full size back length, so with a little improvization I can lay flat. Test conditions: +5C, dry, little wind. Clothing: one thin layer of wool under the shell layer, augmented with a fleece jacket. Bivy: Jerven "fjellduk" (the Jervenbag original, http://jerven.mediabook.no/3/ (brochure in flash format), which is uninsolated, vapor barrier with the typical shiny "radiation reflection" inside.

Results: 4 hours of good, sound sleep - then I woke up and realized I couldn't turn into my favourite sleeping position. If I had brougth a pillow I would have stayed through the night, but I crawled back inside to get some more fresh hours before work next day. I was surprisingly snug, warm and comfortable - and not really too bad and clammy. No doubt I could have stayed much longer and still be fit for fight the next day.

I want to test this further with different configurations and temperatures, but real life kind of gets in the way...

I am curious -- having never used a bivy. How would one perform in a snow shelter? Presumably the snow shelter is near the freezing temp, a shelter for 2 or 3 supposedly could be heated with a couple of tea lights. Too warm and then you have water dripping inside the shelter. I'm thinking a bivy is probably waterproof and adds a few degrees of comfort to most sleeping bags. Add a couple of foam pads underneath.

I have spent several nights in a bivvy with a sleeping bag during snow storms and been rather comfortable. It is important to have a top of the line bivvy bag, preferably with waterproof, breathable fabric on top and something waterproof on the bottom, and of course a decently warm bag. Usually the pack and spare clothing provides insulation on the bottom. One of my favorites was large enough to hold two people; the shared heat renders the setup quite effective and efficient.

Other advantages are: quick setup and disassembly in a wide variety of situations;low profile in high winds; minimal weight. All of these characteristics are useful in demanding conditions.

I have also spent a few nights out without a bivvy sack - not nearly as comfortable....

Any makes and vendors you'd like to share with us?

I think you're spot on

The makers of my bivy recommends a candle: The extra heat is mostly welcome, and helps with the condensation problem (you combine extra heat with a little ventilation). I've only briefly tested it, so I won't comment on how well it works.



Well, it certainly beats lying in the middle of a snowy field WITHOUT a bivy... Plenty of climbers who has tried something similar when stuck on a naked mountain peak in bad weather and survived because of their bivy.

If you can move just a little bit you can improve the situation a lot by finding somewhere less exposed to the wind. A rock, a trench or just some minor terrain bump makes a huge difference - just make yourself as small as possible behind it.




Igloos are great, but are not really viable options when you need an emergency shelter because an igloo requires time, labour, thinking and precision. Snow caves are a bit better because they require very little thinking and precision - only time and labour.

My local SAR authorities these days recommends the emergency snow trench, which requires much less time and labour than a regular cave. Find a slope with snow, dig a two foot wide trench, always dig so that you can toss the snow horizontally and downwards OUT OF the trench and down the slope. (The need to move excess snow out of the snow cave is a major part of why digging snow caves are so time consuming - use gravity to your advantage is a HUGE time and energy saver). The trench should be about 3-4 feet high, 2 feet/shoulder width plus a little extra wide and as long as you deem nescessary. When the trench is dug you carve out benches in the side walls. Make a roof by placing skiis, branches or snow shoes on top of the trench and put snow blocks on top of that.

Excellent question! I did not mention any names because my period of extensive bivvy use is - uh- "historical" and the types I used are no longer available, especially a double bivvy, which I don't find among current offerings.

A bivvy is not especially complicated. In the early 70s, I ordered a couple of yards of new-fangled Goretex, some coated nylon and simply stitched them together and coated the seams. It worked wonderfully - the first time I used it, I awoke in the Grand Canyon with a six inch puddle atop the bivvy - inside I was wonderfully dry and the loft of my bag was unimpaired.

The double bivvy worked great for SAR operations. We were always partnered up and the bivvy was a key ingredient that enabled us to stay in the search area overnight comfortably. On one occasion we stopped about a half mile from our victim - finding here promptly the next morning after about twenty minutes walking. I often thought that if we had walked that extra half mile and found her, we could have shoehorned three bods into the bivvy and passed the night - tight, but warm, with the outer individuals in sleeping bags and the person in the middle wearing everything available.

For current brands, with which I have no actual field experience, i would look at REI's minimalist bivvy, weighing about a pound and MSR's similar product which appears to be about the same, only twice as expensive. Both feature breathable tops, with coated bottoms.

What puzzles me are products like Outdoor Research's "Advanced Bivvy" which is roomier, but costs over $300, and weighs two and one half pounds. For the same weight, and less money, you can carry a real solo tent, which will give you more room.

Basically, today you can choose a point on a continuum running from AMK's light and cheap (but clammy!) bivvys on up to glorified tents - whatever suits your fancy.

In my old age, I don't seem to utilize a bivvy as much as I did in my youth. But I still carry AMK products - they are light and serviceable. They can come in handy in providing protection for a victim or work as a body bag, if necessary, in addition to providing overnight shelter.

The bottom line is there is no quicker, lighter way to shield your tender bod from the elements, in a variety of situations, than a bivvy sack.

Disaster apps from NIH.

http://disasterinfo.nlm.nih.gov/dimrc/disasterapps.html

Another issue with igloos is that easy construction requires a certain type of snow that cuts nicely into blocks (wind packed snow is best), and an appropriate tool (snow saw) to make the blocks. As MostlyHarmless notes, there are other options that often work better. Which option works best depends on the situation. What kind of snow? How deep? Terrain? Etc etc. If you spend much time in snow country, it is a good idea to try to build a few different kinds of shelters just for fun. Then when/if you really need one, it will be much quiker and easier to select and construct what you need.

One book I can highly recommend is "How To Build An Igloo, and Other Snow Shelters" by Norbert Yankielun and Amelia Baur. It covers much more than igloos, including construction of quinzees slab shelters, caves, tree wells, and other expedient and emergency shelter techniques. It also has a good discussion of the nature of snow, and camping in snow. It is a delightful little book: "In this instructive, whimsical, illustrated manual, Norbert E. Yankielun, a seasoned cold-regions explorer and researcher, takes readers step-by-step through the process of constructing and inhabiting a range of useful snow structures—from the most basic to the more complex. Whether you’re a veteran backcountry skier or a backyard builder, this is one book you won’t want to be without."

If you spend much time in snowy areas with coniferous trees, you should think about "tree wells" (aka "spruce traps") as emergency shelters. Deep snow covers the branches, but leaves a big hole next to the tree. With a little bit of work with a shovel, one can convert this into a good shelter. You can excavate the hole a bit larger, and shovel the snow up to complete the walls. In really deep snow, tree wells can actually be a hazard if you fall into one accidently.

On one occasion when I tried to build a snow shelter, the snow was so powdery that I could not achieve any consolidation at all, and basically I wound up crouched in an enlarged tree well, with just a little bit of improvised cover overhead.. It was a long, bitterly cold night. The previous evening I had shared a cozy snow cave with three others. Snow condition is everything when it comes to shelters.

The AMK escape bivy is now available on amazon for $40. I just bought one. Only one review there and it was very good.

I have summer and fall camped in the northeast on the AT using the AMK emergency bivy in place of a sleeping bag and it worked fine - except for the interior condensation. So I expect if this works half as well as AMK claims, it will be a winner.

Here's a link --
http://www.amazon.com/Adventure-Medical-...0550&sr=1-2