How Tiny Is Your Sack? Upgrade Your Backcountry Emergency Kit

Post by blogger | August 16, 2007      

This summer’s disturbing string of mountaineering tragedies in the alps, many caused by carrying too little or the wrong gear, got me thinking about shelter. Specifically, lightweight “bivvy” sacks.

Emergency bivouac shelter.
Lisa enjoying life in an Adventure Medical bivvy sack.

I’ve always liked the idea of carrying some sort of emergency shelter during backcountry travel, though for shorter jaunts in familiar areas I usually leave such items at home. Reason, everything adds up, and an emergency bivvy shelter is just one more small but significant addition to total pack mass.

But I do carry a bivvy sack on occasion, and the less it weighs the more likely I am to haul it.

Heetsheets Bivvy
Adventure Medical’s Heatsheets Bivvy.

Thus, it was good the OR show reminded me of two super-lightweight shelter sacks made by Adventure Medical.

Their Heatsheets Bivvy is the one I like best, as it is super light (4 oz) and so small it could be packed inside a medium size first aid kit. More, it comes in a sil-nyl stuff sack that’s thoughtfully oversized so repacking is easy. Adventure Medical also provides a slightly larger and more durable sack called the Thermo-Lite 2 which for only 2.5 ounces more weight is somewhat more durable and perhaps reusable — though in my opinion both sacks are one-time emergency deployment items unless they’re used with utmost care.

One caveat about any bivvy shelter: A thin layer of plastic or nylon provides very little insulation. Heat is lost by air circulation (convection), radiation and conduction. The reflective Mylar plastic of the Heetsheet provides a modicum of reflective insulation but does little to block convection and nearly nothing to prevent conductive heat loss — ditto for most other materials.

Thus, Heatsheet and other thin lightweight bivouac shelters (such as those from Space Blanket)are most importantly a way to stay dry during a stay in the backcountry while waiting for a rescue or spending an unplanned night out. For insulation in such a situation you’ll have to depend on your clothing, so carrying a system of well planned layers is key to safety, as it always has been. More, any group should always consider carrying at least one lightweight synthetic sleeping bag when they venture far from civilization. (At the least, always have a sleeping bag in your trailhead vehicle you can retrieve if you’re skiing nearby laps and someone gets hurt.)

My plan for the winter is to acquire several of the tiny HeatSheet Bivvys and make sure we’re carrying at least one during most backcountry trips. I might even stuff mine in a shovel handle — it is that small.


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11 Responses to “How Tiny Is Your Sack? Upgrade Your Backcountry Emergency Kit”

  1. Mark August 16th, 2007 10:01 am

    Those Adventure Medical sacks are great. Highly recommended.

  2. David Aldous August 16th, 2007 10:21 am

    If you need to spend the night in something like that you can sit or lay on your pack or a climbing rope to help insulate you from the ground. Some packs even have a removable pad intended for bivy situations. It is also possible to carry a small foam seat pad that can make lunch stops more comfortable and make a bivy less miserable.

  3. Clyde August 16th, 2007 11:43 am

    Lou, check out the Integral Designs Guides Silsack, a modern Zdarsky tent. It weighs 13oz. but fits 2-3 people. So you get more body heat, better storm protection, and a lot more options for rigging. Not cheap but will last forever and can make a nice respite at lunch when the wind is howling.

  4. Mark August 16th, 2007 12:34 pm

    Either Mark Twight or Jeff Lowe said (paraphrasing) that if you take a bivy sack on a climb, you’ll use it. Something to ponder, but the emergency sack is different. If you get caught out and benighted, maybe continuing to move is an option; just be sure you have a reliable headlamp, one of the most usefyl pieces of gear any of us carries.

  5. Lou August 17th, 2007 11:33 am

    Clyde, that thing looks great, especially as an emergency shelter for big groups doing mega one-day epics.

    Here is the URL

  6. Sky August 17th, 2007 12:52 pm

    That Zdarsky setup looks nice. Lowell extols the virtues of Zdarskies. It’s definitely much more efficient to cuddle with your alpine buddies in a true emergency.

    Clever blog title, Lou.

    Mark, I always remember it as a Yvon Chouinard quote. “If you take bivy gear, you will bivy.” Something like that. I’m going to go flip through _Climbing Ice_ now. I love that book.

  7. Barry August 18th, 2007 3:24 pm

    I thought bivouac was french for, I climb slowly. I’m thinking something that’s 4 oz. and fits in the palm of my hand might be handy for vitually every trip, even the close to home ones.
    Do you have any recommendations for a light weight synthetic sleeping bag?

  8. Lou August 18th, 2007 3:31 pm

    Yeah, you step over the line with carrying too much junk and you are predestined to end up using it…. The idea is to have just enough, and minimal versions of things that don’t get used much. That’s what we’re always striving for…

  9. Skiing at Homw August 18th, 2007 6:38 pm

    Wow, that is a small sack! I would love to try backcountry skiing, but here in Virginia, not a lot of options. I ski on my private hill, but not sure that is true backcountry.

  10. Walter Underwood September 19th, 2007 2:40 pm

    For 6.5 ounces and $60, you can have a bivy made of nylon. It breathes, is reasonably waterproof, and can be used more than once. It is coated silnylon on the bottom and 1.1 oz ripstop on the top. The Equinox Ultralite Mummy Bivi:

    I have one and tend to take it along for both regular and emergency use.

    For a lot more money ($300), Bozeman Mountain Works makes ultralight, breathable bivys the same weight as the heatsheet.

  11. kurt feeter September 21st, 2007 9:59 am

    hi walter, I am looking into the equinox bivy for backpacking in conjunction with a tarp and am trying to get info on it’s breathability. Have you had condensation problems with yours.
    I really just need a sleeping bag cover that will let vapors escape and keep light dew and rain off the down bag. what do ya think? I have the bibler winter bivy now and while it is great at waterproofing, it sucks at breathing (epic) under cold, humid conditions.

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