Gear Review -- Adventure Medical Kits Bivy Sacks

Sometimes the simplest innovations are among the best. Thus is the case with two new bivy sacks from Adventure Medical Kits (, which are essentially improvements on the decades-old concept of the Space Blanket.

A bivy sack is a sleeping-bag-like product, a large shell to slip inside and lie down, though without lofting insulation. They repel rain, wind and snow and are used in lieu of tents or tarps by mountaineers, minimalist backpackers, and other hard core adventure types who sacrifice comfort, and some protection, for weight savings.


Bivy sacks, which are usually made of Gore-Tex or other waterproof-and-breathable materials, are used with a sleeping bag inside, the system functioning as an insulating and protecting package.

But Adventure Medical Kits’ two new bivy sacks are made to be used alone. You can put a sleeping bag inside the larger one, as a friend of mine did to increase warmth during a recent mountaineering trip. Though the Thermo-Lite 2 Bivvy and Heatsheets Emergency Bivvy, both made of a reflective Space-Blanket-like material, are best employed alone.

Made for emergency situations as well as ambitious fast-and-light adventures, these two bivy sack products, which measure about 36×84 inches, weigh almost nothing. They are water- and wind-resistant.

As per my tests, they provide adequate warmth, as well, keeping me fine and cozy in lightweight clothing during a recent overnight mountain bike adventure where temps dropped to the high 50s.

To keep off the desert ground, I slept out on a slab of cement at a campsite alongside the backcountry trail. I wrapped up in the Heatsheets Emergency Bivvy and used a bike shoe as a pillow. With nothing but stars above I slept hard for four hours before getting up and on the go again.


One caveat: Both these bivy sacks are made of non-breathable material, meaning they get clammy if sealed tight around the body for long periods.

The Emergency Bivvy is made of a polyethylene material that is metalicized to reflect back body heat. It’s different from Mylar or Space-Blanket-type products in that the fabric is plastic-like and somewhat stretchy. It won’t tear and shred like an old-school Mylar job.

At 3.5 ounces, the Emergency Bivvy is something that can be thrown in a pack and forgotten. It costs $15. It’ll be there when it’s needed, in an emergency or otherwise. An orange shell adds visibility should you be stranded awaiting rescue.

The Thermo-Lite 2 Bivvy is a step up. It can be more comfortably used as a lightweight replacement for a sleeping bag when nighttime temperatures are 50 degrees or higher, though I’d recommend having a warm top like a rain shell and a hat of some sort, like a Buff or a fleece beanie, if you’re going to attempt this ultra-light feat.

At 6.9 ounces the Thermo-Lite 2 Bivvy is made of a heavier, more durable material. Velcro tabs seal it shut, letting you get in and wrap up cozy for warmth. It goes for $33, and it is worth every penny.

(Stephen Regenold writes The Gear Junkie column for eight U.S. newspapers; see for video gear reviews, a daily blog, and an archive of Regenold’s work.)

Posted by Phil - 08/05/2007 06:40 AM

Hi, nice product. I’m wondering if we can use that product more than once, by folding it back in its bag. Here in France we have what we call “survival blankets”, I believe they’re like the space blankets and can only be used once, right ?

Posted by Stephen Regenold - 09/18/2007 06:52 AM

nope, you can use it over and over. they are thicker than traditional “space” blankets.

Posted by Erik - 08/19/2009 05:28 AM

I bought the first bivy sack the thinner one. I used it about 4 days ago when camping with friends because I forgot my blankets in the car. So I pulled this out, set it up and used my backpack as a pillow. I was dressed to keep comfortable at day, sweatshirt, jeans, and more lays under that, like shorts and ect. But I must say that bivy did not give me a good night sleep. I go through the night but went to the car in the morning to grab my blankets. Not a “comfort” item really survival. If you are ever stuck with one of these out in the woods or somewhere my advise is in order to stay warmer use leaves and ever green branches in the sack with you. Will keep it much warmer, and yes you can stuff the bivy back in it’s bag, idk about the new 2.0 bag, I’ve looked at it first hand and the bag has little room to re stuff unlike the 1.0 where there’s enough to.
But over all it is worth the money.

Posted by TE - 11/24/2009 09:44 AM

Can you fit a sleeping bag inside the thermolite II for winter bivy?

Posted by Timmy - 04/05/2010 03:03 AM

I used the 2.0 the other night. The temp was in the high 40’s. This thing kept my plenty warm (maybe even a little too warm). I woke up in the morning with a terible case of “swamp ass”.

Posted by Tom - 02/02/2011 10:11 AM

I really love this product and usually carry on of the AMK bivvy’s with me. AMK is comming out with a new bivvy in about a month. You will be able to buy them at 7summitsgear

Posted by Dave - 05/11/2011 02:15 AM

I have carried this bivy on many rescues. I have slept in it with temps around freezing on 4-5 nights. It works well but does not breathe. I started making my own using a waterproof/breathable fabric.

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