A good bivy sack can be used as your primary shelter, or as
a back-up plan when it might rain and you are planning to sleep
under the stars without a shelter. They don't necessarily reduce
the weight in your pack, though, thanks to all the new ultralight
tarps that are even lighter. The primary advantage is their simplicity.
Roll it out and climb in.
Bivy sacks can be a bit confining, especially if you are at
all claustrophobic. In that case you might try something like
the Bibler Tents Hooped Bivy Sack. With its netting
and headroom it is a little like a tent, but still only 22 ounces.
There is a full description at the bottom of the page.
Another bivy sack I would like to try is the Black Diamond
Winter Bivy Sack, which weighs only nine ounces. Although
it may not be technically waterproof, it has had good reviews,
even by those who have used it on rainy trips. You can find a
full description at the bottom of the page.
Latest Video on Bivy Camping
The Lightest Bivy Sacks
To keep it really light, try the Adventure Medical Thermo-Lite
Bivy. It is really just a high-tech plastic bag (bet
they don't like that description). I had my reservations when
I first saw it. I thought I'd wake up soaked by condensation,
but I have used it on a rainy summer night (with a small umbrella
over my head) and I was dry in the morning. It has screened ventilation
at the foot of the bag . I especially like the light weight:
6.5 ounces. Also, there aren't any bivy sacks I know of that
are cheaper, except one.
The Cheapest Bivy Sacks
My experience with the Thermo-Lite Bivy made me realize that
maybe the warnings of bivy sack condensation were over-blown.
I have since experimented with simple garbage bag bivies. To
try this, get the extra large bags, duct tape the open ends of
two bags together, then cut open one end. My garbage-bag-bivy
weighs 4 ounces.
I discovered that in a dry climate, I'm only a bit damp in
the morning, and dry quickly hiking. These bivies will wear out
easily, but you can just throw them out after each trip and make
new ones. At less than a dollar, the price is right.
Precautions When Using Bivy Sacks
When using bivy sacks, be careful not to breath inside them.
Even the ones that are waterproof and breathable can't
handle much moisture. In the morning check inside the sack, and
if there is moisture, take a break at some point during the day
to turn it inside-out to dry.
Finally, if you have a bivy sack that can be used with either
side down, be sure to always use it with the same side down.
Small holes that wear in the fabric will allow rain in if they
are on top, but usually won't let much moisture seep in from
the ground. Just keep the damage to one surface of the bivy sack