One of the best ways to cut weight when overnight hiking or mountaineering is eliminating a tent. A bivy bag is an excellent alternative to a heavy tent. That's why bivy bags become popular among mountaineers and ultralight backpackers or bikepackers as well. The combination of a tarp or lightweight floorless shelter with a bivy is a great option for hikers who are looking for a lot of flexibility from their shelter. The ultralight bivy sacks are often hand-made by smaller gear manufacturers.
Read some benefits of using bivy bags:
The main benefit of using a bivy sack is weight and size reduction. It’s a lot smaller and lighter than a tent and even if you use it with a tarp you will get lighter and versatile shelter system. Bivy sacks have the extra value of being much smaller than tents as well. They’re well worth considering if you’re heading out for an overnight hiking trip.
It’s cheaper than a tent.
You are at one with nature. If you like to feel close to nature you enjoy bivy camping. In a bivy bag you are not keep out from the environment as you are in a tent and you really are outside. You feel the breeze on your face, look up at the stars before you sleep and sit up to a brilliant view in the morning. It feels more exciting and more wild than if you sleep in a tent or more enclosed shelter.
Very quick to setup or pack away, even in the dark. Helpful if you need to make a quick departure.
Do not need a lot of space.It is easy to find a place to lay a bivy sack at night, since it only requires as much space as your sleeping bag or quilt. All you need is a flat surface big enough for you to lie down on. Bivy won't need securing to the ground as tents require, there are no guylines to set up or tent stakes to pound into the ground.
Bivy bag is usually made from resilient and waterproof materials with better dealing with even the strongest weather conditions. It will deflect wind, rain, snow and cold weather easily. If the material is lightweight and breathable the bivy bag doesn't suffer with condensation like many tents. Nevertheless also the best bivy bags can leave some condensation on your sleeping bag and need to dry occasionally.
Bivy bag also add a few degrees of insulation to your sleep system, which can also help reduce the weight of gear you need to carry.
Bivys are best used in combination with a tarp or other floorless shelters. Bivy bag protects you and your sleeping bag or quilt from wetness, wind, bugs and dirt under your tarp during the night.
The ultralight bivy sacks are often hand-made by smaller gear manufacturers.