The Bivvy Bag/wind shelter is a cheap and lightweight life insurance. It's also excellent as a windbreak when you take breaks.
Bivvy Bag/wind shelter is mandatory for winter trips in the mountains. It provides protection from weather and wind when you take a break or need to change clothes, as well as good protection over extended periods if it's difficult to dig into the snow due to shallow snow cover or similar conditions. The wind shelter keeps the wind out and insulates well, but it can get cold if you sit for a long time or have to spend the night. If you also bring a sleeping bag and sleeping pad, you'll be even better protected against the cold.
Even in summer, you can be surprised by storms with snow, rain, and wind in the mountains. Then it's good to get inside the wind shelter for protection from the weather.
On sunny and windy days, the wind shelter can function as a windbreak during breaks, set up between two skis or on poles. Other uses include as a sail while skiing, but then it's important to check your compass bearing and be aware of wind slabs and the terrain in general.
What is a windsack?
A wind shelter is a large bag approximately one and a half by two meters that can accommodate two adults and one child. It's sewn from lightweight, thin synthetic material, often nylon, and weighs about 500 grams. The wind shelter is windproof on both sides, and often waterproof on one side to withstand sleet, rain, and snow.
There are several types of wind shelters and mountain tarps, in various sizes and with zippers. When buying a wind shelter, you should consider that it must be as simple and lightweight as possible. Features like windows and zippers are not necessary. The wind shelter must be easy to use.
