Why a bivy sack?

Technical terrain, light packs, two people. Tent is best.

I got a question from a former student this week. Scott was in Peru with the Ishinca Valley SIET course I taught in June of 2015. He asked "When you're out winter camping what are your thoughts on bivy's?" That's a great question, and a common one. I have fairly strong opinions on the matter, based on my experiences and preferences, in addition to some logic. Certainly, a solo, pole-less shelter has its place in the mountains. In my experience, however, the circumstances under which a bivouac sack is the best shelter are extremely rare. This is how I answered Scott:


Good question... In short, I don't even own a bivy sack. People use them to make their bag warmer, to keep snow off their bag in a snow shelter, for solo camping, and for camping on small ledges on technical alpine climbs. One by one, I can address those reasons and justify my avoidance of bivy sacks.

• First, a bag warm enough on its own is way lighter than one with too little insulation plus a bivy. Adding more clothes is more versatile and more economical than adding a bivy sack. 
• Next, sleeping in a snow shelter is wet, regardless of whether you bivy or not. 
• For solo camping, a tarp is lighter and more comfortable. 
• For technical alpine climbing, I'll have a partner. And a Black Diamond Firstlight tent is lighter than two bivys and way more comfortable. The ledge you need for the tent is bigger than spots for two bivys. With snow, I've never failed to find a spot for a First Light. On dry ground, like technical ridge traverses or big wall climbs, I don't go if the weather forecast is poor. I'll get away with an ultralight tarp then, "just in case."