So I saw this thing on television briefly the other day... seemed pretty neat. The natives to Siberia (I'm not quite sure of there name...) dont use the concept of a sleeping bag. Rather, they make these small rooms out of Reindeer pelts. You simply lay in these small rooms, and apparently they are warm enough, even to -50C. Thought it had potential...

I'm seeing such an idea having usability in 3 or 4+ people winter treks in a single tent. Line the tent walls with down. It might end up equaling immense weight savings...haven't done any calculations or anything though.

EDIT: And just a clarification - I see this as being different to a simple multi person sleeping bag, or quilt, in that you are utilizing heat released during respiration to warm your living space as well.

Edited by Mad_Musher on 04/23/2008 14:11:09 MDT.

I always get excited about contemporary adaptations of little known traditional survival techniques (sleeping over smoldering peat, igloos, sleeping under duff piles, etc.), but I think it might turn out that a down tent couldn't compete with a shared sleeping bag or quilt in terms of weight.

One of the reasons that mummy bags are warmer per unit loft than rectangular bags is that they have less surface area. A small, spherical bag that required the sleeper to be curled up in a ball would be even warmer. Like a CPU cooler with fins or a car radiator, the more surface area there is, the more rapidly heat can be exchanged.

The reindeer hide tents in siberia probably weigh several hundred pounds. A down tent with a given loft would not only be less warm than a shared quilt with the same loft, but also much heavier (it would require a lot more down and fabric). I don't think heating of the tent by exhaled air could compensate for losses through the insulation. It could be a fun experiment, though, for trips that don't demand the lightest gear.