>>1084403>>1084406Tyvek itself doesn't do much besides block the wind and rain (and allow vapor from sweat to pass through and out), but the particular type that I'm using, 14-S, has an aluminiumized layer that increases the effective loft of your bag by about 70%. (it's the same stuff they make the SOL escape bivvy out of). I don't have pictures of the current build, since everything is still coming in the mail, but pic related is the previous prototype without tyvek, that shows the general design and how the insulation isn't compressed because the sleeping bag is on the outside. The new one will use a lighter summer bag (the current 5F with a 70% increase would cook me alive), and the Tyvek will extend upwards to cover the open hood of the bag, like a tiny tent for your face. Effectively, it'll eliminate the need for over half the insulation, especially since the sleeping bag is its own underquilt, as well as the rain fly and bug net.
