Originally Posted by Mundele
Could you sew tyvek and use it as one layer (either inner or outer) of a down underquilt? Is it important that an underquilt be breathable? I know folks make "protectors" so could you make the outer shell out of Tyvek and have a shell and protector all in one, then make the inner shell out of 1.1 ripstop?
One of your main drawbacks will be compression and compressability. #1, the inflexability of tyvek may actually compress the down, not allowing the down to loft. #2, packikng the UQ will be difficult as it tends to do better folded than stuffed.
All said, others may have a different opinion, HYOH.