It all depends on what you are trying to achieve. I have used two quilts , one inside the other, to below 0 on a good pad.
You can also do the Nalgene bottle trick , which will create a lot of heat for a couple hours.
Synthetic , over down, in long term below freezing can offer some technical benefits. However, most of it is likely more theoretical, and quality of items matters a lot. A liner, keeps you bag cleaner , and can be a bit of a vapor barrier if desired.
You can also do the Nalgene bottle trick , which will create a lot of heat for a couple hours.
Synthetic , over down, in long term below freezing can offer some technical benefits. However, most of it is likely more theoretical, and quality of items matters a lot. A liner, keeps you bag cleaner , and can be a bit of a vapor barrier if desired.