What’s the benefit of synthetic?

With the Vapor barrier liner of suit is a dedicated set of undies needed of does it go next to skin.

I hate crawling out of my bag at -5, it would especially be bad with damp skin or skivies.

Would a vapor barrier shirt alone provide enough moisture protection?

So Harold,

To make sure I'm applying the information in your spreadsheet correctly to real world applications, I offer the following example:

Using your numbers and, assuming that we only care about weight (not bulk), then we should be constructing garments to allow fully uncompressed loft of the down.

For example, if we were to construct a vest using 3 oz. of down, such that it would fully loft, the garment might be about 1.5 in. thick (depending on size).

If we made that exact same size vest with the same 3 oz. of down but made it only 3/4 in. thick, it would not be as warm as the thicker vest, even though the same amount of down was used. Right?

Michael,

Yes, from the data that Richard generously shared with us, I would draw the conclusion that your garment with 3 oz of down would be warmer if it is built to allow the down to fully loft than if it were built with narrower baffles.

The final garment weight would include the extra weight of wider baffles. My guess is that that wouldn't add enough to change the conclusion.

Right now, this only includes the data from Richard's first post, which apparently was made using quite inferior down (430 fill). I would expect similar to hold true for, say, 800 fill down, but that is only my opinion — I have no data to back it up. If Richard shares with us his data from his last post, or plots it in a way where I can see the values,
I'd be happy to add those data points to the picture.