Let's talk overfill (down-filled gear)

[hangNyak]

I don't know what Adam does and probably don't really need to. All I know is my 40* Phoenix UQ has the standard loft and I've had it in the mid 30's and been warm and toasty. Good enough for me.

[cba191]

I have absolutely no idea what I'm doing, but I just ordered a 20* incubator and a 20* burrow on black friday. From what I gather, the underquilt is the most important part. I Don't plan on cold camping, but I don't want to be cold. I got an extra 2oz on the uq and regular on the tq. Is that good, logical thinking? Or am I just nuts?

[Boston]

@Boston,
My example was simplified to try and explain my point. The real question about the baseline volume was, is it calculated based solely on the shell volume (actual formula dependent on the shape) or is there some arbitrary "extra" added to that so the baffles "puff". Sounds like the answer is the former - if you get zero overfill then, under optimal conditions, the down will just fill that volume with no additional humps or puffs between the baffles. Is that what you're saying?

Base volume is 100% based on calculated chamber volume. There is no extra added. the baffle is actually the divider between the chambers. Baffle height is not equal to loft (aka chamber height). Generally you have more loft than baffle height. Play around with the underquilt calculator I linked and it might make a bit more sense.

Everyone overfills to some extent. The general industry standard seems to be about 20-30%. This is the "standard" fill for the quilt - it helps ensure full loft and helps deal with down loss over time. When you have an option to add extra, that's on top of the "standard" over fill. So the calculation I showed is for a standard fill.

Regarding the question about fill power: that ones a little harder to explain. The root of the question is, does the loft of higher fill-power down degrade more or less than lower fill-power down (given the same sub-optimal conditions)? If there's a difference in degradation with different fill powers, then the recommended overfill percentage might be different depending on the fill power.

My understanding is Loft doesn't really degrade due to down FP, although it could impact it.. Degrading loft is usually due to 2 factors: 1) Down loss over time, and 2) down clumping.

1) Down loss is due to down cluster's escaping the quilt. This happens to an extent regardless. Higher FP down has more large clusters that are less likely to escape. It also generally has less feather content, as feathers down't loft the same as down. Feathers can put holes in the fabric, and as they work their way out, they can pull down along with them. If you ever see a feather poking out don't pull it out, but pull it back into the quilt. This can be mitigated to an extent using heavier, down proof fabric that is more resistant to puncture.

2) Down clumping is usually due to the down getting dirty and sticking together. Usually a gentle washing, or even just throwing the quilt into a dryer with some tennis balls is enough to counteract this. Be careful with washing, as it can remove the calendaring effect that helps down proof fabric be down proof.

Also, for the other question about moisture: down FP and over stuff has no impact on how the quilt will react to moisture. Moisture basically causes the down to clump, and reduces loft.