In discussions about down garments, people often mention the fill weight and the total weight but the actual values of this ratio (or fill volume/total weight) are not often used explicitly for garment comparisons. Values for clo/oz. are obviously preferable, but they aren't always available. For someone that is principally interested in warmth per unit weight (a person for whom water resistance, tear resistance, zipper configuration, etc. are secondary considerations), the fill weight/total weight ratio, or the fill volume/total weight = (fill weight*fill power)/total weight ratio seems like a useful way to give initial rankings to available products before considering other factors.

In considering down vests, for example, one might quickly assemble this ranking:



For the Nunatak Skaha vest, one gets about 600 cubic inches of theoretical loft per ounce of garment weight. This vest is about 70% down by weight.

There are several obvious caveats. This is not an indication of warmth per unit weight. Fabric properties and construction details make an enormous difference to the real insulative value of the garment. Also, the Skaha vest is certainly too warm for some seasons in some areas, and the cost is about twice that of some of the other vests on the list.

I'm just suggesting that the values of fill weight/total weight and fill volume/total weight seem little used, and might be handy tools for evaluating down jackets, vests, or pants when clo is not available.

Watch out for marketing hype with these charts.

My Nunatak Skaha Plus is over the weight spec.

My WM Flight Vest (perhaps particularly noteworthy in this discussion) is also over the weight spec. My Small is somewhere between 6.0-6.5oz, I can't recall at the moment. Maybe that extra weight is overfill, but I suspect it's not.

Stephan, I agree that the reported total weights are questionable. There is probably a large variance, and a little bit of positive systematic bias (fibbing) in the nominal fill power value of the down used in those garments, too. The real value for any of them is probably within one standard deviation of any of the others.

Independent data (from scrupulous distributors or consumers) is preferable to data from manufacturers. None of this estimation would be necessary if reliable data about weight and clo value were available.

I like it, Colin. I've been looking over similar comparisons for down parkas and sleeping bags for a few weeks as a way to compare similar products between manufacturers. If you take the manufacturers' specs as truth (which is the best you can do in many cases), it's a good way to compare with real numbers, rather than trying to figure out how a zero degree bag by one company compares to a -10 degree bag by another company. I've mostly been looking at total fill volume between various jackets or bags, since many jackets and sleeping bags seem to have vague claims about how warm they are, but have wildly different amounts of down.

for bags look at the en-rating

since thats actual measure insulation capacity ... rather than something that assumes a certain insulation capacity given another variable, amount of down ...

That's great if you want to limit yourself to the small handful of bags that have EN ratings.

alot of bags are actually en-rated now

including everyone's favorite ... WM

and most things sold out of and in euroland ...

And that only matters to me if they post their data with each sleeping bag like Marmot does.