Originally Posted by Brad
Originally Posted by Windfall
so I guess the question is does 6 ounces of 500 fill down in a North Face equal 4.2 ounces of 800 fill down in a Montbell or Kuiu?


Yes (quality being essentially equal, and provided each is allowed to loft to equal thickness).

Higher lofting down primarily provides two things...

1). The same warmth (loft) for less weight.
2). Smaller compressed sized (ie, in a stuff sack).



Take a sleeping bag as an example... the classic mummy bag is one with a 6" loft / 15* +/- temp rating:

A Western Mountaineering Versalite (6" loft) uses 20 oz's of 800 ci down... 800 x 20 = 16,000 ci

The same bag, with 550 ci down will require 29 oz's of down. 550 x 29 = 16,000 ci.

Warmth will be the same. Just more weight and bulk with 550 ci down fill.



Finally, some make the argument that 800 ci lofting down will last longer than 550 ci down... if both are of high quality, I'm doubtful of that argument.


This. HIgher loft gets the same insulation value as a greater quantity of lower loft. A low loft jacket might take 3oz for a certain degree rating while a higher loft can do it with 2oz. You pay more for higher loft but what you get for the money is less weight and it'll compress smaller.

If you're going for ultra light, you want a higher loft. If you just want warmth but won't be hauling it in a backpack very far, you'll get more for your money with a lower loft.

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