Jul 31, 2013 at 12:53 pm #1306047
Simple question (I think). When referring to sleeping bags and puffy layers I've seen an item's warming power described as both ounces and loft.
I don't think I really understand them. Loft describes how high a given layer will puff out and how much air it traps. When an item is described in 'ounces' does this mean 'ounces per square foot'? Does this vary by the quality of insulation?
RichardJul 31, 2013 at 1:38 pm #2011219
"Ounces of down" means the weight of the down used.
It helps understanding where the weight of the item resides – the shell, #5 zippers, froofra, or the down.Jul 31, 2013 at 1:38 pm #2011220
@aroth87Locale: Missouri Ozarks
Depends on the type of insulation you're talking about :D
For down the loft (given in inches) tells you how thick the layer of down. The more loft, the more insulation you'll have. Fill power refers to the volume, in cubic inches, one ounce of down occupies. So one ounce of 900 FP down fills 900 cubic inches. Obviously, the higher the FP the less down you'll need to fill a given volume.
For synthetic the unit you usually see is grams per square meter. In this case the heavier the material, the warmer you'll be (generally speaking). For example, the Patagonia Nanopuff uses 60g/m2 insulation while the Micropuff 100g/m2 insulation. So you'd expect the Micropuff to keep you warmer than the Nanopuff. But much like down, not all synthetic insulations provide the same insulative properties.
Of course, there are numerous other variables that affect how warm you will feel.
AdamJul 31, 2013 at 1:53 pm #2011231
@b-g-2-2Locale: Silicon Valley
Often, how a sleeping bag or garment is marketed will dictate how it is described in product advertising. For some consumers, inches of loft will sound best. For some, fill power means something. For many, ounces of down will sound best. It kind of depends on what they are trying to hide.
Ounces of down probably relates most to the cost of raw material in production. Loft is probably more important to a sophisticated backpacker.
–B.G.–Jul 31, 2013 at 4:19 pm #2011283
"It kind of depends on what they are trying to hide." Good one!
OK, an example, I bought a 40 degree quilt listed as being filled with 7oz of 900 fill-power down. I requested one ounce of overfill. The bag lofts to 1 7/8ths of an inch. Which is perfect for my needs down here… actually it may be too warm.
So, in this quilt, one ounce of it's down will fill 900 cubic inches. It contains 8 ounces of the stuff and it puffs out to 1 7/8ths of an inch.
An equivalent bag with 650 fill-power down would puff less, be cooler and weigh the same.
Correct?Jul 31, 2013 at 4:30 pm #2011286
@bzhayesLocale: So. California
essentially, but since the baffles are designed to puff out a certain amount, they would probably just put more 650 down in it. As a result it would puff the same, be just as warm, and weight more.Jul 31, 2013 at 5:57 pm #2011300
thanks! i needed help understanding how the pieces fit together.
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