950 Fill Power?

Weight and compressibility are the only reason for higher FP that I know of.

Exactly as you said, MW. Stick with the "lower" fill power and save yourself the money. The 950+ stuff has all kinds of stuff done to it to get the lab result of 950. The second it's removed from the lab, it'll be far, far less.

The 750-850 stuff has been around a long time and they don't fudge the tests to artificially inflate the fill power.

It really is a gimmick, and is false advertising, IMO.

Fill power is basically a measument of loft. They only are performed under selativly strict guide lines, though. They do NOT take into account real world conditions for a sleeping bag. The EN standard allows for this by simply saying fill is 800+. Yes, there is higher loft measuments. But the weight of the dirt, the humidity, and temperature all have minor effects on the loft of a batch of down. Air pressure has a minor effect. In the US, the manufacturors go out of their way to wash down till it is "crispy", removing all the dirt (and a lot of oils) to remove any excess weight. Allowed, and it makes the down a bit stiffer. They dry it to near absolute dryness. Again, it is allowed but most down in use has 3+% water content making it slightly heavier, it would pack tighter in a test. And so on. No, they do not cheat, they just test to the limits of the test. The result is high fill power numbers. 850, 900, 950 and I have even seen 1000 bandied about.

In the real world, while camping, Anything over 750-800 is probably wasted. On a pound of fill, you *might* save an ounce or two at 900-950 fill The whole bag would be 2-3oz lighter, provided you used 2 pounds of fill. 2 pounds of 800fill down is roughly a 0F or lower bag. You are bumping in to diminishing returns. If you want the best, I wouldn't consider goose down, but go with eider down. It "clings" better forming a much more even layer, hence much warmer.

While sleeing, your body will evaporate off about 2 liters of water over 8 hours. This adds a lot of moisture to a bag. Mosture that needs to be convected out of the bag. So you need some heat loss to allow for this. Too heavy of a bag will just get wet inside, leading to a cold night. Too light of a bag means you get cold. Most bags will only perform well within 10-20F of their rated value. Don't overdo it.

The super fills (over 800) are of questionable utility anyway. In damp conditions, you loose any advantage in loft right away. The down gets sofer, more resiliant and compress far easier than 750-800 fill down. On most mornings, you will find that 900FP down bags are actually less lofty that an equivalent 800FP bag and may be less warm. You might find that the 2-3oz you might save will be needed anyway to maintain the loft overnight, negating any savings due to increased fill. The only time it helps is when you first crawl into a 900FP bag. After that they degrade over the night more rapidly than 800FP. I don't care to wake up at 0200 getting cold.

If you do a lot of desert camping, sure, go for it. In the PNW or the NE, or if you hike around water (Great lakes, oceans) more than 800FP doesn't pay. For inbetween, it is about even. In Ontario, I would suggest that it is similar to USA NE conditions. At least the last ime I was up there it was, 'cept a few degrees colder and less mountainous.

Well, the water resistant down might be better for loft. But I don't really care for it. It will not prevent condensation. It might help with sleeping in a lake for short period of time. Or sleeping in a rainstorm for an hour. If you like it, I see no harm with it, though. The jury is still out for me. It will take some real returns on usage over the long haul(10 years) to make any measuring possible.

EDIT for correction
Sorry all, that should be about 1-2 POUNDS of water, not two liters. My bad…

Edit on Edit
Acually, I was using the AMERICAN standard . . .

My myog quilt has 11.1oz of 850FP water resistant down. It's my first down bag/quilt I've used so I don't have much experience with it, but I must say, it did a dang fine job of keeping me toasty at 22* at Mt. Rainier last weekend. Snowed several inches during the night (already 10+ feet of snow where we made camp). The fabric on the left side of my quilt was damp from rubbing against the condensation on my tent wall, and my breath would condense on the neck area and be wet, but the quilt looked just as lofty as it does when I have it sitting at home.

I only slept in my baselayers (200wt merino top/bottom) and was so warm I didn't even wear the down hood I made.

I put off a lot of moisture, probably more than most people, so even though I don't have experience with normal down to compare to, I'm really happy with the water resistant stuff.

"While sleeing, your body will evaporate off about 2 liters of water over 8 hours."

4.4 lbs of water? I weigh 4.4lbs less in the morning than I do when I go to bed? Weigh yourself before and after and see how accurate this is….

Steve

I haven't used a 700, 750, 800, 850, and 900 fill bag so I have no personal experience in the differences in the performance.

However if I may point out that if you used the same weight of 850 fill down and 750 fill down the 900 would be warmer. So, why not just use the same weight of down and have more safety factor against loss of loft due to age, compression, and humidity?

It doesn't cost that much more really… and if you lock at the total cost of the project the extra expenses of going from 750 to 850 and having a bag that performs better is well worth it.

Anthony

I believe that we CAN loose up to 2 liters over a night's sleep if the ambient temperature of our sleeping environment is consistently above 95 degrees throughout the night – causing us to sweat. That and/or lots of "physical activity" during the night can create that kind of moisture.

Under normal circumstances, no one would recommend becoming so hot in your sleeping bag that you sweat.

I also remember reading once that we typically loose about .2 liters of water on a typical night's sleep, primarily through exhalation – not insensible perspiration.

Matt

"My myog quilt has 11.1oz of 850FP after resistant down."

Is this some new thing?

–B.G.–

Be aware that ever since IDFL started faking the system, USA down FP figures have been unreliable. What they (IDFL) call 950 is probably only 800 or at the best 850, and certainly won't be sustainable in the field.

On the other hand, the so-called 'water-resistant' treatment is very new and very suspect as well. Knock off the top few feet of all the claims as marketing spin.

Cheers

"Knock off the top few feet of all the claims as marketing spin."

I wonder what a few feet of marketing claim sells for these days.

–B.G.–

Over on yesterday's cabin fever Chaff thread, Doug seemed to want to sell off central Maryland. I bet you could swap 3' of high-end marketing spin for Chevy Chase, and he might even throw in Frederick.

but it was not a cabin fever thread Gary, it was a celebrating winter one :-)

Three feet of high-end marketing spin isn't worth warm spit.

–B.G.–

The physics I understand to be that the lower FP downs have are less water-absorbant (less plumes/fibres more quills); as you up the FP, the down gets finer, more plumes/fibres – it increases its ability to absorb moisture…

Overstuffing does nothing in this equation – other than increase the amount of material to absorb moisture?

Correct?

I think lower FP just doesn't collapse as much, probably absorbs the same amount of water, but same difference

I think overstuffing makes it more resistant to water absorbtion. It collapses a little, but since you have extra down, it still fills the tubes.

Not sure, but there definitely is more surface area for moisture to settle/collect on, I suppose.

The way US down is rated/tested is cheating, in my opinion, as they alter the down to conditions that will only remain at that loft if never used. Shoot, if I were just an inch shy of being the world's tallest person, I would go to space and hang out at the ISS for awhile and have my height measured there. Bam! Instant couple inches of height and a new record holder since I'd technically be taller, but only in space. Being allowed to game the system and rate down higher than it actually is is unfair to those that don't participate in such shady practices. Plus, it drives honest competitors to do the same for fear of losing market share/sales due to the perceived inferiority of their lesser FP down.

When sleeping bags are EN rated, they try to use real world conditions, conditions that the user of the product will experience. They might as well send the down to space and have it rated at the ISS where gravity will have little effect on the down.

Just look at what's happened to the headlamp industry:
http://www.outdoorgearlab.com/a/11165/Why-Headlamp-Claims-are-Deceptive

They started rating headlamps with a standard, but found that cheating and changing the conditions of the test and the definition of what is usable looked/sold better so now they just outright lie and have abandoned the ANSI standards.

The down products in the US may go the same route.

I can't comment 950 fp but I've used 800 and 900 fp down in projects, both from Thru-Hiker. The 800 fp down definitely had more feathers in it. It was a marginal but the 900 had just no feathers whatsoever. I don't necessarily trust 950 but I'd say 900 might be worth it.