Another advantage to compressing a sleeping bag is that if you do get a little leakage into your pack a compressed bag seems to only get wet in the little spot that got direct water. It doesn't seem to sponge it's way through the bag like a looser sleeping bag will.

Mad_Mat wrote on May 5^th, 2010 at 1:10pm:

Most likely the loss was due to moisture build-up. 
The true test would be to measure the loft before use.  Measure at the end of the trip.  Wash & dry the bag, don't forget tennis balls to beat out the down clumps, measure again.

I know that compression kills synthetic fill bags, as it breaks down/ "kinks" some of the fiber types reducing their ability to loft. Down on the other hand maybe more affected by dirt, body oils, and even soap residue from the cleaning process

Mountain Hard does supply true compression sacks with some of their bags, a long with the storage sack.

I have a 30 degree down bag from Kelty, so it's not too big to begin with. But I've had good success with the Sea to Summit Evac dry sack. It's not a compression sack, but it packs down pretty well--you roll it from the top and buckle it closed. I've only used it for two seasons, so I can't really tell if it's had an effect on the bag, but I doubt it. The thing I like about the evac sack is that it's oval-shaped, not round. Won't roll away! Not that I've ever inadvertently set a sleeping bag down on a slope and had it roll into the lake...

Oh, and while it is waterproof, I do line with a plastic bag, just to be safe.

"On the other hand, it is quite likely this has already been tested numerous times over and I suspect the loft impact is negligible,(or the results would be made known) especially when you consider the average tripper may only spend a few weeks a year using it."


its likely that the "average tripper" won't notice a significant decrease in loft/warmth unitl several or many years of use.  Most of the comment I recall from backpacking forums were from thru-hikers on Appalacian Trail or whatever - some of thier comments were more or less that they noticed a definite loss of loft/warmtn after about a month of steady use on the trail.  

The "problem" with this issue is there are no "statistics" to look at - i.e., how much compression is too much; how many times is too much; how much loft was lost.  I've never precisely mesured the loft in any of my bags, so I have no way to tell if I have lost any loft - I doubt that 1 person in a million would have measured that precisely enough to quantify any loss of loft.  So all the people who say they haven't had any loss can't really prove that either.  So its all subjective - I go by the logic, that it can't be good for the bag, and may be bad, do I don't want to do it if I don't have to.

Out of curiosity, I looked at the Western Mountaineering, Feathered Friends, Marmot and Montbell websites (all top quality down bag makers) - they were all mute regarding compresion sacks - nothing said for or against (though agian, none of these companies give you a compression sack with thier bags, but rather a simple stuff sack.

Kind of expanding on Matt's theme, and seeing the latest square compression & stuff sacks in the Piragis catalog.

You compress a normal round compression bag till you've got a round rock,,,throw it in your pack,,,and add your small items in the voids between the round rocks you compressed. Verses packing slightly compressed bags that smash into the voids and stuffing small items till it all fits.

I know from packing hard sided "Blue Barrels" on river trips you can get more into a blue barrel if everything gives some, i.e. stuffing loose stuff into the barrel works best.

Think about the total system. Not just how small one bag will get, but how it all works together.

Personally I like Matt's suggestion that a large compression bag is easier to stuff something into, and only meant to be compressed slightly. I don't know about how it damages a down bag. I'm still using a Eddie Bauer down bag from ~1970. When they only had a Seattle & Chicago store. Proof again that buying the best you can afford is cheaper in the long run.

Oh that would be awesome.  I'd totally wear that camping.

[quote author=Preacher link=1272854000/10#12 date=1272992808
I'm a big fan of dedicated bedclothes & will pack a comfy fleece onesie, complete with back-door, for chilly nights on early/late season trips.  Saving up for a merino wool set. [/quote]

For whatever reason Preacher, I just envisioned someone in the bunnysuit from A Christmas Story  .
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Snow_Dog wrote on May 4^th, 2010 at 1:26pm:

Agree.  Though if this is your one & only bag you'll be sweaty in summer or chilly in spring/fall depending on which way you go.

What you wear to bed on the cold nights makes the difference.

Since it's down, try to avoid the clothes you wore that day.  Moisture in your clothing will end up in the bag.  I'm a big fan of dedicated bedclothes & will pack a comfy fleece onesie, complete with back-door, for chilly nights on early/late season trips.  Saving up for a merino wool set.

This has been helpful. Still leaning toward a waterproof compression sack but Mat re-interated my chief concern about repeatedly compacting the bag. It has the ring of truth.

On the other hand, it is quite likely this has already been tested numerous times over and I suspect the loft impact is negligible,(or the results would be made known) especially when you consider the average tripper may only spend a few weeks a year using it.

Probably what I will do is snug the straps up but only in moderation. In any event I am so looking forward to one tidy little bundle of mat, bag, pillow and sleeping clothes. I have one of the therm-a-rest pillows and by golly I wouldn't leave home without it. (Aye Matey, gettin soft in my old age)