more down or no down at the bottom of the sleeping bag.

[S W]

The quilt has less down or no down at the bottom, because the fact that down provides warmth by trapping air, the down at the bottom is compressed by our body when we sleep in it, the compressed down squeeze the air out, thus does not provide the same warmth as other areas with loft.
As a result, it is easy to understand from UL backpacker perspective that nixing the bottom down, fabric and zipper saves weight, also given the fact that most users are already leveraging a sleeping pad to insulate the bottom.

While some Alpine manufactures are using variable fill/deferential fill, they purposely fill more down at the bottom to provide more insulation, because it is touching the cold ground and compressed.
As Alpine mountaineers/climbers may not using any sort of mat to insulate the bottom and solely rely on the bottom of the sleeping bag, is it right? If yes, given the fact that the compressed down does not insulate well, why compensating this by filling more down at the bottom instead of just use some sorta light weight sleeping pad? If no, they are using pad like backpackers, then still why filling more down at the bottom, it is not very effective anyway, and the weight saving is also crucial for mountaineers/climbers, because apparently they have more gears to carry than backpackers. Is there a contradictory here?

Another question is whether the down at the bottom really a waste/dead weight? I doubt it, because in reality, only the down completely under your body are compressed, all the rest areas, such as the gaps between your legs, the areas between you arms and your body, the surroundings between your neck and head etc. are all not fully compressed, I would argue for the areas under your body are not 100% compressed, assuming it does, it most likely still have more insulation power than 2 layers of fabric, and when you toss and turn, the previous compressed down regains their loft and becomes uncompressed and live again. Isn't it?

Overall the sleeping bag is enclosed chamber and prevent your body heat escaping outside. So for winter, sleeping bag is far superior than quilt in my experience. YMMV.

Maybe putting some sorta stretchy fabric like spandex to close the bottom of the quilt and making the quilt fully enclosed to provide more warmth as well as maintaining the weight saving with no down at the bottom and no zipper at the side is a good compromise?

Sorry for my rambling…

[Link .]

Fabric on the bottom has been around for years Nunatak Catabatic
Nunatak Catabatic SL
It depends on how you use a quilt Katabatic Gear Sawatch quilt and the size.

[Franco Darioli]

A common reason for the 50-50 fill used by many manufacturers is because often folk take their bag with them when they turn , so that the bottom becomes a side or even the top.
I was not aware that Alpine manufacturers use more down at the bottom but on the converse I have used a top bag, that is, one with no insulation at the bottom but a built in sleeve for the mat.

[Rick M]

del

[Jorge Falcon]

Check this: http://www.outdoorgearlab.com/Ultralight-Sleeping-Bag-Reviews/Feathered-Friends-Vireo

I own a quilt (ZPacks), combined with your insulated jacket and a good quality pad it's a light option in cold temps.

[Edward Jursek]

I have a custom Vireo that is an amazing bag. It has the best foot-box I have ever seen. Mine has 5oz of overfill in the top half and is comfortable to 20 degrees and is 22oz, with a great performance shell. Check out this BPL link for the Vireo:http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=73812

[Franco Darioli]

NM

[Mitch Chesney]

I wish I remember the climber/alpinist who described his perfect sleeping bag, but basically it was that he and his partner traveled fast and light in traditional aid climbing, his vision of the perfect bag would be a double-sleeper so they could share body warmth, and have only fabric on the bottom… like a super-quilt. I'm not sure why some manufacturers put more down in the bottom but it could be because their clientele haven't adopted the quilt philosophy yet. Demand dictates supply.

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