Is the down in the top half of your quilt redundant with the down in your puffy? In other words, could you save weight by wearing your down jacket to bed and using a shorter quilt?

Yes.

Potential Savings

My current quilt is an Enlightened Equipment Enigma 20F in size long/wide, weighing 684g. My current jacket is an original Mountain Hardwear Ghost Whisperer, 232g. So, any combination weighing less than 916g is an improvement.

Nunatak’s Akula half-bag weighs in at 454g for the 54″ version, but that would go all the way up to my armpits. The 46″ version would give about a foot of overlap with a typical jacket and weighs only 397g. That’s 287g in savings, and Nunatak’s now-discontinued Nano Half Quilt was significantly lighter. Another bag option would be Feathered Friends’s Vireo UL, which has less fill in the top half and is intended to be paired with a jacket, at only 408g for the 62″ version.

On the jacket side, as much as I’d love to hold onto the Ghost Whisperer it only has about 2.5oz of down. For 345g the Cumulus Incredilite Endurance doubles the amount of down for a measly 100g weight penalty. Overall I can expect 200g to 400g in weight savings depending on whether my jacket needs an upgrade (or, no savings if I end up needing a significantly warmer jacket).

How Much Down Does My Jacket Need?

Quilts are typically paired with down balaclavas in order to provide whole-body warmth. If we want to determine how much down our jacket needs, we can use a down balaclava as a starting point.

Montbell’s down balaclava has 1.1oz of 800 fill. According to a review on The Trek, it kept one individual warm down to 25-30F. Of course, a balaclava only covers the head and neck whereas a jacket also covers the arms and torso. Fortunately, we can use the Lund-Browder burn area chart to approximate the difference in area covered:

For a balaclava, the area covered is somewhere between 5.5% and 9% depending on how much of the face you want to treat as covered. For a jacket, the numbers are 45.5-49% (7% for each arm, 26% for the torso, and then the head and neck – hands are excluded). Dividing 45.5% by 5.5% and 49% by 9%, we find that our jacket should have somewhere between 5.4 and 8.3 times the amount of down as a balaclava. For the Montbell, this means 6.0 to 9.1oz (or 4,800 to 7,280 “fluff”). After fully zipping and cinching a handful of jackets that I have lying around (an original Ghost Whisperer and Rab’s Xenon-X and Microlight Alpine) I can see that the face coverage is definitely towards the higher end, implying that our down factor is smaller rather than larger. Also note that the Montbell balaclava (like many others) includes some shoulder coverage which would push the numbers ever so slightly lower.

As a sanity check, the Zpacks goose hood weighs in at 1.3oz in total and is also reportedly good down to 20F per Richard Nisley. The Katabatic Windom contains 0.85oz of 850 fill-power down, is reported good down to single digits in multiple places (product page reviews as well as Backpacking Light), and yields a down range of 4.6 to 7.1oz (or 3,910 to 6,035 “fluff”) according to our methodology.

For simplicity’s sake I’m going to say that a 5oz down jacket is all you need down to around freezing.

Backyard Testing

My overnight excursions are on hiatus due to the baby, however, my yard is as cold and snowy as they get. About halfway through February we had a cold snap with nighttime temps in the low teens, a perfect opportunity for temperature testing. Here was my setup:

  • Six Moon Designs Lunar Solo tent
  • Therm-A-Rest ProLite Apex sleeping pad
  • Enlightened Equipment Enigma 20F quilt
  • Mountain Hardwear Mountain Tech Dome windproof beanie
  • Columbia PFG Zero Rules long-sleeve shirt
  • Columbia Omni-Heat Touch liner gloves
  • Saxx Quest Loose Cannon boxer briefs
  • Prana Stretch Zion pants
  • DryMax Max Pro Trail Running 1/4 crew socks

In addition, I was alternating between two different jackets:

  • Mountain Hardwear Ghost Whisperer, 2.53oz of 800 fill-power down
  • Rab Microlight Alpine, 5oz of 750 fill-power down

The tent was pitched on snow and there was no wind. For the experiment I would pull the top of the quilt down to my waist while wearing each jacket and then take a short nap (10-15 minutes) to prove that I could comfortably fall asleep in those conditions. Hands were placed in either jacket or pants pockets, whichever was more comfortable given the position. To prevent any issues with pre-warming of the jackets I stored them outside on the porch both before the experiment and between each iteration. The lowest observed temperature was 14F.

I was able to comfortably sleep in both jackets down to 14F.

This is a surprising result given that both jackets are considerably less warm than our estimation predicted would be necessary. On the other hand, if reviews are to be believed, even lightweight balaclavas with less than an ounce of down are warm enough down to 0F. Still, I’d feel more comfortable in the wilderness with the 5oz jacket, and personally I’ve been looking to upgrade to something warmer regardless.

Availability

As of this writing, Nunatak has temporarily slimmed down their offerings such that their Nano half-quilt and Akula elephant’s foot bag are no longer available. Gryphon Gear’s elephant’s foot quilt looks like a perfect match, although the lowest temperature rating is 35F which might be a tad chilly depending on how they rate their quilts. Feathered Friends’s Vireo sleeping bag offers full length but with less insulation in the top half of the bag, which might appeal to those who don’t want to upgrade to a heavier down jacket.

Other Observations

Normally, I’m a cold sleeper. The fact that I was perfectly comfortable in such cold temperatures while wearing my usual gear was bizarre to say the least. On the other hand I’m a good ten pounds heavier than I was this time last year so maybe that has something to do with it. In any case, I’m thinking I can safely “downgrade” my quilt and sleeping pad to something less warm, yielding even more savings.

History

  • 2021-03-13 Original version
  • 2021-03-17 Added section on product availability