Marmot Hydrogen

I've taken it twice to 10 F and 11 F wearing a 100 fleece hat, 200 vest, 100 microfleece pants, liner/wicking socks, Prolite 3 (full) and and plenty of hydration and food. I was in an enclosed 4-season tent both times (Eureka K2 or Marmot Haven). This was in central MN of about 1000 feet above sea level. Mine is an 07 model with a 1/2 zip.

This was last winter, and since that time I have procured mont-bell thermawrap parka and pants. I have yet to test this setup without the fleece clothes. I think it would push the bag to about zero F. Note that I have a high metabolism and sleep warm.

Hi Dave,

The lowest I've taken mine is 19F. This was last winter in Linville Gorge, so it was fairly humid compared to some places in winter.

Additional layers/shelter: 8×8 tarp in a flying diamond pitch; Thermarest Guidelite 3/4 (1.5 in. thick); wool thermals; Ibex Skifans pants; Driclime windshirt; insulated socks; powerstretch facemask; Patagonia down hoody. Also had my Bibler hoop bivy along, but didn't use it (spindrift wasn't bad enough to use it, and it would've increased the potential for inner condensation in the system dramatically).

Woke up at around 2 am and felt a little too warm, it was 22F then. Loosened the hood cinches and lowered the zip about 6-8 inches. Awoke for the day about 6:30; I was toasty warm at 19F!

This winter, I'll be adding Montbell down pants and a more breathable bivy for GSMNP trips. In a more enclosed shelter, I'm pretty confident I'll be warm down to single digits. Not bad for 24.1 ounces! Don't forget to shake the down to the top for those really cold nights. Also thinking a DAM might add significantly to my system's warmth.

Of course the other factors: I was well-fed and hydrated; I also pre-warmed my bag (used it to insulate dinner while it was rehydrating, then put my hot snow melt bottles in before bed). This can save you quite a few calories I've found, YMMV.

I have had my hydrogen down to 22 degrees in the Shenandoah mountains in January. I was sleeping under a tarp with a Montbell Dry-Tech Breeze bivy. I was sleeping in REI Lightweight MTS LS zip-T, columbia silver ridge pants, & wool socks. During the night I did at my Mont-Bell UL down jacket but would have been ok without it. I was sleeping on a Gos. Gear 3/8" thinlight pad with a Montbell 90 self inflating pad. I have the older 1/2 zip version it weight 1 lbs 7 oz (a bit more then spec'd). I think this bag would have gone down to 10-15 degrees with my setup. My base weight for that trip was under 7.5 lbs. I'm impressed with the temps you can squeeze out of this bag with it still having low weight.

Jamie