Best 15F-20F synthetic sleeping bag?

Synthetic runs out of steam around 30-35 degrees. A 15-20 degree synthetic bag is just heavy.

I have a NF Orion 20deg. It's really a 25-30 degree bag and weighs 2.5lb. It is a nice bag, but not as good as a down bag.

The best synth bag I know of is the MH Ultralamina 15. It's a smidge under 3lb and is pretty true to it's rating. It's also $200, which will get you a used down bag that will be 1lb lighter and last forever…

You best bet to get a realistic temperature rating for synthetics is to check the standardized EN 13537 ratings. Fortunately for those of us in the USA, some of the big boys are starting to provide them, so we don't have to rely on subjective ratings. The new version of the Cats Meow with Climashield Prism gets a lower limit rating of 19F and weighs 2lb., 10oz. This edges out the Ultralamina 15 which also gets a 19F lower limit rating but weighs 2lb., 14 oz.

The tests are not 100% objective, as there is flexibility in the test setup and procedure.. NF bags, in my experience, run colder than the ratings suggest. The MH bag is heavier because it has more insulation, of a similar CLO – it's gotta be warmer.

>Synthetic runs out of steam around 30-35 degrees. A 15-20 degree synthetic bag is just heavy.

+1 on this. IMO, don't expect synthethics to do the job without a weight serious weight penalty.

Stargazer

Another +1 for down.

Even though down bags are generally more expensive up front, they're cheaper in the long run because they last much longer than synthetic bags.

Well, it depends on how long the OP plans on staying out in temps requiring a 15-20 degree bag.

I’m far from an expert, but certainly for overnighters a down bag would seen the best solution since I wouldn’t expect that you’d encounter much down-killing precipitation in sub-freezing temps.

However, when you start talking about extended trips there is an arguement for synthetics, despite the weight penalty, because they’ll resist the condensation caused loft-loss over multiple nights in the winter in situations when drying out your bag during the day isn’t an option. Sure, you could use a vapor barrier, but 15-20 degrees is, in my own experience, a still a bit warm for VB. There’s at least a couple article on BPL that discuss loss of loft in down bags on longer trips; the Crater Lake trip and Andrew Skurka talks about loft-loss in down bags and the use of VB in this article.

Down versus synthetic in a sleeping bag is a debate that will go on forever.

My first attempt on a serious peak in winter was a disaster for me because I simply did not know how to keep my down bag dry. That was a knowledge problem that was solved before I went out on a second one.

The mention of Crater Lake was nostalgic for me. A bunch of us went there in the springtime to ski around the lake, and we ended up taking 48 hours. We slept in decent tents that had insufficient ventilation, so condensation became a problem. My down bag had about 40 degrees F of warmth rating that was unneeded at the start. After two damp nights out, everything was still good enough. Next time, I would simply work more on the tent ventilation.

–B.G.–

I use this in the wet highlands of Ecuador. Last trip I was rewarded with 35-40 mph winds pushing rain through my 3 season tent. Pulled my pack liner up over the foot of my bag for some protection but everything was wet by the morning. Low temp hit 33 f inside the tent. I had to take off my pants and jacket and slept only in my EB wool long underwear.

It seems synthetic takes a bit longer to warm up but once warm I was toasty and stripping. Bag was really damp on the outside but not on the inside. Bag was dry by mid day.

The zippers on each side are really convenient for temp control but you must open and close them with care. A fast zip pretty much guarantees a hung zipper.

I'm 6'2" and 220(I have the long version) and sleep comfy on my side or any position. Hood is big enough you can have your puffy jacket floating around in it as a pillow.

Long version weighs about 3lbs.