Best 2-bag Sleep System for Deep Winter?

I think this is probably the most helpful post possible. Your insight with the difference between 20 and 30 is invaluable. Thank you for taking the time to write this. My question is essentially answered.

Cheers!

I agree that a bag/quilt combo will give you move options and a greater range of use. Check out this review I did of a 0 F bag:

http://tinyurl.com/c7acw4a

I used a couple different quilts with it. My son too has used some of my quilts along with his 20 F Sierra Designs bag to take it below 0 F a few times.

Enjoy whatever you do decide to get.

My extreme cold weather system is an older -20 F. MH Polarguard insulated bag with a zippered expanding gore so I can insert my WM Megalite inside. This combo does not compress the down bag and is not restrictive.

Down inside and synthetic or DWR treated down outside means that your body moisture, when migrating to the outer layer (& THEN CONDENSING), will be in a layer that is not as much affected by moisture and likely let the frozen moisture at least sublimate off to the atmosphere when the bag is aired. Further, double bags can be separated for better airing.

Personally I feel every down winter bag should have the down fill treated with one of the new down DWRs. Patagucci seems to have one of the best of thse treatments but, Mon Dieu! the $$$.

"Personally I feel every down winter bag should have the down fill treated with one of the new down DWRs"

Why? At -20 F you aren't going to fall in a creek or get caught in a rain storm.

If you have condensation in the bag freeze, it will do so in whatever insulation you have, DWR or not.

I like the tech, but don't see it useful/needed at extreme temps.

My Dear Raymond,

Down bags in winter have the dreaded "outer shell condensation" problem. Believe me, without the ability to get rid of this frost your down bag gets progressively heavier each night, eventually becoming unstuffable and unuseable over weeks. (See Scott's disasterous South Pole attempt).

A DWR treated down MAY let this frost detatch from the down more easily and MAY sublimate if exposed to sub zero airing daily. (I'm surmising here.)

I've experienced frost buildup in both down and synthetic in sub freezing weather over many days. It ain't fun and it ain't warm.

Yes, I know that Eric. (And it happens with any bag, not just down.) The only way to "get rid of it" is to let the bag thaw so you may be right that it could help there. But when it never gets above freezing it would be hard to get to the point of needing the DWR down, right?

Well I am off to Paul Bunyan State Forest for a few days. No frost in the forecast, just heat, humidity and huge mosquitoes. Have a good weekend.