I have a Nunatak Arc Alipinist that I would like to use in Sierra winter conditions, with low temps possibly reaching single digits. I plan to layer with a Merino base layer, Western Mountaineering down parka, Montbell Down Pants, and Nunatak down booties or perhaps hot socks. I also plan to use a winter Bivy. I am a fairly warm sleeper. My question is this: Will I be warm enough?

I appreciate your wisdom/experience.

I'd recommend something well insulated, of course.

Paul,
What will you be using underneath?

It needs to be substantial, like a combination of a full length Thermaraest and 3/4" Evasote, or something similar.

There are a few recent threads on the importance of excellent ground pads for winter conditions that are worth finding.

I hope so, because I've got an Arc Expedition on order, along with a balaclava, down pants, and mukluks. This, combined with a down parka, should work well in a hammock in New England winters. My hiking partner uses the Arc Alpinist with another quilt plus insulated gear, and has stayed quite warm.

Paul, during winter I use the following to sleep:
Arc-alpinist, with 2 oz overfill
Nunatak Bacalava
Bibler winter Bivy - to seal out drafts and add few degrees.
Golite Tarp
Recently switched to Stephensen DAM pad. Very warm/comfy
Mid to exp weight Wickers base layer bottoms
100 weight fleece base top
sometimes 200 weight fleece also
Nunuatak Down Booties - very warm

I have been comfortable in the teens, but it never got into single digits where I go.

I just bought Flight Jacket and have Montbell down Pants on christmas list to get pack weight down.

However, my concern with sleeping with down clothing on especially with Bivy is your sweat wetting out down clothes thereby making them less insulative when needed around camp. If you are in humid weather, of which I am, I think this could be problem in morning before it has time to dry out.

Has anyone else had a probnlem with body produced condensation in down clothes while sleeping?

Chuck

"However, my concern with sleeping with down clothing on especially with Bivy is your sweat wetting out down clothes thereby making them less insulative when needed around camp. If you are in humid weather, of which I am, I think this could be problem in morning before it has time to dry out.

Has anyone else had a probnlem with body produced condensation in down clothes while sleeping?"

I should have added that I *always* use a VBL layer over my long underwear while in camp. Always. It stops perspiration caused by the dry winter air, and keeps the insulating layers around you from getting soaked. It doesn't make that much of a difference over a single night, but the longer you're out the more important it is to use a VBL.

Personally, I'm unable to use a VBL during the day, but YMMV.

Not a problem with sweat, but I've just spent two nights at -2 degC/28 degF with 100% humidity, which was not at all comfortable - the down suffered badly.
Once the temperature drops a few more degrees and the humidity drops down is fine - but I'm seriously thinking of getting a synthetic quilt for below freezing, but humid conditions.

For high humidity situations, synthetic insulation is definitely the way to go, both for sleeping bags and clothing.