(NOTE: I updated this post+title from " --25c: Pad + Bag + Tarp OK?")
This will be my first year doing winter camping. I'll be doing this in Montreal (a city), up to 7 days a week, every week of the winter (I sleep at other people's homes sometimes). I want to be ready for temps of -25c/-13f. I have an Exped Downmat 9 l/w and a MEC Thor -30c/-22f bag with Windstopper NR55 shell. The shell is completely windproof, but only "water resistant". What that means is unclear and Gore won't help. As things are now, the sleeping bag's fabric isn't humid in the morning. I don't know how this will be after extended use, especially once the Canadian winter goddess has free reign. This said, I will air out my bag at least once a week inside my university's library.
1. Bivy or no bivy?
I've ruled out a tent due to visibility, though I'll experiment with a friends' tent for fun. I'm inclined to use a bivy instead of a tarp tent because this allows easier setup + lower visibility. Unfortunately, there doesn't seem to be such a thing as storm and blizzard proof bivy, in part because fully closing a waterproof bivy leads to condensation problems and suffocation if there's a lot of snow, while leaving it open requires at least shelter for the head.
This said, as things are now I'm tempted to get Canadian military bivy (very straightforward: just a gore-tex bag with
drawstrings, no zip). Advantages I see:
*Better temp control. If I unzip the bag without a bivy or tent, I expose myself to drafts. This should make it easier for me to control temps since this way I can unzip the sleeping bag a bit while still having a windproof shell.
I assume (???) that light snow fall, either from the sky or pushed by the wind, will not cause problems as long as I have a balaclava. I may be dead wrong.
I'll still carry a tarp to cover my head when there's significant snow. I'm thinking of building a snow shelter that just covers my head.
2. Extra-sized sleeping bag?
My current sleeping bag is for 185cm people and I'm 185cm. (+/- 6ft). It's not too tight, but I can't fit anything else in there with me (except a jacket to snuggle with). I can return and replace it with the long size, but that's 15cm longer (0.5 feet). I don't know if this is a problem in terms of the time it takes to heat things up.
3. Transition in/out of the bag.
I'm a bit concerned about the in and out transitions. There are two issues I see:
At the moment, it's warm enough that I can handle brief exposure to the elements. However, if it's -25c, that might be very uncomfortable, and, done repetitively, dangerous.
Also, I don't want to get snow inside the sleeping/bivy bags. I can imagine some different ways of dealing with this, but I'd like to hear it from the experienced.
Any additional tips are welcome. Here are the one's I've read about already:
*1L pee bottle
*Nalgene bottle with boiling water covered with clean sock
*Clean wool socks