20F bag to 0F?

Garrett, there are many things that contribute to a cold weather system. I am afraid that the system you outline is skimpy in every regard for winter nights.

The Conundrum 20 would not work too well at 0F without a lot of help which you seem to have. For 0F you really want between 4-5″ of insulation over you. However you get there… Helios down hooded jacket, MLD Balaclava, WM down pants, GooseFeet socks all contribute to that. But at 10-15F help, that still leaves you slightly short of 0F. Due to drafts, I would say you need at least an additional breathable bivy to elimanate drafts. All quilts have draft problems. I do not usually suggest a quilt for below 20F. I typically use a SS 0, for expecting 0F worst case temps.

As Roger says, the ground insulation is important. There are many ways to hit the 0F. Basically you are looking at a 0F temp which is R8 or R9. I don’t believe your system has enough to meet the 0F criterium. Your stated specs call for around a R5.5. Well balanced for 20F, but a little lacking for less than that. CCF has greater insulating value per inch, but is a lot heavier. Your pad coupled with two thicker CCF pads (say a regular Zrest below and a Zrest Sol above) would be adequate to 0F. You are talking worst case, not sustained 0F temps.

Your tent will work well, provided it can handle snow loads, has a full fabric inner, and is small enough to let you warm it up a bit. Any winds can really make a tent loose heat badly if it is a mesh inner. To large and it will loose heat as quick as you add it (from body heat/breathing.)

Other things can help, like a hot Nalgene, warm rocks from the fire, etc.

Please be aware that 0F can draw heat from your system much more rapidly than in three season temps. Here is a chart https://www.weather.gov/safety/cold-wind-chill-chart Even a light wind of 5-10mph can draw the heat loss temp down to around -10 to -15F, offsetting any warmth you might get from your tent.

So worst case, if you plan on 20F and the night time temps dip down to 0F with the gear you describe, you will survive, but it will not be real comfortable. There is a pretty clear difference for cold weather camping. (70F to 50F is doable easily. 20F to 0F could be a bit trying.) For a lower hard limit with the gear you have, 0F is reasonable. I am assuming you are talking about an average of 20F with a worst case of 0F.

I have taken my old 40F bag down to 20F on a couple occasions and my 20F quilt down to 10F several times. But shooting for 0F with that gear is not high on my “I want to do that” list. While it is possible to boost the performance of the system about 10-20F or more (with a tent and additional clothing,) you are talking the limit of what can be done. Generally speaking, you can get 20F out of most systems with additional “boosters.” But, you will be cutting in to the safety margin. At the limit, you will be out of “Comfortable” trending towards “Survivable”.

So…  The EE Conundrum 20F bag has been replaced with a FF Lark 10F sleeping bag + 50F overquilt (undetermined, but likely myog with 2.5 apex).

Exped Downmat XP9 should be arriving anyday now : )

You think I still need a Therm-a-Rest pad or would a GG 1/4” foam pad suffice?

Yes I use a vertical carry for the RidgeRest plus whatever other I happen to use A bit of a pain in scrub but I usually walk or ski in open terrain or use a pulk when setting up a base camp for skiing

If I can ever get an second RR Solar I might be tempted to cut the spare down to fit my shoulder to hip length or maybe just cut down a standard wide RR to suit. No data but I have found that the very thin RFL on foam used as flooring underlay does make a difference when used in conjunction with the RR and that stuff is only 3mm thick

I always think “Worst case” and pick my foam pads for insulation and the air filled mattress for comfort. Also with 2 bad experiences with ExPed I simply do not trust them and want back-up. YMMV and a lot depends on how many nights you are out, 3 nights or more I personally take the extra mats. Naturally it is the shoulder to hip part that needs most insulation so a three-quarter RidgeRest is what I would use if they made a wide version but I can’t bring myself to cut mine down.

Like you, I tend to plan for worst case as well. That said, I don’t think I can make two 25” wide pads work with any backpack. I can carry one vertically on the back of my pack, but horizontally would just be too wide to carry. Unfortunately, the regular size pads aren’t wide enough for me.

Garrett, Yes, your new system will be fine at 0F. There would be a -10F or so safety margin. I know here in the ADKs they actually recommend a -20bag/pad for most winter camping. Even then it gets a little thin sometimes when temps hit -20 to -30. A 50F overquilt over a FF 10F bag will do it. The XP9 is a good pad but I still like my 3/4″ CCF to put over that. Anyway, the R8 is enough for 0F. I usually figure one R value more for each 10F below 30F, starting at R4 for 30F. Soo, the Exped should be OK at -10F. IE, a neoair+CCF back pad (3/4″x20″x52″.) But, a CCF provides “wiggle room.”

The quilt+bag+pad combination is enough to hold you at 0F in a lean-to (open to breezes.) Of course, the system minimizes the effect of clothing/extra layers inside. Make sure you have plenty of room inside the Lark, it is generally cut a little thin at around a 60″ circumference. Some manufacturers measure differently, for example measuring rom the outside MINUS the loft…not sure how FF does it. The Marmot SS bags allow a lot of room (up to 68″.) I would highly recommend the long bag, too. You can keep water, fuel, other clothing, in the foot section keeping them from freezing up, for use in the morning. The Lark is actually a late Fall/early Spring bag. With the over-quilt and heavier pad, you should be fine. Any extra clothing is just a safety margin.