NeoAir XTherm (OG Version)

Adding on to what Massey said **Sleeping bags** At those temps you would want gear rated to handle temps at least at -40F, maybe even -60F depending g on how you sleep and the manufacturer. Many will list the lower limit or survival temp so a -40f bag may only be comfortable down to -15 for you. You are hitting highly specialized gear at this point, even REI has very few bags rated for those temps. I would not try to DIY bag layering with your experience level and those temps. Your choices also break down in to two basic categories - down: lighter, packs smaller, expensive, different care requirements - synthetic: significantly heavier and bulkier but can be much more affordable For down bags western mountaineering is probably the gold standard but bags will be over $1,000. There are a few other major brands in this space but prices will be of a similar range, maybe a few hundred less. There are also some custom gear makers like feathered friends that make down bags in that temp range. For synthetic bags I have used a layered sleep system used by a company called wiggy's. Their two bag system for use down to -40 would take up most of my 60l bag even in the compression sack. I've had it down to about -10 or -15 and was comfy. A large percentage of my scout troop in Alaska used the -40 system from them. The other main synthetic system that I'm familiar with is the military modular sleep system which is supposedly rated to -50 when you use all 3 layers. **Sleeping pads** R value can be additive so you could get one really good pad like a nemo tensor extreme, exped megamat, Therm-a-Rest NeoAir XTherm, or other high r value pad or you could layer multiple closed cell foam pads together and put those on top of a lower r-value Sleeping pad. **Body Sleeping system** Sleeping bags are rated with the following assumptions - the "average" man - wearing base layers - on a well insulated sleeping pad I covered the bag and pad but you also need to have some decent base layers and at those temps you should also be considering what to wear on your head and face. You will probably want to sleep wearing a buff and hat or balaclava and maybe even a hat as well. You want your mouth to be breathing out through the face opening in the bag whenever possible due to condensation buildup. Make sure you have a set of clothes ONLY for sleeping, you want to be completely dry getting in to the bag. **tent** Many tents will work as long as weather isnt a concern. I've used both coleman and ozark trails tent in below zero conditions. The big issue is good ventilation so that any condensation doesn't build up on your bag or on an inner tent wall that may touch your bag and saturate it with water. Double layer tents with a full rainfly would be my go to, especially one with a partial solid interior (the bottom half or so being a solid fabric) that will help block blowing snow and winds. Very few people actually need a dedicated winter tent. In my 4 years in Alaska I never ran in to anyone with an actual 4 season tent and we camped out every month of the year.

Great summary! FWIW my (particularly specific) alternate take on sizing is: having a Neoair Xtherm revolutionized my experience on the trail thanks to a proper nights sleep (including on snow) - HOWEVER my first one was standard width, and my brain never fully shook the underlaying feeling that I was about to roll off (obligate side sleeper, so always a degree of instability). I did use my pack to my back to help ease this, but very suboptimal, especially in a small or shared tent. Getting the wide version was the final peg in giving me a warm stress free sleep - the increased weight was negligible for me in this case. Of course everyone’s mileage will vary wildly, but sometimes it’s the myriad little things that make the difference - I always recommend trying to find a friend or rental you can try your top 2-3 options in the field before sinking the dough :)

Get something with a super high R rating - higher than you think you need. Look for a baffling system that is either dimpled or vertical. For whatever reason, horizontal baffles don’t have a lot of “give” to them so they are less comfortable for side sleepers in general.  Therm-a-Rest Neoair Xtherm is probably the warmest pad out there (not the highest R rating per se but the most effective insulation system means it is still warmer than other pads with higher R values). It may not the most comfortable for a side sleeper because of the horizontal baffles, however. But this is the pad you want if you want to prioritize warmth. If you want to prioritize comfort, Sea to Summit Ether Light XR Pro will probably not sleep as warm but will be more comfortable for a side sleeper because of the dimpled baffling system. Nemo Tensor Extreme Conditions is also very warm and only slightly less comfy than the Ether Light.  Exped Ultra 7R is a bit heavier and bulkier but is very comfy for a side sleeper. It uses down rather than reflective film for insulation. So it won’t be quite as crinkly as a lot of warm pads, but I’m not sure if the down insulation is more or less effective in this application.  Big Agnes Campmeister Deluxe is quite bulky and heavy for a backpacking pad but is super, super comfortable and has a very respectable R value of 7.  The other big, bulky “luxury” comfort backpacking pads - Exped Megamat Ultra and Therm-a-Rest Neoloft - are great options for comfort but with lower R values so they may be less warm than you might want.  Other things to consider - even a well-insulated sleeping pad will only stay as warm as your body is able to heat it. The bigger the pad, the more of your body’s heat it will draw away from you. So don’t buy a massively oversized sleeping pad thinking it will automatically be more comfortable. For insulating purposes, something that is only as big as you need it to be will be more efficient for your body to keep warm.  Make sure you take advantage of all the usual strategies for staying warm in the backcountry: Use your Nalgene as a hot water bottle and keep it in your sleeping bag/quilt with at night. Do some jumping jacks or other activity to get your heartrate and body temperature up before going to bed. Make sure you are properly hydrated and getting enough food to keep warm. Etc. 

\+1 on the NeoXTherm. Have used one for 20 years. Recently got a Sea2Summit Etherlite XT it is more comfortable for a side sleeper.

You should be okay sleeping in the shelters with the bivy. My concern is the short and insulation ot the mat. Could you add a foam mat? Even a sit on pad would help. The shelter floors are cold. Add a vapor barrier over your thermals, such as, windshirt, wind pants, and plastic bags for feet. On ypur feet ise Poly liner socks, plastic bag, then wool socks. I have used a 15° F sleeping bag, neoair xtherm long mat, with thermals, and vapor barrier, sock cap, and puffy in 0° F camping several times; always comfortable.

Xtherm is worth it 100%

At Philmont, even in summer, you’re going to be dealing with elevation, cold ground and nights that can dip into the 30s. In those conditions, an R-value around 4.0 or higher is a safe target if you want consistent and comfortable sleep yk. A tent doesn’t provide insulation on its own so your pad is doing almost all the work underneath you. That’s why an insulated air pad makes a lot more sense than an uninsulated one for this use case…I’d recommend: - the Therm-a-Rest NeoAir XTherm (regular or MAX) OR - the Big Agnes Insulated Air Core Ultra If you’re on a tighter budget, the REI Flash Insulated would probably be better. There are these [ultralight sleeping pads](https://alaskanarrows.com/5-best-ultralight-sleeping-pads-for-backpacking/) that you can also look into

For -5C and durability I would personally take the Thermarest X-Therm mummy. R7.3, 440gr (although mine weighs 460gr in reality), and a 70D material on the underside. Anecdotally, I can feel the cold seep through my Nemo Tensor Insulated (R4.2) from around freezing.