What is the "ideal" R value for a winter mattress?

R-values are additive. your Ridgerest has an R-value between 2.8 and 3.5 depending on the model so when you add that to the proposed REI pad of 3.7 you would obtain an R-value of 6.5 or 7.2 depending on your model of the Ridgrest. Section Hiker has a good chart of different pads and a basic understanding of R-value. https://sectionhiker.com/sleeping-pad-r-values/

I have used a SynMat UL7 (R4.9) on snow and was a little chilled but not unbearable except for one trip where I was pretty cold even in an older -20f Marmot. That particular trip I was worn out from post holing in 30″ snowshoes on top of normally being a cold sleeper and temps were just below zero. I now have a TR All Season that I like and I have started to pair it with a TR Z-lite closed cell for the extra R as well as having a closed cell back up in case something catastrophic happen.

Mike

On my last 20 day January trip I used a Thermarest Trail Pro (the upgraded version) at 4R with a ridgerest Solar ccf pad at 3.5R—combined total 7.5R.

I have found thru long trial and error on 0F nights that I stay warmer with the Solar pad on top of the inflatable–and not underneath.

Published R values are a starting point. I’ve had mixed results from supposedly comparable r-value products, presumably due to design factors and possibly measurement bias. Anyway, tough to put a temp rating to it without working out a specific combo in the field.

Well, people sleep differently. But generally, if an R4 is comfortable at 30F (a plain-jane Xlite,) then you need an R5 at 20F and an R6 at 10F and R7 at 0F. This “rule of thumb” corresponds to Tipi’s 7.5 at 0F roughly.

A lot depends on the surface below you. Ice, rock, sand are poor insulators. Snow is a good insulator. If you can get down to forest duff, that is a good insulator. Wood planks are not that great but better than rock, avoid sleeping on the floor in a lean-to or back country cabin with unheated floors below you. Add or subtract an 1 or 2 from the above, according to the surface you sleep on. Warm snow at 32F is worse than cold snow at 20F. It packs too easily making it dense. Generally dense things are poor insulators but there are exceptions…glass for example.

Hmmm… I’ve slept on packed snow (floored tent) with an original 3/4 length Thermarest at -5 F. and been OK with outer clothes under my bag for my lower legs and feet.  And on my full length Trail Pro Regular in same conditions at -10F. and been OK.

I “think” my old Ridgerest with the Trail Pro should get me to -20 F. but it may not and that would not be fun. My new -20 F. LL Bean down bag would not compensate for a cold mattress setup.

Ridgerest “Solar”? I need to look it up.

BTW, It seems like backpacking mattress technology is heating up more than any other piece of our gear. Show to go ya just how important gear for a good night’s sleep (with minimum weight) can be.

Thanks for the help guys.

it also depends on the rest of your insulation, sleeping bag and so forth

loose snow is a good insulator

ice is a poor insulator. As you sleep on it, snow packs down and gets closer to ice, but it depends

Plus, it has a lot of heat capacity so it takes a while for the temperature to increase.  Plus, if you’re melting it, it’s a lot worse.

Insulation and comfort are different and doesn’t packability also come into it?

I “know” that my new S2S dual layer mat is comfortable and it should be warm enough but I do worry about damage and deflation that can’t be repaired. I know I pack my fears but I almost always take the CCF in various combinations and then add in the comfort factor but it is difficult to have a mattress system that is too warm and far too easy to take one that is marginal

If you’re backpacking, winter camping requires a lot of volume and that can be hard to fit in the UL pack.  If you’re using a sled, then you’ve got more volume, and a few extra pads make things a lot more comfortable without adding much weight.  I’ve taken two Z-lites, laid from perpendicular to my body, and then laid a 6-foot inflatable over those.  Then most of the tent / snow cave floor is insulated, and I’m less rudely awaken in the middle of the night if my hips or shoulders get a little off the inflatable pad.

Plus I like the belt&suspenders aspect of it: a frozen-closed valve or ember or hole in the inflatable doesn’t ruin the trip.

I like David’s idea of “belt & suspenders” for winter mattresses. If I knew I was facing -15 F. to -30 F. nights in a double wall tent I for sure would take my Ridgerest to place under my Thermarest Trail Pro.

Yeah, the Ridgerest is bulky but I’d just strap it to the bottom of my pack. Also I’d leave my Thermarest closed cell sit pad at home and use the Ridgerest for sitting on when cooking and enjoying my brandy aperitif.

Reconsidering the Neo-Air X-Therm:

At an R value of 5.7 the X-Therm is the warmest-for-the-weight mattress I’ve found. I don’t like Neo-Air mattresses (owned the first version out and returned it to REI) but really, for that warmth and that weight I could learn to like it. (Sorta like learning to like an arranged marriage bride. ;o)

Jus’ saying’…