Is there a rule of thumb as how a pads r value relates to temps you would be
comfortable at? I know their are a hundred variables involved but would be curious what folks have found. For instance a pad with an r- value of 2.5 keeps you comfortable down to 20 or ?
In my experience stated R-values are nearly superfluous. I had a Thermarest prolite 4 for about a year (R-value 3.2), and I sleep warmer on both my Z-lite (2.2) and Neoair (2.2) than I did on the prolite with the same bags in a broad range of temps and conditions. I also sleep warmer on the Neoair than I did the BA insulated air core (4.1), which was actually consistently "cooler" than almost every pad I have used--despite having the highest R-value.
I'm not sure how standardized the thermal resistance measurement system is but I know it's all but useless to me. I had to try a lot of different pads until I figured out what I prefer in unique sets of conditions.
What did you come up with Snowy? I was thinking I'd buy a cheaper thermarest closed cell pad (maybe the reflective one) and see if I can make it with that. If I'm not sleeping well then spend the bucks on the neoair. I'd gladly pay an extra $100 for a good nights sleep, but don't won't to spend the money if it's not necessary.
My experience matchs Snowymountaineer's. A Neo Air with a 3/8" Gossamer Gear Closed Cell foam pad on top is the best combo I have tried.
This is an interesting topic. I just purchased my first Big Agnes bag, a yellow wall 0 degree mummy along with an insulated air core pad. BA rates the insulated air core to 15 degrees and says to add another pad for temps below that. My thermarest is rectangular and the bag is a mummy. I haven't tried to put the thermarest in yet butr if it doesn't fit I was thinking of adding a closed cell foam pad and trimming it to shape. I'll be using one of these combinations in a few weeks and I expect to see temps around 0F. I'll try to post me results.
I was thinking I'd buy a cheaper thermarest closed cell pad (maybe the reflective one) and see if I can make it with that. If I'm not sleeping well then spend the bucks on the neoair. I'd gladly pay an extra $100 for a good nights sleep, but don't won't to spend the money if it's not necessary.
I think that's a great plan. If you did end up with a neoair, you can always add a 3/8" or 1/2" ultralight pad like the GG Ed is talking about you'll be pretty much set for as cold as it gets.
As SM stated, one just haves to find what works for them. The closed cell pads, IME/O, are plenty warm but give up much in comfort compared to the inflatible pads. For the temps you'll likely be facing in KY, I can't imagine any pad not working. I sleep warm and have used an uninsulated Air Core down to 10�F. Any colder than that and or not packing the weight, I'll also bring along a REI thermarest knock off or if horse packing, have used saddle blankets/pads if colder.