Older Therm a rest any idea of R value?

[Loneoak]

I have an older Therm a rest pad. It is kinda burnt orange in color and measures 1 1/2" thick by 20 " wide and 4 foot long, when inflated. Anyone have any idea of the R value? In cold weather, is this enough with a 15 degree bag?

thanks

[Tinker]

I have one of those and have slept in a tent on the snow in 0 degrees and been fine. Of course in your case you have a 15 degree bag, so .................
R value? No clue. I know mine doesn't self inflate the way it used to. I have to add a few of puffs to get it firm, which, of course, adds moisture which can turn to ice in the open cell foam making it harder to roll (and inflate) with time. You'll probably want to bring a small piece of closed cell foam to insulate your legs and feet, though.

[johnnyblisters]

The new ones have an R value of 2.2 (http://cascadedesigns.com/therm-a-rest/mattresses/fast-and-light/prolite/product) so its more than likely similar to the older ones. Like Tinker, I have used the older orange version down to about 10 degrees F and have been just fine. YMMV

[rockytop7]

The current prolite is 1" thick with a 2.2R and the prolite plus is 1.5" with a 3.8R, so yours is probably somewhere in between. A 2.5R is usually okay down to about freezing depending on how hot or cold you sleep. Even with a 15 degree bag, you may get cold around temps in the teens. Warmth is all relative though, but you may want to take an extra CCF pad just in case...