At my local REI garage sale, I picked up a Big Agnes Insulated Air Core (20" x 78") that was returned because it was "too long." Well, since that is not a problem for me, I went against all the advice of 'don't buy air pads there because they all leak' and I bought it for $35. I blew it up and slept on it inside one night to make sure it held air, and it did not leak even a bit. Last night I blew it up again and slept out on my concrete slab porch to see how it felt at a known temperature of 22*F. I did not put any other pads beneath it or on top of it, because I wanted to see how the pad performed on its own. My sleeping bag is an old 0* bag with 650 fill in it, and is probably more like a 10 - 15* bag now. I also wore lightweight base layer pants, 1 pair of normal wool hiking socks, lightweight base layer top + a medium pile fleece and wool hat. I went to bed toasty warm (almost too warm) but I woke up at about 2am with a chilly backside. Wasn't too terribly cold, but it was more comfortable to turn onto my side to go back to sleep. I had to wake up and turn to my other side about four more times during the night, rotating to switch my cold 'pad side' with the super-warm 'bag side.' I thought with an R-Value of about 3.8 that this pad would be warmer? The concrete is probably less warm than actual ground at that temperature, but still... I have slept on an old school 3/4 length self inflatable pad (maybe 1/2" to 3/4" thick at absolute max) in temps around 5 - 10* and felt the same way as I did on this larger, better rated pad at 22*. What gives?

I have been using the IAC since they first came out and have used one down to 17 F, but I do feel it around 20 F.

I think one problem you had was putting it on concrete that acted as a heat drain all night long.

To tell the truth, once the temps get below freezing on a regular basis I switch to either my Big Agnes Dual Core or go to my Kooka Bay or Exped DownMat.

Every one is different, and IMO, your concrete pad is a very cold object to be sleeping over, for example a forest floor would maybe have a little more insulation value. Anyway, for me, my BA IAC is only good to about 30 degrees. If it is much colder than that, I need to add my ridgerest on top, no problems, a pain to backpack with thou. I just bring my thermarest if it is colder than 30.

You may be able to use it at lower temp than me, but I think you have found the lower comfy limit temp wise. Good on you for testing. Adding a ccf pad if you want will help a lot.

a true R 3.8 should keep you fairly decent down to that temp IMO ... not ideal, but better than a simple foamy or even a neo air

question is ... has BPL tested the BAIC to that R value yet?

I have been wondering about this topic myself recently. I have a birthday coming up and was considering a opportunity to upgrade my old thermarest. Planning to do the Ga section of the AT in late spring, and the old back doesn't like mother earth as it once did. I was considering a combination similar to this with a 2.5" air pad combined with a ridgerest or a z rest. Also I am interested on opinions regarding opting for a short pad vs a long pad for legs and feet. Does anyone really notice the need for a pad for legs and feet since the head and torso hips and butt are the major cushion points on the pad.

I have used a 3/4 length pad for most of my outdoor life, and have been fairly satisfied with it. However, I really *really* like the full length pads. They are more comfortable than a 3/4 length with a pack or whatnot under your feet, and my tents always leak, so the floor is always wet in the morning after even a light rain, so the full length pad keeps my down bag more dry.

---I will test the Big Agnes Insulated Air Core out again on Friday night, but with a standard blue foam pad underneath it this time. The night-time temps should be around 16*F in my area, so I will see how effective it is with the additional foam.

---Question, though- should I put the foam underneath it or on top of it? Underneath the air pad seems like a better way to go to me, but maybe not?

The consensus from discussions last year was that foam on top was slightly warmer. This agrees with theory too. Thick air pads lose some heat due to convective currents inside the pad caused by a warm body on top, and cold ground beneath. They also theoretically loose heat through the sides of the pad. Whether this is noticeable seems to depend on how firmly you blow up the pad.

would you happen to have a link to the thread discussing pad on top/bottom and all that?