I recently cut a piece of 1/8" thick closed cell flooring foam to match the profile of my Pro Lite reg. mattress.

?? Could I get perhaps one more "R" rating using this under my Pro Lite pad?

It would surely cut down on convection within the holes of my Pro Lite mattress foam to some degree.

The stuff I used is a "seafoam green" if color means anything in terms of density with this material. It's used beneath wood flooring.

I guess testing will be the way to get an answer. My wife will think I'm even crazier when I lay out on the cold cement patio "testing" but better to know at home if it is worth carrying.

I've got enough for 8 more pads so if anyone in the 'Vegas Valley wants one let me know. (Free)

How much does it weigh?

My wife thinks I'm crazy because I slept on the patio when it was 20 F.

That's okay - I admit it

In Roger's article measuring matts, a 14 mm thickness had an R value of 2, so maybe 1/8" would be 0.5 R

Mark Verber lists the Gossamer Gear 1/8" Thinlite with an R value of 0.4.
http://www.verber.com/mark/outdoors/gear/sleep-system.html
Page way down to "What's Under You?"

That's probably why I couldn't tell any difference when using it under another pad (it did keep the other pad from sliding around, though).

Yeah, you'll likely only get half an R-value with that thin of pad. There have been some studies by the US Military (via Richard N) and humans seem to be really only notice a difference in temp between roughly .5 R. That is to say that you may or may not feel a difference and if you do it will be slight. Our bodies really just register a few types of temperatures. On the lower side that's roughly:
Cool, Cold, Bitter, and "There isn't a word because even the Eskimo's teeth are chattering too much to speak"

The numbers are great but our bodies just aren't that finely tuned to measure temperature =/

I don't think it is even that high. From my figures it should add between 0.37 and 0.43 which jives with what Mary wrote.

You can't tell the difference between 0.37, 0.4, and 0.5

Maybe you can tell the difference between 0 and 0.5

While that thin CCF pad does reduce slippage a bit, it does more to protect your inflatable pad from sharp objects on the ground than to insulate you from said ground.

So, either carry a heavier pad with a higher R value (NeoAire Thermo R = 5.7) or go for the multi-tasking CCF pad. Just don't fool yourself about its primary function.

Thanks folks. Not too encouraging but better than no pad beneath the ProLite. Perhaps I'll use the flooring foam pad with my Ridgerest instead of the ProLite.

Backyard testing shall commence. The sub freezing weather has arrived in the 'Vegas Valley. First I'll test on my cement patio and then on the grass W/ plastic ground cloth for both tests. The cement patio should be the best test due to better condictivity of heat into the cement.

As soon as I get my new Scarp 2 this week I may head to 9,000 ft. in the nearby Spring Mountains to test successful mattress combos in weather in the teens. I'll keep you posted as to the results.

BTW, including a light nylon stuff sack the floring pad weighed 4 oz. Alone it was 2.4 oz.

Under the Prolite, it would prevent punctures

Under the Ridgerest, it would serve no purpose?

You could use more than one if you need the R factor?
Two 1/8" pads can be easier to pack than one 1/4".