Foam vs. the Thermarest

I've always been a fan of the thermarest comfort when sleeping out, but a recent experience has called this into question. Camping out on frozen/lightly snow covered dirt, I had a nice little campfire for a few hours before bed on a 20F Cascade night. I bunked down on a space blanket and thermarest with a 15F Marmot down bag plus a down innerbag. I couldn't sleep too well- I seemed to just get colder through the night. When I got up and put away my bag, the defrosted section of ground under my core was twice as big as the section the fire made the night before. I've read that the air in the thermarest transfers heat and that closed cell foam is a better insulator- is this really true?

I usually camp on snow when I camp. I use both with the thermarest on top.

Closed cell foam is a better insulator; thermarest offers more comfort (and some insulation). For snow or real cold, I do as Ron does with a thin foamie plus thermarest. I'm far too brittle to sleep with only the foam pad.

I have in the past used a therm-a-rest ridge rest closed cel foam doubled w/ my therm-a-rest guidlelite short for comfort. stuff a bag or extra clothes between the sleeping bag and closed cell foam and voila a cozy sleeping situation. Over all on frozen parcels of camp space I have had best luck w/ the above combo

Depends on the closed cell foam and the Thermarest. The lighter and thinner the Thermarest, the less insulation it provides. And in general, closed cell foam of a given thickness insulates better than a Thermarest of the same thickness.<br><br>Comb through the REI website comparing mattresses, looking through the Specs for the R-value. Higher the R-value, the better the insulation.<br><br><br><br>

Ive been using the thicker thermarests (I think its the Camprest LE - 2" thick) on the snow for the last couple years and been very happy and plenty warm. I think it weighs a little less than the thermarest+foam combo, is comfy, and arguably easier to pack.<br><br>The biggest issue I have had is when around lazy people with crampons  &gt;<br><br>I have one of the new Thermarest 4s and want to try it on the snow...doubt its quite enough.<br><br>Michael