Cons and I got a chance to play with the new Infrared Camera during Isopod and winter sleeping bag testing up here on the Mt. Washington summit.
Here are two pics taken seconds apart. The first is with the metalized reflective liner door open, exposing only the shell door which separates us from the howling 30mph winds and sub 20F temperatures (below 0 with windchill).
The second shows the door closed and how important an air gap can be to thermal efficiency. Just cutting down the convection currents with a second layer can do an amazing amount for the comfort of a tent. We slept toasty warm inside our protective cave as the weather raged on outside.