I'm still running with the ball on this one.
From a Mercedes forum
Here are some materials for which I could find specific information:
Thermozite: specific R= 1.3 (standard R= 3.7) {http://www.perfectfit.com/15269/154086/Carpet--Padding/Thermozite.html} Price: ~$1/sq.ft.
KOOLMAT: standard R=1.65 {http://www.koolmat.com/what.shtml} Price: $14/sq.ft.
EZ Cool Insulation: specific R= 1.6 {http://lobucrod.com/} Price: ~$0.68/sq.ft. - I am not so sure about the claimed R-values and the material collapses easily.
VB-3 with lead septum: specific R= 1 (standard R = 4) {http://cascadeaudio.com/car_noise_control/car_barriers.htm} Price: ~$17/sq.ft.
VB-4 barrier: specific R= 1 (standard R = 4) {http://cascadeaudio.com/car_noise_control/car_barriers.htm} Price: ~$8/sq.ft.
These values are in general agreement with the tabulated information for polymers provided in the Wikipedia article
A few more
http://www.insulshield.net
http://www.thermotec.com/
http://store.secondskinaudio.com/heat-wave-pro/
http://www.lizardskin.com/
http://www.designengineering.com/cat...er-carpet-lite
http://www.hushmat.com/NEW_Restoration_Megabond.php
Some of the Cascadeaudio looks like the sh!t, but not at $17 a sq.ft.. I really like how some of its made.