I use FatMat, then a thin layer of closed cell foam, then a thin layer of mass-loaded vinyl, and then regular carpet padding, just a little thinner. You might hear me coming three blocks away, but the wife can still sleep in the passenger seat.
Not sure what it is made of. I have used it in dozens of vehicles. Nobody has complained of smells, and it does not smell in mine.
Butyl rubber based products should be used as the main deadener on metal surfaces. Cheaper products like asphalt based products, will NOT remain bonded to the panel if installed vertically or upside down (on the roof). Below is a picture of an asphalt product under the seat of a Chevelle. It is a prime example of what happens with the inferior quality mats. Working on your car after this product deteriorates and melts all over everything is a nightmare. Dynamat Xtreme or Stinger Roadkill Expert will not do this and will remain bonded to the panel even if installed upside down. After the butyl product, Dynamat and Stinger offer foams and carpet pads (foam bonded to a vinyl sheet). The carpet pads are awesome. Deadening or insulating a vehicle will require multiple materials for maximum results. Do not waste your money on asphalt based products or roofing materials.
I looked it up. It says butyl rubber. Mine has been on the under side of the roof, exposed, for over four years. It hasn't budged.
I use "Cool It" by Thermo Tech. It's used by drag racers on the firewalls of their cars to cut heat and if it works for them it works for me. It's available at Speed Shops, runs about $60.00 for a 3 foot by 60 inch roll. Works well in all areas of the car, not only cuts the heat but it deadens sound as well. R-
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