Insulation: Asphalt mats

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Asphalt mats are primarily sound deadeners - they're affixed to the center of body panels to increase mass and absorb vibration. They're made of asphalt-impregnated rubber (butyl or styrene-butadiene) and are essentially roofing material! They provide great sound insulation, and probably thermal insulation as well, but with significant downsides:

The sounddeadenershowdown.com site again has good information about this material. I think a good recommendation would be to avoid it; if you decide to use it, do so in combination with another material. These aren't meant as all-over insulation, but instead as strategically-placed sound deadener.

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