RE: the roofing stuff loren linked from lowe's is about $1.30 sqft. And it
does

> not have foil backing which gives you better radiant heat retention.
>

Actually, it does have a heavy foil backing.  And it is very, very sticky
going onto a smooth surface, once in place and pressed down it ain't coming
off without a hell of a mess and a lot of work.

On the other had I have no doubt that the materials marketed specifically
for this purpose (vehicle sound deadening) probably do a better job

>
>