Maybe it was just because my car was in such poor condition
BUT............
when I stripped out the glued in K-Mart carpet, installed a new
floor pan with no 12" diameter open holes to the road,
installed new tranny tunnel and handbrake tunnel, took apart
the doors and sound deadened them then
installed a quality, alumnum clad insulation layer over everthing-
followed by Wilton wool carpet.
The temperature inide my car is at least 20*F cooler, I can hear my
wife talking with me.
BTW- Because I live in thropics with high humidity,
after I painted the bare bones metal interior, I installed
the insulation and carpet with velcro. It leaves a very nice air
circulation layer under the insulation; so no moisture builtup.
Just my opinion and I know zip about auto mechanics.
But after 12 months not a speck of rust.
d