
Originally Posted by
oj88
Heat and NHV insulation are two different things. There are specific products that can handle one better than the other. You were asking specifically about Dynamat, which my answer was loosely based on. Noise reduction by dampening uses the mass of the deadening material to absorb most of the noise and vibration. The thicker the material, the better it is at doing its job at the cost of added weight. Dynamat is somewhat good at NHV reduction and has some inherent heat insulation properties.
On the other end of the spectrum, heat insulation materials does very little to prevent road noise. In fact, the material itself may even contribute to added noise inside the cabin if it is not the right kind or if it not installed properly.
For your application, use Dynamat or equivalent sound deadening material for the portion of the car below the windows and use heat barrier/insulation inside the roof lining. Of course, you may want to switch your window tints to a premium one that cuts down UV and heat radiation coming into the cabin.