spitfire - I believe the stuff I used has some good insulation properties.  On the plus side, once it heats up inside (in the winter) it stays pretty warm, and if you use A/C, it will stay cooler longer.  But you're right, if you don't use your A/C, it seems hotter inside to me also.
joe isuzu - If you are budget conscious, i would look into some of Dynamat's competitors, as IMO they are overpriced.  I used B-Quiet's "Brown Bread" and couldn't be happier.  I've heard pretty good stuff about "Ram Mat" also, but I have no personal experience with it.
				
			 
			
		 
			
				
			
			
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