When you're traveling down the road in 100-degree heat, you'll really enjoy insulation in the roof! Don't skimp--this stuff is not cheap, but it is priceless. Troy Trepanier turned me on to the virtues of Dynamat when he built the Sniper. That car was like a tomb at well over 125 mph. Insulation is one of the big differences between a Cavalier and a Cadillac--it's what you don't hear and feel that makes an impression!