Has anyone used the water heater insulation that you can buy at one of the home improvement stores to insulate a firewall? I am ready to install my a/c and I want to insulate the firewall the best I can. I have the original firewall pad in there now, but I'm wondering if I can do more. I would be interested in using this behind the rear seat and coveing it with the original pad also.

I had a small gap around my steering column and I could feel heat coming through and I sealed that up last night with the expanding foam....no heat coming through now. Any ideas or suggestions would be greatly appreciated.