I used the Frost King insulation material recommended in the ERA manual. It's foil on one side and adhesive backed foam on the other. Very easy to work with and easy to form around curves, bends and corners. Can get it at any building supply store. Here's the link to the stuff at Lowe's
http://www.lowes.com/lowes/lkn?actio...929-1410-FV516
Matt