I used two inches of DOW blue board in some places (bottom and aft side). On the forward side of the box, I used a somewhat more efficient insulator in 1/2" thickness with foil on both sides. My records are at home. The Cryogel-Z used for a small space inside the box is probably the most efficient (high R value) of anything commercially available. The cost was nominal for the small amount I used above the evaporator.