Step 4: Insulated panels
The insulated panels are 24 gauge sheet metal panels. They are composed of two square "pans" that have a one inch blanket of insulation between them. The pans were then rivetted together. One of the pans has a longer edge at the top where I formed a channle to hook onto the wood side. I am a sheet metal worker by trade so I have made similar panels before, and I have easy access to the materials for free. If I didn't have access to the metal I could have just used the insulated blanket, which had one foil side, and foil taped it directly to the wood. Since the bottom of the box is not exposed to as much heat I settled for just using the insulation material to cover it. The panels have worked remarkably well. There is absolutely no noticeable rise in temperature on the outside of the box or the internal surface of the wood, even though the inside reaches 450 degrees.