Insulation
You can buy some very expensive high tech insulation - VACUUM FOAM - from the company that makes the Red Baron Wind Generator (also makes the Four Winds). Best if you have to insulate on the inside of the box. (Some type of NASA developed insualation - very thin, but expensive. 1 inch = 5 inches urethane foam).I was able to get to the outside of most of my icebox so I went a cheaper. I bought rigid insualation at a home improvement center and used construction adhesive to cover as much of the outside of the box I could get too. There seems to be a real advantage to getting the stuff with the thermal barrier - looks like foil - glued to one surface.Don't forget to add some weather seal to the lid. I also picked up some rolls of a blue foam insualation and some thermal barrier - again and Home Depot - and added that to the inside of the box - the sides and bottom seemed to be OK, but the top was just 1 inch marine ply. I also insulated the lid itself.Now my Grunnert runs about half the time - a little more in the day, a little less at night. And I don't get too much frost from condensation.What will work best for you will depend on how well it is insulated to begin with, and whether or not you can get to the outside of the box w/o taking the galley apart. Mine backs into a sail locker, and one side is behind the drawers in the galley, and the front is next to the stove. The outside (against the hull) was problematic, and I ended up adding some of the blue foam and thermal barrier (in a sandwich arrangement) in the one area where there was a problem.