Dear Ed, I've been very respectful of your posts in the past, and continue to greatly respect you. This would be a great time for us'ns to tell the folks about the three ways to transfer heat.
Conduction: When heat transfers from one object to another, when they are in physical contct. A wonderful example of this is the cold freezer, and after a while the door feels cool. The heat is conducting. You can reduce this with fiberglass, or bubble wrap.
Convection: This is when hot or cold "something" is physically moved. As Mr. P so wisely noted, when the freezer is full, you get less heat loss. Th is is because when you open an empty freezer, ALL the freezer cold air comes out. And when you open a full freezer, you only lose a little iar. You can reduce this with duct tape, fiberglass, or bubble wrap.
Radiation: This is less a concern here. An example is a glowing camp fire that makes you feel warm. Not an issue with refrigs. Unless your freezer is near a camp fire.