A hay box (or hay cooker, insulated box, straw box or fireless cooker) is a method of cooking that saves energy.
From Wikipedia: “Food items to be cooked are heated to boiling point, and then insulated. Over a period of time, the food items cook by the heat captured in the insulated container. Generally, it takes three times the normal cooking time to cook food in a hay box.”
Hay and straw, even blanketing can be used as insulation — but we now have so many insulation options. A quick trip to a big hardware store reveals that, that we can build super-insulated hay cookers.
This is old technology that is now being revived. You can get fancy with the box building it out of wood or as in the following video keep it simple by using a cardboard box. According to Wikipedia, in the past, “Some types were provided with soapstone or iron plates which were heated during the preliminary cooking on the stove and then placed in the fireless cooker either over or under the cooking pot. In these types, a non-inflammable insulating material was used.”
Advantage: Can save on huge amounts of energy. Risk/Disadvantage: Again via Wiki “…there is a risk of bacterial growth if the food items are allowed to remain in the danger zone for one or more hours. For this reason, food cooked in hay boxes is normally reheated to boiling before eating. Using a food thermometer eliminates the guesswork.”
In this video Aaron Mackley shows us how to build a hay box using a cardboard box, styrofoam panels and aluminum foil. I would probably go with an insulator other than styrofoam, especially around something hot because it is just nasty, toxic stuff, but…