I live in Alaska so refrigeration is easy. The problem is to keep things from freezing. My 4.5 cu ft top loader is made of 2 inch blue board, 3/8 plywood and liquid nails. I put a 3 inch PVC pipe through the wall with a flapper over it to adjust the airflow. Below zero I stick a wash cloth in it to slow down the cold. An indoor outdoor thermometer tells me the temperature from the sensor in the refrigerator. No fan no electricity no propane etc.