This is a project building small root cellars out of 55 gallon plastic drums patterned from the information in Purdue Extension Application note HO-125. This is my nephew Ben lending me a hand. It is January and they are working great. Additional info: you do have to put a drain hole in the bottom for condensate. Just pour some water in the bottom and drill a 1/2' hole in the center of where ever the water pools. The lids are uninsulated and in Jan and Feb with nightly lows in the teens, the temperature inside was 34F. This was with 4" of straw thatch and 18" of course thatch, covered with a tarp. Note that 34 degrees is ideal for a lot of vegs like cabbage. However, potatoes and fruits like it around 40-45F. I would recommend additional insulation on the exposed barrel and also insulating the lid. Also fruits like it drier and right now the barrels are at 95% humidity because I didn't put the heavy thatch on until later. I would recommend for fruits to thatch the barrels completely from the start so the temperature is does not go up slightly during the day - which causes it to breath in humid air at night when the barrel top cools. Over time this condenses driving the humidity up.