I wonder if it would help if you put some large containers of water in the spaces between the shelves. As the water freezes, it'll give a little heat off to the surroundings. Plus it'll help even out the temperature in there.

Rena --- Excellent suggestion! I like to keep jugs of drinking water on hand, and that sounds like a good spot to store them since the fridge isn't full this year, killing two birds with one stone.

I like the idea of the thermo cube. My "root cellar" is an insulated room originally built to hang meat and game by the previous owners. I am hoping it will maintain above freezing temps. So far, it has. We had one night of only 3 degrees and I put a single 60 watt bulb in there, but otherwise it seems to be holding. It has not gotten below 40 degrees so far. Being able to set a thermostat for the light bulb would be great, especially when we go out of town.

It will be interesting to see if that works. Because for the water to starts freezing, its surroundings have to bee cooler than the water; there has to be a temperature difference before there can be heat flow.

A related idea;

If you warm some jugs of water up slightly next to the woodstove, and put them in the root cellar in the evening, it might give off enough heat to keep the frost away during the night. Of course you'd have to balance the heat flow from the jug to the cellar and from the cellar to the outside.

A root cellar takes advantage of the steady 55degF temp of the ground down 5 feet or so from the surface. Yours has been placed to give convenient access and protection from varmints, but with so much surface exposed to the air, and not buried very deep, it seems little better (and maybe worse) than not burying it at all...Water has a higher heat content than air, so it can be used as a heat sink, but the volume required to make an adeaquate difference is pretty large. Using only a couple of gallons is probably insignificant (Sorry I sound so negative about what seemed like a great idea at first.)...And weren't the Nannycrats doing us a big favor by trying to take away our incandescent bulbs?

doc --- I disagree --- I think it's doing quite well. The earth enclosing the fridge has kept the humidity extremely high, which is what you need for root crops, and it hasn't frozen inside despite 10 days with lows around 22. As a frame of reference, the surrounding ground has frozen hard, and down in the floodplain where it doesn't get much sun, it's stayed frozen most of the day. Definitely much colder than our average November!

Other root cellar I've used (real ones) have required a light bulb when the outside temperature gets into the teens. (Most root cellars aren't dug five feet down because that's quite an engineering feat.)

Incandescent lightbulbs make good heaters (as opposed to light sources ). But aren't the vegatables in the root cellar susceptible to light (like e.g. potatoes)?

Roland --- Yeah, light is suboptimal. On the other hand, if it just comes on for an hour every few days, the light shouldn't be enough to cause sprouts. We were considering heat tape instead, but Mark didn't think it would give off enough heat.

You can get ceramic heating elements from about 125 W. They essentially only give off infra-red radiation. They do need to about 8 inches away from the vegetables when run at full power. Of course if you use them with a temperature controlled switch, they won't get that hot.

Ideal carrot storage is at 32 degrees, so you may be just fine with the heat tape--I'm guessing it's the sort to keep pipes from freezing. The carrots won't freeze at "freezing" because of the sugars. Jugs of water are a good idea--maybe what you want is glass water jugs wrapped in the heat tape. . .

I wonder if you were to add extra rigid insulation to the side walls if that would help

Why do people have to be so technical, it was an idea, and it works, thats all that matters.