We bit the bullet and built a root cellar several years back as we need the increased storage space. But before then we used a used fridge we picked up at an auction and kept it - running of course - in the basement. Works well as it is cool, dark and dry. Only limitation is how much it will hold.

Dave

I would not suggest an old refrigerator, they are terribly inefficient, noisy, and not nearly as cost effective as newer ones (less than 5 yrs old). I live in the South too and it is most difficult to do things like fermentation when internal insulated garage temps reach 80 or more, like it does all summer here. Even my basement with insulation and AC, it never gets below 75. Whatever root crops I can't eat within a few weeks from the refrigerator, or freeze for cooking, I dehydrate. Making vegetable soup is just a matter of re-hydrating a selection from the pantry shelves in meat broth or water.

In particular - sweet potatoes like it never below 55 and never over 60 max. I found an old wine cooler on Freecycle that keeps them at the perfect temperature but must be "aired out" every week or so with fresh air (just open the door and leave for a few minutes while you check to be sure there aren't any soft spots or mold development. If they have been cured properly they will be fine for months. Also, dried or deep fried sweet potato chips are wonderful, as are turnip chips from the dehydrator.
Onions are cut up in slices or diced and frozen as is, without blanching needed, laid on baking sheets then tossed into Food Saver quart or gallon bags. In the middle of winter when I want to make a mirepoix they are there! For longer fresh storage, anything you put them into besides a refrigerator will hasten their demise. About a month to 6 weeks max for properly cured onions is all I can get from the pantry option.
Moving from the South to a cooler basement year 'round is the only other option for keeping root crops. Sorry, or you can dig a cellar cold storage, but who that in these times does that?
Nancy