One of the attractions to this house when we bought it 6 years ago was the root cellar. I never had a root cellar before, and only a general idea of all the ways they could or should function. Now that I have used it increasingly more every year for several years, I have learned some short-comings that should be improved if I am to depend on it for storing more than a few foods over winter.
I thought I'd pass on my thoughts here since a lot of folks seem to be considering longer-term perishable food storage as our economy tanks. Food storage doesn't have to be a separate building... it could be part of a basement, or garage, or a closet in a cool room. It could be a stack of straw/hay bales covered with a tarp, or garbage cans buried in the ground. There are many possibilities, but the requirements are all pretty similar where the food is concerned. The faults in my root cellar may be helpful if you are planning a food storage area.
Some known problems with my concrete block root cellar:
1. There is no constant air exchange; fresh air only enters when I open the door. All perishable foods need some minimal air circulation, and especially so in more humid environments. Air exchange is easily accomplished by a low pvc pipe to the outside, and a ceiling height pvc pipe to the outside on the opposite wall; natural convection does the rest. Be sure to screen the pipe from bugs and critters.
2. There is only one humidity range: moist ...or even somewhat wet when rain runoff seeps down and into the back wall at the concrete floor joint. Most vegetables require different humidity levels for optimum storage and well-planned storage areas are generally zoned. Plus, any foods in my cellar that are dried have to be in sealed glass jars to prevent dampness seeping in. (I seal them by dipping the lids and jar necks in melted paraffin unless the jars have an old-fashioned rubber ring seal.)
I'll do a follow-up post on some requirements for different foods. The "zones" are cold and very moist, cold and moist, cool and moist, cool and dry, and moderately warm and dry.
3. Too much natural light. The window and the glass in the door let in enough light to allow potatoes to sprout in early spring, long before it's time to plant potatoes. The light also robs vitamins/nutrients from all the visible fruits and vegetables, or any ferments stored in clear glass jars.
4. No provision for preventing summer heat. Nothing much has frozen inside my cellar in during winter since it's built partway into the hillside. However, as the weather starts to warm up in late spring, so does the root cellar. Any foods remaining decline rapidly. They would be still edible for longer if the building had some insulation besides the dirt mounded mostly up the rear wall and barely up the side walls.
5. It is not varmint-proof. I see signs of field mice nesting inside, and I saw where they munched on apples over this last winter. There is a gable roof over my cellar and the ceiling above the cellar is not sealed well, so that's an entry point. Also, the door weather-stripping has failed, and field mice can get through amazingly narrow openings!
6. It is not large enough. Well, it was when I first began using it, but as I'm learning what all can be stored successfully, it has grown too small! To be fair, it also houses the spring water pressure tank that I use for the garden, and now also houses my cheese cave and the mini-cheese cave for blue cheese.
In previous years it has been useful to store potted perennials like my 2 fig trees, a patio peach which I just gave away, and 3 blueberry bushes... but now those will have to go in the ground before this winter. (The blueberries were only potted because I have been acidifying a proper place to plant them. The figs will freeze to the ground here but should come back each spring.)
Even without the potted plants, the cellar is now too small to store as much variety as I have discovered I can safely store. The shelving (which is only on the back wall and one side wall) runs from waist-high up to the low ceiling, and is filled with jars of dry goods that will not be harmed by freezing... things like pasta, beans, rice, powdered milk and home-dried vegetables that won't fit in my pantry in the house. Below the shelving is all the space I have remaining for vegetables (3' tall x 1' deep x about 11' feet in length), leaving a narrow walkway in the center; the cheese caves and water tank take up the opposite wall. I try not to store anything near the doorway since that uninsulated wall no doubt allows some freezing temps inside a foot or more during winter.
With more storage area, I could keep and easily access several containers of carrots, beets, rutabagas, sunchokes and parsnips, etc. stored in slightly damp soil or sawdust. Potatoes I can store loose in a bin, but not with apples in the same room. The ethylene gas given off by apples causes the 'taters to sprout, and affects the storage life of some other vegetables. Last year I stored 3 bushels of apples but I didn't have any potatoes to store. I did have winter squash that didn't keep like they usually did before I started storing apples. I threw away over a bushel of butternuts that rotted. I don't know if it was the apples or not, because it was so moist in the cellar last winter. (Winter squash and pumpkins need fairly dry storage conditions.)
With more storage area, I could also keep 5 gallon buckets that were "early fall planted" with carrots, Belgian endive, celery, lettuce and other greens. All I'd have to do to use the celery and greens is bring a bucket inside the house to natural light for a few days, and harvest. Carrots and Belgian endive would be harvested right from the buckets in the cellar.
The seemingly simple solution to most of my root cellar problems would be to add a drier room onto one side, and insulate what's already in place. However, the land falls off pretty steeply on one side, and heavy equipment cannot access the other side to dig out the rocky hill. Tearing it down and building it back with a bigger footprint and better design would be too expensive, although the smart thing to do if I could afford it.
Some remedy will come to me, sooner or later. In the meantime, I hope my observations have given you some ideas to consider.