Root Cellars: How to Keep It Cool

Before refrigeration, the root cellar was an essential way to keep carrots, turnips, beets, parsnips, potatoes, and other root vegetables fresh through the winter months.

This time-tested storage method still makes sense today—whether you stock a root cellar with your own homegrown produce or the bounty from local farmers' markets.

Start With a Hole in the Ground

Technically, a root cellar is any storage location that uses natural cooling, insulating, and humidifying properties of the earth.

• To work properly, a root cellar must be able to hold a temperature of 32º to  40º F and a humidity level of 85 to 95 percent.
• The cool temperature slows the release of ethylene gas and stops the grow of microorganisms that cause decomposition.
• The humidity level prevents loss of moisture through evaporation—and the withering looks that go along with it.

Today, root cellars are often attached to houses for easy access, though it can take some effort to create a cold basement corner.

• The best method is to use the foundation walls on the northeast corner for two sides.
• Build the other two walls in the basement with stud and board.
• Insulate the interior walls, ceiling, and door (and any pipes or ducts) to keep the heat out.
• Ensure there is a ventilation system that allows cool, fresh air from the outside to be brought into the root cellar and stale air to be exhausted out.

Another option outside the house is to dig down into the ground or horizontally into a hillside. A third option is to create is to bury suitable containers such as metal garbage cans or barrels, leaving about 4 inches exposed at the top. Heap earth around the circumference, then cover the lid with straw or mulch and a sheet of plastic to keep everything dry.

How to Keep It Cool

To create the best atmosphere in your root cellar, consider this:

• Complete temperature stability is reached about 10 feet (3 m) deep.
   
• Don’t dig a root cellar near a large tree; the tree’s roots can be difficult to dig through, and they will eventually grow and crack the cellar walls.
   
• Inside, wooden shelving, bins, and platforms are the norm, as wood does not conduct heat and cold as rapidly as metal does.
   
• Air circulation is critical for minimizing airborne mold, so shelves should stand 1 to 3 inches (3 to 8 cm) away from the walls.
   
• For outdoor root cellars, packed earth is the preferred flooring. Concrete works well and is practical for a cellar in a basement.
   
• Every root cellar needs a thermometer and a hygrometer (to measure temperature and humidity, respectively), which should be checked daily, if possible.
   
• Heat is usually regulated using ventilation to the outside or an exhaust pipe—usually to allow cold air in, often on fall nights to get the temperature down.

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